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    <link:label xlink:label="us-gaap_LossContingencyAccrualCarryingValueCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Contract loss reserve</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LossContingencyAccrualCarryingValueCurrent" xlink:to="us-gaap_LossContingencyAccrualCarryingValueCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Award [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Disclosure of Compensation Related Costs, Share-based Payments [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:to="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash flows from investing activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityWellKnownSeasonedIssuer" xlink:label="dei_EntityWellKnownSeasonedIssuer" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityWellKnownSeasonedIssuer-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Well-known Seasoned Issuer</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityWellKnownSeasonedIssuer" xlink:to="dei_EntityWellKnownSeasonedIssuer-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_NetCashProvidedByUsedInOperatingActivities</link:label>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net cash used in operating activities</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_CommonStockDisclosurePolicyTextBlock" xlink:label="optt_CommonStockDisclosurePolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="optt_CommonStockDisclosurePolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock Disclosure [Policy Text Block]</link:label>
    <link:label xlink:label="optt_CommonStockDisclosurePolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Disclosure of accounting policy for disclosing common stock issuance and reverse stock splits.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_CommonStockDisclosurePolicyTextBlock" xlink:to="optt_CommonStockDisclosurePolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CorporationMember" xlink:label="us-gaap_CorporationMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CorporationMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Corporation [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CorporationMember" xlink:to="us-gaap_CorporationMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercised. (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Granted. (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_AggregateOfferingPriceCommonStockMaximum" xlink:label="optt_AggregateOfferingPriceCommonStockMaximum" xlink:type="locator"/>
    <link:label xlink:label="optt_AggregateOfferingPriceCommonStockMaximum-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_AggregateOfferingPriceCommonStockMaximum</link:label>
    <link:label xlink:label="optt_AggregateOfferingPriceCommonStockMaximum-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Aggregate Offering Price, Common Stock, Maximum</link:label>
    <link:label xlink:label="optt_AggregateOfferingPriceCommonStockMaximum-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The maximum aggregate offering price of common stock to be offered through a shelf registration that has been meditated through an underwriter.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_AggregateOfferingPriceCommonStockMaximum" xlink:to="optt_AggregateOfferingPriceCommonStockMaximum-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LegalEntityTypeOfCounterpartyDomain" xlink:label="us-gaap_LegalEntityTypeOfCounterpartyDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LegalEntityTypeOfCounterpartyDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Legal Entity Type of Counterparty [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LegalEntityTypeOfCounterpartyDomain" xlink:to="us-gaap_LegalEntityTypeOfCounterpartyDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis" xlink:label="us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Legal Entity of Counterparty, Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis" xlink:to="us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Forfeited. (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="us-gaap_AccountsReceivableNetCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountsReceivableNetCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AccountsReceivableNetCurrent</link:label>
    <link:label xlink:label="us-gaap_AccountsReceivableNetCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Accounts receivable</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsReceivableNetCurrent" xlink:to="us-gaap_AccountsReceivableNetCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementTable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement [Table]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementTable-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Outstanding April 30, 2013. (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LineOfCredit" xlink:label="us-gaap_LineOfCredit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LineOfCredit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LineOfCredit</link:label>
    <link:label xlink:label="us-gaap_LineOfCredit-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long-term Line of Credit</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCredit" xlink:to="us-gaap_LineOfCredit-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and cash equivalents</link:label>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Cash and cash equivalents, beginning of period</link:label>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Cash and cash equivalents, end of period</link:label>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash and cash equivalents</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_ReverseStockSplitMember" xlink:label="optt_ReverseStockSplitMember" xlink:type="locator"/>
    <link:label xlink:label="optt_ReverseStockSplitMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Reverse Stock Split [Member]</link:label>
    <link:label xlink:label="optt_ReverseStockSplitMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The conversion of a reverse stock split where there is a reduction in the shares outstanding</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_ReverseStockSplitMember" xlink:to="optt_ReverseStockSplitMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restricted cash</link:label>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Restricted cash</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" xlink:label="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty</link:label>
    <link:label xlink:label="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party Transaction, Expenses from Transactions with Related Party</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" xlink:to="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="us-gaap_LineOfCreditMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LineOfCreditMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditMember" xlink:to="us-gaap_LineOfCreditMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_ScheduleOfCashAndCashEquivalentsTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Cash and Cash Equivalents [Table Text Block]</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RestrictedCashAndInvestmentsCurrentAbstract" xlink:label="us-gaap_RestrictedCashAndInvestmentsCurrentAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RestrictedCashAndInvestmentsCurrentAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Current:</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="us-gaap_AssetsAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AssetsAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">ASSETS</link:label>
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    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Outstanding as of April 30, 2015</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercisable as of October 31, 2015 (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents" xlink:label="us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Effect of exchange rate changes on cash and cash equivalents</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost" xlink:label="us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Product development costs</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost" xlink:to="us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:label="us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease</link:label>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net decrease in cash and cash equivalents</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:to="us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1</link:label>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncomeStatementAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Statement [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_IncomeStatementAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercisable as of October 31, 2015 (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Exercisable as of October 31, 2015</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EuropeMember" xlink:label="us-gaap_EuropeMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EuropeMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Europe [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EuropeMember" xlink:to="us-gaap_EuropeMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NorthAmericaMember" xlink:label="us-gaap_NorthAmericaMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NorthAmericaMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">North America [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NorthAmericaMember" xlink:to="us-gaap_NorthAmericaMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_NetCashProvidedByUsedInFinancingActivities</link:label>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net cash used in financing activities</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementGeographicalAxis" xlink:label="us-gaap_StatementGeographicalAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementGeographicalAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Geographical [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementGeographicalAxis" xlink:to="us-gaap_StatementGeographicalAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CreditFacilityDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Credit Facility [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_CreditFacilityDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CreditFacilityAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Credit Facility [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Outstanding as of April 30, 2015 (in shares)</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_StockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockholdersEquity</link:label>
    <link:label xlink:label="us-gaap_StockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total Ocean Power Technologies, Inc. stockholders&#8217; equity</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquity" xlink:to="us-gaap_StockholdersEquity-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Selling, general and administrative costs</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SellingGeneralAndAdministrativeExpense" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpense-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_TableTextBlock" xlink:label="us-gaap_TableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_TableTextBlock</link:label>
    <link:label xlink:label="us-gaap_TableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Notes Tables</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TableTextBlock" xlink:to="us-gaap_TableTextBlock-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:type="locator"/>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_StockholdersEquityNoteStockSplitConversionRatio1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockholdersEquityNoteStockSplitConversionRatio1</link:label>
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    <link:label xlink:label="us-gaap_PreferredStockSharesIssued-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock, shares issued (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesIssued" xlink:to="us-gaap_PreferredStockSharesIssued-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_EarningsPerSharePolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Earnings Per Share, Policy [Policy Text Block]</link:label>
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    <link:label xlink:label="us-gaap_PreferredStockSharesAuthorized-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock, shares authorized (in shares)</link:label>
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    <link:label xlink:label="us-gaap_NonmonetaryTransactionTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Nonmonetary Transaction Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NonmonetaryTransactionTypeAxis" xlink:to="us-gaap_NonmonetaryTransactionTypeAxis-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_NonmonetaryTransactionTypeDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Nonmonetary Transaction Type [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NonmonetaryTransactionTypeDomain" xlink:to="us-gaap_NonmonetaryTransactionTypeDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Expected volatility</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock par value (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockParOrStatedValuePerShare" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PaymentsToAcquireMachineryAndEquipment" xlink:label="us-gaap_PaymentsToAcquireMachineryAndEquipment" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PaymentsToAcquireMachineryAndEquipment-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_PaymentsToAcquireMachineryAndEquipment</link:label>
    <link:label xlink:label="us-gaap_PaymentsToAcquireMachineryAndEquipment-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Purchases of equipment</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquireMachineryAndEquipment" xlink:to="us-gaap_PaymentsToAcquireMachineryAndEquipment-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Expected life (in years)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" xlink:label="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Foreign Currency Transactions and Translations Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" xlink:to="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Foreign currency translation adjustment</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits-label" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Reverse stock split (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" xlink:to="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfRevenueByMajorCustomersByReportingSegmentsTableTextBlock" xlink:label="us-gaap_ScheduleOfRevenueByMajorCustomersByReportingSegmentsTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfRevenueByMajorCustomersByReportingSegmentsTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfRevenueByMajorCustomersByReportingSegmentsTableTextBlock" xlink:to="us-gaap_ScheduleOfRevenueByMajorCustomersByReportingSegmentsTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NoncurrentAssets" xlink:label="us-gaap_NoncurrentAssets" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NoncurrentAssets-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-lived assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NoncurrentAssets" xlink:to="us-gaap_NoncurrentAssets-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="us-gaap_TreasuryStockSharesAcquired" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TreasuryStockSharesAcquired-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Acquisition of treasury stock (in shares)</link:label>
    <link:label xlink:label="us-gaap_TreasuryStockSharesAcquired-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Treasury Stock, Shares, Acquired</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockSharesAcquired" xlink:to="us-gaap_TreasuryStockSharesAcquired-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_Revenues" xlink:label="us-gaap_Revenues" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_Revenues-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revenues</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Revenues" xlink:to="us-gaap_Revenues-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OtherAssetsCurrent" xlink:label="us-gaap_OtherAssetsCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherAssetsCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other current assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAssetsCurrent" xlink:to="us-gaap_OtherAssetsCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="us-gaap_PreferredStockSharesOutstanding" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PreferredStockSharesOutstanding-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock, shares outstanding (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesOutstanding" xlink:to="us-gaap_PreferredStockSharesOutstanding-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="us-gaap_OperatingExpensesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingExpensesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating expenses:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OperatingExpensesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharesOutstanding-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharesOutstanding</link:label>
    <link:label xlink:label="us-gaap_SharesOutstanding-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Balance (in shares)</link:label>
    <link:label xlink:label="us-gaap_SharesOutstanding-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Balance (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharesOutstanding" xlink:to="us-gaap_SharesOutstanding-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Expected dividend yield</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod-label" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Forfeited (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccruedProfessionalFeesCurrent" xlink:label="us-gaap_AccruedProfessionalFeesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccruedProfessionalFeesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Legal and accounting fees</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedProfessionalFeesCurrent" xlink:to="us-gaap_AccruedProfessionalFeesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber-label" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Issued and unvested at April 30, 2015 (in shares)</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber-label" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:type="resource" xml:lang="en-US">Issued and unvested at October 31, 2015 (in shares)</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OtherAccruedLiabilitiesCurrent</link:label>
    <link:label xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Other</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAccruedLiabilitiesCurrent" xlink:to="us-gaap_OtherAccruedLiabilitiesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restricted Cash and Cash Equivalents [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Granted (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock" xlink:label="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Restricted Cash and Cash Equivalents [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock" xlink:to="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:type="locator"/>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTax-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_Assets-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Total assets</link:label>
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    <link:label xlink:label="us-gaap_StockholdersEquityAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Ocean Power Technologies, Inc. stockholders&#8217; equity:</link:label>
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    <link:label xlink:label="us-gaap_PaymentsToAcquireMarketableSecurities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_PaymentsToAcquireMarketableSecurities</link:label>
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    <link:label xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Commitments and Contingencies Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Major Types of Debt and Equity Securities [Axis]</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="us-gaap_OtherAssetsNoncurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherAssetsNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other noncurrent assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAssetsNoncurrent" xlink:to="us-gaap_OtherAssetsNoncurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Major Types of Debt and Equity Securities [Domain]</link:label>
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    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="dei_EntityCommonStockSharesOutstanding" xlink:type="locator"/>
    <link:label xlink:label="dei_EntityCommonStockSharesOutstanding-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Entity Common Stock, Shares Outstanding (in shares)</link:label>
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    <link:label xlink:label="us-gaap_CommitmentsAndContingencies-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Commitments and contingencies (note 9)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingencies" xlink:to="us-gaap_CommitmentsAndContingencies-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_Liabilities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_Liabilities</link:label>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_Liabilities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SupplementalBalanceSheetDisclosuresTextBlock" xlink:label="us-gaap_SupplementalBalanceSheetDisclosuresTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SupplementalBalanceSheetDisclosuresTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Supplemental Balance Sheet Disclosures [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SupplementalBalanceSheetDisclosuresTextBlock" xlink:to="us-gaap_SupplementalBalanceSheetDisclosuresTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SegmentReportingDisclosureTextBlock" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SegmentReportingDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Segment Reporting Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SegmentReportingDisclosureTextBlock" xlink:to="us-gaap_SegmentReportingDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CustomerAdvancesAndDeposits" xlink:label="us-gaap_CustomerAdvancesAndDeposits" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CustomerAdvancesAndDeposits-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_CustomerAdvancesAndDeposits</link:label>
    <link:label xlink:label="us-gaap_CustomerAdvancesAndDeposits-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Customer Advances and Deposits</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CustomerAdvancesAndDeposits" xlink:to="us-gaap_CustomerAdvancesAndDeposits-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_TradingSymbol" xlink:label="dei_TradingSymbol" xlink:type="locator"/>
    <link:label xlink:label="dei_TradingSymbol-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Trading Symbol</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_TradingSymbol" xlink:to="dei_TradingSymbol-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementScenarioAxis" xlink:label="us-gaap_StatementScenarioAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementScenarioAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Scenario [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementScenarioAxis" xlink:to="us-gaap_StatementScenarioAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="us-gaap_ScenarioUnspecifiedDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScenarioUnspecifiedDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Scenario, Unspecified [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScenarioUnspecifiedDomain" xlink:to="us-gaap_ScenarioUnspecifiedDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalents" xlink:label="us-gaap_RestrictedCashAndCashEquivalents" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalents-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_RestrictedCashAndCashEquivalents</link:label>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalents-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Restricted Cash and Cash Equivalents</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedCashAndCashEquivalents" xlink:to="us-gaap_RestrictedCashAndCashEquivalents-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="us-gaap_AssetsCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AssetsCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AssetsCurrent</link:label>
    <link:label xlink:label="us-gaap_AssetsCurrent-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total current assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsCurrent" xlink:to="us-gaap_AssetsCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DisclosureTextBlockAbstract" xlink:label="us-gaap_DisclosureTextBlockAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DisclosureTextBlockAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_DisclosureTextBlockAbstract</link:label>
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    <link:loc xlink:href="optt-20151031.xsd#optt_LongTermDebtPaymentTerms1" xlink:label="optt_LongTermDebtPaymentTerms1" xlink:type="locator"/>
    <link:label xlink:label="optt_LongTermDebtPaymentTerms1-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-term Debt Payment Terms</link:label>
    <link:label xlink:label="optt_LongTermDebtPaymentTerms1-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Long-erm debt payment terms</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_LongTermDebtPaymentTerms1" xlink:to="optt_LongTermDebtPaymentTerms1-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_MitsuiEngineeringAndShipBuildingMember" xlink:label="optt_MitsuiEngineeringAndShipBuildingMember" xlink:type="locator"/>
    <link:label xlink:label="optt_MitsuiEngineeringAndShipBuildingMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Mitsui Engineering and Ship Building [Member]</link:label>
    <link:label xlink:label="optt_MitsuiEngineeringAndShipBuildingMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Mitsui engineering and ship building [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_MitsuiEngineeringAndShipBuildingMember" xlink:to="optt_MitsuiEngineeringAndShipBuildingMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_EuropeanUnionWaverPortProjectMember" xlink:label="optt_EuropeanUnionWaverPortProjectMember" xlink:type="locator"/>
    <link:label xlink:label="optt_EuropeanUnionWaverPortProjectMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">European Union Waver Port Project [Member]</link:label>
    <link:label xlink:label="optt_EuropeanUnionWaverPortProjectMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">European union waver port project [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_EuropeanUnionWaverPortProjectMember" xlink:to="optt_EuropeanUnionWaverPortProjectMember-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_MinorityInterestDecreaseFromRedemptions-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Additional investment in subsidiary</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MinorityInterestDecreaseFromRedemptions" xlink:to="us-gaap_MinorityInterestDecreaseFromRedemptions-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sale of Common Stock,net</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_LiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LiabilitiesCurrent</link:label>
    <link:label xlink:label="us-gaap_LiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total current liabilities</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrent" xlink:to="us-gaap_LiabilitiesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_LiquidityDisclosurePolicyTextBlock" xlink:label="optt_LiquidityDisclosurePolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="optt_LiquidityDisclosurePolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Liquidity Disclosure [Policy Text Block]</link:label>
    <link:label xlink:label="optt_LiquidityDisclosurePolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Disclosure of liquidity accounting policy.</link:label>
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    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sale of Common Stock,net (in shares)</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Shares, New Issues</link:label>
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    <link:loc xlink:href="optt-20151031.xsd#optt_CurrentMember" xlink:label="optt_CurrentMember" xlink:type="locator"/>
    <link:label xlink:label="optt_CurrentMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Current [Member]</link:label>
    <link:label xlink:label="optt_CurrentMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Current [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_CurrentMember" xlink:to="optt_CurrentMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_USTreasuryobligationsMember" xlink:label="optt_USTreasuryobligationsMember" xlink:type="locator"/>
    <link:label xlink:label="optt_USTreasuryobligationsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">US Treasury Obligations [Member]</link:label>
    <link:label xlink:label="optt_USTreasuryobligationsMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">US treasury obligations [member]</link:label>
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    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Granted (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_NewJerseyBoardOfPublicUtilities1Member" xlink:label="optt_NewJerseyBoardOfPublicUtilities1Member" xlink:type="locator"/>
    <link:label xlink:label="optt_NewJerseyBoardOfPublicUtilities1Member-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">New Jersey Board of Public Utilities 1 [Member]</link:label>
    <link:label xlink:label="optt_NewJerseyBoardOfPublicUtilities1Member-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The entity of New jersey board of public utilities 1</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_NewJerseyBoardOfPublicUtilities1Member" xlink:to="optt_NewJerseyBoardOfPublicUtilities1Member-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod</link:label>
    <link:label xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Forfeited (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_CustomerAdvancesAndDepositsDisclosureTextBlock" xlink:label="optt_CustomerAdvancesAndDepositsDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="optt_CustomerAdvancesAndDepositsDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Customer Advances and Deposits Disclosure [Text Block]</link:label>
    <link:label xlink:label="optt_CustomerAdvancesAndDepositsDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Customer Advances And Deposits Disclosure</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_CustomerAdvancesAndDepositsDisclosureTextBlock" xlink:to="optt_CustomerAdvancesAndDepositsDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_DeferredCreditsPayableOptionDetails" xlink:label="optt_DeferredCreditsPayableOptionDetails" xlink:type="locator"/>
    <link:label xlink:label="optt_DeferredCreditsPayableOptionDetails-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_DeferredCreditsPayableOptionDetails</link:label>
    <link:label xlink:label="optt_DeferredCreditsPayableOptionDetails-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred Credits Payable Option Details</link:label>
    <link:label xlink:label="optt_DeferredCreditsPayableOptionDetails-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Deferred credits payable option details</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_DeferredCreditsPayableOptionDetails" xlink:to="optt_DeferredCreditsPayableOptionDetails-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_DeferredCreditsPayableMarketDiscountRate" xlink:label="optt_DeferredCreditsPayableMarketDiscountRate" xlink:type="locator"/>
    <link:label xlink:label="optt_DeferredCreditsPayableMarketDiscountRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_DeferredCreditsPayableMarketDiscountRate</link:label>
    <link:label xlink:label="optt_DeferredCreditsPayableMarketDiscountRate-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred Credits Payable Market Discount Rate</link:label>
    <link:label xlink:label="optt_DeferredCreditsPayableMarketDiscountRate-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Deferred Credits Payable Market Discount Rate</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_DeferredCreditsPayableMarketDiscountRate" xlink:to="optt_DeferredCreditsPayableMarketDiscountRate-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_DeferredCreditsPayableMarketLiquidatedDamagesRate" xlink:label="optt_DeferredCreditsPayableMarketLiquidatedDamagesRate" xlink:type="locator"/>
    <link:label xlink:label="optt_DeferredCreditsPayableMarketLiquidatedDamagesRate-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_DeferredCreditsPayableMarketLiquidatedDamagesRate</link:label>
    <link:label xlink:label="optt_DeferredCreditsPayableMarketLiquidatedDamagesRate-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred Credits Payable Market Liquidated Damages Rate</link:label>
    <link:label xlink:label="optt_DeferredCreditsPayableMarketLiquidatedDamagesRate-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Deferred Credits Payable Market Liquidated Damages Rate</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_DeferredCreditsPayableMarketLiquidatedDamagesRate" xlink:to="optt_DeferredCreditsPayableMarketLiquidatedDamagesRate-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_OwnershipPercentage" xlink:label="optt_OwnershipPercentage" xlink:type="locator"/>
    <link:label xlink:label="optt_OwnershipPercentage-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_OwnershipPercentage</link:label>
    <link:label xlink:label="optt_OwnershipPercentage-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Ownership Percentage</link:label>
    <link:label xlink:label="optt_OwnershipPercentage-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The percentage of ownership of common stock or equity participation in the investee.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_OwnershipPercentage" xlink:to="optt_OwnershipPercentage-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Changes in operating assets and liabilities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_OfferingAgreementMember" xlink:label="optt_OfferingAgreementMember" xlink:type="locator"/>
    <link:label xlink:label="optt_OfferingAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Offering Agreement [Member]</link:label>
    <link:label xlink:label="optt_OfferingAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Offering-agreement.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_OfferingAgreementMember" xlink:to="optt_OfferingAgreementMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SupplementalCashFlowInformationAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Supplemental disclosure of noncash investing and financing activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_SupplementalCashFlowInformationAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="us-gaap_DepreciationDepletionAndAmortization" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DepreciationDepletionAndAmortization-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Depreciation and amortization</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DepreciationDepletionAndAmortization" xlink:to="us-gaap_DepreciationDepletionAndAmortization-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_BarclaysBankAgreementMember" xlink:label="optt_BarclaysBankAgreementMember" xlink:type="locator"/>
    <link:label xlink:label="optt_BarclaysBankAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Barclays Bank Agreement [Member]</link:label>
    <link:label xlink:label="optt_BarclaysBankAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Barclays bank agreement [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_BarclaysBankAgreementMember" xlink:to="optt_BarclaysBankAgreementMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_CheckingAndSavingsAccountsMember" xlink:label="optt_CheckingAndSavingsAccountsMember" xlink:type="locator"/>
    <link:label xlink:label="optt_CheckingAndSavingsAccountsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Checking and Savings Accounts [Member]</link:label>
    <link:label xlink:label="optt_CheckingAndSavingsAccountsMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Checking and savings accounts [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_CheckingAndSavingsAccountsMember" xlink:to="optt_CheckingAndSavingsAccountsMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetIncomeLossAttributableToNoncontrollingInterest-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_NetIncomeLossAttributableToNoncontrollingInterest</link:label>
    <link:label xlink:label="us-gaap_NetIncomeLossAttributableToNoncontrollingInterest-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Less: Net (profit) loss attributable to the noncontrolling interest in Ocean Power Technologies (Australasia) Pty Ltd.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:to="us-gaap_NetIncomeLossAttributableToNoncontrollingInterest-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LiabilitiesAndStockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LiabilitiesAndStockholdersEquity</link:label>
    <link:label xlink:label="us-gaap_LiabilitiesAndStockholdersEquity-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total liabilities and stockholders&#8217; equity</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_OregonDepartmentOfStateLandsMember" xlink:label="optt_OregonDepartmentOfStateLandsMember" xlink:type="locator"/>
    <link:label xlink:label="optt_OregonDepartmentOfStateLandsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Oregon Department of State Lands [Member]</link:label>
    <link:label xlink:label="optt_OregonDepartmentOfStateLandsMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Oregon department of state lands [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_OregonDepartmentOfStateLandsMember" xlink:to="optt_OregonDepartmentOfStateLandsMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_NJBPUAgreementMember" xlink:label="optt_NJBPUAgreementMember" xlink:type="locator"/>
    <link:label xlink:label="optt_NJBPUAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">NJBPU Agreement [Member]</link:label>
    <link:label xlink:label="optt_NJBPUAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">NJBPU agreement [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_NJBPUAgreementMember" xlink:to="optt_NJBPUAgreementMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_ScheduleOfForeignCurrencyDenominatedCertificatesOfDepositAndCashAccountsTableTextBlock" xlink:label="optt_ScheduleOfForeignCurrencyDenominatedCertificatesOfDepositAndCashAccountsTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="optt_ScheduleOfForeignCurrencyDenominatedCertificatesOfDepositAndCashAccountsTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Foreign Currency Denominated Certificates of Deposit and Cash Accounts [Table Text Block]</link:label>
    <link:label xlink:label="optt_ScheduleOfForeignCurrencyDenominatedCertificatesOfDepositAndCashAccountsTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Schedule of foreign currency denominated certificates of deposit and cash accounts</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_ScheduleOfForeignCurrencyDenominatedCertificatesOfDepositAndCashAccountsTableTextBlock" xlink:to="optt_ScheduleOfForeignCurrencyDenominatedCertificatesOfDepositAndCashAccountsTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueOfAssetsAcquired" xlink:label="us-gaap_FairValueOfAssetsAcquired" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_FairValueOfAssetsAcquired-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Capitalized purchases of equipment financed through accounts payable and accrued expenses</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueOfAssetsAcquired" xlink:to="us-gaap_FairValueOfAssetsAcquired-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_ScheduleOfForeignExchangeGainLossTableTextBlock" xlink:label="optt_ScheduleOfForeignExchangeGainLossTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="optt_ScheduleOfForeignExchangeGainLossTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Foreign Exchange Gain Loss [Table Text Block]</link:label>
    <link:label xlink:label="optt_ScheduleOfForeignExchangeGainLossTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Schedule of foreign exchange gain (loss).</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_ScheduleOfForeignExchangeGainLossTableTextBlock" xlink:to="optt_ScheduleOfForeignExchangeGainLossTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_UnrestrictedMember" xlink:label="optt_UnrestrictedMember" xlink:type="locator"/>
    <link:label xlink:label="optt_UnrestrictedMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unrestricted [Member]</link:label>
    <link:label xlink:label="optt_UnrestrictedMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Unrestricted Transactions.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_UnrestrictedMember" xlink:to="optt_UnrestrictedMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_RestrictedMember" xlink:label="optt_RestrictedMember" xlink:type="locator"/>
    <link:label xlink:label="optt_RestrictedMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Restricted [Member]</link:label>
    <link:label xlink:label="optt_RestrictedMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Restricted transactions.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_RestrictedMember" xlink:to="optt_RestrictedMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accumulated other comprehensive loss</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_USDepartmentOfEnergyMember" xlink:label="optt_USDepartmentOfEnergyMember" xlink:type="locator"/>
    <link:label xlink:label="optt_USDepartmentOfEnergyMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">US Department of Energy [Member]</link:label>
    <link:label xlink:label="optt_USDepartmentOfEnergyMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">US department of energy [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_USDepartmentOfEnergyMember" xlink:to="optt_USDepartmentOfEnergyMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accumulated deficit</link:label>
    <link:label xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Retained Earnings (Accumulated Deficit)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_ForeignCurrencyDenominatedCertificatesOfDepositAndCashAccounts" xlink:label="optt_ForeignCurrencyDenominatedCertificatesOfDepositAndCashAccounts" xlink:type="locator"/>
    <link:label xlink:label="optt_ForeignCurrencyDenominatedCertificatesOfDepositAndCashAccounts-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Foreign currency denominated certificates of deposit and cash accounts</link:label>
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    <link:loc xlink:href="optt-20151031.xsd#optt_ShelfRegistrationAmountRemainingOfOfferingAmount" xlink:label="optt_ShelfRegistrationAmountRemainingOfOfferingAmount" xlink:type="locator"/>
    <link:label xlink:label="optt_ShelfRegistrationAmountRemainingOfOfferingAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_ShelfRegistrationAmountRemainingOfOfferingAmount</link:label>
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    <link:label xlink:label="us-gaap_IncomeTaxAuthorityNameAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Tax Authority, Name [Axis]</link:label>
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    <link:label xlink:label="optt_CashAndCashEquivalentsMarketableSecuritiesAndRestrictedCash-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_CashAndCashEquivalentsMarketableSecuritiesAndRestrictedCash</link:label>
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    <link:label xlink:label="us-gaap_StatementOfFinancialPositionAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Financial Position [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementOfFinancialPositionAbstract-label" xlink:type="arc"/>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="us-gaap_ShareBasedCompensation" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ShareBasedCompensation-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Compensation expense related to stock option grants &amp; restricted stock</link:label>
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    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Issuance (forfeiture) of restricted stock, net (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures" xlink:to="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Exercised (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures</link:label>
    <link:label xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Issuance (forfeiture) of restricted stock, net</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures" xlink:to="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_StatementOfCashFlowsAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Cash Flows [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_StatementOfCashFlowsAbstract-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_ProfitLoss-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net loss</link:label>
    <link:label xlink:label="us-gaap_ProfitLoss-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net loss</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_ProfitLoss-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest</link:label>
    <link:label xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total comprehensive loss</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:to="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_TreasuryStockValue" xlink:label="us-gaap_TreasuryStockValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TreasuryStockValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_TreasuryStockValue</link:label>
    <link:label xlink:label="us-gaap_TreasuryStockValue-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Treasury stock, at cost; 4,318 and 3,866 shares, respectively</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockValue" xlink:to="us-gaap_TreasuryStockValue-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_StatementOfStockholdersEquityAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Stockholders' Equity [Abstract]</link:label>
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    <link:label xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_TreasuryStockValueAcquiredCostMethod</link:label>
    <link:label xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Acquisition of treasury stock</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:to="us-gaap_TreasuryStockValueAcquiredCostMethod-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash flows from operating activities:</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_InvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock" xlink:label="us-gaap_InvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock" xlink:type="locator"/>
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    <link:label xlink:label="us-gaap_MarketableSecuritiesTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Marketable Securities [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MarketableSecuritiesTextBlock" xlink:to="us-gaap_MarketableSecuritiesTextBlock-label" xlink:type="arc"/>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock" xlink:to="us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Weighted average shares used to compute basic and diluted net loss per share (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:to="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted-label" xlink:type="arc"/>
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    <link:label xlink:label="us-gaap_LongTermDebtCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Current portion of long-term debt</link:label>
    <link:label xlink:label="us-gaap_LongTermDebtCurrent-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Current portion of long-term debt</link:label>
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    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Restricted cash</link:label>
    <link:label xlink:label="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">NJBPU agreement</link:label>
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    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrecognized Tax Benefits, Period Increase (Decrease)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease" xlink:to="us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue" xlink:label="us-gaap_StockRepurchasedAndRetiredDuringPeriodValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StockRepurchasedAndRetiredDuringPeriodValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_StockRepurchasedAndRetiredDuringPeriodValue</link:label>
    <link:label xlink:label="us-gaap_StockRepurchasedAndRetiredDuringPeriodValue-label" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Reverse stock split</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockRepurchasedAndRetiredDuringPeriodValue" xlink:to="us-gaap_StockRepurchasedAndRetiredDuringPeriodValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_UnrecognizedTaxBenefits" xlink:label="us-gaap_UnrecognizedTaxBenefits" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefits-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_UnrecognizedTaxBenefits</link:label>
    <link:label xlink:label="us-gaap_UnrecognizedTaxBenefits-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrecognized Tax Benefits</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnrecognizedTaxBenefits" xlink:to="us-gaap_UnrecognizedTaxBenefits-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncreaseDecreaseInOtherCurrentAssets" xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentAssets" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentAssets-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInOtherCurrentAssets</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentAssets-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Other current assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOtherCurrentAssets" xlink:to="us-gaap_IncreaseDecreaseInOtherCurrentAssets-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentAssets" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInOtherNoncurrentAssets</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Other noncurrent assets</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets" xlink:to="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccruedSalariesCurrent" xlink:label="us-gaap_AccruedSalariesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccruedSalariesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accrued salary and benefits</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedSalariesCurrent" xlink:to="us-gaap_AccruedSalariesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount</link:label>
    <link:label xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OtherEmployeeRelatedLiabilitiesCurrent" xlink:label="us-gaap_OtherEmployeeRelatedLiabilitiesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherEmployeeRelatedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Employee incentive payments</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherEmployeeRelatedLiabilitiesCurrent" xlink:to="us-gaap_OtherEmployeeRelatedLiabilitiesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SharePrice" xlink:label="us-gaap_SharePrice" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SharePrice-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_SharePrice</link:label>
    <link:label xlink:label="us-gaap_SharePrice-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Share Price</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharePrice" xlink:to="us-gaap_SharePrice-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="us-gaap_AccruedLiabilitiesCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccruedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_AccruedLiabilitiesCurrent</link:label>
    <link:label xlink:label="us-gaap_AccruedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Accrued expenses total</link:label>
    <link:label xlink:label="us-gaap_AccruedLiabilitiesCurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Accrued expenses</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedLiabilitiesCurrent" xlink:to="us-gaap_AccruedLiabilitiesCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EarningsPerShareBasicAndDiluted-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Basic and diluted net loss per share (in dollars per share)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasicAndDiluted" xlink:to="us-gaap_EarningsPerShareBasicAndDiluted-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="us-gaap_AccountsPayableCurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountsPayableCurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounts payable</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsPayableCurrent" xlink:to="us-gaap_AccountsPayableCurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash flows from financing activities:</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_NetCashProvidedByUsedInInvestingActivities</link:label>
    <link:label xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Net cash provided by investing activities</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock based compensation</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncreaseDecreaseInRestrictedCash" xlink:label="us-gaap_IncreaseDecreaseInRestrictedCash" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInRestrictedCash-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInRestrictedCash</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInRestrictedCash-label" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Restricted cash</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInRestrictedCash" xlink:to="us-gaap_IncreaseDecreaseInRestrictedCash-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RevenueRecognitionPolicyTextBlock" xlink:label="us-gaap_RevenueRecognitionPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RevenueRecognitionPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revenue Recognition, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueRecognitionPolicyTextBlock" xlink:to="us-gaap_RevenueRecognitionPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_AssociatedServicePeriodMember" xlink:label="optt_AssociatedServicePeriodMember" xlink:type="locator"/>
    <link:label xlink:label="optt_AssociatedServicePeriodMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Associated Service Period [Member]</link:label>
    <link:label xlink:label="optt_AssociatedServicePeriodMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents associated service period.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_AssociatedServicePeriodMember" xlink:to="optt_AssociatedServicePeriodMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common stock, $0.001 par value; 105,000,000 shares authorized as of April 30, 2015, and 50,000,000 shares authorized as of October 31, 2015; issued 1,836,620 and 1,838,720 shares, respectively</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockValue" xlink:to="us-gaap_CommonStockValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InvestmentTypeAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Type [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_CompanyPerformanceGoalsAndCompensationExpenseMember" xlink:label="optt_CompanyPerformanceGoalsAndCompensationExpenseMember" xlink:type="locator"/>
    <link:label xlink:label="optt_CompanyPerformanceGoalsAndCompensationExpenseMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Company Performance Goals and Compensation Expense [Member]</link:label>
    <link:label xlink:label="optt_CompanyPerformanceGoalsAndCompensationExpenseMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents company performance goals and compensation expense.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_CompanyPerformanceGoalsAndCompensationExpenseMember" xlink:to="optt_CompanyPerformanceGoalsAndCompensationExpenseMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementClassOfStockAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Class of Stock [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_StatementClassOfStockAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount" xlink:label="us-gaap_LettersOfCreditOutstandingAmount" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LettersOfCreditOutstandingAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LettersOfCreditOutstandingAmount</link:label>
    <link:label xlink:label="us-gaap_LettersOfCreditOutstandingAmount-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Letters of Credit Outstanding, Amount</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LettersOfCreditOutstandingAmount" xlink:to="us-gaap_LettersOfCreditOutstandingAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockSharesIssued-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common stock, issued (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesIssued" xlink:to="us-gaap_CommonStockSharesIssued-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncreaseDecreaseInUnbilledReceivables" xlink:label="us-gaap_IncreaseDecreaseInUnbilledReceivables" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInUnbilledReceivables-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInUnbilledReceivables</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInUnbilledReceivables-label" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Unbilled receivables</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInUnbilledReceivables" xlink:to="us-gaap_IncreaseDecreaseInUnbilledReceivables-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SignificantAccountingPoliciesTextBlock" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Significant Accounting Policies [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SignificantAccountingPoliciesTextBlock" xlink:to="us-gaap_SignificantAccountingPoliciesTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockSharesAuthorized-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common stock, authorized (in shares)</link:label>
    <link:label xlink:label="us-gaap_CommonStockSharesAuthorized-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Common Stock, Shares Authorized</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesAuthorized" xlink:to="us-gaap_CommonStockSharesAuthorized-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccountingPoliciesAbstract" xlink:label="us-gaap_AccountingPoliciesAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccountingPoliciesAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounting Policies [Abstract]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_AccountingPoliciesAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_InterestIncomeExpenseNet" xlink:label="us-gaap_InterestIncomeExpenseNet" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InterestIncomeExpenseNet-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest income (expense), net</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestIncomeExpenseNet" xlink:to="us-gaap_InterestIncomeExpenseNet-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:to="us-gaap_CashAndCashEquivalentsPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Basis of Accounting, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:to="us-gaap_BasisOfAccountingPolicyPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy" xlink:label="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy" xlink:to="us-gaap_CashAndCashEquivalentsRestrictedCashAndCashEquivalentsPolicy-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInAccountsReceivable</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable-label" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Accounts receivable</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:to="us-gaap_IncreaseDecreaseInAccountsReceivable-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockParOrStatedValuePerShare-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common stock, par value (in dollars per share)</link:label>
    <link:label xlink:label="us-gaap_CommonStockParOrStatedValuePerShare-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Common Stock, Par or Stated Value Per Share</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockParOrStatedValuePerShare" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_UnbilledContractsReceivable" xlink:label="us-gaap_UnbilledContractsReceivable" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UnbilledContractsReceivable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Unbilled receivables</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnbilledContractsReceivable" xlink:to="us-gaap_UnbilledContractsReceivable-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InvestmentTypeCategorizationMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investments [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="us-gaap_InvestmentTypeCategorizationMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="us-gaap_PreferredStockValue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PreferredStockValue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred stock, $0.001 par value; authorized 5,000,000 shares, none issued or outstanding</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockValue" xlink:to="us-gaap_PreferredStockValue-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfDebtTableTextBlock" xlink:label="us-gaap_ScheduleOfDebtTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfDebtTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Debt [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfDebtTableTextBlock" xlink:to="us-gaap_ScheduleOfDebtTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_UseOfEstimates" xlink:label="us-gaap_UseOfEstimates" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_UseOfEstimates-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Use of Estimates, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UseOfEstimates" xlink:to="us-gaap_UseOfEstimates-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Foreign exchange loss</link:label>
    <link:label xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Foreign exchange loss</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">New Accounting Pronouncements, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:to="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfOtherAssetsAndOtherLiabilitiesTableTextBlock" xlink:label="us-gaap_ScheduleOfOtherAssetsAndOtherLiabilitiesTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfOtherAssetsAndOtherLiabilitiesTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Other Assets and Other Liabilities [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfOtherAssetsAndOtherLiabilitiesTableTextBlock" xlink:to="us-gaap_ScheduleOfOtherAssetsAndOtherLiabilitiesTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Share-based Compensation, Activity [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RepaymentsOfDebt" xlink:label="us-gaap_RepaymentsOfDebt" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RepaymentsOfDebt-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_RepaymentsOfDebt</link:label>
    <link:label xlink:label="us-gaap_RepaymentsOfDebt-label" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:type="resource" xml:lang="en-US">Repayment of debt</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfDebt" xlink:to="us-gaap_RepaymentsOfDebt-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">AOCI Attributable to Parent [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OperatingExpenses" xlink:label="us-gaap_OperatingExpenses" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingExpenses-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_OperatingExpenses</link:label>
    <link:label xlink:label="us-gaap_OperatingExpenses-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total operating expenses</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OperatingExpenses-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party Transactions Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:to="us-gaap_RelatedPartyTransactionsDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementLineItems-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement [Line Items]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementLineItems-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SubsidiarySaleOfStockAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sale of Stock [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SubsidiarySaleOfStockAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RelatedPartyDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="us-gaap_RelatedPartyDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Sale of Stock [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Related Party Transactions [Table Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock" xlink:to="us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_TreasuryStockShares" xlink:label="us-gaap_TreasuryStockShares" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TreasuryStockShares-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Treasury stock (in shares)</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockShares" xlink:to="us-gaap_TreasuryStockShares-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_RelatedPartyTransactionMonthlyConsultingFee" xlink:label="optt_RelatedPartyTransactionMonthlyConsultingFee" xlink:type="locator"/>
    <link:label xlink:label="optt_RelatedPartyTransactionMonthlyConsultingFee-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_RelatedPartyTransactionMonthlyConsultingFee</link:label>
    <link:label xlink:label="optt_RelatedPartyTransactionMonthlyConsultingFee-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party Transaction Monthly Consulting Fee</link:label>
    <link:label xlink:label="optt_RelatedPartyTransactionMonthlyConsultingFee-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The amount of the consulting fee that is paid on a reoccurring basis.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_RelatedPartyTransactionMonthlyConsultingFee" xlink:to="optt_RelatedPartyTransactionMonthlyConsultingFee-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_RelatedPartyTransactionTermOfAgreement" xlink:label="optt_RelatedPartyTransactionTermOfAgreement" xlink:type="locator"/>
    <link:label xlink:label="optt_RelatedPartyTransactionTermOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_RelatedPartyTransactionTermOfAgreement</link:label>
    <link:label xlink:label="optt_RelatedPartyTransactionTermOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party Transaction Term of Agreement</link:label>
    <link:label xlink:label="optt_RelatedPartyTransactionTermOfAgreement-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Period of the Executive Transition Agreement under which the executive will receive a monthly consulting fee.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_RelatedPartyTransactionTermOfAgreement" xlink:to="optt_RelatedPartyTransactionTermOfAgreement-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_CustomerRevenuePercentage" xlink:label="optt_CustomerRevenuePercentage" xlink:type="locator"/>
    <link:label xlink:label="optt_CustomerRevenuePercentage-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Revenues, percentage</link:label>
    <link:label xlink:label="optt_CustomerRevenuePercentage-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The percentage of revenue that is designated to a particular customer.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_CustomerRevenuePercentage" xlink:to="optt_CustomerRevenuePercentage-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_OvernightRepurchaseAccountMember" xlink:label="optt_OvernightRepurchaseAccountMember" xlink:type="locator"/>
    <link:label xlink:label="optt_OvernightRepurchaseAccountMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Overnight Repurchase Account [Member]</link:label>
    <link:label xlink:label="optt_OvernightRepurchaseAccountMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents overnight repurchase account.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_OvernightRepurchaseAccountMember" xlink:to="optt_OvernightRepurchaseAccountMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_GrossProfit" xlink:label="us-gaap_GrossProfit" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_GrossProfit-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_GrossProfit</link:label>
    <link:label xlink:label="us-gaap_GrossProfit-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Gross loss</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GrossProfit" xlink:to="us-gaap_GrossProfit-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConsolidationPolicyTextBlock" xlink:label="us-gaap_ConsolidationPolicyTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ConsolidationPolicyTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Consolidation, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConsolidationPolicyTextBlock" xlink:to="us-gaap_ConsolidationPolicyTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CostOfRevenue" xlink:label="us-gaap_CostOfRevenue" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CostOfRevenue-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cost of revenues</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CostOfRevenue" xlink:to="us-gaap_CostOfRevenue-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_AsiaAndAustraliaMember" xlink:label="optt_AsiaAndAustraliaMember" xlink:type="locator"/>
    <link:label xlink:label="optt_AsiaAndAustraliaMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Asia and Australia [Member]</link:label>
    <link:label xlink:label="optt_AsiaAndAustraliaMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Asia and australia [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_AsiaAndAustraliaMember" xlink:to="optt_AsiaAndAustraliaMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DebtDisclosureTextBlock" xlink:label="us-gaap_DebtDisclosureTextBlock" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_DebtDisclosureTextBlock-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Disclosure [Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtDisclosureTextBlock" xlink:to="us-gaap_DebtDisclosureTextBlock-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_InterimPeriodCostsNotAllocableDomain" xlink:label="us-gaap_InterimPeriodCostsNotAllocableDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_InterimPeriodCostsNotAllocableDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interim Period, Costs Not Allocable [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterimPeriodCostsNotAllocableDomain" xlink:to="us-gaap_InterimPeriodCostsNotAllocableDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_BarclaysBankMember" xlink:label="optt_BarclaysBankMember" xlink:type="locator"/>
    <link:label xlink:label="optt_BarclaysBankMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Barclays Bank [Member]</link:label>
    <link:label xlink:label="optt_BarclaysBankMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The entity of Barclays bank.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_BarclaysBankMember" xlink:to="optt_BarclaysBankMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_VictorianWavePartnersPtyLtdMember" xlink:label="optt_VictorianWavePartnersPtyLtdMember" xlink:type="locator"/>
    <link:label xlink:label="optt_VictorianWavePartnersPtyLtdMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Victorian Wave Partners Pty. Ltd. [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_VictorianWavePartnersPtyLtdMember" xlink:to="optt_VictorianWavePartnersPtyLtdMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_OptaMember" xlink:label="optt_OptaMember" xlink:type="locator"/>
    <link:label xlink:label="optt_OptaMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">OPTA [Member]</link:label>
    <link:label xlink:label="optt_OptaMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">OPTA [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_OptaMember" xlink:to="optt_OptaMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NatureOfExpenseAxis" xlink:label="us-gaap_NatureOfExpenseAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NatureOfExpenseAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Nature of Expense [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NatureOfExpenseAxis" xlink:to="us-gaap_NatureOfExpenseAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_ProceedsFromS3ShelfForPeriodMember" xlink:label="optt_ProceedsFromS3ShelfForPeriodMember" xlink:type="locator"/>
    <link:label xlink:label="optt_ProceedsFromS3ShelfForPeriodMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Proceeds from S-3 Shelf for Period [Member]</link:label>
    <link:label xlink:label="optt_ProceedsFromS3ShelfForPeriodMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Proceeds rom s-3 shelf for period [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_ProceedsFromS3ShelfForPeriodMember" xlink:to="optt_ProceedsFromS3ShelfForPeriodMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_ATMFacilityMember" xlink:label="optt_ATMFacilityMember" xlink:type="locator"/>
    <link:label xlink:label="optt_ATMFacilityMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">ATM Facility [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_ATMFacilityMember" xlink:to="optt_ATMFacilityMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_UnderwritingAgreementMember" xlink:label="optt_UnderwritingAgreementMember" xlink:type="locator"/>
    <link:label xlink:label="optt_UnderwritingAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Underwriting Agreement [Member]</link:label>
    <link:label xlink:label="optt_UnderwritingAgreementMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Underwriting agreement [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_UnderwritingAgreementMember" xlink:to="optt_UnderwritingAgreementMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_ShelfRegistrationAuthorizedAmount" xlink:label="optt_ShelfRegistrationAuthorizedAmount" xlink:type="locator"/>
    <link:label xlink:label="optt_ShelfRegistrationAuthorizedAmount-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_ShelfRegistrationAuthorizedAmount</link:label>
    <link:label xlink:label="optt_ShelfRegistrationAuthorizedAmount-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Shelf Registration Authorized Amount</link:label>
    <link:label xlink:label="optt_ShelfRegistrationAuthorizedAmount-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Amount of stock authorized under the S-3 Shelf registration filing.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_ShelfRegistrationAuthorizedAmount" xlink:to="optt_ShelfRegistrationAuthorizedAmount-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity</link:label>
    <link:label xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Maximum Borrowing Capacity</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:to="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_SpanishTaxAuthoritiesMember" xlink:label="optt_SpanishTaxAuthoritiesMember" xlink:type="locator"/>
    <link:label xlink:label="optt_SpanishTaxAuthoritiesMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Spanish Tax Authorities [Member]</link:label>
    <link:label xlink:label="optt_SpanishTaxAuthoritiesMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Spanish tax authorities [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_SpanishTaxAuthoritiesMember" xlink:to="optt_SpanishTaxAuthoritiesMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_EquityComponentDomain-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Component [Domain]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_EquityComponentDomain-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_MarketableSecuritiesPolicy" xlink:label="us-gaap_MarketableSecuritiesPolicy" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_MarketableSecuritiesPolicy-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Marketable Securities, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MarketableSecuritiesPolicy" xlink:to="us-gaap_MarketableSecuritiesPolicy-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_StatementEquityComponentsAxis-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equity Components [Axis]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_StatementEquityComponentsAxis-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="us-gaap_OtherNonoperatingIncomeExpense" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OtherNonoperatingIncomeExpense-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other income (expense), net</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherNonoperatingIncomeExpense" xlink:to="us-gaap_OtherNonoperatingIncomeExpense-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_ShelfRegistrationMarketCapitalization" xlink:label="optt_ShelfRegistrationMarketCapitalization" xlink:type="locator"/>
    <link:label xlink:label="optt_ShelfRegistrationMarketCapitalization-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_ShelfRegistrationMarketCapitalization</link:label>
    <link:label xlink:label="optt_ShelfRegistrationMarketCapitalization-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Shelf Registration Market Capitalization</link:label>
    <link:label xlink:label="optt_ShelfRegistrationMarketCapitalization-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents market capitalization amount to further limit the ability to sell securities under the S3 Shelf.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_ShelfRegistrationMarketCapitalization" xlink:to="optt_ShelfRegistrationMarketCapitalization-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_InputTax" xlink:label="optt_InputTax" xlink:type="locator"/>
    <link:label xlink:label="optt_InputTax-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_InputTax</link:label>
    <link:label xlink:label="optt_InputTax-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Input Tax</link:label>
    <link:label xlink:label="optt_InputTax-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Input tax.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_InputTax" xlink:to="optt_InputTax-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LongTermDebtNoncurrent" xlink:label="us-gaap_LongTermDebtNoncurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_LongTermDebtNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-term debt</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtNoncurrent" xlink:to="us-gaap_LongTermDebtNoncurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskCreditRisk" xlink:label="us-gaap_ConcentrationRiskCreditRisk" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_ConcentrationRiskCreditRisk-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Concentration Risk, Credit Risk, Policy [Policy Text Block]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskCreditRisk" xlink:to="us-gaap_ConcentrationRiskCreditRisk-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CommonStockMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockMember" xlink:to="us-gaap_CommonStockMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_AdditionalPaidInCapitalMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Additional Paid-in Capital [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalMember" xlink:to="us-gaap_AdditionalPaidInCapitalMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PolicyTextBlockAbstract" xlink:label="us-gaap_PolicyTextBlockAbstract" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_PolicyTextBlockAbstract-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_PolicyTextBlockAbstract</link:label>
    <link:label xlink:label="us-gaap_PolicyTextBlockAbstract-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Accounting Policies</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PolicyTextBlockAbstract" xlink:to="us-gaap_PolicyTextBlockAbstract-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_TreasuryStockMember" xlink:label="us-gaap_TreasuryStockMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_TreasuryStockMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Treasury Stock [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockMember" xlink:to="us-gaap_TreasuryStockMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CustomerAdvancesOrDepositsNoncurrent" xlink:label="us-gaap_CustomerAdvancesOrDepositsNoncurrent" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_CustomerAdvancesOrDepositsNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred credits</link:label>
    <link:label xlink:label="us-gaap_CustomerAdvancesOrDepositsNoncurrent-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Customer Advances or Deposits, Noncurrent</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CustomerAdvancesOrDepositsNoncurrent" xlink:to="us-gaap_CustomerAdvancesOrDepositsNoncurrent-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_RetainedEarningsMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Retained Earnings [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsMember" xlink:to="us-gaap_RetainedEarningsMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_NonVestedRestrictedStockMember" xlink:label="optt_NonVestedRestrictedStockMember" xlink:type="locator"/>
    <link:label xlink:label="optt_NonVestedRestrictedStockMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Non-vested Restricted Stock [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_NonVestedRestrictedStockMember" xlink:to="optt_NonVestedRestrictedStockMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="us-gaap_OperatingIncomeLoss" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_OperatingIncomeLoss-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating loss</link:label>
    <link:label xlink:label="us-gaap_OperatingIncomeLoss-label" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Operating loss</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingIncomeLoss" xlink:to="us-gaap_OperatingIncomeLoss-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">us-gaap_IncreaseDecreaseInAccountsPayable</link:label>
    <link:label xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Accounts payable</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccountsPayable" xlink:to="us-gaap_IncreaseDecreaseInAccountsPayable-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_IncludingNonEmployeeCompensationMember" xlink:label="optt_IncludingNonEmployeeCompensationMember" xlink:type="locator"/>
    <link:label xlink:label="optt_IncludingNonEmployeeCompensationMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Including Non-employee Compensation [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_IncludingNonEmployeeCompensationMember" xlink:to="optt_IncludingNonEmployeeCompensationMember-label" xlink:type="arc"/>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="us-gaap_NoncontrollingInterestMember" xlink:type="locator"/>
    <link:label xlink:label="us-gaap_NoncontrollingInterestMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Noncontrolling Interest [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NoncontrollingInterestMember" xlink:to="us-gaap_NoncontrollingInterestMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_RelatedPartyTransactionDailyConsultingFee" xlink:label="optt_RelatedPartyTransactionDailyConsultingFee" xlink:type="locator"/>
    <link:label xlink:label="optt_RelatedPartyTransactionDailyConsultingFee-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">optt_RelatedPartyTransactionDailyConsultingFee</link:label>
    <link:label xlink:label="optt_RelatedPartyTransactionDailyConsultingFee-label" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Related Party Transaction Daily Consulting Fee</link:label>
    <link:label xlink:label="optt_RelatedPartyTransactionDailyConsultingFee-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The amount of consulting fee that will be at a daily rate.</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_RelatedPartyTransactionDailyConsultingFee" xlink:to="optt_RelatedPartyTransactionDailyConsultingFee-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_PerformanceBasedVestingMember" xlink:label="optt_PerformanceBasedVestingMember" xlink:type="locator"/>
    <link:label xlink:label="optt_PerformanceBasedVestingMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Performance based vesting [Member]</link:label>
    <link:label xlink:label="optt_PerformanceBasedVestingMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Performance based vesting [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_PerformanceBasedVestingMember" xlink:to="optt_PerformanceBasedVestingMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_FormerExecutiveViceChairmanMember" xlink:label="optt_FormerExecutiveViceChairmanMember" xlink:type="locator"/>
    <link:label xlink:label="optt_FormerExecutiveViceChairmanMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Former Executive Vice Chairman [Member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_FormerExecutiveViceChairmanMember" xlink:to="optt_FormerExecutiveViceChairmanMember-label" xlink:type="arc"/>
    <link:loc xlink:href="optt-20151031.xsd#optt_InterimChiefExecutiveOfficerMember" xlink:label="optt_InterimChiefExecutiveOfficerMember" xlink:type="locator"/>
    <link:label xlink:label="optt_InterimChiefExecutiveOfficerMember-label" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interim Chief Executive Officer [Member]</link:label>
    <link:label xlink:label="optt_InterimChiefExecutiveOfficerMember-label" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Interim chief executive officer [member]</link:label>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="optt_InterimChiefExecutiveOfficerMember" xlink:to="optt_InterimChiefExecutiveOfficerMember-label" xlink:type="arc"/>
  </link:labelLink>
</link:linkbase>
