EX-10.5





 Exhibit 10.5 

Execution Version 

CANADIAN GUARANTEE 

CANADIAN GUARANTEE (as amended, modified, restated and/or supplemented from time to time, this “Guarantee”), dated as of
October 28, 2019, made by and among each of the undersigned guarantors (each, a “Guarantor” and, together with any other entity that becomes a guarantor hereunder pursuant to Section 23 hereof, collectively, the
“Guarantors”) in favour of Bank of America, N.A., as administrative agent (together with any successor administrative agent, the “Administrative Agent”), for the benefit of the Secured Parties (as defined below).
Certain capitalized terms as used herein are defined in Section 1 hereof. Except as otherwise defined herein, all capitalized terms used herein and defined in the Credit Agreement (as defined below) shall be used herein as therein defined. 

W I T N E S S E T H: 

WHEREAS, Ciena Corporation, a Delaware corporation (the “Company”, together with the Domestic Subsidiaries of the Company
that are or become a U.S. Borrower pursuant to the terms of the Credit Agreement, the “U.S. Borrowers”), Ciena Canada, Inc., a corporation incorporated under the laws of Canada (together with the other Canadian Subsidiaries of the
Company that are or become a Canadian Borrower pursuant to the terms of the Credit Agreement, the “Borrowers” and each a “Borrower”), the lenders from time to time party thereto (the “Lenders”) and
Bank of America, N.A., as administrative agent and collateral agent have entered into that certain ABL Credit Agreement, dated as of October 28, 2019 (as amended, modified, restated and/or supplemented from time to time, the “Credit
Agreement”), providing for the making of Loans to the Borrowers and the U.S. Borrowers as contemplated therein (the Lenders, the Administrative Agent and the other “Secured Parties” (as defined in the Credit Agreement) are herein
called the “Secured Parties”); 
 WHEREAS, it is a condition precedent to the making of Loans to the Borrowers and the U.S.
Borrowers under the Credit Agreement that each Guarantor shall have executed and delivered to the Administrative Agent this Guarantee; and 

WHEREAS, each Guarantor will benefit from the incurrence of Loans by the Borrowers and the U.S. Borrowers and, accordingly, desires to execute
this Guarantee in order to (i) satisfy the condition described in the preceding paragraph and (ii) induce the Lenders to make Loans to the Borrowers and the U.S. Borrowers; 












 NOW, THEREFORE, in consideration of the foregoing and other benefits accruing to each
Guarantor, the receipt and sufficiency of which are hereby acknowledged, each Guarantor hereby makes the following representations and warranties to the Administrative Agent for the benefit of the Secured Parties and hereby covenants and agrees with
each other Guarantor and the Administrative Agent for the benefit of the Secured Parties as follows: 
 1. GUARANTEE. (a) Each
Guarantor, jointly and severally, irrevocably, absolutely and unconditionally guarantees as a primary obligor and not merely as surety: to the Secured Parties the full and prompt payment when due (whether at the stated maturity, by required
prepayment, declaration, acceleration, demand or otherwise) of (x) all Canadian Obligations and (y) all other obligations (including, without limitation, obligations which, but for the automatic or any other stay under applicable Debtor
Relief Laws, would become due), liabilities and indebtedness owing by the Borrowers to the Secured Parties under the Credit Agreement and each other Loan Document to which any Borrower is a party (including, without limitation, indemnities, fees and
interest thereon (including, without limitation, in each case any interest, fees or expenses accruing after the commencement of any bankruptcy, insolvency, receivership, arrangement, reorganization or similar proceeding at the rate provided for in
the Credit Agreement, whether or not such interest, fees or expenses are an allowed claim in any such proceeding)), whether now existing or hereafter incurred under, arising out of or in connection with each such Loan Document (all such principal,
premium, interest, liabilities, indebtedness and obligations under this clause (a), being herein collectively called the “Guaranteed Obligations”). 

Each Guarantor understands, agrees and confirms that the Secured Parties may enforce this Guarantee up to the full amount of the Guaranteed
Obligations against such Guarantor without proceeding against any other Guarantor or any Borrower, or against any security for the Guaranteed Obligations, or under any other guarantee covering all or a portion of the Guaranteed Obligations. This
Guarantee is a guarantee of prompt payment and performance and not of collection. For purposes of this Guarantee, the term “Guarantor” as applied to any Borrower or any other Guarantor shall refer to such Borrower or such other Guarantor
as a guarantor of indebtedness incurred by another Borrower, and not indebtedness directly incurred by such Guarantor, in its capacity as Borrower or otherwise. 

The following capitalized terms used herein shall have the definitions specified below: 

“Guarantee Supplement” shall mean a guarantee supplement, in a form reasonably satisfactory to the Administrative Agent and
attached hereto as Exhibit A, signed and delivered to the Administrative Agent for the purpose of adding a Subsidiary as a party hereto pursuant to Section 23. 

“Termination Date” shall mean the date upon which Payment in Full occurs. 

(b) Additionally, each Guarantor, jointly and severally, unconditionally, absolutely and irrevocably, guarantees the payment of any and all
Guaranteed Obligations whether or not due and payable by any Borrower upon the occurrence, in respect of any Borrower, of any of the events specified in Section 8.01(f) of the Credit Agreement, and unconditionally, absolutely and irrevocably,
jointly and severally, promises to pay such Guaranteed Obligations to the Secured Parties, or order, on demand. 
 2. LIABILITY OF
GUARANTORS ABSOLUTE. The liability of each Guarantor hereunder is primary, absolute, joint and several, and unconditional and is exclusive and independent of any security for or other guarantee of the indebtedness of any Borrower whether
executed by such Guarantor, any other Guarantor, any other guarantor or by any other party, and the liability of each Guarantor hereunder shall not be affected or impaired by any circumstance or occurrence whatsoever, including, without limitation:
(a) any direction as to application of 

  
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payment by any Borrower or any other party, (b) any other continuing or other guarantee, undertaking or maximum liability of a Guarantor or of any other party as to the Guaranteed
Obligations, (c) any payment on or in reduction of any such other guarantee or undertaking, (d) any dissolution, termination or increase, decrease or change in personnel by any Borrower, (e) the failure of a Guarantor to receive any
benefit from or as a result of its execution, delivery and performance of this Guarantee, (f) any payment made to any Secured Party on the indebtedness which any Secured Party repays any Borrower pursuant to court order in any bankruptcy,
reorganization, arrangement, moratorium or other debtor relief proceeding, and each Guarantor waives any right to the deferral or modification of its obligations hereunder by reason of any such proceeding, (g) any action or inaction by the
Secured Parties as contemplated in Section 5 hereof or (h) any invalidity, rescission, irregularity or unenforceability of all or any part of the Guaranteed Obligations or of any security therefor. 

3. OBLIGATIONS OF GUARANTORS INDEPENDENT. The obligations of each Guarantor hereunder are independent of the obligations of any other
Guarantor, any other guarantor or any Borrower, and a separate action or actions may be brought and prosecuted against each Guarantor whether or not action is brought against any other Guarantor, any other guarantor or any Borrower and whether or
not any other Guarantor, any other guarantor or any Borrower is joined in any such action or actions. Each Guarantor waives (to the fullest extent permitted by applicable law) the benefits of any statute of limitations affecting its liability
hereunder or the enforcement thereof. Any payment by any Borrower or other circumstance which operates to toll any statute of limitations as to any Borrower shall operate to toll the statute of limitations as to each Guarantor. 

4. WAIVERS BY GUARANTORS. (a) Each Guarantor hereby waives (to the fullest extent permitted by applicable law) notice of acceptance of
this Guarantee and notice of the existence, creation or incurrence of any new or additional liability to which it may apply, and waives promptness, diligence, presentment, demand of payment, demand for performance, protest, notice of dishonor or
nonpayment of any such liabilities, suit or taking of other action by the Administrative Agent or any other Secured Party against, and any other notice to, any party liable thereon (including such Guarantor, any other Guarantor, any other guarantor
or any Borrower) and each Guarantor further hereby waives any and all notice of the creation, renewal, extension or accrual of any of the Guaranteed Obligations and notice or proof of reliance by any Secured Party upon this Guarantee, and the
Guaranteed Obligations shall conclusively be deemed to have been created, contracted or incurred, or renewed, extended, amended, modified, supplemented or waived, in reliance upon this Guarantee. 

(b) Each Guarantor waives any right (except as shall be required by applicable statute and cannot be waived) to require the Secured Parties to:
(i) proceed against any Borrower, any other Guarantor, any other guarantor of the Guaranteed Obligations or any other party; (ii) proceed against or exhaust any security held from any Borrower, any other Guarantor, any other guarantor of
the Guaranteed Obligations or any other party; or (iii) pursue any other remedy in the Secured Parties’ power whatsoever. Each Guarantor waives any defense based on or arising out of any defense of any Borrower, any other Guarantor, any
other guarantor of the Guaranteed Obligations or any other party other than the occurrence of the Termination Date, including, without limitation, any defense based on or arising out of the disability of any Borrower, any other Guarantor, any other
guarantor of the Guaranteed Obligations or any other 

  
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party, or the unenforceability of the Guaranteed Obligations or any part thereof from any cause, or the cessation from any cause of the liability of any Borrower other than the occurrence of the
Termination Date. The Secured Parties may, at their election, upon the occurrence and during the continuance of an Event of Default, foreclose on any collateral serving as security held by the Administrative Agent or the other Secured Parties by one
or more judicial or nonjudicial sales, whether or not every aspect of any such sale is commercially reasonable (to the extent such sale is permitted by applicable law), or exercise any other right or remedy the Secured Parties may have against any
Borrower, or any other party, or any security, without affecting or impairing in any way the liability of any Guarantor hereunder except to the extent the Termination Date has occurred. Each Guarantor waives any defense arising out of any such
election by the Secured Parties, even though such election may operate to impair or extinguish any right of reimbursement, contribution, indemnification or subrogation or other right or remedy of such Guarantor against any Borrower, any other
guarantor of the Guaranteed Obligations or any other party or any security. 
 (c) Each Guarantor has knowledge and assumes all
responsibility for being and keeping itself informed of each Borrower’s and each other Guarantor’s financial condition, affairs and assets, and of all other circumstances bearing upon the risk of nonpayment of the Guaranteed Obligations
and the nature, scope and extent of the risks which such Guarantor assumes and incurs hereunder, and has adequate means to obtain from each Borrower and each other Guarantor on an ongoing basis information relating thereto and each Borrower’s
and each other Guarantor’s ability to pay and perform its respective Guaranteed Obligations, and agrees to assume the responsibility to keep so informed for so long as such Guarantor is a party to this Guarantee. Each Guarantor acknowledges and
agrees that (x) the Secured Parties shall have no obligation to investigate the financial condition or affairs of any Borrower or any other Guarantor for the benefit of such Guarantor nor to advise such Guarantor of any fact respecting, or any
change in, the financial condition, assets or affairs of any Borrower or any other Guarantor that might become known to any Secured Party at any time, whether or not such Secured Party knows or believes or has reason to know or believe that any such
fact or change is unknown to such Guarantor, or might (or does) increase the risk of such Guarantor as guarantor hereunder, or might (or would) affect the willingness of such Guarantor to continue as a Guarantor hereunder and (y) the Secured
Parties shall have no duty to advise any Guarantor of information known to them regarding any of the aforementioned circumstances or risks. 

(d) Each Guarantor hereby acknowledges and agrees that no Secured Party nor any other Person shall be under any obligation (a) to marshal
any assets in favour of such Guarantor or in payment of any or all of the liabilities of any Borrower under the Loan Documents or the obligation of such Guarantor hereunder or (b) to pursue any other remedy that such Guarantor may or may not be
able to pursue itself any right to which such Guarantor hereby waives. 
 (e) Each Guarantor warrants and agrees that each of the waivers set
forth in Section 3 hereof and in this Section 4 is made with full knowledge of its significance and consequences and that if any of such waivers are determined to be contrary to any applicable law or public policy, such waivers shall be
effective only to the maximum extent permitted by applicable law. 

  
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 5. RIGHTS OF SECURED PARTIES. Any Secured Party may (except as shall be required by
applicable statute and cannot be waived) at any time and from time to time without the consent of, or notice to, any Guarantor, without incurring responsibility to such Guarantor, without impairing or releasing the obligations or liabilities of such
Guarantor hereunder, upon or without any terms or conditions and in whole or in part: 
 (a) change the manner, place or
terms of payment of, and/or change, increase or extend the time of payment of, renew, increase, accelerate or alter, any of the Guaranteed Obligations (including, without limitation, any increase or decrease in the rate of interest thereon or the
principal amount thereof), any security therefor, or any liability incurred directly or indirectly in respect thereof, and the guarantee herein made shall apply to the Guaranteed Obligations as so changed, extended, increased, accelerated, renewed
or altered; 
 (b) take and hold security for the payment of the Guaranteed Obligations and sell, exchange, release,
surrender, impair, realize upon or otherwise deal with in any manner and in any order any property or other collateral by whomsoever at any time pledged or mortgaged to secure, or howsoever securing, the Guaranteed Obligations or any liabilities
(including any of those hereunder) incurred directly or indirectly in respect thereof or hereof, and/or any offset thereagainst; 

(c) exercise or refrain from exercising any rights against any Borrower, any other Loan Party, any Subsidiary thereof, any
other guarantor of any Borrower or others or otherwise act or refrain from acting; 
 (d) release or substitute any one or
more endorsers, Guarantors, other guarantors, any Borrower or other obligors; 
 (e) settle or compromise any of the
Guaranteed Obligations, any security therefor or any liability (including any of those hereunder) incurred directly or indirectly in respect thereof or hereof, and may subordinate the payment of all or any part thereof to the payment of any
liability (whether due or not) of any Borrower to creditors of any Borrower other than the Secured Parties; 
 (f) apply any
sums by whomsoever paid or howsoever realized to any liability or liabilities of any Borrower to the Secured Parties regardless of what liabilities of such Borrower remain unpaid; 

(g) consent to or waive any breach of, or any act, omission or default under, any of the Loan Documents or any of the
instruments or agreements referred to therein, or otherwise amend, modify or supplement any of the Loan Documents or any of such other instruments or agreements; 

(h) act or fail to act in any manner which may deprive such Guarantor of its right to subrogation against any Borrower to
recover full indemnity for any payments made pursuant to this Guarantee; and/or 

  
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 (i) take any other action or omit to take any other action which would,
under otherwise applicable principles of common law, give rise to a legal or equitable discharge of such Guarantor from its liabilities under this Guarantee (including, without limitation, any action or omission whatsoever that might otherwise vary
the risk of such Guarantor or constitute a legal or equitable defense to or discharge of the liabilities of a guarantor or surety or that might otherwise limit recourse against such Guarantor). 

No invalidity, illegality, irregularity or unenforceability of all or any part of the Guaranteed Obligations, the Loan Documents or any other agreement or
instrument relating to the Guaranteed Obligations or of any security or guarantee therefor shall affect, impair or be a defense to this Guarantee, and this Guarantee shall be primary, absolute and unconditional notwithstanding the occurrence of any
event or the existence of any other circumstances which might constitute a legal or equitable discharge of a surety or guarantor except the occurrence of the Termination Date. 

6. CONTINUING GUARANTEE. This Guarantee is a continuing one and all liabilities to which it applies or may apply under the terms hereof
shall be conclusively presumed to have been created in reliance hereon. No failure or delay on the part of any Secured Party in exercising any right, power or privilege hereunder shall operate as a waiver thereof, nor shall any single or partial
exercise of any right, power or privilege hereunder preclude any other or further exercise thereof or the exercise of any other right, power or privilege. The rights and remedies herein expressly specified are cumulative and not exclusive of any
rights or remedies which any Secured Party would otherwise have. No notice to or demand on any Guarantor in any case shall entitle such Guarantor to any other further notice or demand in similar or other circumstances or constitute a waiver of the
rights of any Secured Party to any other or further action in any circumstances without notice or demand. It is not necessary for any Secured Party to inquire into the capacity or powers of any Borrower or the officers, directors, partners or agents
acting or purporting to act on its behalf, and any indebtedness made or created in reliance upon the professed exercise of such powers shall be guaranteed hereunder. 

7. SUBORDINATION OF INDEBTEDNESS HELD BY GUARANTORS. Any indebtedness of any Borrower now or hereafter held by any Guarantor is hereby
subordinated to the Guaranteed Obligations of such Borrower to the Secured Parties; and the indebtedness of such Borrower to any Guarantor, if the Administrative Agent, after an Event of Default has occurred and is continuing, so requests, shall be
collected, enforced and received by such Guarantor as trustee for the Secured Parties and be paid over to the Secured Parties on account of the Guaranteed Obligations of such Borrower to the Secured Parties, but without affecting or impairing in any
manner the liability of such Guarantor under the other provisions of this Guarantee. Without limiting the generality of the foregoing, each Guarantor hereby agrees with the Secured Parties that it will not exercise any right of subrogation which it
may at any time otherwise have as a result of this Guarantee (whether contractual or under any applicable Debtor Relief Law, or otherwise) until the Termination Date; provided, that if any amount shall be paid to such Guarantor on account of
such subrogation rights at any time prior to the Termination Date, such amount shall be held in trust for the benefit of the Secured Parties and shall promptly be paid to the Secured Parties to be credited and applied upon the Guaranteed
Obligations, whether matured or unmatured, in accordance with the terms of the Loan Documents or, if the Loan Documents do not provide for the application of such amount, to be held by the Secured Parties as collateral security for any Guaranteed
Obligations thereafter existing. 

  
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 8. GUARANTEE ENFORCEABLE BY THE ADMINISTRATIVE AGENT. Notwithstanding anything to the
contrary contained elsewhere in this Guarantee, the Secured Parties agree (by their acceptance of the benefits of this Guarantee) that this Guarantee may be enforced only by the action of the Administrative Agent, acting upon the instructions of the
Required Lenders and that no other Secured Party shall have any right individually to seek to enforce or to enforce this Guarantee or to realize upon the security to be granted by the Collateral Documents, it being understood and agreed that such
rights and remedies may be exercised by the Administrative Agent, for the benefit of the Secured Parties upon the terms of this Guarantee and the Collateral Documents. The Secured Parties further agree that this Guarantee may not be enforced against
any director, officer, employee, partner, member or stockholder of any Guarantor (except to the extent such partner, member or stockholder is also a Guarantor hereunder). It is understood and agreed that the agreement in this Section 8 is among
and solely for the benefit of the Secured Parties and that, if the Required Lenders so agree (without requiring the consent of any Guarantor), this Guarantee may be directly enforced by any Secured Party. 

9. REPRESENTATIONS, WARRANTIES AND COVENANTS OF GUARANTORS. In order to induce the Lenders to make Loans to the Borrowers pursuant to
the Credit Agreement each Guarantor represents, warrants and covenants that: 
 (a) such Guarantor (i) is duly organized
or formed, validly existing and, as applicable, in good standing under the Laws of the jurisdiction of its incorporation or organization (to the extent such concept is applicable in the relevant jurisdiction), (ii) has all requisite power and
authority and all requisite governmental licenses, authorizations, consents and approvals to (A) own or lease its assets and carry on its business and (B) execute, deliver and perform its obligations hereunder, and (iii) is duly
qualified and is licensed and, as applicable, in good standing (to the extent such concept is applicable in the relevant jurisdiction) under the Laws of each jurisdiction where its ownership, lease or operation of properties or the conduct of its
business requires such qualification or license; except in each case referred to in clause (ii)(A) or (iii), to the extent that failure to do so could not reasonably be expected to have a Material Adverse Effect; 

(b) the execution, delivery and performance by such Guarantor of each Loan Document to which such Guarantor is a party has been
duly authorized by all necessary corporate or other organizational action, and do not and will not (i) contravene the terms of any of such Guarantor’s Organization Documents; (ii) conflict with or result in any breach or contravention
of, or the creation of any Lien (other than Liens created under the Loan Documents) under, or require any payment to be made under (A) any material Contractual Obligation to which such Guarantor is a party or affecting such Guarantor or the
properties of such Guarantor or any of its Subsidiaries or (B) any order, injunction, writ or decree of any Governmental Authority or any arbitral award to which such Guarantor or its property is subject; or (iii) violate any Law; 

  
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 (c) such Guarantor has duly executed and delivered each of the Loan
Documents that it is party thereto. This Agreement constitutes, and each other Loan Document when so delivered will constitute, a legal, valid and binding obligation of such Guarantor, enforceable against such Guarantor that is party thereto in
accordance with its terms, subject to applicable bankruptcy, insolvency, reorganization, moratorium or other laws affecting creditors’ rights generally and subject to general principles of equity, regardless of whether considered in a
proceeding in equity or at law; 
 (d) no approval, consent, exemption, authorization, or other action by, or notice to, or
filing with, any Governmental Authority or any other Person is necessary or required in connection with (i) the execution, delivery or performance by such Guarantor of this Agreement or any other Loan Document, or for the consummation of the
Transaction, (ii) the grant by such Guarantor of the Liens granted by it pursuant to the Collateral Documents, or (iii) the perfection or maintenance of the Liens created under the Collateral Documents (including, subject to the
Intercreditor Agreement, the first priority nature thereof) other than (A) those that have already been obtained and are now in full force and effect, (B) filings to perfect the Liens created by the Collateral Documents, and (C) those
actions as contemplated by Section 2.1 of the Canadian Security Agreement; 
 (e) there are no actions, suits,
proceedings, investigations, claims or disputes pending or, to the knowledge of any Responsible Officer of such Guarantor, threatened or contemplated in writing, at law, in equity, in arbitration or before any Governmental Authority, by or against
such Guarantor or against any of its properties or revenues that (i) purport to affect or pertain to this Agreement, any other Loan Document or the consummation of the Transaction, or (ii) either individually or in the aggregate could
reasonably be expected to have a Material Adverse Effect; and 
 (f) until the Termination Date, such Guarantor will comply,
and will cause each of its Subsidiaries to comply, with all of the applicable provisions, covenants and agreements contained in Articles 6 and 7 of the Credit Agreement which are expressly applicable to such Guarantor and/or such Guarantor’s
Subsidiaries, and will take, or will refrain from taking, as the case may be, all actions that are necessary to be taken or not taken so that no violation of any provision, covenant or agreement contained in Articles 6 and 7 of the Credit Agreement
which are expressly applicable to such Guarantor and/or such Guarantor’s Subsidiaries, and so that no Default or Event of Default, is caused by the actions of such Guarantor or any of its Subsidiaries. 

10. EXPENSES. The Guarantors hereby jointly and severally agree to pay (i) all reasonable and documented out-of-pocket expenses incurred by the Administrative Agent and its Affiliates (including the reasonable fees, charges and disbursements of counsel for the Administrative
Agent), in connection with any amendment, waiver or consent relating hereto and (ii) all reasonable and documented out-of-pocket expenses incurred by the
Administrative Agent or any Secured Party (including the reasonable fees, charges and disbursements of (x) one counsel to the Administrative Agent (plus one local counsel in each applicable jurisdiction and one specialty counsel in each
applicable specialty), (y) one counsel to the Secured Parties (plus one local counsel in each applicable jurisdiction and one specialty counsel in each applicable 

  
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specialty) and (z) in the case of an actual conflict of interest, one additional counsel for each group of similarly situated affected persons, taken as a whole), in connection with the
enforcement or protection of its rights in connection with this Guarantee and the other Loan Documents, including its rights under this Section. 

11. BENEFIT AND BINDING EFFECT. This Guarantee shall be binding upon each Guarantor and its successors and assigns and shall inure to
the benefit of the Secured Parties and their successors and assigns. 
 12. AMENDMENTS; WAIVERS. Neither this Guarantee nor any
provision hereof may be changed, waived, discharged or terminated except with the written consent of each Guarantor directly affected thereby (it being understood that the addition or release of any Guarantor hereunder shall not constitute a change,
waiver, discharge or termination affecting any Guarantor other than the Guarantor so added or released) and with the written consent of the Required Lenders (or, to the extent required by Section 10.01 of the Credit Agreement, with the written
consent of each Lender) at all times prior to the Termination Date. 
 13. SET OFF. In addition to any rights now or hereafter granted
under applicable law (including, without limitation, applicable Debtor Relief Laws) and not by way of limitation of any such rights, upon the occurrence and during the continuance of an Event of Default, each Secured Party and each of their
respective Affiliates is hereby authorized, at any time or from time to time, without notice to any Guarantor or to any other Person, any such notice being expressly waived, to set off and to appropriate and apply any and all deposits (general or
special) and any other indebtedness at any time held or owing by such Secured Party to or for the credit or the account of such Guarantor, against and on account of the obligations and liabilities of such Guarantor to such Secured Party under this
Guarantee, irrespective of whether or not such Secured Party shall have made any demand hereunder and although said obligations, liabilities, deposits or claims, or any of them, shall be contingent or unmatured. 

14. NOTICE. Except as otherwise specified herein, all notices, requests, demands or other communications to or upon the respective
parties hereto shall be sent or delivered by mail, telecopy or courier service and all such notices and communications shall, when mailed, telecopied or sent by courier, be effective when deposited in the mail, delivered to the overnight courier or
sent by telecopier, except that notices and communications to the Administrative Agent or any Guarantor shall not be effective until received by the Administrative Agent or such Guarantor, as the case may be. All notices and other communications
shall be in writing and addressed to such party at (i) in the case of any Secured Party, as provided in the Credit Agreement and (ii) in the case of any Guarantor, at its address set forth opposite its signature page below; or in any case
at such other address as any of the Persons listed above may hereafter notify the others in writing. 
 15. REINSTATEMENT.
Notwithstanding anything to the contrary contained herein, if any claim is ever made upon any Secured Party for repayment or recovery of any amount or amounts received in payment or on account of any of the Guaranteed Obligations and any of the
aforesaid payees repays all or part of said amount by reason of (i) any judgment, decree or order of any court or administrative body having jurisdiction over such payee or any of its property or (ii) any settlement or compromise of any
such claim effected by such payee with 

  
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any such claimant (including, without limitation, any Borrower), then and in such event each Guarantor agrees that any such judgment, decree, order, settlement or compromise shall be binding upon
such Guarantor, notwithstanding any revocation hereof or the cancellation of any Note, any other Loan Document or any other instrument evidencing any liability of any Borrower, and such Guarantor shall be and remain liable to the aforesaid payees
hereunder for the amount so repaid or recovered to the same extent as if such amount had never originally been received by any such payee. 

16. CONSENT TO JURISDICTION; SERVICE OF PROCESS; AND WAIVER OF TRIAL BY JURY. (a) THIS GUARANTEE AND ANY CLAIMS, CONTROVERSY, DISPUTE OR
CAUSE OF ACTION (WHETHER IN CONTRACT OR TORT OR OTHERWISE) BASED UPON, ARISING OUT OF OR RELATING TO THIS GUARANTEE AND THE TRANSACTIONS CONTEMPLATED HEREBY SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAW OF THE PROVINCE OF ONTARIO
AND THE FEDERAL LAWS OF CANADA APPLICABLE THEREIN. EACH GUARANTOR IRREVOCABLY AND UNCONDITIONALLY AGREES THAT IT WILL NOT COMMENCE ANY ACTION, LITIGATION OR PROCEEDING OF ANY KIND OR DESCRIPTION, WHETHER IN LAW OR EQUITY, WHETHER IN CONTRACT OR IN
TORT OR OTHERWISE, AGAINST ANY SECURED PARTY, OR ANY RELATED PARTY THEREOF IN ANY WAY RELATING TO THIS GUARANTEE OR THE TRANSACTIONS RELATING HERETO, IN ANY FORUM OTHER THAN THE COURTS OF THE PROVINCE OF ONTARIO SITTING IN TORONTO, AND ANY APPELLATE
COURT THEREFROM, AND EACH OF THE PARTIES HERETO IRREVOCABLY AND UNCONDITIONALLY SUBMITS TO THE JURISDICTION OF SUCH COURTS AND AGREES THAT ALL CLAIMS IN RESPECT OF ANY SUCH ACTION, LITIGATION OR PROCEEDING MAY BE HEARD AND DETERMINED IN SUCH ONTARIO
COURT. EACH OF GUARANTORS HEREBY AGREES THAT A FINAL JUDGMENT IN ANY SUCH ACTION, LITIGATION OR PROCEEDING SHALL BE CONCLUSIVE AND MAY BE ENFORCED IN OTHER JURISDICTIONS BY SUIT ON THE JUDGMENT OR IN ANY OTHER MANNER PROVIDED BY LAW. NOTHING IN THIS
GUARANTEE OR IN ANY OTHER LOAN DOCUMENT SHALL AFFECT ANY RIGHT THAT ANY SECURED PARTY MAY OTHERWISE HAVE TO BRING ANY ACTION OR PROCEEDING RELATING TO THIS GUARANTEE OR ANY OTHER LOAN DOCUMENT AGAINST EACH GUARANTOR OR ITS PROPERTIES IN THE COURTS
OF ANY JURISDICTION. EACH GUARANTOR IRREVOCABLY AND UNCONDITIONALLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, ANY OBJECTION THAT IT MAY NOW OR HEREAFTER HAVE TO THE LAYING OF VENUE OF ANY ACTION OR PROCEEDING ARISING OUT OF OR
RELATING TO THIS GUARANTEE OR ANY OTHER LOAN DOCUMENT IN ANY COURT REFERRED TO IN SUBSECTION (a) OF THIS SECTION. EACH OF THE GUARANTORS HEREBY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, THE DEFENSE OF AN
INCONVENIENT FORUM TO THE MAINTENANCE OF SUCH ACTION OR PROCEEDING IN ANY SUCH COURT. 

  
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 (b) EACH GUARANTOR HEREBY IRREVOCABLY CONSENTS TO SERVICE OF PROCESS IN THE MANNER PROVIDED
FOR NOTICES IN SECTION 14. NOTHING IN THIS GUARANTEE WILL AFFECT THE RIGHT OF ANY GUARANTOR TO SERVE PROCESS IN ANY OTHER MANNER PERMITTED BY APPLICABLE LAW. 

(c) EACH GUARANTOR HEREBY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, ANY RIGHT IT MAY HAVE TO A TRIAL BY JURY IN
ANY LEGAL PROCEEDING DIRECTLY OR INDIRECTLY ARISING OUT OF OR RELATING TO THIS GUARANTEE OR ANY OTHER LOAN DOCUMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY (WHETHER BASED ON CONTRACT, TORT OR ANY OTHER THEORY). EACH GUARANTOR
(A) CERTIFIES THAT NO REPRESENTATIVE, AGENT OR ATTORNEY OF ANY OTHER PERSON HAS REPRESENTED, EXPRESSLY OR OTHERWISE, THAT SUCH OTHER PERSON WOULD NOT, IN THE EVENT OF LITIGATION, SEEK TO ENFORCE THE FOREGOING WAIVER AND (B) ACKNOWLEDGES
THAT IT AND THE OTHER PARTIES HERETO HAVE BEEN INDUCED TO ENTER INTO THIS GUARANTEE AND THE OTHER LOAN DOCUMENTS BY, AMONG OTHER THINGS, THE MUTUAL WAIVERS AND CERTIFICATIONS IN THIS SECTION. 

17. RELEASE OF LIABILITY OF GUARANTOR. In the event that a Guarantor becomes an Immaterial Subsidiary or all of the Equity Interests of
one or more Guarantors (other than the Company) is sold or otherwise disposed of or liquidated in compliance with the requirements of Section 7.04 or 7.05 of the Credit Agreement (or such sale, other disposition or liquidation has been approved
in writing by the Required Lenders (or all the Lenders if required by Section 10.01 of the Credit Agreement)) and the proceeds of such sale, disposition or liquidation will be applied in accordance with the provisions of the Credit Agreement,
to the extent applicable, such Immaterial Subsidiary, or such Guarantor, as applicable, shall, or upon consummation of such sale or other disposition (except to the extent that such sale or disposition is to the Company or another Subsidiary
thereof), as applicable, shall be released from this Guarantee automatically and without further action and this Guarantee shall, as to each such Guarantor or Guarantors, terminate, and have no further force or effect (it being understood and agreed
that the sale of one or more Persons that own, directly or indirectly, all of the Equity Interests of any Guarantor shall be deemed to be a sale of such Guarantor for the purposes of this Section 17). Subject to Section 15, on the
Termination Date this Guarantee shall terminate (provided that all indemnities set forth herein shall survive such termination) and each Guarantor shall be released from its obligations under this Guarantee. 

18. CONTRIBUTION. At any time a payment in respect of the Guaranteed Obligations is made under this Guarantee, the right of contribution
of each Guarantor against each other Guarantor shall be determined as provided in the immediately following sentence, with the right of contribution of each Guarantor to be revised and restated as of each date on which a payment (a “Relevant
Payment”) is made on the Guaranteed Obligations under this Guarantee. At any time that a Relevant Payment is made by a Guarantor that results in the aggregate payments made by such Guarantor in respect of the Guaranteed Obligations to and
including the date of the Relevant Payment exceeding such Guarantor’s Contribution Percentage (as defined below) of the aggregate payments made by all Guarantors in respect of the Guaranteed Obligations to and including the date of the Relevant
Payment (such excess, the “Aggregate Excess Amount”), each such Guarantor shall have a right of contribution against each other Guarantor who has made payments in respect of the Guaranteed Obligations to and


  
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including the date of the Relevant Payment in an aggregate amount less than such other Guarantor’s Contribution Percentage of the aggregate payments made to and including the date of the
Relevant Payment by all Guarantors in respect of the Guaranteed Obligations (the aggregate amount of such deficit, the “Aggregate Deficit Amount”) in an amount equal to (x) a fraction the numerator of which is the Aggregate
Excess Amount of such Guarantor and the denominator of which is the Aggregate Excess Amount of all Guarantors multiplied by (y) the Aggregate Deficit Amount of such other Guarantor. A Guarantor’s right of contribution pursuant to the
preceding sentences shall arise at the time of each computation, subject to adjustment to the time of each computation; provided that no Guarantor may take any action to enforce such right until the Termination Date, it being expressly
recognized and agreed by all parties hereto that any Guarantor’s right of contribution arising pursuant to this Section 18 against any other Guarantor shall be expressly junior and subordinate to such other Guarantor’s obligations and
liabilities in respect of the Guaranteed Obligations and any other obligations owing under this Guarantee. As used in this Section 18: (i) each Guarantor’s “Contribution Percentage” shall mean the percentage obtained by
dividing (x) the Adjusted Net Worth (as defined below) of such Guarantor by (y) the aggregate Adjusted Net Worth of all Guarantors; (ii) the “Adjusted Net Worth” of each Guarantor shall mean the greater of
(x) the Net Worth (as defined below) of such Guarantor and (y) zero; and (iii) the “Net Worth” of each Guarantor shall mean the amount by which the fair saleable value of such Guarantor’s assets on the date of
any Relevant Payment exceeds its existing debts and other liabilities (including contingent liabilities, but without giving effect to any Guaranteed Obligations arising under this Guarantee or any guaranteed obligations arising under any guarantee
of any Permitted Additional Indebtedness) on such date. Notwithstanding anything to the contrary contained above, any Guarantor that is released from this Guarantee pursuant to Section 17 hereof shall thereafter have no contribution
obligations, or rights, pursuant to this Section 18, and at the time of any such release, if the released Guarantor had an Aggregate Excess Amount or an Aggregate Deficit Amount, same shall be deemed reduced to $0, and the contribution rights
and obligations of the remaining Guarantors shall be recalculated on the respective date of release (as otherwise provided above) based on the payments made hereunder by the remaining Guarantors. All parties hereto recognize and agree that, except
for any right of contribution arising pursuant to this Section 18, each Guarantor who makes any payment in respect of the Guaranteed Obligations shall have no right of contribution or subrogation against any other Guarantor in respect of such
payment until the Termination Date. Each of the Guarantors recognizes and acknowledges that the rights to contribution arising hereunder shall constitute an asset in favour of the party entitled to such contribution. In this connection, each
Guarantor has the right to waive its contribution right against any Guarantor to the extent that after giving effect to such waiver such Guarantor would remain solvent, in the determination of the Required Lenders. 

19. LIMITATION ON GUARANTEED OBLIGATIONS. Each Guarantor and each Secured Party (by its acceptance of the benefits of this Guarantee)
hereby confirms that it is its intention that this Guarantee not constitute a transfer at undervalue or fraudulent transfer or conveyance for purposes of any applicable Debtor Relief Law. To effectuate the foregoing intention, each Guarantor and
each Secured Party (by its acceptance of the benefits of this Guarantee) hereby irrevocably agrees that the Guaranteed Obligations guaranteed by such Guarantor shall be limited to such amount as will, after giving effect to such maximum amount and
all other (contingent or otherwise) liabilities of such Guarantor that are relevant under such laws and after giving effect to any rights to contribution pursuant to any agreement providing for an equitable contribution among such Guarantor and the
other Guarantors, result in the Guaranteed Obligations of such Guarantor in respect of such maximum amount not constituting a fraudulent transfer or conveyance. 

  
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 20. COUNTERPARTS. This Guarantee may be executed in any number of counterparts and by
the different parties hereto on separate counterparts, each of which when so executed and delivered shall be an original, but all of which shall together constitute one and the same instrument. A set of counterparts executed by all the parties
hereto shall be lodged with the Company and the Administrative Agent. 
 21. PAYMENTS. All payments made by any Guarantor hereunder
will be made without setoff, counterclaim or other defense and on the same basis as payments are made by the applicable Borrowers under the Credit Agreement. 

22. JUDGMENT CURRENCY. 

The parties hereto agree that the terms of Section 1.11 of the Credit Agreement are incorporated herein by reference, mutatis
mutandis. 
 23. ADDITIONAL GUARANTORS. It is understood and agreed that any Wholly-Owned Domestic Subsidiary of the Company that
is required to execute a counterpart of this Guarantee after the date hereof pursuant to the Credit Agreement shall become a Guarantor hereunder by (x) executing and delivering a counterpart hereof, a Joinder Agreement or a Guarantee Supplement
in the form attached hereto as Exhibit A, and delivering the same to the Administrative Agent (provided such Guarantee Supplement shall not require the consent of any Guarantor) and (y) taking all actions as specified in this Guarantee
as would have been taken by such Guarantor had it been an original party to this Guarantee, in each case with all documents required above to be delivered to the Administrative Agent and actions required to be taken above to be taken to the
reasonable satisfaction of the Administrative Agent. 
 24. HEADINGS DESCRIPTIVE. The headings of the several Sections of this
Guarantee are inserted for convenience only and shall not in any way affect the meaning or construction of any provision of this Guarantee. 

* * * 

  
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 IN WITNESS WHEREOF, each Guarantor has caused this Canadian Guarantee to be executed and
delivered as of the date first above written. 
  

							
		 	    	 	 GUARANTORS:

	 7035 Ridge Road
 Hanover, Maryland 21076

Attention: Treasurer’s Office
 Facsimile:
	 		 	 CIENA CANADA, INC.

		 		 	By:	 	 /s/ Jiong Liu

	with a copy to:	 		 		 	Name: Jiong Liu
	  
 7035 Ridge Road

Hanover, Maryland 21076
 Attention: General Counsel’s
Office
 Facsimile:
	 		 		 	Title: Jiong Liu


  
 [Signature Page to
Canadian Guarantee] 














			
	Accepted and Agreed to:
	
	 BANK OF AMERICA, N.A.,
 as
Administrative Agent

		
	By:	 	 /s/ John M. Olsen

		 	Name: John M. Olsen
		 	Title: John M. Olsen


  
 [Signature Page to
Canadian Guarantee]