Document:

EX-10.4

 Exhibit 10.4 

ACACIA COMMUNICATIONS, INC. 

2009 STOCK PLAN 

NOTICE OF RESTRICTED STOCK UNIT AWARD 

You (“Participant”) have been granted Restricted Stock Units (“RSUs”) representing shares of Common Stock of Acacia
Communications, Inc. (the “Company”) on the following terms: 
  

			
	Name:	  	«Name»
		
	Total Number of Stock Units Granted:	  	«Share Number»
		
	Date of Grant:	  	«DateGrant»
		
	Vesting Commencement Date:	  	«VestComDate»
		
	Expiration Date:	  	«Expiration Date»1
		
	Vesting:	  	You will receive a benefit with respect to a RSU only if it vests. In order for an RSU to vest, two vesting requirements must be satisfied on or before the Expiration Date specified above: (i) the Time-Based Requirement and (ii)
the Liquidity Event Requirement. If both the Time-Based Requirement and the Liquidity Event Requirement are satisfied on or before the Expiration Date, the vesting date (“Vesting Date”) of a RSU will be the first date upon which
both of those requirements are satisfied with respect to that particular RSU. Your RSUs will not vest (in whole or in part) if only one (or if neither) of such requirements is satisfied on or before the Expiration Date.
		
	Time-Based Requirement:	  	The Time-Based Requirement will be satisfied in installments as to 37.5% of the RSUs subject to this award when you complete 18 months of continuous Service and as to 6.25% for each period of three months of continuous Service
thereafter, in each case measured from the Vesting Commencement Date set forth above, subject to Section 2 of the Restricted Stock Unit Agreement.
		
	Liquidity Event Requirement:	  	The Liquidity Event Requirement will be satisfied (as to any then-outstanding RSUs that

  

	1 	To be seven years less one day following the Date of Grant. 

			
		  	have not theretofore been terminated pursuant to Section 2 of the Restricted Stock Unit Agreement) on the earlier to occur of (i) an IPO, or (ii) a Sale Event (each, a “Liquidity Event”).
		
	Settlement:	  	Settlement of RSUs refers to the issuance of Shares (or, if applicable, cash) once the award is vested. If a RSU vests as a result of satisfaction of both applicable vesting requirements as described above, the Company will
deliver one Share for that RSU at the time of settlement, unless at the time of settlement the Board of Directors, in its sole discretion, determines that settlement shall, in whole or in part, be in the form of cash, based on the then Fair Market
Value of a Share. Settlement shall occur on or following the Vesting Date, but not later than two and one-half (2 1⁄2) months following the end of the year in
which the Vesting Date applicable to a RSU occurs (the last day of such two and one-half month period is referred to as the “Short Term Deferral End Date”). Notwithstanding the above, settlement of RSUs that become vested
RSUs upon (i) a Sale Event will be made in Shares, unless otherwise specified in the definitive agreement for such Sale Event, or (ii) an IPO shall occur on the earlier of (a) the 185th day
following the IPO Date or (b) the Short Term Deferral End Date.

 By signing below, you and the Company agree that the RSUs are granted under and governed by the terms and conditions of the
Company’s 2009 Stock Plan (the “Plan”) and the Restricted Stock Unit Agreement, both of which are attached to and made a part of this document. Capitalized terms not otherwise defined herein shall have the meaning set forth in
the Plan. You hereby acknowledge that the vesting of the RSUs pursuant to this Notice of Restricted Stock Unit Award is conditioned on the satisfaction of the Time-Based Requirement and the Liquidity Event
Requirement on or before the Expiration Date. You shall have no right with respect to the RSUs to the extent a Liquidity Event does not occur on or before the Expiration Date (regardless of the extent to which the Time-Based Requirement is
satisfied). 

 You further agree to accept by email all documents relating to the Company, the Plan or these RSUs and all other
documents that the Company is required to deliver to its security holders (including, without limitation, disclosures that may be required by the Securities and Exchange Commission). You also agree that the Company may deliver these documents by
posting them on a website maintained by the Company or by a third party under contract with the Company. If the Company posts these documents on a website, it will notify you by email. You acknowledge that you may incur costs in connection with
electronic delivery, including the cost of accessing the internet and printing fees, and that an interruption of internet access may interfere with your ability to access the documents. 

 

							
	PARTICIPANT:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

	Address for Mailing Stock Certificate:	 		 	Title:	 	  

				
	  
	 		 		 	
	  
	 		 		 	

 ACACIA COMMUNICATIONS, INC. 

2009 STOCK PLAN 

RESTRICTED STOCK UNIT AGREEMENT 

SECTION 1. GRANT OF RESTRICTED STOCK UNITS. 

(a) Grant. On the terms and conditions set forth in the Notice of Restricted Stock Unit Award and this Agreement, the Company grants to
you on the Date of Grant the number of RSUs set forth in the Notice of Restricted Stock Unit Award. Each RSU represents the right to receive one share of the Company’s Common Stock on the terms and conditions set forth in this Agreement. 

(b) Consideration. No payment is required for the RSUs that have been granted to you. 

(c) Nature of RSUs; No Rights As a Stockholder. The RSUs are mere bookkeeping entries and represent only the Company’s unfunded
and unsecured promise to issue Shares on a future date under specified conditions. As a holder of RSUs, you have no rights other than the rights of a general creditor of the Company. The RSUs carry neither voting rights nor rights to cash dividends.
You have no rights as a stockholder of the Company unless and until the RSUs vest and are settled pursuant to Section 4. 
 (d)
Stock Plan and Defined Terms. The RSUs are granted pursuant to the Plan, a copy of which you acknowledge having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 10 of this Agreement. 
 SECTION 2. VESTING. 

(a) Generally. The RSUs vest in accordance with the vesting schedule set forth in the Notice of Restricted Stock Unit Award. You will
receive a benefit with respect to a RSU only if both the Time-Based Requirement and the Liquidity Event Requirement are satisfied on or before the Expiration Date. The RSUs will not vest (in whole or in part) if only one (or if neither) of such
requirements is satisfied on or before the Expiration Date. 
 (b) Termination of Service. If your Service terminates for any reason,
all RSUs as to which the Time-Based Requirement has not been satisfied as of your termination date shall automatically terminate and be cancelled. You will not satisfy the Time-Based Requirement for any additional RSUs after your Service has
terminated, regardless of the reason for such termination. Upon such termination of Service, any RSUs as to which the Time-Based Requirement has been satisfied will (if the Liquidity Event Requirement has not yet been satisfied) remain outstanding
until the first to occur of: (A) the satisfaction of the Liquidity Event Requirement, (B) the Expiration Date or (C) the second anniversary of your Service termination date. In case of any dispute as to whether your Service has
terminated, the Board of Directors shall have sole discretion to determine whether such termination has occurred and the effective date of such termination. 

 (c) Expiration of RSUs. If the Liquidity Event Requirement is not satisfied on or before
the Expiration Date, all RSUs (regardless of whether or not, or to the extent which, the Time-Based Requirement had been satisfied as to such RSUs) shall automatically terminate upon such date. Upon a termination of one or more RSUs pursuant to this
Section 2, you will have no further right with respect to such RSUs or the Shares previously allocated thereto. 
 (d) Part-Time
Employment and Leaves of Absence. If you commence working on a part-time basis, then the Company may adjust the Time-Based Requirement set forth in the Notice of Restricted Stock Unit Award. If you go on a leave of absence, then the Company may
adjust the Time-Based Requirement set forth in the Notice of Restricted Stock Unit Award in accordance with the Company’s leave of absence policy or the terms of such leave. Except as provided in the preceding sentence, Service shall be deemed
to continue for any purpose under this Agreement while you are on a bona fide leave of absence, if (i) such leave was approved by the Company in writing and (ii) continued crediting of Service for such purpose is expressly required
by the terms of such leave or by applicable law (as determined by the Company). Service shall be deemed to terminate when such leave ends, unless you immediately return to active work. 

SECTION 3. RESTRICTIONS APPLICABLE TO RSUS. 

(a) Restrictions on Transfer. Except as otherwise provided in this Agreement, the RSUs and the rights and privileges conferred hereby
shall not be sold, assigned, transferred, pledged, hypothecated, or otherwise disposed of by you prior to the settlement of the RSUs. However, you may designate a third party who, in the event of your death, shall thereafter be entitled to receive
any distribution of Shares to which you were entitled at the time of your death pursuant to this Agreement by delivering a written beneficiary designation to the Company’s headquarters on the prescribed form. If you deliver no such beneficiary
designation or if your designated beneficiaries do not survive you, your estate will receive payments in respect of any vested RSUs. 
 (b)
Forfeiture of RSUs. In connection with the RSUs, the Company may be required to provide you with certain highly confidential information about the Company, including information regarding its financial condition and business prospects.
Unauthorized disclosure of such information is prohibited under your existing Proprietary Information and Inventions Agreement with the Company and under Company policy, and you may be required to sign an additional nondisclosure agreement prior to
receiving this type of information. In addition, unauthorized disclosure of the Company’s confidential information could result in the immediate forfeiture of the RSUs, including vested RSUs as well as termination of your Service with the
Company. 

  
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 SECTION 4. SETTLEMENT OF RSUS. 

(a) Settlement Date. Upon a Vesting Date with respect to a particular RSU, the Company will deliver one Share for that RSU, unless at
the time of settlement the Board of Directors, in its sole discretion, determines that settlement shall, in whole or in part, be in the form of cash, based on the then-Fair Market Value of a Share. Settlement shall occur on or following the Vesting
Date, but not later than Short-Term Deferral End Date (as defined in the Notice of Restricted Stock Unit Grant). Notwithstanding the above, for RSUs that become vested upon a Sale Event, settlement will be made in Shares, unless otherwise
specified in the definitive agreement for such Sale Event, and for RSUs that become vested upon an IPO, settlement shall occur on the earlier of (i) the 185th day following the IPO Date or
(ii) the Short-Term Deferral End Date. 
 (b) Form of Delivery. The form of any delivery of Shares (e.g., a stock certificate or
electronic entry evidencing such shares) shall be determined by the Company. 
 (c) Legality of Issuance. No Shares shall be issued
to you upon settlement of the RSUs unless and until the Company has determined that (i) you and the Company have taken any actions required to register the Shares under the Securities Act or to perfect an exemption from the registration
requirements thereof; (ii) any applicable listing requirement of any stock exchange or other securities market on which stock is listed has been satisfied; and (iii) any other applicable provision of federal, State or foreign law has been
satisfied. The Company shall have no liability to issue Shares in respect of the RSUs unless it is able to do so in compliance with applicable law. 

SECTION 5. TAXES. 
 (a) Withholding
Taxes. Upon the Vesting Date and/or settlement date for the RSUs, the Fair Market Value of the Shares is treated as income subject to withholding by the Company and/or the Parent or Subsidiary employing you (your “Employer”) for
the payment of all applicable federal, State, local and foreign income and employment withholding taxes which arise in connection with the vesting or settlement of the RSUs (the “Withholding Taxes”). No consideration will be paid to
you in respect of this award unless you have made arrangements satisfactory to your Employer to satisfy the Withholding Taxes. To the extent that you fail to make such arrangements with respect to certain RSUs, then you will permanently forfeit such
RSUs. At the discretion of the Company, these arrangements may include (i) withholding from other compensation or amounts that are owed to you by your Employer, (ii) payment in cash, (iii) if the Stock is publicly traded, payment from
the proceeds of the sale of shares through a Company-approved broker, (iv) withholding a number of Shares that otherwise would be issued to you when the RSUs are settled with a Fair Market Value equal to the minimum statutory amount required to
be withheld, or (v) any other method permitted by the Company. However, if you are a Company officer subject to Section 16 of the Exchange Act, then the Withholding Taxes will be satisfied pursuant to clause (iv) of the preceding
sentence, unless otherwise determined in advance by the Board of Directors. If the Withholding Taxes are satisfied pursuant to clause (iv), you will be deemed to have been issued the full number of Shares subject to the RSUs and the Fair Market
Value of the withheld Shares, determined as of the date when taxes otherwise would have been 

  
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withheld in cash, will be applied to the Withholding Taxes and such amount will be remitted to appropriate tax authorities by the Company or your Employer. The Company will not withhold
fractional shares pursuant to clause (iv), so if the Withholding Taxes are satisfied pursuant to clause (iv), you hereby authorize the Company or your Employer to withhold the amount of any remaining Withholding Taxes from your wages or other cash
compensation. 
 (b) Section 409A. The settlement of the RSUs is intended to be exempt from the application of Code
Section 409A pursuant to the “short-term deferral exemption” in Treasury Regulation 1.409A-1(b)(4) and shall be administered and interpreted in a manner that complies with such exemption. To the extent that any provision of this
Agreement is ambiguous as to its exemption from Code Section 409A, the provision shall be read in such a manner so that all payments hereunder are exempt from Code Section 409A. Notwithstanding the foregoing, if this award of RSUs is
interpreted as not being exempt from Code Section 409A, it shall be interpreted to comply with the requirement of Code Section 409A so that this award is not subject to additional tax or interest under Code Section 409A. In this
regard, if this award is payable upon your “separation from service” within the meaning of Code Section 409A(a)(2)(A)(i) (a “Separation”) and you are a “specified employee” of the Company or any affiliate
thereof within the meaning of Code Section 409A(a)(2)(B)(i) on the day of your Separation, then no such payment shall be made prior to the date that is the earlier of (i) six months and one day after your Separation, or (ii) your
death, but only to the extent such delay is necessary so that this award is not subject to additional tax or interest under Code Section 409A. 

(c) Acknowledgements. You acknowledge that there will be tax consequences upon vesting and/or settlement of the RSUs and/or disposition
of the Shares, if any, received hereunder, and you should consult a tax advisor regarding your tax obligations prior to such event. You acknowledge that the Company is not providing any tax, legal, or financial advice, nor is the Company making any
recommendations regarding your participation in the Plan or acquisition or sale of Shares subject to this award. You are hereby advised to consult with your own personal tax, legal, and financial advisors regarding your participation in the Plan.
You further acknowledge that the Company (i) makes no representations or undertakings regarding the tax treatment of the award of RSUs, including, but not limited to the grant, vesting, or settlement of the RSUs, the subsequent sale of Shares
acquired pursuant to such RSUs, and the receipt of any dividends; and (ii) does not commit to and is under no obligation to structure the terms of the grant of the RSUs to reduce or eliminate your tax liability or achieve any particular tax
result. You agree that the Company does not have a duty to design or administer the RSUs, the Plan or its other compensation programs in a manner that minimizes your tax liability. You shall not make any claim against the Company or its Board of
Directors, officers, or employees related to tax matters arising from this award or your other compensation. 
 SECTION 6. RIGHT OF FIRST REFUSAL.

 (a) Right of First Refusal. In the event that you propose to sell, pledge or otherwise transfer to a third party any Shares
acquired under this Agreement, or any interest in such Shares, the Company shall have the Right of First Refusal with respect to all (and not less than all) of such Shares. If you desire to transfer Shares acquired under this Agreement, you must
give a written Transfer Notice to the Company describing fully the proposed transfer, 

  
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including the number of Shares proposed to be transferred, the proposed transfer price, the name and address of the proposed Transferee and proof satisfactory to the Company that the proposed
sale or transfer will not violate any applicable federal, State or foreign securities laws. The Transfer Notice shall be signed both by you and by the proposed Transferee and must constitute a binding commitment of both parties to the transfer of
the Shares. The Company shall have the right to purchase all, and not less than all, of the Shares on the terms of the proposal described in the Transfer Notice (subject, however, to any change in such terms permitted under Section 6(b) below)
by delivery of a notice of exercise of the Right of First Refusal within 30 days after the date when the Transfer Notice was received by the Company. 

(b) Transfer of Shares. If the Company fails to exercise its Right of First Refusal within 30 days after the date when it received
the Transfer Notice, you may, not later than 90 days following receipt of the Transfer Notice by the Company, conclude a transfer of the Shares subject to the Transfer Notice on the terms and conditions described in the Transfer Notice,
provided that any such sale is made in compliance with applicable federal, State and foreign securities laws and not in violation of any other contractual restrictions to which you are bound. Any proposed transfer on terms and conditions different
from those described in the Transfer Notice, as well as any subsequent proposed transfer by you, shall again be subject to the Right of First Refusal and shall require compliance with the procedure described in Section 6(a) above. If the
Company exercises its Right of First Refusal, the parties shall consummate the sale of the Shares on the terms set forth in the Transfer Notice within 60 days after the date when the Company received the Transfer Notice (or within such longer
period as may have been specified in the Transfer Notice); provided, however, that in the event the Transfer Notice provided that payment for the Shares was to be made in a form other than cash or cash equivalents paid at the time of transfer, the
Company shall have the option of paying for the Shares with cash or cash equivalents equal to the present value of the consideration described in the Transfer Notice. 

(c) Additional or Exchanged Securities and Property. In the event of a merger or consolidation of the Company with or into another
entity, any other corporate reorganization, a stock split, the declaration of a stock dividend, the declaration of an extraordinary dividend payable in a form other than stock, a spin-off, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities, any securities or other property (including cash or cash equivalents) that are by reason of such transaction exchanged for, or
distributed with respect to, any Shares subject to this Section 6 shall immediately be subject to the Right of First Refusal. Appropriate adjustments to reflect the exchange or distribution of such securities or property shall be made to the
number and/or class of the Shares subject to this Section 6. 
 (d) Termination of Right of First Refusal. Any other provision
of this Section 6 notwithstanding, in the event that the Stock is readily tradable on an established securities market when you desire to transfer Shares, the Company shall have no Right of First Refusal, and you shall have no obligation to
comply with the procedures prescribed by Sections 6(a) and 6(b) above. 
 (e) Permitted Transfers. This Section 6 shall not
apply to (i) a transfer by beneficiary designation, will or intestate succession or (ii) a transfer to one or more members of 

  
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the your Immediate Family or to a trust established by you for the benefit of you and/or one or more members of your Immediate Family, provided in either case that the Transferee agrees in
writing on a form prescribed by the Company to be bound by all provisions of this Agreement. If you transfer any Shares acquired under this Agreement, either under this Section 6(e) or after the Company has failed to exercise the Right of First
Refusal, then this Agreement shall apply to the Transferee to the same extent as to you. 
 (f) Termination of Rights as Stockholder.
If the Company makes available, at the time and place and in the amount and form provided in this Agreement, the consideration for the Shares to be purchased in accordance with this Section 6, then after such time the person from whom such
Shares are to be purchased shall no longer have any rights as a holder of such Shares (other than the right to receive payment of such consideration in accordance with this Agreement). Such Shares shall be deemed to have been purchased in accordance
with the applicable provisions hereof, whether or not the certificate(s) therefor have been delivered as required by this Agreement. 
 (g)
Assignment of Right of First Refusal. The Board of Directors may freely assign the Company’s Right of First Refusal, in whole or in part. Any person who accepts an assignment of the Right of First Refusal from the Company shall assume
all of the Company’s rights and obligations under this Section 6. 
 SECTION 7. RESTRICTIONS APPLICABLE TO SHARES. 

(a) Securities Law Restrictions. Regardless of whether the offering and sale of Shares under the Plan have been registered under the
Securities Act or have been registered or qualified under the securities laws of any State, the Company, at its discretion, may impose restrictions upon the sale, pledge or other transfer of the Shares (including the placement of appropriate legends
on stock certificates or the imposition of stop-transfer instructions) if, in the judgment of the Company, such restrictions are necessary or desirable in order to achieve compliance with the Securities Act,
the securities laws of any State or any other law. You (or the beneficiary or your personal representative in the event of your death or incapacity, as the case may be) shall deliver to the Company any representations or other documents or
assurances as the Company may deem necessary or reasonably desirable to ensure compliance with all applicable legal and regulatory requirements. 

(b) Market Stand-Off. In connection with any underwritten public offering by the Company of its equity securities pursuant to an
effective registration statement filed under the Securities Act, including the Company’s initial public offering, you or a Transferee shall not directly or indirectly sell, make any short sale of, loan, hypothecate, pledge, offer, grant or sell
any option or other contract for the purchase of, purchase any option or other contract for the sale of, or otherwise dispose of or transfer, or agree to engage in any of the foregoing transactions with respect to, any Shares acquired under this
Agreement without the prior written consent of the Company or its managing underwriter. Such restriction (the “Market Stand-Off”) shall be in effect for such period of time following the date of the final prospectus for the offering
as may be requested by the Company or such underwriter. In no event, however, shall such period exceed 180 days plus such additional period as may reasonably be requested by the 

  
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Company or such underwriter to accommodate regulatory restrictions on (i) the publication or other distribution of research reports or (ii) analyst recommendations and opinions,
including (without limitation) the restrictions set forth in Rule 2711(f)(4) of the National Association of Securities Dealers and Rule 472(f)(4) of the New York Stock Exchange, as amended, or any similar successor rules. The Market
Stand-Off shall in any event terminate two years after the date of the Company’s initial public offering. In the event of the declaration of a stock dividend, a spin-off, a stock split, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities without receipt of consideration, any new, substituted or additional securities which are by reason of such transaction distributed
with respect to any Shares subject to the Market Stand-Off, or into which such Shares thereby become convertible, shall immediately be subject to the Market Stand-Off. In order to enforce the Market Stand-Off, the Company may impose stop-transfer
instructions with respect to the Shares acquired under this Agreement until the end of the applicable stand-off period. The Company’s underwriters shall be beneficiaries of the agreement set forth in this Section 7(b). This
Section 7(b) shall not apply to Shares registered in the public offering under the Securities Act. 
 (c) Investment Intent at
Grant. You represent and agree that the Shares to be acquired upon settlement of the RSUs will be acquired for investment, and not with a view to the sale or distribution thereof. 

(d) Investment Intent at Settlement. In the event that the sale of Shares under the Plan is not registered under the Securities Act but
an exemption is available that requires an investment representation or other representation, you shall represent and agree at the time of issuance that the Shares being acquired upon settlement of the RSUs are being acquired for investment, and not
with a view to the sale or distribution thereof, and shall make such other representations as are deemed necessary or appropriate by the Company and its counsel. 

(e) Rights of the Company. The Company shall not be required to (i) transfer on its books any Shares that have been sold or
transferred in contravention of this Agreement or (ii) treat as the owner of Shares, or otherwise to accord voting, dividend or liquidation rights to, any Transferee to whom the Shares have been transferred in contravention of this Agreement.

 (f) Legends. All certificates evidencing the Shares issued under this Agreement shall bear the following legend: 

“THE SHARES REPRESENTED HEREBY MAY NOT BE SOLD, ASSIGNED, TRANSFERRED, ENCUMBERED OR IN ANY MANNER DISPOSED OF, EXCEPT IN COMPLIANCE WITH
THE TERMS OF A WRITTEN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER OF THE SHARES (OR THE PREDECESSOR IN INTEREST TO THE SHARES). SUCH AGREEMENT GRANTS TO THE COMPANY CERTAIN RIGHTS OF FIRST REFUSAL UPON AN ATTEMPTED TRANSFER OF THE
SHARES. THE SECRETARY OF THE COMPANY WILL UPON WRITTEN REQUEST FURNISH A COPY OF SUCH AGREEMENT TO THE HOLDER HEREOF WITHOUT CHARGE.” 

  
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 All certificates evidencing Shares issued under this Agreement in an unregistered transaction shall bear the
following legend (and such other restrictive legends as are required or deemed advisable under the provisions of any applicable law): 

“THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR
OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.” 

If required by the authorities of any State in connection with the issuance of the Shares, the legend or legends required by such State authorities shall also
be endorsed on all such certificates. 
 (g) Removal of Legends. If, in the opinion of the Company and its counsel, any legend placed
on a stock certificate representing Shares issued under this Agreement is no longer required, the holder of such certificate shall be entitled to exchange such certificate for a certificate representing the same number of Shares but without such
legend. 
 (h) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth in
this Section 7 shall be conclusive and binding on you and all other persons. 
 SECTION 8. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 9(a) of the Plan, the terms of the RSUs (including, without limitation, the number
and kind of shares subject to these RSUs) shall be subject to Section 9(a) of the Plan. In the event that the Company is party to certain corporate transactions, the RSUs shall be subject to Section 9(b) of the Plan, provided that any
action taken must either preserve the exemption of the RSUs from Code Section 409A or comply with Code Section 409A. Any additional RSUs and any new, substituted or additional shares, cash or other property that become subject to this
award as a result of any such transaction shall be subject to the same conditions and restrictions as applicable to the RSUs to which they relate. 

SECTION 9. MISCELLANEOUS PROVISIONS. 
 (a)
Successors and Assigns. Except as otherwise expressly provided to the contrary, the provisions of this Agreement shall inure to the benefit of, and be binding upon, the Company and its successors and assigns and be binding upon you and your
legal representatives, heirs, legatees, distributees, assigns and transferees by operation of law, whether or not any such person has become a party to this Agreement or has agreed in writing to join herein and to be bound by the terms, conditions
and restrictions hereof. 
 (b) No Retention Rights. Nothing in this Agreement or in the Plan shall confer upon you the right to
remain in Service in any capacity or for any period of specific duration or interfere with or otherwise restrict in any way the rights of the Company (or any 

  
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Parent or Subsidiary employing or retaining you) or you, which rights are hereby expressly reserved by each, to terminate your Service at any time and for any reason, with or without cause. 

(c) Notice. Any notice required by the terms of this Agreement shall be given in writing. It shall be deemed effective
upon (i) personal delivery, (ii) deposit with the United States Postal Service, by registered or certified mail, with postage and fees prepaid or (iii) deposit with a reputable overnight courier, with shipping charges prepaid. Notice
shall be addressed to the Company at its principal executive office and to you at the address that you most recently provided to the Company in accordance with this Section 9(c). 

(d) Effect on Other Employee Benefit Plans. The value of the RSUs and the Shares issuable thereunder shall not be included as
compensation, earnings, salaries, or other similar terms used when calculating benefits under any employee benefit plan (other than the Plan) sponsored by the Company or a Parent or Subsidiary, except as such plans otherwise expressly provide. 

(e) Entire Agreement. The Notice of Restricted Stock Unit Award, this Agreement and the Plan constitute the entire understanding
between you and the Company regarding the subject matter hereof. They supersede any other agreements, representations or understandings (whether oral or written and whether express or implied) that relate to the subject matter hereof. 

(f) Choice of Law. This Agreement shall be governed by, and construed in accordance with, the laws of the State of Delaware, as such
laws are applied to contracts entered into and performed in such State. 
 SECTION 10. DEFINITIONS. 

(a) “Agreement” shall mean this Restricted Stock Unit Agreement. 

(b) “Board of Directors” shall mean the Board of Directors of the Company, as constituted from time to time or, if a
Committee has been appointed, such Committee. 
 (c) “Code” shall mean the Internal Revenue Code of 1986, as amended. 

(d) “Committee” shall mean a committee of the Board of Directors, as described in Section 2 of the Plan. 

(e) “Company” shall mean Acacia Communications, Inc., a Delaware corporation. 

(f) “Consultant” shall mean a person who performs bona fide services for the Company, a Parent or a Subsidiary as a
consultant or advisor, excluding Employees and Outside Directors. 

  
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 (g) “Date of Grant” shall mean the date specified in the Notice of Restricted
Stock Unit Award. 
 (h) “Employee” shall mean any individual who is a common-law
employee of the Company, a Parent or a Subsidiary. 
 (i) “Exchange Act” shall mean the Securities Exchange Act of 1934, as
amended. 
 (j) “Expiration Date” shall mean the expiration date of the RSUs as set forth in the Notice of Restricted Stock
Unit Award. 
 (k) “Fair Market Value” shall mean the fair market value of a Share, as determined by the Board of Directors
in good faith. Such determination shall be conclusive and binding on all persons. 
 (l) “Immediate Family” shall mean any
child, stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling, mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law or sister-in-law and shall include adoptive relationships. 

(m) “IPO” shall mean the first firm commitment underwritten public offering pursuant to an effective registration statement
on an established national or foreign securities exchange covering the offer and sale by the Company of its equity securities, as a result of or following which the Shares shall be publicly held, and “IPO Date” shall mean the date
on which the IPO occurs. 
 (n) “Liquidity Event Requirement” shall mean the requirement that the Company complete an IPO
or Sale Event. 
 (o) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(p) “Parent” shall mean any corporation (other than the Company) in an unbroken chain of corporations ending with the
Company, if each of the corporations other than the Company owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. A corporation that attains the status of a
Parent on a date after the adoption of the Plan shall be considered a Parent commencing as of such date. 
 (q) “Plan”
shall mean the Acacia Communications, Inc. 2009 Stock Plan, as amended from time to time. 
 (r) “Right of First Refusal”
shall mean the Company’s right of first refusal described in Section 6. 
 (s) “RSUs” shall mean the Restricted
Stock Units granted to you by the Company as set forth in the Notice of Restricted Stock Unit Award. 

  
 10 

 (t) “Sale Event” means the consummation of the following transactions in which
holders of Shares receive cash or marketable securities tradable on an established national or foreign securities exchange: (i) a sale of all or substantially all of the assets of the Company determined on a consolidated basis to an unrelated
person or entity; (ii) a merger, reorganization, or consolidation involving the Company in which the shares of voting stock of the Company outstanding immediately prior to such transaction represent or are converted into or exchanged for
securities of the surviving or resulting entity immediately upon completion of such transaction which represent less than 50% of the outstanding voting power of such surviving or resulting entity; or (iii) the acquisition of all or a majority
of the outstanding voting stock of the Company in a single transaction or series of related transactions by a person or group of persons. For the avoidance of doubt, an initial public offering, any subsequent public offering, another capital raising
event, and a merger effected solely to change the Company’s domicile shall not constitute a “Sale Event.” In addition, a transaction shall not constitute a Sale Event unless such transaction also qualifies as an event under Treasury
Regulation Section 1.409A-3(i)(5)(v) (change in the ownership of a corporation), Treasury Regulation Section 1.409A-3(i)(5)(vi) (change in the effective control of a corporation), or Treasury Regulation Section 1.409A-3(i)(5)(vii)
(change in the ownership of a substantial portion of a corporation’s assets). 
 (u) “Securities Act” shall mean the
Securities Act of 1933, as amended. 
 (v) “Service” shall mean service as an Employee, Consultant or Outside Director.

 (w) “Share” shall mean one share of Stock, as adjusted in accordance with Section 9 of the Plan (if applicable).

 (x) “Stock” shall mean the Common Stock of the Company. 

(y) “Subsidiary” shall mean any corporation entity (other than the Company) in an unbroken chain or corporations beginning
with the Company, if each of the corporations other than the last corporation in the unbroken chain owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. A
corporation that attains the status of a Subsidiary on a date after the adoption of the Plan shall be considered a Subsidiary commencing as of such date. 

(z) “Time-Based Requirement” shall mean the requirement to provide Service over the period of time set forth in the Notice of
Restricted Stock Unit Award. 
 (aa) “Transferee” shall mean any person to whom you have directly or indirectly transferred
any Shares acquired under this Agreement. 
 (bb) “Transfer Notice” shall mean the notice of a proposed transfer of Shares
described in Section 6. 
 (cc) “Vesting Date” shall mean the first date on or before the Expiration Date upon which
both the Time-Based Requirement and the Liquidity Event Requirement are satisfied. 

  
 11 

 ACACIA COMMUNICATIONS, INC. 

2009 STOCK PLAN 

NOTICE OF RESTRICTED STOCK UNIT AWARD 

You (“Participant”) have been granted Restricted Stock Units (“RSUs”) representing shares of Common Stock of Acacia
Communications, Inc. (the “Company”) on the following terms: 
  

			
	Name:	  	
		
	Total Number of Stock Units Granted:	  	
		
	Date of Grant:	  	
		
	Vesting Commencement Date:	  	
		
	Expiration Date:	  	
		
	Vesting:	  	You will receive a benefit with respect to a RSU only if it vests. In order for an RSU to vest, two vesting requirements must be satisfied on or before the Expiration Date specified above: (i) the Time-Based Requirement and (ii)
the Liquidity Event Requirement. If both the Time-Based Requirement and the Liquidity Event Requirement are satisfied on or before the Expiration Date, the vesting date (“Vesting Date”) of a RSU will be the first date upon which
both of those requirements are satisfied with respect to that particular RSU. Your RSUs will not vest (in whole or in part) if only one (or if neither) of such requirements is satisfied on or before the Expiration Date.
		
	Time-Based Requirement:	  	The Time-Based Requirement will be satisfied in the following installments: (i) 33% of the RSUs subject to this award will vest when you complete 12 months of continuous Service, (ii) an additional 33% of the RSUs will vest when
you complete 24 months of continuous Service, (iii) and an additional 34% of the RSUs will vest when you complete 36 months of continuous Service, in each case measured from the Vesting Commencement Date set forth above, subject to Section 2 of the
Restricted Stock Unit Agreement.

			
	Liquidity Event Requirement:	  	In addition to the Time-Based Requirement, the Liquidity Event Requirement must also be satisfied (as to any then-outstanding RSUs that have not theretofore been terminated pursuant to
Section 2 of the Restricted Stock Unit Agreement) prior to the Expiration Date, and will occur on the earlier of (i) an IPO, or (ii) a Sale Event, in each case before April 28, 2022 (each, a “Liquidity Event”).
		
		  	
	Settlement:	  	Settlement of RSUs refers to the issuance of Shares (or, if applicable, cash) once the award is vested. If a RSU vests as a result of satisfaction of both applicable vesting requirements as described above, the Company will
deliver one Share for that RSU at the time of settlement, unless at the time of settlement the Board of Directors, in its sole discretion, determines that settlement shall, in whole or in part, be in the form of cash, based on the then Fair Market
Value of a Share. Settlement shall occur on or following the Vesting Date, but not later than two and one-half (2 1⁄2) months following the end of the year in
which the Vesting Date applicable to a RSU occurs (the last day of such two and one-half month period is referred to as the “Short Term Deferral End Date”). Notwithstanding the above, settlement of RSUs that become vested
RSUs upon (i) a Sale Event will be made in Shares, unless otherwise specified in the definitive agreement for such Sale Event, or (ii) an IPO shall occur on the earlier of (a) the 185th day
following the IPO Date or (b) the Short Term Deferral End Date.

 By signing below, you and the Company agree that the RSUs are granted under and governed by the terms and conditions of the
Company’s 2009 Stock Plan (the “Plan”) and the Restricted Stock Unit Agreement, both of which are attached to and made a part of this document. Capitalized terms not otherwise defined herein shall have the meaning set forth in
the Plan. You hereby acknowledge that the vesting of the RSUs pursuant to this Notice of Restricted Stock Unit Award is conditioned on the satisfaction of the Time-Based Requirement and the Liquidity Event
Requirement on or before the Expiration Date. You shall have no right with respect to the RSUs to the extent a Liquidity Event does not occur on or before the Expiration Date (regardless of the extent to which the Time-Based Requirement is
satisfied). 

 You further agree to accept by email all documents relating to the Company, the Plan or these RSUs and all other
documents that the Company is required to deliver to its security holders (including, without limitation, disclosures that may be required by the Securities and Exchange Commission). You also agree that the Company may deliver these documents by
posting them on a website maintained by the Company or by a third party under contract with the Company. If the Company posts these documents on a website, it will notify you by email. You acknowledge that you may incur costs in connection with
electronic delivery, including the cost of accessing the internet and printing fees, and that an interruption of internet access may interfere with your ability to access the documents. 

 

							
	PARTICIPANT:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

	Address for Mailing Stock Certificate:	 		 	Title:	 	  

				
	  
	 		 		 	
	  
	 		 		 	

 ACACIA COMMUNICATIONS, INC. 

2009 STOCK PLAN 

RESTRICTED STOCK UNIT AGREEMENT 

SECTION 1. GRANT OF RESTRICTED STOCK UNITS. 

(a) Grant. On the terms and conditions set forth in the Notice of Restricted Stock Unit Award and this Agreement, the Company grants to
you on the Date of Grant the number of RSUs set forth in the Notice of Restricted Stock Unit Award. Each RSU represents the right to receive one share of the Company’s Common Stock on the terms and conditions set forth in this Agreement. 

(b) Consideration. No payment is required for the RSUs that have been granted to you. 

(c) Nature of RSUs; No Rights As a Stockholder. The RSUs are mere bookkeeping entries and represent only the Company’s unfunded
and unsecured promise to issue Shares on a future date under specified conditions. As a holder of RSUs, you have no rights other than the rights of a general creditor of the Company. The RSUs carry neither voting rights nor rights to cash dividends.
You have no rights as a stockholder of the Company unless and until the RSUs vest and are settled pursuant to Section 4. 
 (d)
Stock Plan and Defined Terms. The RSUs are granted pursuant to the Plan, a copy of which you acknowledge having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 10 of this Agreement. 
 SECTION 2. VESTING. 

(a) Generally. The RSUs vest in accordance with the vesting schedule set forth in the Notice of Restricted Stock Unit Award. You will
receive a benefit with respect to a RSU only if both the Time-Based Requirement and the Liquidity Event Requirement are satisfied on or before the Expiration Date. The RSUs will not vest (in whole or in part) if only one (or if neither) of such
requirements is satisfied on or before the Expiration Date. 
 (b) Termination of Service. If your Service terminates for any reason,
all RSUs as to which the Time-Based Requirement has not been satisfied as of your termination date shall automatically terminate and be cancelled. You will not satisfy the Time-Based Requirement for any additional RSUs after your Service has
terminated, regardless of the reason for such termination. Upon such termination of Service, any RSUs as to which the Time-Based Requirement has been satisfied will (if the Liquidity Event Requirement has not yet been satisfied) remain outstanding
until the first to occur of: (A) the satisfaction of the Liquidity Event Requirement, (B) the Expiration Date or (C) the second anniversary of your Service termination date. In case of any dispute as to whether your Service has terminated, the Board
of Directors shall have sole discretion to determine whether such termination has occurred and the effective 

 
date of such termination. Notwithstanding the foregoing in this Section 2(b), if the Company is subject to a Change in Control prior to a termination of your Service, then the Time-Based
Requirement and Liquidity Event Requirement will be deemed satisfied as to all of the RSUs as of your termination date. 
 (c) Expiration
of RSUs. If the Liquidity Event Requirement is not satisfied on or before the Expiration Date, all RSUs (regardless of whether or not, or to the extent which, the Time-Based Requirement had been satisfied as to such RSUs) shall automatically
terminate upon such date. Upon a termination of one or more RSUs pursuant to this Section 2, you will have no further right with respect to such RSUs or the Shares previously allocated thereto. 

(d) Part-Time Employment and Leaves of Absence. If you commence working on a part-time basis, then the Company may adjust the
Time-Based Requirement set forth in the Notice of Restricted Stock Unit Award. If you go on a leave of absence, then the Company may adjust the Time-Based Requirement set forth in the Notice of Restricted Stock Unit Award in accordance with the
Company’s leave of absence policy or the terms of such leave. Except as provided in the preceding sentence, Service shall be deemed to continue for any purpose under this Agreement while you are on a bona fide leave of absence, if
(i) such leave was approved by the Company in writing and (ii) continued crediting of Service for such purpose is expressly required by the terms of such leave or by applicable law (as determined by the Company). Service shall be deemed to
terminate when such leave ends, unless you immediately return to active work. 
 SECTION 3. RESTRICTIONS APPLICABLE TO RSUS. 

(a) Restrictions on Transfer. Except as otherwise provided in this Agreement, the RSUs and the rights and privileges conferred hereby
shall not be sold, assigned, transferred, pledged, hypothecated, or otherwise disposed of by you prior to the settlement of the RSUs. However, you may designate a third party who, in the event of your death, shall thereafter be entitled to receive
any distribution of Shares to which you were entitled at the time of your death pursuant to this Agreement by delivering a written beneficiary designation to the Company’s headquarters on the prescribed form. If you deliver no such beneficiary
designation or if your designated beneficiaries do not survive you, your estate will receive payments in respect of any vested RSUs. 
 (b)
Forfeiture of RSUs. In connection with the RSUs, the Company may be required to provide you with certain highly confidential information about the Company, including information regarding its financial condition and business prospects.
Unauthorized disclosure of such information is prohibited under your existing Proprietary Information and Inventions Agreement with the Company and under Company policy, and you may be required to sign an additional nondisclosure agreement prior to
receiving this type of information. In addition, unauthorized disclosure of the Company’s confidential information could result in the immediate forfeiture of the RSUs, including vested RSUs as well as termination of your Service with the
Company. 

  
 2 

 SECTION 4. SETTLEMENT OF RSUS. 

(a) Settlement Date. Upon a Vesting Date with respect to a particular RSU, the Company will deliver one Share for that RSU, unless at
the time of settlement the Board of Directors, in its sole discretion, determines that settlement shall, in whole or in part, be in the form of cash, based on the then-Fair Market Value of a Share. Settlement shall occur on or following the Vesting
Date, but not later than Short-Term Deferral End Date (as defined in the Notice of Restricted Stock Unit Grant). Notwithstanding the above, for RSUs that become vested upon a Sale Event, settlement will be made in Shares, unless otherwise
specified in the definitive agreement for such Sale Event, and for RSUs that become vested upon an IPO, settlement shall occur on the earlier of (i) the 185th day following the IPO Date or
(ii) the Short-Term Deferral End Date. 
 (b) Form of Delivery. The form of any delivery of Shares (e.g., a stock certificate or
electronic entry evidencing such shares) shall be determined by the Company. 
 (c) Legality of Issuance. No Shares shall be issued
to you upon settlement of the RSUs unless and until the Company has determined that (i) you and the Company have taken any actions required to register the Shares under the Securities Act or to perfect an exemption from the registration
requirements thereof; (ii) any applicable listing requirement of any stock exchange or other securities market on which stock is listed has been satisfied; and (iii) any other applicable provision of federal, State or foreign law has been
satisfied. The Company shall have no liability to issue Shares in respect of the RSUs unless it is able to do so in compliance with applicable law. 

SECTION 5. TAXES. 
 (a) Withholding
Taxes. Upon the Vesting Date and/or settlement date for the RSUs, the Fair Market Value of the Shares is treated as income subject to withholding by the Company and/or the Parent or Subsidiary employing you (your “Employer”) for
the payment of all applicable federal, State, local and foreign income and employment withholding taxes which arise in connection with the vesting or settlement of the RSUs (the “Withholding Taxes”). No consideration will be paid to
you in respect of this award unless you have made arrangements satisfactory to your Employer to satisfy the Withholding Taxes. To the extent that you fail to make such arrangements with respect to certain RSUs, then you will permanently forfeit such
RSUs. At the discretion of the Company, these arrangements may include (i) withholding from other compensation or amounts that are owed to you by your Employer, (ii) payment in cash, (iii) if the Stock is publicly traded, payment from
the proceeds of the sale of shares through a Company-approved broker, (iv) withholding a number of Shares that otherwise would be issued to you when the RSUs are settled with a Fair Market Value equal to the minimum statutory amount required to
be withheld, or (v) any other method permitted by the Company. However, if you are a Company officer subject to Section 16 of the Exchange Act, then the Withholding Taxes will be satisfied pursuant to clause (iv) of the preceding
sentence, unless otherwise determined in advance by the Board of Directors. If the Withholding Taxes are satisfied pursuant to clause (iv), you will be deemed to have been issued the full number of Shares subject to the RSUs and the Fair Market
Value of the withheld Shares, determined as of the date when taxes otherwise would have been 

  
 3 

 
withheld in cash, will be applied to the Withholding Taxes and such amount will be remitted to appropriate tax authorities by the Company or your Employer. The Company will not withhold
fractional shares pursuant to clause (iv), so if the Withholding Taxes are satisfied pursuant to clause (iv), you hereby authorize the Company or your Employer to withhold the amount of any remaining Withholding Taxes from your wages or other cash
compensation. 
 (b) Section 409A. The settlement of the RSUs is intended to be exempt from the application of Code
Section 409A pursuant to the “short-term deferral exemption” in Treasury Regulation 1.409A-1(b)(4) and shall be administered and interpreted in a manner that complies with such exemption. To the extent that any provision of this
Agreement is ambiguous as to its exemption from Code Section 409A, the provision shall be read in such a manner so that all payments hereunder are exempt from Code Section 409A. Notwithstanding the foregoing, if this award of RSUs is
interpreted as not being exempt from Code Section 409A, it shall be interpreted to comply with the requirement of Code Section 409A so that this award is not subject to additional tax or interest under Code Section 409A. In this
regard, if this award is payable upon your “separation from service” within the meaning of Code Section 409A(a)(2)(A)(i) (a “Separation”) and you are a “specified employee” of the Company or any affiliate
thereof within the meaning of Code Section 409A(a)(2)(B)(i) on the day of your Separation, then no such payment shall be made prior to the date that is the earlier of (i) six months and one day after your Separation, or (ii) your
death, but only to the extent such delay is necessary so that this award is not subject to additional tax or interest under Code Section 409A. 

(c) Acknowledgements. You acknowledge that there will be tax consequences upon vesting and/or settlement of the RSUs and/or disposition
of the Shares, if any, received hereunder, and you should consult a tax advisor regarding your tax obligations prior to such event. You acknowledge that the Company is not providing any tax, legal, or financial advice, nor is the Company making any
recommendations regarding your participation in the Plan or acquisition or sale of Shares subject to this award. You are hereby advised to consult with your own personal tax, legal, and financial advisors regarding your participation in the Plan.
You further acknowledge that the Company (i) makes no representations or undertakings regarding the tax treatment of the award of RSUs, including, but not limited to the grant, vesting, or settlement of the RSUs, the subsequent sale of Shares
acquired pursuant to such RSUs, and the receipt of any dividends; and (ii) does not commit to and is under no obligation to structure the terms of the grant of the RSUs to reduce or eliminate your tax liability or achieve any particular tax
result. You agree that the Company does not have a duty to design or administer the RSUs, the Plan or its other compensation programs in a manner that minimizes your tax liability. You shall not make any claim against the Company or its Board of
Directors, officers, or employees related to tax matters arising from this award or your other compensation. 
 SECTION 6. RIGHT OF FIRST REFUSAL.

 (a) Right of First Refusal. In the event that you propose to sell, pledge or otherwise transfer to a third party any Shares
acquired under this Agreement, or any interest in such Shares, the Company shall have the Right of First Refusal with respect to all (and not less than all) of such Shares. If you desire to transfer Shares acquired under this Agreement, you must
give a written Transfer Notice to the Company describing fully the proposed transfer, 

  
 4 

 
including the number of Shares proposed to be transferred, the proposed transfer price, the name and address of the proposed Transferee and proof satisfactory to the Company that the proposed
sale or transfer will not violate any applicable federal, State or foreign securities laws. The Transfer Notice shall be signed both by you and by the proposed Transferee and must constitute a binding commitment of both parties to the transfer of
the Shares. The Company shall have the right to purchase all, and not less than all, of the Shares on the terms of the proposal described in the Transfer Notice (subject, however, to any change in such terms permitted under Section 6(b) below)
by delivery of a notice of exercise of the Right of First Refusal within 30 days after the date when the Transfer Notice was received by the Company. 

(b) Transfer of Shares. If the Company fails to exercise its Right of First Refusal within 30 days after the date when it received
the Transfer Notice, you may, not later than 90 days following receipt of the Transfer Notice by the Company, conclude a transfer of the Shares subject to the Transfer Notice on the terms and conditions described in the Transfer Notice,
provided that any such sale is made in compliance with applicable federal, State and foreign securities laws and not in violation of any other contractual restrictions to which you are bound. Any proposed transfer on terms and conditions different
from those described in the Transfer Notice, as well as any subsequent proposed transfer by you, shall again be subject to the Right of First Refusal and shall require compliance with the procedure described in Section 6(a) above. If the
Company exercises its Right of First Refusal, the parties shall consummate the sale of the Shares on the terms set forth in the Transfer Notice within 60 days after the date when the Company received the Transfer Notice (or within such longer
period as may have been specified in the Transfer Notice); provided, however, that in the event the Transfer Notice provided that payment for the Shares was to be made in a form other than cash or cash equivalents paid at the time of transfer, the
Company shall have the option of paying for the Shares with cash or cash equivalents equal to the present value of the consideration described in the Transfer Notice. 

(c) Additional or Exchanged Securities and Property. In the event of a merger or consolidation of the Company with or into another
entity, any other corporate reorganization, a stock split, the declaration of a stock dividend, the declaration of an extraordinary dividend payable in a form other than stock, a spin-off, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities, any securities or other property (including cash or cash equivalents) that are by reason of such transaction exchanged for, or
distributed with respect to, any Shares subject to this Section 6 shall immediately be subject to the Right of First Refusal. Appropriate adjustments to reflect the exchange or distribution of such securities or property shall be made to the
number and/or class of the Shares subject to this Section 6. 
 (d) Termination of Right of First Refusal. Any other provision
of this Section 6 notwithstanding, in the event that the Stock is readily tradable on an established securities market when you desire to transfer Shares, the Company shall have no Right of First Refusal, and you shall have no obligation to
comply with the procedures prescribed by Sections 6(a) and 6(b) above. 
 (e) Permitted Transfers. This Section 6 shall not
apply to (i) a transfer by beneficiary designation, will or intestate succession or (ii) a transfer to one or more members of 

  
 5 

 
the your Immediate Family or to a trust established by you for the benefit of you and/or one or more members of your Immediate Family, provided in either case that the Transferee agrees in
writing on a form prescribed by the Company to be bound by all provisions of this Agreement. If you transfer any Shares acquired under this Agreement, either under this Section 6(e) or after the Company has failed to exercise the Right of First
Refusal, then this Agreement shall apply to the Transferee to the same extent as to you. 
 (f) Termination of Rights as Stockholder.
If the Company makes available, at the time and place and in the amount and form provided in this Agreement, the consideration for the Shares to be purchased in accordance with this Section 6, then after such time the person from whom such
Shares are to be purchased shall no longer have any rights as a holder of such Shares (other than the right to receive payment of such consideration in accordance with this Agreement). Such Shares shall be deemed to have been purchased in accordance
with the applicable provisions hereof, whether or not the certificate(s) therefor have been delivered as required by this Agreement. 
 (g)
Assignment of Right of First Refusal. The Board of Directors may freely assign the Company’s Right of First Refusal, in whole or in part. Any person who accepts an assignment of the Right of First Refusal from the Company shall assume
all of the Company’s rights and obligations under this Section 6. 
 SECTION 7. RESTRICTIONS APPLICABLE TO SHARES. 

(a) Securities Law Restrictions. Regardless of whether the offering and sale of Shares under the Plan have been registered under the
Securities Act or have been registered or qualified under the securities laws of any State, the Company, at its discretion, may impose restrictions upon the sale, pledge or other transfer of the Shares (including the placement of appropriate legends
on stock certificates or the imposition of stop-transfer instructions) if, in the judgment of the Company, such restrictions are necessary or desirable in order to achieve compliance with the Securities Act,
the securities laws of any State or any other law. You (or the beneficiary or your personal representative in the event of your death or incapacity, as the case may be) shall deliver to the Company any representations or other documents or
assurances as the Company may deem necessary or reasonably desirable to ensure compliance with all applicable legal and regulatory requirements. 

(b) Market Stand-Off. In connection with any underwritten public offering by the Company of its equity securities pursuant to an
effective registration statement filed under the Securities Act, including the Company’s initial public offering, you or a Transferee shall not directly or indirectly sell, make any short sale of, loan, hypothecate, pledge, offer, grant or sell
any option or other contract for the purchase of, purchase any option or other contract for the sale of, or otherwise dispose of or transfer, or agree to engage in any of the foregoing transactions with respect to, any Shares acquired under this
Agreement without the prior written consent of the Company or its managing underwriter. Such restriction (the “Market Stand-Off”) shall be in effect for such period of time following the date of the final prospectus for the offering
as may be requested by the 

  
 6 

 
Company or such underwriter. In no event, however, shall such period exceed 180 days plus such additional period as may reasonably be requested by the Company or such underwriter to accommodate
regulatory restrictions on (i) the publication or other distribution of research reports or (ii) analyst recommendations and opinions, including (without limitation) the restrictions set forth in Rule 2711(f)(4) of the National
Association of Securities Dealers and Rule 472(f)(4) of the New York Stock Exchange, as amended, or any similar successor rules. The Market Stand-Off shall in any event terminate two years after the date of the Company’s initial public
offering. In the event of the declaration of a stock dividend, a spin-off, a stock split, an adjustment in conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding
securities without receipt of consideration, any new, substituted or additional securities which are by reason of such transaction distributed with respect to any Shares subject to the Market Stand-Off, or into which such Shares thereby become
convertible, shall immediately be subject to the Market Stand-Off. In order to enforce the Market Stand-Off, the Company may impose stop-transfer instructions with respect to the Shares acquired under this Agreement until the end of the applicable
stand-off period. The Company’s underwriters shall be beneficiaries of the agreement set forth in this Section 7(b). This Section 7(b) shall not apply to Shares registered in the public offering under the Securities Act. 

(c) Investment Intent at Grant. You represent and agree that the Shares to be acquired upon settlement of the RSUs will be acquired for
investment, and not with a view to the sale or distribution thereof. 
 (d) Investment Intent at Settlement. In the event that the
sale of Shares under the Plan is not registered under the Securities Act but an exemption is available that requires an investment representation or other representation, you shall represent and agree at the time of issuance that the Shares being
acquired upon settlement of the RSUs are being acquired for investment, and not with a view to the sale or distribution thereof, and shall make such other representations as are deemed necessary or appropriate by the Company and its counsel. 

(e) Rights of the Company. The Company shall not be required to (i) transfer on its books any Shares that have been sold or
transferred in contravention of this Agreement or (ii) treat as the owner of Shares, or otherwise to accord voting, dividend or liquidation rights to, any Transferee to whom the Shares have been transferred in contravention of this Agreement.

 (f) Legends. All certificates evidencing the Shares issued under this Agreement shall bear the following legend: 

“THE SHARES REPRESENTED HEREBY MAY NOT BE SOLD, ASSIGNED, TRANSFERRED, ENCUMBERED OR IN ANY MANNER DISPOSED OF, EXCEPT IN COMPLIANCE WITH
THE TERMS OF A WRITTEN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER OF THE SHARES (OR THE PREDECESSOR IN INTEREST TO THE SHARES). SUCH AGREEMENT GRANTS TO THE COMPANY CERTAIN RIGHTS OF FIRST REFUSAL UPON AN ATTEMPTED TRANSFER OF THE
SHARES. THE SECRETARY OF THE COMPANY WILL UPON WRITTEN REQUEST FURNISH A COPY OF SUCH AGREEMENT TO THE HOLDER HEREOF WITHOUT CHARGE.” 

  
 7 

 All certificates evidencing Shares issued under this Agreement in an unregistered transaction shall bear the
following legend (and such other restrictive legends as are required or deemed advisable under the provisions of any applicable law): 

“THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR
OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.” 

If required by the authorities of any State in connection with the issuance of the Shares, the legend or legends required by such State authorities shall also
be endorsed on all such certificates. 
 (g) Removal of Legends. If, in the opinion of the Company and its counsel, any legend placed
on a stock certificate representing Shares issued under this Agreement is no longer required, the holder of such certificate shall be entitled to exchange such certificate for a certificate representing the same number of Shares but without such
legend. 
 (h) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth in
this Section 7 shall be conclusive and binding on you and all other persons. 
 SECTION 8. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 9(a) of the Plan, the terms of the RSUs (including, without limitation, the number
and kind of shares subject to these RSUs) shall be subject to Section 9(a) of the Plan. In the event that the Company is party to certain corporate transactions, the RSUs shall be subject to Section 9(b) of the Plan, provided that any
action taken must either preserve the exemption of the RSUs from Code Section 409A or comply with Code Section 409A. Any additional RSUs and any new, substituted or additional shares, cash or other property that become subject to this
award as a result of any such transaction shall be subject to the same conditions and restrictions as applicable to the RSUs to which they relate. 

SECTION 9. MISCELLANEOUS PROVISIONS. 
 (a)
Successors and Assigns. Except as otherwise expressly provided to the contrary, the provisions of this Agreement shall inure to the benefit of, and be binding upon, the Company and its successors and assigns and be binding upon you and your
legal representatives, heirs, legatees, distributees, assigns and transferees by operation of law, whether or not any such person has become a party to this Agreement or has agreed in writing to join herein and to be bound by the terms, conditions
and restrictions hereof. 
 (b) No Retention Rights. Nothing in this Agreement or in the Plan shall confer upon you the right to
remain in Service in any capacity or for any period of specific duration or interfere with or otherwise restrict in any way the rights of the Company (or any Parent or Subsidiary employing or retaining you) or you, which rights are hereby expressly
reserved by each, to terminate your Service at any time and for any reason, with or without cause. 

  
 8 

 (c) Notice. Any notice required by the terms of this Agreement shall be
given in writing. It shall be deemed effective upon (i) personal delivery, (ii) deposit with the United States Postal Service, by registered or certified mail, with postage and fees prepaid or (iii) deposit with a reputable
overnight courier, with shipping charges prepaid. Notice shall be addressed to the Company at its principal executive office and to you at the address that you most recently provided to the Company in accordance with this Section 9(c).

 (d) Effect on Other Employee Benefit Plans. The value of the RSUs and the Shares issuable thereunder shall not be included as
compensation, earnings, salaries, or other similar terms used when calculating benefits under any employee benefit plan (other than the Plan) sponsored by the Company or a Parent or Subsidiary, except as such plans otherwise expressly provide. 

(e) Entire Agreement. The Notice of Restricted Stock Unit Award, this Agreement and the Plan constitute the entire understanding
between you and the Company regarding the subject matter hereof. They supersede any other agreements, representations or understandings (whether oral or written and whether express or implied) that relate to the subject matter hereof. 

(f) Choice of Law. This Agreement shall be governed by, and construed in accordance with, the laws of the State of Delaware, as such
laws are applied to contracts entered into and performed in such State. 
 SECTION 10. DEFINITIONS. 

(a) “Agreement” shall mean this Restricted Stock Unit Agreement. 

(b) “Board of Directors” shall mean the Board of Directors of the Company, as constituted from time to time or, if a
Committee has been appointed, such Committee. 
 (c) “Change in Control” shall mean (i) the consummation of a merger
or consolidation of the Company with or into another entity, (ii) the acquisition of all or a majority of the outstanding voting stock of the Company in a single transaction or series of related transactions by a person or group of persons or
(iii) the sale, transfer or other disposition of all or substantially all of the Company’s assets. The foregoing notwithstanding, a merger or consolidation of the Company shall not constitute a “Change in Control” if immediately
after such merger or consolidation a majority of the voting power of the capital stock of the continuing or surviving entity, or any direct or indirect parent corporation of such continuing or surviving entity, will be owned by persons who were the
Company’s stockholders immediately prior to such merger or consolidation in substantially the same proportions as their ownership of the voting power of the Company’s capital stock immediately prior to such merger or consolidation. For the
avoidance of doubt, an IPO, any subsequent public offering and another capital raising event shall not constitute a “Change in Control.” 

  
 9 

 (d) “Code” shall mean the Internal Revenue Code of 1986, as amended. 

(e) “Committee” shall mean a committee of the Board of Directors, as described in Section 2 of the Plan. 

(f) “Company” shall mean Acacia Communications, Inc., a Delaware corporation. 

(g) “Consultant” shall mean a person who performs bona fide services for the Company, a Parent or a Subsidiary as a
consultant or advisor, excluding Employees and Outside Directors. 
 (h) “Date of Grant” shall mean the date specified in
the Notice of Restricted Stock Unit Award. 
 (i) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (j) “Exchange Act” shall
mean the Securities Exchange Act of 1934, as amended. 
 (k) “Expiration Date” shall mean the expiration date of the RSUs
as set forth in the Notice of Restricted Stock Unit Award. 
 (l) “Fair Market Value” shall mean the fair market value of a
Share, as determined by the Board of Directors in good faith. Such determination shall be conclusive and binding on all persons. 
 (m)
“Immediate Family” shall mean any child, stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling, mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law or sister-in-law and shall include adoptive
relationships. 
 (n) “IPO” shall mean the first firm commitment underwritten public offering pursuant to an effective
registration statement on an established national or foreign securities exchange covering the offer and sale by the Company of its equity securities, as a result of or following which the Shares shall be publicly held, and “IPO
Date” shall mean the date on which the IPO occurs. 
 (o) “Liquidity Event Requirement” shall mean the requirement
that the Company complete an IPO or Sale Event. 
 (p) “Outside Director” shall mean a member of the Board of Directors who
is not an Employee. 

  
 10 

 (q) “Parent” shall mean any corporation (other than the Company) in an unbroken
chain of corporations ending with the Company, if each of the corporations other than the Company owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. A
corporation that attains the status of a Parent on a date after the adoption of the Plan shall be considered a Parent commencing as of such date. 

(r) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as amended from time to time. 

(s) “Right of First Refusal” shall mean the Company’s right of first refusal described in Section 6. 

(t) “RSUs” shall mean the Restricted Stock Units granted to you by the Company as set forth in the Notice of Restricted Stock
Unit Award. 
 (u) “Sale Event” means the consummation of the following transactions in which holders of Shares receive
cash or marketable securities tradable on an established national or foreign securities exchange: (i) a sale of all or substantially all of the assets of the Company determined on a consolidated basis to an unrelated person or entity;
(ii) a merger, reorganization, or consolidation involving the Company in which the shares of voting stock of the Company outstanding immediately prior to such transaction represent or are converted into or exchanged for securities of the
surviving or resulting entity immediately upon completion of such transaction which represent less than 50% of the outstanding voting power of such surviving or resulting entity; or (iii) the acquisition of all or a majority of the outstanding
voting stock of the Company in a single transaction or series of related transactions by a person or group of persons. For the avoidance of doubt, an IPO, any subsequent public offering, another capital raising event, and a merger effected solely to
change the Company’s domicile shall not constitute a “Sale Event.” In addition, a transaction shall not constitute a Sale Event unless such transaction also qualifies as an event under Treasury Regulation
Section 1.409A-3(i)(5)(v) (change in the ownership of a corporation), Treasury Regulation Section 1.409A-3(i)(5)(vi) (change in the effective control of a corporation), or Treasury Regulation Section 1.409A-3(i)(5)(vii) (change in the
ownership of a substantial portion of a corporation’s assets). 
 (v) “Securities Act” shall mean the Securities Act
of 1933, as amended. 
 (w) “Service” shall mean service as an Employee, Consultant or Outside Director. 

(x) “Share” shall mean one share of Stock, as adjusted in accordance with Section 9 of the Plan (if applicable). 

(y) “Stock” shall mean the Common Stock of the Company. 

(z) “Subsidiary” shall mean any corporation entity (other than the Company) in an unbroken chain or corporations beginning
with the Company, if each of the corporations other than the last corporation in the unbroken chain owns stock possessing 50% or more of the 

  
 11 

 
total combined voting power of all classes of stock in one of the other corporations in such chain. A corporation that attains the status of a Subsidiary on a date after the adoption of the Plan
shall be considered a Subsidiary commencing as of such date. 
 (aa) “Time-Based Requirement” shall mean the requirement to
provide Service over the period of time set forth in the Notice of Restricted Stock Unit Award. 
 (bb) “Transferee” shall
mean any person to whom you have directly or indirectly transferred any Shares acquired under this Agreement. 
 (cc) “Transfer
Notice” shall mean the notice of a proposed transfer of Shares described in Section 6. 
 (dd) “Vesting Date”
shall mean the first date on or before the Expiration Date upon which both the Time-Based Requirement and the Liquidity Event Requirement are satisfied. 

  
 12EX-10.5

 Exhibit 10.5 

ACACIA COMMUNICATIONS, INC. 2009 STOCK PLAN: 

SUMMARY OF STOCK GRANT (FOR SERVICES) 

The Transferee is acquiring shares of the Common Stock of Acacia Communications, Inc. on the following terms: 

 

			
	Name of Transferee:	  	«Name»
		
	Total Number of Transferred Shares:	  	«TotalShares»
		
	Date of Transfer:	  	«DateTransfer»
		
	Vesting Commencement Date:	  	«VestComDate»
		
	Vesting Schedule:	  	The Forfeiture Condition shall lapse with respect to 1/60 of the Transferred Shares when the Transferee completes each month of continuous Service after the Vesting Commencement Date set forth above. The Forfeiture Condition may
lapse on an accelerated basis under Section 2(b) of the Stock Grant Agreement.

 By signing below, the Transferee and the Company agree that the acquisition of the Transferred Shares is governed by the terms
and conditions of the 2009 Stock Plan and the Stock Grant Agreement. Both of these documents are attached to, and made a part of, this Summary of Stock Grant. The Transferee agrees to accept by email all documents relating to the Company, the Plan
or this grant and all other documents that the Company is required to deliver to its security holders (including, without limitation, disclosures that may be required by the Securities and Exchange Commission). The Transferee also agrees that the
Company may deliver these documents by posting them on a website maintained by the Company or by a third party under contract with the Company. If the Company posts these documents on a website, it shall notify the Transferee by email of their
availability. The Transferee acknowledges that he or she may incur costs in connection with electronic delivery, including the cost of accessing the internet and printing fees, and that an interruption of internet access may interfere with his or
her ability to access the documents. This consent shall remain in effect until the Transferee gives the Company written notice that it should deliver paper documents. 
  

							
	TRANSFEREE:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

	Address for Mailing Stock Certificate:	 		 	Title:	 	  

				
	  
	 		 		 	
	  
	 		 		 	

 ACACIA COMMUNICATIONS, INC. 2009
STOCK PLAN: 
 STOCK GRANT AGREEMENT (FOR
SERVICES) 
 SECTION 1. ACQUISITION OF SHARES. 

(a) Transfer. On the terms and conditions set forth in the Summary of Stock Grant and this Agreement, the Company agrees to transfer to
the Transferee the number of Shares set forth in the Summary of Stock Grant. The transfer shall occur at the offices of the Company on the date of transfer set forth in the Summary of Stock Grant or at such other place and time as the parties may
agree. 
 (b) Consideration. The Transferee and the Company agree that the Transferred Shares are being issued to the Transferee as
consideration for a portion of the services performed by the Transferee for the Company. The value of such portion is agreed to be not less than 100% of the Fair Market Value of the Transferred Shares. 

(c) Stock Plan and Defined Terms. The transfer of the Transferred Shares is subject to the Plan, a copy of which the Transferee
acknowledges having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in Section 12 of this Agreement. 

SECTION 2. FORFEITURE CONDITION. 
 (a)
Scope of Forfeiture Condition. All Transferred Shares initially shall be Restricted Shares and shall be subject to forfeiture to the Company. The Transferee shall not transfer, assign, encumber or otherwise dispose of any Restricted Shares
without the Company’s written consent, except as provided in the following sentence. The Transferee may transfer Restricted Shares to one or more members of the Transferee’s Immediate Family or to a trust established by the Transferee for
the benefit of the Transferee and/or one or more members of the Transferee’s Immediate Family, provided in either case that the Transferee agrees in writing on a form prescribed by the Company to be bound by all provisions of this Agreement. If
the Transferee transfers any Restricted Shares, then this Agreement shall apply to the Subsequent Transferee to the same extent as to the Transferee. 

(b) Vesting. The Forfeiture Condition shall lapse and the Restricted Shares shall become vested in accordance with the vesting schedule
set forth in the Summary of Stock Grant. In addition, (i) if the Company is subject to a Change in Control before the Transferee’s Service terminates, then at all times after the Change in Control the portion of the Shares that are
Restricted Shares and subject to the Forfeiture Condition shall be determined by adding six (6) months to the Transferee’s actual Service; and (ii) if the Transferee is subject to an Involuntary Termination at any time following a
Change in Control then the Forfeiture Condition shall immediately lapse with respect to 100% of the then Restricted Shares. 

 (c) Execution of Forfeiture. The Forfeiture Condition shall be applicable only if the
Transferee’s Service terminates for any reason, with or without cause, including (without limitation) death or disability, before all Restricted Shares have become vested. In the event that the Transferee’s Service terminates for any
reason, the certificate(s) representing any remaining Restricted Shares shall be delivered to the Company. The Company shall make no payment for Restricted Shares that are forfeited. 

(d) Additional Shares or Substituted Securities. In the event of the declaration of a stock dividend, the declaration of an
extraordinary dividend payable in a form other than stock, a spin-off, a stock split, an adjustment in conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding
securities without receipt of consideration, any new, substituted or additional securities or other property (including money paid other than as an ordinary cash dividend) which are by reason of such transaction distributed with respect to any
Restricted Shares or into which such Restricted Shares thereby become convertible shall immediately be subject to the Forfeiture Condition. Appropriate adjustments to reflect the distribution of such securities or property shall be made to the
number and/or class of the Restricted Shares. 
 (e) Termination of Rights as Stockholder. If Restricted Shares are forfeited in
accordance with this Section 2, then the person who is to forfeit such Restricted Shares shall no longer have any rights as a holder of such Restricted Shares. Such Restricted Shares shall be deemed to have been forfeited in accordance with the
applicable provisions hereof, whether or not the certificate(s) therefor have been delivered as required by this Agreement. 
 (f)
Escrow. Upon issuance, the certificates for Restricted Shares shall be deposited in escrow with the Company to be held in accordance with the provisions of this Agreement. Any new, substituted or additional securities or other property
described in Subsection (d) above shall immediately be delivered to the Company to be held in escrow, but only to the extent the Transferred Shares are at the time Restricted Shares. All regular cash dividends on Restricted Shares (or other
securities at the time held in escrow) shall be paid directly to the Transferee and shall not be held in escrow. Restricted Shares, together with any other assets or securities held in escrow hereunder, shall be (i) surrendered to the Company
for forfeiture and cancellation in the event that the Forfeiture Condition or Right of First Refusal applies or (ii) released to the Transferee upon the Transferee’s request to the extent the Transferred Shares are no longer Restricted
Shares (but not more frequently than once every six months). In any event, all Transferred Shares that have vested (and any other vested assets and securities attributable thereto) shall be released within 60 days after the earlier of (i) the
termination of the Transferee’s Service or (ii) the lapse of the Right of First Refusal. 
 (g) Part-Time Employment and Leaves
of Absence. If the Transferee commences working on a part-time basis, then the Company may adjust the vesting schedule set forth in the Summary of Stock Grant. If the Transferee goes on a leave of absence, then the Company may adjust the vesting
schedule set forth in the Summary of Stock Grant in accordance with the Company’s leave of absence policy or the terms of such leave. Except as provided in the preceding sentence, Service shall be deemed to continue while the Transferee is on a
bona fide leave of absence, if (i) such leave was approved by the Company in writing and (ii) continued 

  
 2 

 
crediting of Service is expressly required by the terms of such leave or by applicable law (as determined by the Company). Service shall be deemed to terminate when such leave ends, unless the
Transferee immediately returns to active work. 
 SECTION 3. RIGHT OF FIRST REFUSAL. 

(a) Right of First Refusal. In the event that the Transferee proposes to sell, pledge or otherwise transfer to a third party any
Transferred Shares, or any interest in Transferred Shares, the Company shall have the Right of First Refusal with respect to all (and not less than all) of such Transferred Shares. If the Transferee desires to transfer Transferred Shares, the
Transferee shall give a written Transfer Notice to the Company describing fully the proposed transfer, including the number of Transferred Shares proposed to be transferred, the proposed transfer price, the name and address of the proposed
Subsequent Transferee and proof satisfactory to the Company that the proposed sale or transfer will not violate any applicable federal, State or foreign securities laws. The Transfer Notice shall be signed both by the Transferee and by the proposed
Subsequent Transferee and must constitute a binding commitment of both parties to the transfer of the Transferred Shares. The Company shall have the right to purchase all, and not less than all, of the Transferred Shares on the terms of the proposal
described in the Transfer Notice (subject, however, to any change in such terms permitted under Subsection (b) below) by delivery of a notice of exercise of the Right of First Refusal within 30 days after the date when the Transfer Notice was
received by the Company. 
 (b) Transfer of Shares. If the Company fails to exercise its Right of First Refusal within 30 days
after receiving the Transfer Notice, the Transferee may, not later than 90 days after the Company received the Transfer Notice, conclude a transfer of the Transferred Shares subject to the Transfer Notice on the terms and conditions described
in the Transfer Notice, provided that any such sale is made in compliance with applicable federal, State and foreign securities laws and not in violation of any other contractual restrictions to which the Transferee is bound. Any proposed transfer
on terms and conditions different from those described in the Transfer Notice, as well as any subsequent proposed transfer by the Transferee, shall again be subject to the Right of First Refusal and shall require compliance with the procedure
described in Subsection (a) above. If the Company exercises its Right of First Refusal, the parties shall consummate the sale of the Transferred Shares on the terms set forth in the Transfer Notice within 60 days after the Company received
the Transfer Notice (or within such longer period as may have been specified in the Transfer Notice); provided, however, that in the event the Transfer Notice provided that payment for the Transferred Shares was to be made in a form other than cash
or cash equivalents paid at the time of transfer, the Company shall have the option of paying for the Transferred Shares with cash or cash equivalents equal to the present value of the consideration described in the Transfer Notice. 

(c) Additional or Exchanged Securities and Property. In the event of a merger or consolidation of the Company with or into another
entity, any other corporate reorganization, a stock split, the declaration of a stock dividend, the declaration of an extraordinary dividend payable in a form other than stock, a spin-off, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities, any securities or other property (including cash or cash equivalents) that are by reason

  
 3 

 
of such transaction exchanged for, or distributed with respect to, any Transferred Shares subject to this Section 3 shall immediately be subject to the Right of First Refusal. Appropriate
adjustments to reflect the exchange or distribution of such securities or property shall be made to the number and/or class of the Transferred Shares subject to this Section 3. 

(d) Termination of Right of First Refusal. Any other provision of this Section 3 notwithstanding, in the event that the Stock is
readily tradable on an established securities market when the Transferee desires to transfer Transferred Shares, the Company shall have no Right of First Refusal, and the Transferee shall have no obligation to comply with the procedures prescribed
by Subsections (a) and (b) above. 
 (e) Permitted Transfers. This Section 3 shall not apply to (i) a transfer by
beneficiary designation, will or intestate succession or (ii) a transfer to one or more members of the Transferee’s Immediate Family or to a trust established by the Transferee for the benefit of the Transferee and/or one or more members
of the Transferee’s Immediate Family, provided in either case that the Transferee agrees in writing on a form prescribed by the Company to be bound by all provisions of this Agreement. If the Transferee transfers any Transferred Shares, either
under this Subsection (e) or after the Company has failed to exercise the Right of First Refusal, then this Agreement shall apply to the Subsequent Transferee to the same extent as to the Transferee. 

(f) Termination of Rights as Stockholder. If the Company makes available, at the time and place and in the amount and form provided in
this Agreement, the consideration for the Shares to be purchased in accordance with this Section 3, then after such time the person from whom such Shares are to be purchased shall no longer have any rights as a holder of such Shares (other than
the right to receive payment of such consideration in accordance with this Agreement). Such Shares shall be deemed to have been purchased in accordance with the applicable provisions hereof, whether or not the certificate(s) therefor have been
delivered as required by this Agreement. 
 (g) Assignment of Right of First Refusal. The Board of Directors may freely assign the
Company’s Right of First Refusal, in whole or in part. Any person who accepts an assignment of the Right of First Refusal from the Company shall assume all of the Company’s rights and obligations under this Section 3. 

SECTION 4. OTHER RESTRICTIONS ON TRANSFER. 

(a) Transferee Representations. In connection with the issuance and acquisition of Shares under this Agreement, the Transferee hereby
represents and warrants to the Company as follows: 
 (i) The Transferee is acquiring and will hold the Transferred Shares
for investment for his or her account only and not with a view to, or for resale in connection with, any “distribution” thereof within the meaning of the Securities Act. 

  
 4 

 (ii) The Transferee understands that the Transferred Shares have not been
registered under the Securities Act by reason of a specific exemption therefrom and that the Transferred Shares must be held indefinitely, unless they are subsequently registered under the Securities Act or the Transferee obtains an opinion of
counsel, in form and substance satisfactory to the Company and its counsel, that such registration is not required. The Transferee further acknowledges and understands that the Company is under no obligation to register the Transferred Shares. 

(iii) The Transferee is aware of the adoption of Rule 144 by the Securities and Exchange Commission under the Securities
Act, which permits limited public resales of securities acquired in a non-public offering, subject to the satisfaction of certain conditions, including (without limitation) the availability of certain current public information about the issuer, the
resale occurring only after the holding period required by Rule 144 has been satisfied, the sale occurring through an unsolicited “broker’s transaction,” and the amount of securities being sold during any three-month period not exceeding specified limitations. The Transferee acknowledges and understands that the conditions for resale set forth in Rule 144 have not been satisfied and that the Company has no plans
to satisfy these conditions in the foreseeable future. 
 (iv) The Transferee will not sell, transfer or otherwise dispose of
the Transferred Shares in violation of the Securities Act, the Securities Exchange Act of 1934, or the rules promulgated thereunder, including Rule 144 under the Securities Act. The Transferee agrees that he or she will not dispose of the
Transferred Shares unless and until he or she has complied with all requirements of this Agreement applicable to the disposition of Transferred Shares and he or she has provided the Company with written assurances, in substance and form satisfactory
to the Company, that (A) the proposed disposition does not require registration of the Transferred Shares under the Securities Act or all appropriate action necessary for compliance with the registration requirements of the Securities Act or
with any exemption from registration available under the Securities Act (including Rule 144) has been taken and (B) the proposed disposition will not result in the contravention of any transfer restrictions applicable to the Transferred
Shares under applicable state law. 
 (v) The Transferee has been furnished with, and has had access to, such information as
he or she considers necessary or appropriate for deciding whether to invest in the Transferred Shares, and the Transferee has had an opportunity to ask questions and receive answers from the Company regarding the terms and conditions of the issuance
of the Transferred Shares. 
 (vi) The Transferee is aware that his or her investment in the Company is a speculative
investment that has limited liquidity and is subject to the risk of complete loss. The Transferee is able, without impairing his or her financial condition, to hold the Transferred Shares for an indefinite period and to suffer a complete loss of his
or her investment in the Transferred Shares. 

  
 5 

 (b) Securities Law Restrictions. Regardless of whether the offering and sale of Shares
under the Plan have been registered under the Securities Act or have been registered or qualified under the securities laws of any State, the Company at its discretion may impose restrictions upon the sale, pledge or other transfer of the
Transferred Shares (including the placement of appropriate legends on stock certificates or the imposition of stop-transfer instructions) if, in the judgment of the Company, such restrictions are necessary or
desirable in order to achieve compliance with the Securities Act, the securities laws of any State or any other law. 
 (c) Market
Stand-Off. In connection with any underwritten public offering by the Company of its equity securities pursuant to an effective registration statement filed under the Securities Act, including the Company’s initial public offering, the
Transferee or a Subsequent Transferee shall not directly or indirectly sell, make any short sale of, loan, hypothecate, pledge, offer, grant or sell any option or other contract for the purchase of, purchase any option or other contract for the sale
of, or otherwise dispose of or transfer, or agree to engage in any of the foregoing transactions with respect to, any Transferred Shares without the prior written consent of the Company or its managing underwriter. Such restriction (the “Market
Stand-Off”) shall be in effect for such period of time following the date of the final prospectus for the offering as may be requested by the Company or such underwriter. In no event, however, shall such period exceed 180 days plus such
additional period as may reasonably be requested by the Company or such underwriter to accommodate regulatory restrictions on (i) the publication or other distribution of research reports or (ii) analyst recommendations and opinions,
including (without limitation) the restrictions set forth in Rule 2711(f)(4) of the National Association of Securities Dealers and Rule 472(f)(4) of the New York Stock Exchange, as amended, or any similar successor rules. The Market
Stand-Off shall in any event terminate two years after the date of the Company’s initial public offering. In the event of the declaration of a stock dividend, a spin-off, a stock split, an adjustment in
conversion ratio, a recapitalization or a similar transaction affecting the Company’s outstanding securities without receipt of consideration, any new, substituted or additional securities which are by reason of such transaction distributed
with respect to any Shares subject to the Market Stand-Off, or into which such Shares thereby become convertible, shall immediately be subject to the Market Stand-Off. In order to enforce the Market Stand-Off, the Company may impose stop-transfer
instructions with respect to the Transferred Shares until the end of the applicable stand-off period. The Company’s underwriters shall be beneficiaries of the agreement set forth in this Subsection (c). This Subsection (c) shall not
apply to Shares registered in the public offering under the Securities Act. 
 (d) Rights of the Company. The Company shall not be
required to (i) transfer on its books any Transferred Shares that have been sold or transferred in contravention of this Agreement or (ii) treat as the owner of Transferred Shares, or otherwise to accord voting, dividend or liquidation
rights to, any Subsequent Transferee to whom Transferred Shares have been transferred in contravention of this Agreement. 

  
 6 

 SECTION 5. SUCCESSORS AND ASSIGNS. 

Except as otherwise expressly provided to the contrary, the provisions of this Agreement shall inure to the benefit of, and be binding upon,
the Company and its successors and assigns and be binding upon the Transferee and the Transferee’s legal representatives, heirs, legatees, distributees, assigns and transferees by operation of law, whether or not any such person has become a
party to this Agreement or has agreed in writing to join herein and to be bound by the terms, conditions and restrictions hereof. 
 SECTION 6. NO
RETENTION RIGHTS. 
 Nothing in this Agreement or in the Plan shall confer upon the Transferee any right to continue providing services
to the Company for any period of specific duration or interfere with or otherwise restrict in any way the rights of the Company or of the Transferee, which rights are hereby expressly reserved by each, to terminate his or her service at any time and
for any reason, with or without cause. 
 SECTION 7. TAX ELECTION. 

The acquisition of the Transferred Shares may result in adverse tax consequences that may be avoided or mitigated by filing an election under
Code Section 83(b). Such election may be filed only within 30 days after the date of transfer set forth in the Summary of Stock Grant. The form for making the Code Section 83(b) election is attached to this Agreement as an Exhibit. The
Transferee should consult with his or her tax advisor to determine the tax consequences of acquiring the Transferred Shares and the advantages and disadvantages of filing the Code Section 83(b) election. The Transferee acknowledges that it is
his or her sole responsibility, and not the Company’s, to file a timely election under Code Section 83(b), even if the Transferee requests the Company or its representatives to make this filing on his or her behalf. 

SECTION 8. LEGENDS. 
 All certificates
evidencing Transferred Shares shall bear the following legends: 
 “THE SHARES REPRESENTED HEREBY MAY NOT BE SOLD, ASSIGNED,
TRANSFERRED, ENCUMBERED OR IN ANY MANNER DISPOSED OF, EXCEPT IN COMPLIANCE WITH THE TERMS OF A WRITTEN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED HOLDER OF THE SHARES (OR THE PREDECESSOR IN INTEREST TO THE SHARES). SUCH AGREEMENT GRANTS TO THE
COMPANY CERTAIN RIGHTS OF FIRST REFUSAL UPON AN ATTEMPTED TRANSFER OF THE SHARES AND IMPOSES CERTAIN FORFEITURE CONDITIONS UPON TERMINATION OF SERVICE WITH THE COMPANY. THE SECRETARY OF THE COMPANY WILL UPON WRITTEN REQUEST FURNISH A COPY OF SUCH
AGREEMENT TO THE HOLDER HEREOF WITHOUT CHARGE.” 

  
 7 

 “THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR AN OPINION OF COUNSEL, SATISFACTORY TO THE COMPANY AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.” 

If required by the authorities of any State in connection with the issuance of the Transferred Shares, the legend or legends required by such State
authorities shall also be endorsed on all such certificates. 
 SECTION 9. NOTICE. 

Any notice required by the terms of this Agreement shall be given in writing. It shall be deemed effective upon (i) personal delivery,
(ii) deposit with the United States Postal Service, by registered or certified mail, with postage and fees prepaid or (iii) deposit with Federal Express Corporation, with shipping charges prepaid. Notice shall be addressed to the Company
at its principal executive office and to the Transferee at the address that he or she most recently provided to the Company in accordance with this Section 9. 

SECTION 10. ENTIRE AGREEMENT. 
 The
Summary of Stock Grant, this Agreement and the Plan constitute the entire contract between the parties hereto with regard to the subject matter hereof. They supersede any other agreements, representations or understandings (whether oral or written
and whether express or implied) that relate to the subject matter hereof. 
 SECTION 11. CHOICE OF LAW. 

This Agreement shall be governed by, and construed in accordance with, the laws of the State of Delaware, as such laws are applied to contracts
entered into and performed in such State. 
 SECTION 12. DEFINITIONS. 

(a) “Agreement” shall mean this Stock Grant Agreement. 

(b) “Board of Directors” shall mean the Board of Directors of the Company, as constituted from time to time or, if a
Committee has been appointed, such Committee. 
 (c) “Cause” shall mean a good faith determination by the Board of
Directors of any of the following: 
 (i) An unauthorized use or disclosure by the Transferee of the Company’s
confidential information or trade secrets, which use or disclosure causes material harm to the Company; 

  
 8 

 (ii) A material breach by the Transferee of any material agreement between the
Transferee and the Company; 
 (iii) A material failure by the Transferee to comply with the Company’s written policies
or rules after receiving written notification of such failure from the Board of Directors; 
 (iv) The Transferee’s
conviction of, or plea of “guilty” or “no contest” to, a felony under the laws of the United States or any state thereof; 

(v) The Transferee’s gross negligence or willful misconduct in the course of performing Service; 

(vi) A continuing failure by the Transferee to perform reasonably assigned duties after receiving written notification of such
failure from the Board of Directors; or 
 (vii) A failure by the Transferee to cooperate in good faith with a governmental
or internal investigation of the Company or its directors, officers or employees, if the Company has requested the Transferee’s cooperation. 

(d) “Change in Control” shall mean (i) the consummation of a merger or consolidation of the Company with or into another
entity or (ii) the sale, transfer or other disposition of all or substantially all of the Company’s assets. The foregoing notwithstanding, a merger or consolidation of the Company shall not constitute a “Change in Control” if
immediately after such merger or consolidation a majority of the voting power of the capital stock of the continuing or surviving entity, or any direct or indirect parent corporation of such continuing or surviving entity, will be owned by persons
who were the Company’s stockholders immediately prior to such merger or consolidation in substantially the same proportions as their ownership of the voting power of the Company’s capital stock immediately prior to such merger or
consolidation. 
 (e) “Code” shall mean the Internal Revenue Code of 1986, as amended. 

(f) “Committee” shall mean (i) the consummation of a merger or consolidation of the Company with or into another entity
or (ii) the sale, transfer or other disposition of all or substantially all of the Company’s assets. The foregoing notwithstanding, a merger or consolidation of the Company shall not constitute a “Change in Control” if
immediately after such merger or consolidation a majority of the voting power of the capital stock of the continuing or surviving entity, or any direct or indirect parent corporation of such continuing or surviving entity, will be owned by persons
who were the Company’s stockholders immediately prior to such merger or consolidation in substantially the same proportions as their ownership of the voting power of the Company’s capital stock immediately prior to such merger or
consolidation. 
 (g) “Company” shall mean Acacia Communications, Inc., a Delaware corporation. 

  
 9 

 (h) “Consultant” shall mean a person who performs bona fide services for the
Company, a Parent or a Subsidiary as a consultant or advisor, excluding Employees and Outside Directors. 
 (i) “Employee”
shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 

(j) “Fair Market Value” shall mean the fair market value of a Share, as determined by the Board of Directors in good faith.
Such determination shall be conclusive and binding on all persons. 
 (k) “Forfeiture Condition” shall mean the forfeiture
condition described in Section 2. 
 (l) “Immediate Family” shall mean any child, stepchild, grandchild, parent,
stepparent, grandparent, spouse, sibling, mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law or sister-in-law and shall include adoptive relationships. 

(m) “Involuntary Termination” shall mean the termination of the Transferee’s Service by reason of: 

(i) The involuntary discharge of the Transferee by the Company (or the Parent or Subsidiary employing him) for reasons other
than Cause; or 
 (ii) The voluntary resignation of the Transferee following any of the following events, if such event
occurs without the consent of the Transferee: (A) a change in the Transferee’s position with the Company (or the Parent or Subsidiary employing him or her) that materially reduces his or her level of authority or responsibility (provided
that the Transferee’s level of authority or responsibility shall not be deemed to be reduced merely because there are additional employees more senior to the Transferee as a result of the Change in Control), (B) a reduction in the
Transferee’s base salary by more than 10%, unless such reduction is made in connection with a commensurate reduction in the compensation of employees of the Company generally, or (C) receipt of notice that the Transferee’s principal
workplace will be relocated more than 50 miles. 
 (n) “Outside Director” shall mean a member of the Board of Directors who
is not an Employee. 
 (o) “Parent” shall mean any corporation (other than the Company) in an unbroken chain of
corporations ending with the Company, if each of the corporations other than the Company owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain. 

(p) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as amended. 

  
 10 

 (q) “Restricted Share” shall mean a Transferred Share that is subject to the
Forfeiture Condition. 
 (r) “Right of First Refusal” shall mean the Company’s right of first refusal described in
Section 3. 
 (s) “Securities Act” shall mean the Securities Act of 1933, as amended. 

(t) “Service” shall mean service as an Employee, Outside Director or Consultant. 

(u) “Share” shall mean one share of Stock, as adjusted in accordance with Section 8 of the Plan (if applicable). 

(v) “Stock” shall mean the Common Stock of the Company. 

(w) “Subsequent Transferee” shall mean any person to whom the Transferee has directly or indirectly transferred any
Transferred Shares. 
 (x) “Subsidiary” shall mean any corporation (other than the Company) in an unbroken chain or
corporations beginning with the Company, if each of the corporations other than the last corporation in the unbroken chain owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations
in such chain. 
 (y) “Summary of Stock Grant” shall mean the document so entitled to which this Agreement is attached.

 (z) “Transferee” shall mean the individual named in the Summary of Stock Grant. 

(aa) “Transfer Notice” shall mean the notice of a proposed transfer of Transferred Shares described in Section 3. 

(bb) “Transferred Shares” shall mean the Shares acquired by the Transferee pursuant to this Agreement. 

  
 11 

 EXHIBIT I 

SECTION 83(b) ELECTION 

This statement is made under Section 83(b) of the Internal Revenue Code of 1986, as amended, pursuant to Treasury Regulations
Section 1.83-2. 
  

	 	(1)	The taxpayer who performed the services is: 

  

					
	Name:	 	  
	 	
			
	Address:	 	  
	 	
	  
	 	

							
				
	Social Security No.:	 	  
	 		 	

  

	 	(2)	The property with respect to which the election is made is             shares of the common stock of Acacia Communications, Inc. 

 

	 	(3)	The property was transferred on             ,     2013. 

 

	 	(4)	The taxable year for which the election is made is the calendar year 2013. 

  

	 	(5)	The property is subject to forfeiture if for any reason taxpayer’s service with the issuer terminates. The forfeiture condition lapses in a series of installments over a 5-year period ending on
            ,     2018. 

  

	 	(6)	The fair market value of such property at the time of transfer (determined without regard to any restriction other than a restriction that by its terms will never lapse) is
$        per share. 

  

	 	(7)	No amount was paid for such property. 

  

	 	(8)	A copy of this statement was furnished to Acacia Communications, Inc., for whom taxpayer rendered the services underlying the transfer of such property. 

 

	 	(9)	This statement is executed on             ,     2013. 

 

					
	  
 Spouse (if any)
	 		 	  
 Taxpayer

 Within 30 days after the date of transfer, this election must be filed with the Internal Revenue Service Center where
the Transferee files his or her federal income tax returns. The filing should be made by registered or certified mail, return receipt requested. The Transferee must (a) file a copy of the completed form with his or her federal tax return for
the current tax year and (b) deliver an additional copy to the Company.

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