Document:

EX-10.2

 Exhibit 10.2 

ACACIA COMMUNICATIONS, INC. 

2009 STOCK PLAN 

ADOPTED ON NOVEMBER 23, 2009 

AMENDED ON JUNE 29, 2010, DECEMBER 20,
2011, MARCH 5, 2012, 
 APRIL 17, 2013 AND APRIL 29,
2015 

 TABLE OF CONTENTS 

 

							
	 	 	 	  	Page	 
	 SECTION 1.
	 	 ESTABLISHMENT AND PURPOSE
	  	 	1	  
			
	 SECTION 2.
	 	 ADMINISTRATION
	  	 	1	  
	 (a)
	 	 Committees of the Board of Directors
	  	 	1	  
	 (b)
	 	 Authority of the Board of Directors
	  	 	1	  
			
	 SECTION 3.
	 	 ELIGIBILITY
	  	 	1	  
	 (a)
	 	 General Rule
	  	 	1	  
	 (b)
	 	 Ten-Percent Stockholders
	  	 	1	  
			
	 SECTION 4.
	 	 STOCK SUBJECT TO PLAN
	  	 	2	  
	 (a)
	 	 Basic Limitation
	  	 	2	  
	 (b)
	 	 Additional Shares
	  	 	2	  
			
	 SECTION 5.
	 	 TERMS AND CONDITIONS OF AWARDS OR SALES OF SHARES
	  	 	2	  
	 (a)
	 	 Stock Grant or Purchase Agreement
	  	 	2	  
	 (b)
	 	 Duration of Offers and Nontransferability of Rights
	  	 	2	  
	 (c)
	 	 Purchase Price
	  	 	2	  
	 (d)
	 	 Withholding Taxes
	  	 	3	  
	 (e)
	 	 Transfer Restrictions and Forfeiture Conditions
	  	 	3	  
			
	 SECTION 6.
	 	 TERMS AND CONDITIONS OF OPTIONS
	  	 	3	  
	 (a)
	 	 Stock Option Agreement
	  	 	3	  
	 (b)
	 	 Number of Shares
	  	 	3	  
	 (c)
	 	 Exercise Price
	  	 	3	  
	 (d)
	 	 Exercisability
	  	 	3	  
	 (e)
	 	 Basic Term
	  	 	3	  
	 (f)
	 	 Termination of Service (Except by Death)
	  	 	4	  
	 (g)
	 	 Leaves of Absence
	  	 	4	  
	 (h)
	 	 Death of Optionee
	  	 	4	  
	 (i)
	 	 Post-Exercise Restrictions on Transfer of Shares
	  	 	5	  
	 (j)
	 	 Pre-Exercise Restrictions on Transfer of Options or Shares
	  	 	5	  
	 (k)
	 	 Withholding Taxes
	  	 	5	  
	 (l)
	 	 No Rights as a Stockholder
	  	 	5	  
	 (m)
	 	 Modification, Extension and Assumption of Options
	  	 	5	  
	 (n)
	 	 Company’s Right to Cancel Certain Options
	  	 	5	  
			
	 SECTION 7.
	 	 PAYMENT FOR SHARES
	  	 	6	  
	 (a)
	 	 General Rule
	  	 	6	  
	 (b)
	 	 Services Rendered
	  	 	6	  
	 (c)
	 	 Promissory Note
	  	 	6	  
	 (d)
	 	 Surrender of Stock
	  	 	6	  
	 (e)
	 	 Exercise/Sale
	  	 	6	  
	 (f)
	 	 Other Forms of Payment
	  	 	6	  

  
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	 SECTION 8.
	 	 TERMS AND CONDITIONS OF RESTRICTED STOCK UNITS
	  	 	6	  
	 (a)
	 	 Restricted Stock Unit Agreement
	  	 	6	  
	 (b)
	 	 Payment for Restricted Stock Units
	  	 	7	  
	 (c)
	 	 Vesting Conditions
	  	 	7	  
	 (d)
	 	 Voting and Dividend Rights
	  	 	7	  
	 (e)
	 	 Form and Time of Settlement of Restricted Stock Units
	  	 	7	  
	 (f)
	 	 Modification, Extension and Assumption of Restricted Stock Units
	  	 	7	  
	 (g)
	 	 Forfeiture
	  	 	7	  
	 (h)
	 	 Death of Recipient
	  	 	8	  
	 (i)
	 	 Creditors’ Rights
	  	 	8	  
	 (j)
	 	 Transferability of Restricted Stock Units
	  	 	8	  
			
	 SECTION 9.
	 	 ADJUSTMENT OF SHARES
	  	 	8	  
	 (a)
	 	 General
	  	 	8	  
	 (b)
	 	 Mergers and Consolidations
	  	 	8	  
	 (c)
	 	 Reservation of Rights
	  	 	10	  
			
	 SECTION 10.
	 	 MISCELLANEOUS PROVISIONS
	  	 	10	  
	 (a)
	 	 Securities Law Requirements
	  	 	10	  
	 (b)
	 	 No Retention Rights
	  	 	10	  
	 (c)
	 	 Treatment as Compensation
	  	 	10	  
	 (d)
	 	 Governing Law
	  	 	10	  
	 (e)
	 	 Tax Matters
	  	 	10	  
			
	 SECTION 11.
	 	 DURATION AND AMENDMENTS
	  	 	11	  
	 (a)
	 	 Term of the Plan
	  	 	11	  
	 (b)
	 	 Right to Amend or Terminate the Plan
	  	 	11	  
	 (c)
	 	 Effect of Amendment or Termination
	  	 	12	  
			
	 SECTION 12.
	 	 DEFINITIONS
	  	 	12	  

  
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 ACACIA COMMUNICATIONS, INC. 2009
STOCK PLAN 
 SECTION 1. ESTABLISHMENT AND PURPOSE. 

The purpose of the Plan is to offer selected persons an opportunity to acquire a proprietary interest in the success of the Company, or to
increase such interest, by acquiring Shares of the Company’s Stock. The Plan provides for the direct award or sale of Shares, the grant of Options to purchase Shares and the grant of Restricted Stock Units. Options granted under the Plan may
include Nonstatutory Options as well as ISOs intended to qualify under Section 422 of the Code. 
 Capitalized terms are defined in
Section 12. 
 SECTION 2. ADMINISTRATION. 

(a) Committees of the Board of Directors. The Plan may be administered by one or more Committees. Each Committee shall consist of
one or more members of the Board of Directors who have been appointed by the Board of Directors. Each Committee shall have such authority and be responsible for such functions as the Board of Directors has assigned to it. If no Committee has been
appointed, the entire Board of Directors shall administer the Plan. Any reference to the Board of Directors in the Plan shall be construed as a reference to the Committee (if any) to whom the Board of Directors has assigned a particular function.

 (b) Authority of the Board of Directors. Subject to the provisions of the Plan, the Board of Directors shall
have full authority and discretion to take any actions it deems necessary or advisable for the administration of the Plan. All decisions, interpretations and other actions of the Board of Directors shall be final and binding on all Participants and
all persons deriving their rights from a Participant. 
 SECTION 3. ELIGIBILITY. 

(a) General Rule. Only Employees, Outside Directors and Consultants shall be eligible for the grant of Nonstatutory
Options, Restricted Stock Units or the direct award or sale of Shares. Only Employees shall be eligible for the grant of ISOs. 
 (b)
Ten-Percent Stockholders. A person who owns more than 10% of the total combined voting power of all classes of outstanding stock of the Company, its Parent or any of its Subsidiaries shall
not be eligible for the grant of an ISO unless (i) the Exercise Price is at least 110% of the Fair Market Value of a Share on the Date of Grant and (ii) such ISO by its terms is not exercisable after the expiration of five years from the
Date of Grant. For purposes of this Subsection (b), in determining stock ownership, the attribution rules of Section 424(d) of the Code shall be applied. 

 SECTION 4. STOCK SUBJECT TO PLAN. 

(a) Basic Limitation. Not more than 6,835,895 Shares may be issued under the Plan, subject to Subsection (b) below
and Section 9(a).1 All of these Shares may be issued upon the exercise of ISOs. Except as otherwise provided in Subsection (b) below, the number of Shares that were previously issued or
are subject to Awards outstanding at any time under the Plan shall not exceed the sum of (i) the number of Shares previously issued under the Plan and (ii) the number of Shares that then remain available for issuance under the Plan. The
Company, during the term of the Plan, shall at all times reserve and keep available sufficient Shares to satisfy the requirements of the Plan. Shares offered under the Plan may be authorized but unissued Shares or treasury Shares. 

(b) Additional Shares. In the event that Shares previously issued under the Plan are reacquired by the Company without
the payment of any consideration therefor in excess of the amount (if any) previously paid by the Participant to the Company in respect of such Shares, such Shares shall be added to the number of Shares then available for issuance under the Plan. In
the event that an outstanding Award for any reason expires or is canceled without the payment of any consideration therefor in excess of the amount (if any) previously paid by the Participant to the Company in respect of such Shares, the Shares
allocable to the unexercised or unvested portion of such Award, as applicable, shall be added to the number of Shares then available for issuance under the Plan. 

SECTION 5. TERMS AND CONDITIONS OF AWARDS OR SALES OF SHARES. 

(a) Stock Grant or Purchase Agreement. Each direct award of Shares under the Plan shall be evidenced by a Stock Grant Agreement between
the Grantee and the Company. Each sale of Shares under the Plan (other than upon exercise of an Option or settlement of Restricted Stock Units) shall be evidenced by a Stock Purchase Agreement between the Purchaser and the Company. Such award or
sale shall be subject to all applicable terms and conditions of the Plan and may be subject to any other terms and conditions which are not inconsistent with the Plan and which the Board of Directors deems appropriate for inclusion in a Stock Grant
Agreement or Stock Purchase Agreement. The provisions of the various Stock Grant Agreements and Stock Purchase Agreements entered into under the Plan need not be identical. 

(b) Duration of Offers and Nontransferability of Rights. Any right to purchase Shares under the Plan (other than an Option) shall
automatically expire if not exercised by the Purchaser within 30 days after the grant of such right was communicated to the Purchaser by the Company. Such right shall not be transferable and shall be exercisable only by the Purchaser to whom such
right was granted. 
 (c) Purchase Price. The Board of Directors shall determine the Purchase Price of Shares to be offered under the
Plan at its sole discretion. The Purchase Price shall be payable in a form described in Section 7. 
  

 

	1 	Please refer to Exhibit A for a schedule of the initial share reserve and any subsequent increases in the reserve. 

  
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 (d) Withholding Taxes. As a condition to the award, purchase, vesting or transfer of
Shares, the Grantee or Purchaser shall make such arrangements as the Board of Directors may require for the satisfaction of any federal, state, local or foreign withholding tax obligations that may arise in connection with such event. 

(e) Transfer Restrictions and Forfeiture Conditions. Any Shares awarded or sold under the Plan shall be subject to such special
forfeiture conditions, rights of repurchase, rights of first refusal and other transfer restrictions as the Board of Directors may determine. Such restrictions shall be set forth in the applicable Stock Grant Agreement or Stock Purchase Agreement
and shall apply in addition to any restrictions that may apply to holders of Shares generally. 
 SECTION 6. TERMS AND CONDITIONS OF OPTIONS.

 (a) Stock Option Agreement. Each grant of an Option under the Plan shall be evidenced by a Stock Option Agreement between the
Optionee and the Company. The Option shall be subject to all applicable terms and conditions of the Plan and may be subject to any other terms and conditions which are not inconsistent with the Plan and which the Board of Directors deems appropriate
for inclusion in a Stock Option Agreement. The provisions of the various Stock Option Agreements entered into under the Plan need not be identical. 

(b) Number of Shares. Each Stock Option Agreement shall specify the number of Shares that are subject to the Option and shall provide
for the adjustment of such number in accordance with Section 9. The Stock Option Agreement shall also specify whether the Option is an ISO or a Nonstatutory Option. 

(c) Exercise Price. Each Stock Option Agreement shall specify the Exercise Price. The Exercise Price of an Option shall not be less
than 100% of the Fair Market Value of a Share on the Date of Grant, and in the case of an ISO a higher percentage may be required by Section 3(b). Subject to the preceding sentence, the Exercise Price shall be determined by the Board of
Directors at its sole discretion. The Exercise Price shall be payable in a form described in Section 7. This Subsection (c) shall not apply to an Option granted pursuant to an assumption of, or substitution for, another option in a manner
that complies with Section 424(a) of the Code (whether or not the Option is an ISO). 
 (d) Exercisability. Each Stock Option
Agreement shall specify the date when all or any installment of the Option is to become exercisable. No Option shall be exercisable unless the Optionee (i) has delivered an executed copy of the Stock Option Agreement to the Company or
(ii) otherwise agrees to be bound by the terms of the Stock Option Agreement. The Board of Directors shall determine the exercisability provisions of the Stock Option Agreement at its sole discretion. All of an Optionee’s Options shall
become exercisable in full if Section 9(b)(iv) applies. 
 (e) Basic Term. The Stock Option Agreement shall specify the term of
the Option. The term shall not exceed 10 years from the Date of Grant, and in the case of an ISO a shorter term may be required by Section 3(b). Subject to the preceding sentence, the Board of Directors at its sole discretion shall determine
when an Option is to expire. 

  
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 (f) Termination of Service (Except by Death). If an Optionee’s Service terminates for
any reason other than the Optionee’s death, then the Optionee’s Options shall expire on the earliest of the following dates: 

(i) The expiration date determined pursuant to Subsection (e) above; 

(ii) The date three months after the termination of the Optionee’s Service for any reason other than Disability, or such
earlier or later date as the Board of Directors may determine (but in no event earlier than 30 days after the termination of the Optionee’s Service); or 

(iii) The date six months after the termination of the Optionee’s Service by reason of Disability, or such later date as
the Board of Directors may determine. 
 The Optionee may exercise all or part of the Optionee’s Options at any time before the expiration of such
Options under the preceding sentence, but only to the extent that such Options had become exercisable before the Optionee’s Service terminated (or became exercisable as a result of the termination) and the underlying Shares had vested before
the Optionee’s Service terminated (or vested as a result of the termination). The balance of such Options shall lapse when the Optionee’s Service terminates. In the event that the Optionee dies after the termination of the Optionee’s
Service but before the expiration of the Optionee’s Options, all or part of such Options may be exercised (prior to expiration) by the executors or administrators of the Optionee’s estate or by any person who has acquired such Options
directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that such Options had become exercisable before the Optionee’s Service terminated (or became exercisable as a result of the termination) and
the underlying Shares had vested before the Optionee’s Service terminated (or vested as a result of the termination). 
 (g) Leaves
of Absence. For purposes of Subsection (f) above, Service shall be deemed to continue while the Optionee is on a bona fide leave of absence, if such leave was approved by the Company in writing and if continued crediting of Service for this
purpose is expressly required by the terms of such leave or by applicable law (as determined by the Company). 
 (h) Death of
Optionee. If an Optionee dies while the Optionee is in Service, then the Optionee’s Options shall expire on the earlier of the following dates: 

(i) The expiration date determined pursuant to Subsection (e) above; or 

(ii) The date 12 months after the Optionee’s death, or such earlier or later date as the Board of Directors may determine
(but in no event earlier than six months after the Optionee’s death). 
 All or part of the Optionee’s Options may be exercised at any time before
the expiration of such Options under the preceding sentence by the executors or administrators of the Optionee’s estate 

  
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or by any person who has acquired such Options directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that such Options had become exercisable
before the Optionee’s death (or became exercisable as a result of the death) and the underlying Shares had vested before the Optionee’s death (or vested as a result of the Optionee’s death). The balance of such Options shall lapse
when the Optionee dies. 
 (i) Post-Exercise Restrictions on Transfer of Shares. Any Shares issued upon exercise of an Option shall
be subject to such special forfeiture conditions, rights of repurchase, rights of first refusal and other transfer restrictions as the Board of Directors may determine. Such restrictions shall be set forth in the applicable Stock Option Agreement
and shall apply in addition to any restrictions that may apply to holders of Shares generally. 
 (j) Pre-Exercise Restrictions on
Transfer of Options or Shares. An Option shall be transferable by the Optionee only by (i) a beneficiary designation, (ii) a will or (iii) the laws of descent and distribution, except as provided in the next sentence. If the
applicable Stock Option Agreement so provides, a Nonstatutory Option shall also be transferable by gift or domestic relations order to a Family Member of the Optionee. An ISO may be exercised during the lifetime of the Optionee only by the Optionee
or by the Optionee’s guardian or legal representative. 
 (k) Withholding Taxes. As a condition to the grant or exercise of an
Option, the Optionee shall make such arrangements as the Board of Directors may require for the satisfaction of any federal, state, local or foreign withholding tax obligations that may arise in connection with such grant or exercise. The Optionee
shall also make such arrangements as the Board of Directors may require for the satisfaction of any federal, state, local or foreign withholding tax obligations that may arise in connection with the vesting or transfer of Shares acquired by
exercising an Option or any similar event. 
 (l) No Rights as a Stockholder. An Optionee, or a transferee of an Optionee, shall have
no rights as a stockholder with respect to any Shares covered by the Optionee’s Option until such person becomes entitled to receive such Shares by filing a notice of exercise and paying the Exercise Price pursuant to the terms of such Option.

 (m) Modification, Extension and Assumption of Options. Within the limitations of the Plan, the Board of Directors may modify,
extend or assume outstanding Options or may accept the cancellation of outstanding Options (whether granted by the Company or another issuer) in return for the grant of new Options for the same or a different number of Shares and at the same or a
different Exercise Price. The foregoing notwithstanding, no modification of an Option shall, without the consent of the Optionee, impair the Optionee’s rights or increase the Optionee’s obligations under such Option. 

(n) Company’s Right to Cancel Certain Options. Any other provision of the Plan or a Stock Option Agreement notwithstanding, the
Company shall have the right at any time to cancel an Option that was not granted in compliance with Rule 701 under the Securities Act. Prior to canceling such Option, the Company shall give the Optionee not less than 30 days’ notice in
writing. If the Company elects to cancel such Option, it shall deliver to the Optionee consideration with an aggregate Fair Market Value equal to the excess of (i) the Fair Market 

  
 5 

 
Value of the Shares subject to such Option as of the time of the cancellation over (ii) the Exercise Price of such Option. The consideration may be delivered in the form of cash or cash
equivalents, in the form of Shares, or a combination of both. If the consideration would be a negative amount, such Option may be cancelled without the delivery of any consideration. 

SECTION 7. PAYMENT FOR SHARES. 

(a) General Rule. The entire Purchase Price or Exercise Price of Shares issued under the Plan shall be payable in cash or
cash equivalents at the time when such Shares are purchased, except as otherwise provided in this Section 7. 
 (b) Services
Rendered. At the discretion of the Board of Directors, Shares may be awarded under the Plan in consideration of services rendered to the Company, a Parent or a Subsidiary prior to the Award. 

(c) Promissory Note. At the discretion of the Board of Directors, all or a portion of the Purchase Price or Exercise
Price (as the case may be) of Shares issued under the Plan may be paid with a full-recourse promissory note. The Shares shall be pledged as security for payment of the principal amount of the promissory note and interest thereon. The interest rate
payable under the terms of the promissory note shall not be less than the minimum rate (if any) required to avoid the imputation of additional interest under the Code. Subject to the foregoing, the Board of Directors (at its sole discretion) shall
specify the term, interest rate, amortization requirements (if any) and other provisions of such note. 
 (d) Surrender of
Stock. At the discretion of the Board of Directors, all or any part of the Exercise Price may be paid by surrendering, or attesting to the ownership of, Shares that are already owned by the Optionee. Such Shares shall be
surrendered to the Company in good form for transfer and shall be valued at their Fair Market Value as of the date when the Option is exercised. 

(e) Exercise/Sale. To the extent that a Stock Option Agreement so provides, and if Stock is publicly traded, all or part
of the Exercise Price and any withholding taxes may be paid by the delivery (on a form prescribed by the Company) of an irrevocable direction to a securities broker approved by the Company to sell Shares and to deliver all or part of the sales
proceeds to the Company. 
 (f) Other Forms of Payment. To the extent that a Stock Purchase Agreement or Stock Option
Agreement so provides, the Purchase Price or Exercise Price of Shares issued under the Plan may be paid in any other form permitted by the Delaware General Corporation Law, as amended. 

SECTION 8. TERMS AND CONDITIONS OF RESTRICTED STOCK UNITS. 

(a) Restricted Stock Unit Agreement. Each grant of Restricted Stock Units under the Plan shall be evidenced by a Restricted Stock Unit
Agreement between the recipient and the Company. Restricted Stock Units granted under the Plan shall be subject to all applicable terms and conditions of the Plan and may be subject to any other terms and conditions

  
 6 

 
that are not inconsistent with the Plan and which the Board of Directors deems appropriate for inclusion in a Restricted Stock Unit Agreement. The provisions of the various Restricted Stock Unit
Agreements entered into under the Plan need not be identical. 
 (b) Payment for Restricted Stock Units. No cash consideration shall
be required of the recipient in connection with the grant of Restricted Stock Units. 
 (c) Vesting Conditions. Restricted Stock
Units may or may not be subject to vesting, as determined in the discretion of the Board of Directors. Vesting may occur, in full or in installments, upon the satisfaction of the vesting conditions specified in the Restricted Stock Unit Agreement,
which may include continued Service with the Company or a Parent or Subsidiary, achievement of performance goals and/or such other criteria as the Board of Directors may determine. A Restricted Stock Unit Agreement may provide for accelerated
vesting upon specified events. 
 (d) Voting and Dividend Rights. The recipient of Restricted Stock Units shall have no voting
rights. Prior to settlement or forfeiture, any Restricted Stock Unit granted under the Plan may, at the discretion of the Board of Directors, carry with it a right to dividend equivalents. Such right entitles the recipient to be credited with an
amount equal to all cash dividends paid on one Share for each Restricted Stock Unit held by the recipient at the time the cash dividend is paid. Dividend equivalents may be converted into additional Restricted Stock Units. Settlement of dividend
equivalents may be made in the form of cash, in the form of Shares, or in a combination of both. Prior to distribution, any dividend equivalents that are not paid shall be subject to the same conditions and restrictions as the Restricted Stock Units
to which they attach. 
 (e) Form and Time of Settlement of Restricted Stock Units. Settlement of vested Restricted Stock Units may
be made in the form of (i) cash, (ii) Shares or (iii) any combination of cash and Shares, as determined by the Board of Directors. The actual number of Restricted Stock Units eligible for settlement may be larger or smaller than the
number included in the original award, based on predetermined performance factors. Vested Restricted Stock Units shall be settled in such manner and at such time(s) as specified in the Restricted Stock Unit Agreement. Until Restricted Stock Units
are settled, the number of such Restricted Stock Units shall be subject to adjustment pursuant to Section 9. 
 (f) Modification,
Extension and Assumption of Restricted Stock Units. Within the limitations of the Plan, the Board of Directors may modify, extend or assume outstanding Restricted Stock Units. The foregoing notwithstanding, no modification of a Restricted Stock
Unit shall, without the consent of the Participant, impair the Participant’s rights or increase the Participant’s obligations under such Restricted Stock Unit. 

(g) Forfeiture. Unless a Restricted Stock Unit Agreement provides otherwise, upon termination of the Participant’s Service or upon
such other time specified in the Restricted Stock Unit Agreement, any unvested Restricted Stock Units shall be forfeited to the Company. For this purpose, Service shall be deemed to continue while the Participant is on a bona fide leave of absence,
if such leave was approved by the Company in writing and if continued crediting of Service for this purpose is expressly required by the terms of such leave or by applicable law (as determined by the Company). 

  
 7 

 (h) Death of Recipient. Any Restricted Stock Units that become distributable after the
recipient’s death shall be distributed to the recipient’s beneficiary or beneficiaries. Each recipient may designate one or more beneficiaries for this purpose by filing the prescribed form with the Company, and may thereafter change such
designation by filing the prescribed form with the Company at any time. If no beneficiary is designated or if no designated beneficiary survives the Participant, then any Restricted Stock Units that become payable after the Participant’s death
shall be distributed to his or her estate. 
 (i) Creditors’ Rights. A holder of Restricted Stock Units shall have no rights
other than those of a general creditor of the Company. Restricted Stock Units represent an unfunded and unsecured obligation of the Company, subject to the terms and conditions of the applicable Restricted Stock Unit Agreement. 

(j) Transferability of Restricted Stock Units. Restricted Stock Units shall be transferable by a Participant only by
(a) beneficiary designation, (b) a will or (c) the laws of descent and distribution. 
 SECTION 9. ADJUSTMENT OF SHARES. 

(a) General. In the event of a subdivision of the outstanding Stock, a declaration of a dividend payable in Shares, a
combination or consolidation of the outstanding Stock into a lesser number of Shares, a reclassification, or any other increase or decrease in the number of issued shares of Stock effected without receipt of consideration by the Company,
proportionate adjustments shall automatically be made in each of (i) the number of Shares available for future grants under Section 4, (ii) the number of Shares covered by each outstanding Option or Restricted Stock Unit and
(iii) the Exercise Price under each outstanding Option. In the event of a declaration of an extraordinary dividend payable in a form other than Shares in an amount that has a material effect on the Fair Market Value of the Stock, a
recapitalization, a spin-off, or a similar occurrence, the Board of Directors at its sole discretion may make appropriate adjustments in one or more of (i) the number of Shares available for future grants under Section 4, (ii) the
number of Shares covered by each outstanding Option or Restricted Stock Unit or (iii) the Exercise Price under each outstanding Option; provided, however, that the Board of Directors shall in any event make such adjustments as may be required
by Section 25102(o) of the California Corporations Code. 
 (b) Mergers and Consolidations. In the event that the
Company is a party to a merger or consolidation, all Shares acquired under the Plan and all Awards outstanding on the effective date of the transaction shall be treated in the manner described in the agreement of merger or consolidation, which need
not treat all Awards in an identical manner. The agreement of merger or consolidation shall provide for one or more of the following with respect to each Award: 

(i) The continuation of the outstanding Award by the Company (if the Company is the surviving corporation). 

  
 8 

 (ii) The assumption of the outstanding Award by the surviving corporation or its
parent, provided that the assumption of an Option shall be in a manner that complies with Section 424(a) of the Code (whether or not the Option is an ISO). 

(iii) The substitution by the surviving corporation or its parent of an equivalent award for the outstanding Award (including,
but not limited to, an award to acquire the same consideration paid to the holders of Shares in the transaction), provided that the substitution of an Option shall be in a manner that complies with Section 424(a) of the Code (whether or not the
Option is an ISO). 
 (iv) Full exercisability of the Option and full vesting of the Shares subject to the Option, followed
by the cancellation of the Option. The full exercisability of the Option and full vesting of the Shares subject to the Option may be contingent on the closing of such merger or consolidation. The Optionee shall be able to exercise the Option during
a period of not less than five full business days preceding the closing date of such merger or consolidation, unless (A) a shorter period is required to permit a timely closing of such merger or consolidation and (B) such shorter period
still offers the Optionee a reasonable opportunity to exercise the Option. Any exercise of the Option during such period may be contingent on the closing of such merger or consolidation. 

(v) The cancellation of the outstanding Award and a payment to the Participant with respect to each Share subject to the Award
(including both vested and unvested Shares) as of the merger or consolidation equal to the excess of (A) the Fair Market Value of a Share as of the closing date of such merger or consolidation over (if applicable) (B) the per-Share
Exercise Price of the Award (such excess, if any, the “Spread”). Such payment shall be made in the form of cash, cash equivalents, or securities of the surviving corporation or its parent with a Fair Market Value equal to the
Spread. Subject to Section 409A of the Code, such payment may be made in installments and may be deferred until the date or dates when the Award would have become vested. Such payment may be subject to vesting based on the Participant’s
continuing Service, provided that the vesting schedule shall not be less favorable to the Participant than the schedule under which the Award would have vested. If the Spread applicable to an Award is zero or a negative number, then the Award may be
cancelled without making a payment to the Participant. For purposes of this Paragraph (v), the Fair Market Value of any security shall be determined without regard to any vesting conditions that may apply to such security. In the event that a
Restricted Stock Unit is subject to Section 409A of the Code, the payment described in this Section 9(b)(v) shall be made on the settlement date specified in the applicable Restricted Stock Unit Agreement, provided that settlement may be
accelerated in accordance with Treasury Regulation 1.409A-3(j)(4). 
 Any action taken under this Section 9(b) must either preserve an Award’s
status as exempt from Section 409A of the Code or comply with Section 409A of the Code. 

  
 9 

 (c) Reservation of Rights. Except as provided in this Section 9, a
Participant shall have no rights by reason of (i) any subdivision or consolidation of shares of stock of any class, (ii) the payment of any dividend or (iii) any other increase or decrease in the number of shares of stock of any
class. Any issuance by the Company of shares of stock of any class, or securities convertible into shares of stock of any class, shall not affect, and no adjustment by reason thereof shall be made with respect to, the number of Shares subject to an
Award or the Exercise Price of Shares subject to an Option. The grant of an Award pursuant to the Plan shall not affect in any way the right or power of the Company to make adjustments, reclassifications, reorganizations or changes to its capital or
business structure, to merge or consolidate or to dissolve, liquidate, sell or transfer all or any part of its business or assets. 
 SECTION 10.
MISCELLANEOUS PROVISIONS. 
 (a) Securities Law Requirements. Shares shall not be issued under the Plan unless the issuance
and delivery of such Shares comply with (or are exempt from) all applicable requirements of law, including (without limitation) the Securities Act, the rules and regulations promulgated thereunder, state securities laws and regulations, and the
regulations of any stock exchange or other securities market on which the Company’s securities may then be traded. The Company shall not be liable for a failure to issue Shares that is attributable to such requirements. 

(b) No Retention Rights. Nothing in the Plan or in any right or Award granted under the Plan shall confer upon the
Participant any right to continue in Service 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 the Participant) or of the Participant,
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. 

(c) Treatment as Compensation. Any compensation that an individual earns or is deemed to earn under this Plan shall not
be considered a part of his or her compensation for purposes of calculating contributions, accruals or benefits under any other plan or program that is maintained or funded by the Company, a Parent or a Subsidiary. 

(d) Governing Law. The Plan and all awards, sales and grants under the Plan 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. 

(e) Tax Matters. 

(i) As a condition to the award, grant, issuance, vesting, purchase, exercise or transfer of any Award, or Shares issued
pursuant to any Award, granted under this Plan, the Participant shall make such arrangements as the Board of Directors may require or permit for the satisfaction of any federal, state, local or foreign withholding tax obligations that may arise in
connection with such event. 
 (ii) Unless otherwise expressly set forth in an Award Agreement, it is intended that awards
granted under the Plan shall be exempt from 

  
 10 

 
Section 409A of the Code, and any ambiguity in the terms of an Award Agreement and the Plan shall be interpreted consistently with this intent. To the extent an award is not exempt from
Section 409A of the Code (any such award, a “409A Award”), any ambiguity in the terms of such award and the Plan shall be interpreted in a manner that to the maximum extent permissible supports the award’s compliance with
the requirements of that statute. Notwithstanding anything to the contrary permitted under the Plan, in no event shall a modification of an Award not already subject to Section 409A of the Code be given effect if such modification would cause
the Award to become subject to Section 409A of the Code unless the parties explicitly acknowledge and consent to the modification as one having that effect. A 409A Award shall be subject to such additional rules and requirements as specified by
the Board of Directors from time to time in order for it to comply with the requirements of Section 409A of the Code. In this regard, if any amount under a 409A Award is payable upon a “separation from service” to an individual who is
considered a “specified employee” (as each term is defined under Section 409A of the Code), then no such payment shall be made prior to the date that is the earlier of (i) six months and one day after the Participant’s
separation from service or (ii) the Participant’s death, but only to the extent such delay is necessary to prevent such payment from being subject to Section 409A(a)(1). In addition, if a transaction subject to Section 9(b)
constitutes a payment event with respect to any 409A Award, then the transaction with respect to such award must also constitute a “change in control event” as defined in Treasury Regulation Section 1.409A-3(i)(5) to the extent
required by Section 409A of the Code. 
 (iii) Neither the Company nor any member of the Board of Directors shall have any liability to
a Participant in the event an Award held by the Participant fails to achieve its intended characterization under applicable tax law. 
 SECTION 11.
DURATION AND AMENDMENTS. 
 (a) Term of the Plan. The Plan, as set forth herein, shall become effective on
the date of its adoption by the Board of Directors, subject to the approval of the Company’s stockholders. If the stockholders fail to approve the Plan within 12 months after its adoption by the Board of Directors, then any grants, exercises or
sales that have already occurred under the Plan shall be rescinded and no additional grants, exercises or sales shall thereafter be made under the Plan. The Plan shall terminate automatically 10 years after the later of (i) the date when the
Board of Directors adopted the Plan or (ii) the date when the Board of Directors approved the most recent increase in the number of Shares reserved under Section 4 that was also approved by the Company’s stockholders. The Plan may be
terminated on any earlier date pursuant to Subsection (b) below. 
 (b) Right to Amend or Terminate the Plan. The
Board of Directors may amend, suspend or terminate the Plan at any time and for any reason; provided, however, that any amendment of the Plan shall be subject to the approval of the Company’s stockholders if it (i) increases the number of
Shares available for issuance under the Plan (except as provided in Section 9) or (ii) materially changes the class of persons who are eligible for the grant of ISOs. 

  
 11 

 
Stockholder approval shall not be required for any other amendment of the Plan. If the stockholders fail to approve an increase in the number of Shares reserved under Section 4 within 12
months after its adoption by the Board of Directors, then any grants, exercises or sales that have already occurred in reliance on such increase shall be rescinded and no additional grants, exercises or sales shall thereafter be made in reliance on
such increase. 
 (c) Effect of Amendment or Termination. No Shares shall be issued or sold under the Plan after the
termination thereof, except upon exercise of an Option or settlement of a Restricted Stock Unit (or any other right to purchase Shares) granted under the Plan prior to such termination. The termination of the Plan, or any amendment thereof, shall
not affect any Share previously issued or any Award previously granted under the Plan. 
 SECTION 12. DEFINITIONS. 

(a) “Award” shall mean any award granted under the Plan, including an Option, Restricted Stock Unit or other right to acquire
Shares under the Plan. 
 (b) “Award Agreement” shall mean a Stock Option Agreement, Stock Grant Agreement, Stock Purchase
Agreement or Restricted Stock Unit Agreement. 
 (c) “Board of Directors” shall mean the Board of Directors of the Company,
as constituted from time to time. 
 (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(a). 

(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 of grant
specified in the applicable Stock Option Agreement, which date shall be the later of (i) the date on which the Board of Directors resolved to grant the Option or (ii) the first day of the Optionee’s Service. 

(i) “Disability” shall mean that the Optionee is unable to engage in any substantial gainful activity by reason of any
medically determinable physical or mental impairment. 
 (j) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (k) “Exchange Act” shall
mean the Securities Exchange Act of 1934, as amended. 

  
 12 

 (l) “Exercise Price” shall mean the amount for which one Share may be purchased
upon exercise of an Option, as specified by the Board of Directors in the applicable Stock Option Agreement. 
 (m) “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. 

(n) “Family Member” shall mean (i) any child, stepchild, grandchild, parent, stepparent, grandparent, spouse, former
spouse, sibling, niece, nephew, mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law or sister-in-law, including adoptive relationships, (ii) any person sharing the Participant’s household (other than a tenant or
employee), (iii) a trust in which persons described in Clause (i) or (ii) have more than 50% of the beneficial interest, (iv) a foundation in which persons described in Clause (i) or (ii) or the Participant control the
management of assets and (v) any other entity in which persons described in Clause (i) or (ii) or the Participant own more than 50% of the voting interests. 

(o) “Grantee” shall mean a person to whom the Board of Directors has awarded Shares under the Plan. 

(p) “ISO” shall mean an employee incentive stock option described in Section 422(b) of the Code. 

(q) “Nonstatutory Option” shall mean a stock option not described in Sections 422(b) or 423(b) of the Code. 

(r) “Option” shall mean an ISO or Nonstatutory Option granted under the Plan and entitling the holder to purchase Shares.

 (s) “Optionee” shall mean a person who holds an Option. 

(t) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(u) “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. 
 (v)
“Participant” shall mean an individual who holds an Award granted under the Plan. 
 (w) “Plan” shall mean
this Acacia Communications, Inc. 2009 Stock Plan, as amended from time to time. 

  
 13 

 (x) “Purchase Price” shall mean the consideration for which one Share may be
acquired under the Plan (other than upon exercise of an Option), as specified by the Board of Directors. 
 (y) “Purchaser”
shall mean a person to whom the Board of Directors has offered the right to purchase Shares under the Plan (other than upon exercise of an Option or settlement of a Restricted Stock Unit). 

(z) “Restricted Stock Unit” shall mean a bookkeeping entry representing the equivalent of one Share, as awarded under the
Plan. 
 (aa) “Restricted Stock Unit Agreement” shall mean the agreement between the Company and the recipient of a
Restricted Stock Unit that includes the terms, conditions and restrictions pertaining to such Restricted Stock Unit. 
 (bb)
“Securities Act” shall mean the Securities Act of 1933, as amended. 
 (cc) “Service” shall mean service
as an Employee, Outside Director or Consultant. 
 (dd) “Share” shall mean one share of Stock, as adjusted in accordance
with Section 9 (if applicable). 
 (ee) “Stock” shall mean the Common Stock of the Company. 

(ff) “Stock Grant Agreement” shall mean the agreement between the Company and a Grantee who is awarded Shares under the Plan
that contains the terms, conditions and restrictions pertaining to the award of such Shares. 
 (gg) “Stock Option
Agreement” shall mean the agreement between the Company and an Optionee that contains the terms, conditions and restrictions pertaining to the Optionee’s Option. 

(hh) “Stock Purchase Agreement” shall mean the agreement between the Company and a Purchaser who purchases Shares under the
Plan that contains the terms, conditions and restrictions pertaining to the purchase of such Shares. 
 (ii) “Subsidiary”
shall mean any corporation (other than the Company) in an unbroken chain of 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.

  
 14 

 EXHIBIT A 

SCHEDULE OF SHARES RESERVED FOR ISSUANCE
UNDER THE PLAN 
  

									
	 Date of Board

Approval
	  	Date of Stockholder
Approval	  	Number of
Shares Added	  	Cumulative Number
of Shares	 
	 November 23, 2009
	  	November 23, 2009	  	Not Applicable	  	 	3,414,636	  
	 June 29, 2010
	  	June 29, 2010	  	585,822	  	 	4,000,458	  
	 December 20, 2011
	  	March 5, 2012	  	300,000	  	 	4,300,458	  
	 March 5, 2012
	  	March 5, 2012	  	500,000	  	 	4,800,458	  
	 April 17, 2013
	  	April 17, 2013	  	1,635,437	  	 	6,835,895	  

  
 E-1EX-10.3

 Exhibit 10.3 

ACACIA COMMUNICATIONS, INC. 2009 STOCK PLAN 

NOTICE OF STOCK OPTION GRANT (INSTALLMENT
VESTING) 
 The Optionee has been granted the following option to purchase shares of the Common Stock of Acacia Communications, Inc.:

  

			
	Name of Optionee:	  	«Name»
		
	Total Number of Shares:	  	«TotalShares»
		
	Type of Option:	  	«ISO» Incentive Stock Option (ISO)
		
		  	«NSO» Nonstatutory Stock Option (NSO)
		
	Exercise Price per Share:	  	$«PricePerShare»
		
	Date of Grant:	  	«DateGrant»
		
	Date Exercisable:	  	This option may be exercised with respect to the first 20% of the Shares subject to this option when the Optionee completes 12 months of continuous Service beginning with the Vesting Commencement Date set forth below. This option
may be exercised with respect to an additional 1/60th of the Shares subject to this option when the Optionee completes each month of continuous Service thereafter.
		
	Vesting Commencement Date:	  	«VestComDate»
		
	Expiration Date:	  	«ExpDate». This option expires earlier if the Optionee’s Service terminates earlier, as provided in Section 6 of the Stock Option Agreement.

 By signing below, the Optionee and the Company agree that this option is granted under, and governed by the terms and
conditions of, the 2009 Stock Plan and the Stock Option Agreement. Both of these documents are attached to, and made a part of, this Notice of Stock Option Grant. Section 13 of the Stock Option Agreement includes important acknowledgements
of the Optionee. 
  

							
	OPTIONEE:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

		 		 	Title:	 	  

 THE OPTION GRANTED PURSUANT TO THIS AGREEMENT AND THE SHARES ISSUABLE UPON THE EXERCISE THEREOF 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. 
 ACACIA COMMUNICATIONS, INC. 2009 STOCK
PLAN: 
 STOCK OPTION AGREEMENT (INSTALLMENT
VESTING) 
 SECTION 1. GRANT OF OPTION. 

(a) Option. On the terms and conditions set forth in the Notice of Stock Option Grant and this Agreement, the Company grants to the
Optionee on the Date of Grant the option to purchase at the Exercise Price the number of Shares set forth in the Notice of Stock Option Grant. The Exercise Price is agreed to be at least 100% of the Fair Market Value per Share on the Date of Grant
(110% of Fair Market Value if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). This option is intended to be an ISO or an NSO, as provided in the Notice of Stock Option Grant. 

(b) $100,000 Limitation. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it shall be deemed to be an
NSO to the extent (and only to the extent) required by the $100,000 annual limitation under Section 422(d) of the Code. 
 (c) Stock
Plan and Defined Terms. This option is granted pursuant to the Plan, a copy of which the Optionee acknowledges having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 14 of this Agreement. 
 SECTION 2. RIGHT TO EXERCISE. 

(a) Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or part of this
option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. 
 (b) Stockholder
Approval. Any other provision of this Agreement notwithstanding, no portion of this option shall be exercisable at any time prior to the approval of the Plan by the Company’s stockholders. 

SECTION 3. NO TRANSFER OR ASSIGNMENT OF OPTION. 

Except as otherwise provided in this Agreement, this option and the rights and privileges conferred hereby shall not be sold, pledged or
otherwise transferred (whether by operation of law or otherwise) and shall not be subject to sale under execution, attachment, levy or similar process. 

 SECTION 4. EXERCISE PROCEDURES. 

(a) Notice of Exercise. The Optionee or the Optionee’s representative may exercise this option by giving written notice to the
Company pursuant to Section 12(c). The notice shall specify the election to exercise this option, the number of Shares for which it is being exercised and the form of payment. The person exercising this option shall sign the notice. In the
event that this option is being exercised by the representative of the Optionee, the notice shall be accompanied by proof (satisfactory to the Company) of the representative’s right to exercise this option. The Optionee or the Optionee’s
representative shall deliver to the Company, at the time of giving the notice, payment in a form permissible under Section 5 for the full amount of the Purchase Price. 

(b) Issuance of Shares. After receiving a proper notice of exercise, the Company shall cause to be issued one or more certificates
evidencing the Shares for which this option has been exercised. Such Shares shall be registered (i) in the name of the person exercising this option, (ii) in the names of such person and his or her spouse as community property or as joint
tenants with the right of survivorship or (iii) with the Company’s consent, in the name of a revocable trust. The Company shall cause such certificates to be delivered to or upon the order of the person exercising this option. 

(c) Withholding Taxes. In the event that the Company determines that it is required to withhold any tax as a result of the exercise of
this option, the Optionee, as a condition to the exercise of this option, shall make arrangements satisfactory to the Company to enable it to satisfy all withholding requirements. The Optionee shall also make arrangements satisfactory to the Company
to enable it to satisfy any withholding requirements that may arise in connection with the disposition of Shares purchased by exercising this option. 

SECTION 5. PAYMENT FOR STOCK. 
 (a)
Cash. All or part of the Purchase Price may be paid in cash or cash equivalents. 
 (b) Surrender of Stock. At the discretion
of the Board of Directors, all or any part of the Purchase Price may be paid by surrendering, or attesting to the ownership of, Shares that are already owned by the Optionee. Such Shares shall be surrendered to the Company in good form for transfer
and shall be valued at their Fair Market Value as of the date when this option is exercised. 
 (c) Exercise/Sale. All or part of the
Purchase Price and any withholding taxes may be paid by the delivery (on a form prescribed by the Company) of an irrevocable direction to a securities broker approved by the Company to sell Shares and to deliver all or part of the sales proceeds to
the Company. However, payment pursuant to this Subsection (c) shall be permitted only if (i) Stock then is publicly traded and (ii) such payment does not violate applicable law. 

  
 2 

 SECTION 6. TERM AND EXPIRATION. 

(a) Basic Term. This option shall in any event expire on the expiration date set forth in the Notice of Stock Option Grant, which date
is 10 years after the Date of Grant (five years after the Date of Grant if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). 

(b) Termination of Service (Except by Death). If the Optionee’s Service terminates for any reason other than death, then this
option shall expire on the earliest of the following occasions: 
 (i) The expiration date determined pursuant to
Subsection (a) above; 
 (ii) The date three months after the termination of the Optionee’s Service for any reason
other than Disability; or 
 (iii) The date six months after the termination of the Optionee’s Service by reason of
Disability. 
 The Optionee may exercise all or part of this option at any time before its expiration under the preceding sentence, but only to the extent
that this option had become exercisable before the Optionee’s Service terminated. When the Optionee’s Service terminates, this option shall expire immediately with respect to the number of Shares for which this option is not yet
exercisable. In the event that the Optionee dies after termination of Service but before the expiration of this option, all or part of this option may be exercised (prior to expiration) by the executors or administrators of the Optionee’s
estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s Service terminated. 

(c) Death of the Optionee. If the Optionee dies while in Service, then this option shall expire on the earlier of the following dates:

 (i) The expiration date determined pursuant to Subsection (a) above; or 

(ii) The date 12 months after the Optionee’s death. 

All or part of this option may be exercised at any time before its expiration under the preceding sentence by the executors or administrators of the
Optionee’s estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s death. When
the Optionee dies, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. 

(d) Part-Time Employment and Leaves of Absence. If the Optionee commences working on a part-time basis, then the Company may adjust the
vesting schedule set forth in the Notice of Stock Option Grant. If the Optionee goes on a leave of absence, then the 

  
 3 

 
Company may adjust the vesting schedule set forth in the Notice of Stock Option 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 for any purpose under this Agreement while the Optionee is 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 the Optionee immediately returns to active
work. 
 (e) Notice Concerning ISO Treatment. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it
ceases to qualify for favorable tax treatment as an ISO to the extent that it is exercised: 
 (i) More than three months
after the date when the Optionee ceases to be an Employee for any reason other than death or permanent and total disability (as defined in Section 22(e)(3) of the Code); 

(ii) More than 12 months after the date when the Optionee ceases to be an Employee by reason of permanent and total disability
(as defined in Section 22(e)(3) of the Code); or 
 (iii) More than three months after the date when the Optionee has
been on a leave of absence for 90 days, unless the Optionee’s reemployment rights following such leave were guaranteed by statute or by contract. 

SECTION 7. RIGHT OF FIRST REFUSAL. 
 (a)
Right of First Refusal. In the event that the Optionee proposes 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 the Optionee desires to transfer Shares acquired under this Agreement, the Optionee shall give a written Transfer Notice to the Company describing fully the proposed transfer, 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 the Optionee 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 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 the date when it received the Transfer Notice, the Optionee 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 

  
 4 

 
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
Optionee 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 Optionee, 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 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 7 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 7. 
 (d) Termination of Right of First Refusal. Any other
provision of this Section 7 notwithstanding, in the event that the Stock is readily tradable on an established securities market when the Optionee desires to transfer Shares, the Company shall have no Right of First Refusal, and the Optionee
shall have no obligation to comply with the procedures prescribed by Subsections (a) and (b) above. 
 (e) Permitted
Transfers. This Section 7 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 Optionee’s Immediate Family or to a trust established by
the Optionee for the benefit of the Optionee and/or one or more members of the Optionee’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 Optionee transfers any Shares acquired under this Agreement, 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 Transferee to the
same extent as to the Optionee. 
 (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 7, 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. 

  
 5 

 (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 7. 

SECTION 8. LEGALITY OF INITIAL ISSUANCE. 

No Shares shall be issued upon the exercise of this option unless and until the Company has determined that: 

(a) It and the Optionee have taken any actions required to register the Shares under the Securities Act or to perfect an
exemption from the registration requirements thereof; 
 (b) Any applicable listing requirement of any stock exchange or
other securities market on which Stock is listed has been satisfied; and 
 (c) Any other applicable provision of federal,
State or foreign law has been satisfied. 
 SECTION 9. NO REGISTRATION RIGHTS. 

The Company may, but shall not be obligated to, register or qualify the sale of Shares under the Securities Act or any other applicable law.
The Company shall not be obligated to take any affirmative action in order to cause the sale of Shares under this Agreement to comply with any law. 

SECTION 10. RESTRICTIONS ON TRANSFER OF 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 such 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. 
 (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, the Optionee 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”)

  
 6 

 
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 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
Subsection (b). This Subsection (b) shall not apply to Shares registered in the public offering under the Securities Act. 
 (c)
Investment Intent at Grant. The Optionee represents and agrees that the Shares to be acquired upon exercising this option will be acquired for investment, and not with a view to the sale or distribution thereof. 

(d) Investment Intent at Exercise. 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, the Optionee shall represent and agree at the time of exercise that the Shares being acquired upon exercising this option 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) Legends. All certificates evidencing Shares purchased 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 purchased 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.” 

(f) Removal of Legends. If, in the opinion of the Company and its counsel, any legend placed on a stock certificate representing Shares
sold 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. 

(g) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth in this
Section 10 shall be conclusive and binding on the Optionee and all other persons. 
 SECTION 11. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 8(a) of the Plan, the terms of this option (including, without limitation, the number
and kind of Shares subject to this option and the Exercise Price) shall be adjusted as set forth in Section 8(a) of the Plan. In the event that the Company is a party to a merger or consolidation, this option shall be subject to the agreement
of merger or consolidation, as provided in Section 8(b) of the Plan. 
 SECTION 12. MISCELLANEOUS PROVISIONS. 

(a) Rights as a Stockholder. Neither the Optionee nor the Optionee’s representative shall have any rights as a stockholder with
respect to any Shares subject to this option until the Optionee or the Optionee’s representative becomes entitled to receive such Shares by filing a notice of exercise and paying the Purchase Price pursuant to Sections 4 and 5. 

(b) No Retention Rights. Nothing in this option or in the Plan shall confer upon the Optionee any right to continue in Service 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 the Optionee) or of the Optionee, 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. 
 (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 Federal Express Corporation, with shipping charges prepaid. Notice shall be addressed to the Company at its principal executive office and to the Optionee at the address that he or she most recently provided to the Company in accordance with
this Subsection (c). 
 (d) Modifications and Waivers. No provision of this Agreement shall be modified, waived or discharged
unless the modification, waiver or discharge is agreed to in writing and signed by the Optionee and by an authorized officer of the Company (other than the 

  
 8 

 
Optionee). No waiver by either party of any breach of, or of compliance with, any condition or provision of this Agreement by the other party shall be considered a waiver of any other condition
or provision or of the same condition or provision at another time. 
 (e) Entire Agreement. The Notice of Stock Option 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. 
 (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 13.
ACKNOWLEDGEMENTS OF THE OPTIONEE. 
 (a) Tax Consequences. The Optionee agrees that the Company does not have a duty to design or
administer the Plan or its other compensation programs in a manner that minimizes the Optionee’s tax liabilities. The Optionee shall not make any claim against the Company or its Board of Directors, officers or employees related to tax
liabilities arising from this option or the Optionee’s other compensation. In particular, the Optionee acknowledges that this option is exempt from Section 409A of the Code only if the Exercise Price is at least equal to the Fair Market
Value per Share on the Date of Grant. Since Shares are not traded on an established securities market, the determination of their Fair Market Value is made by the Board of Directors or by an independent valuation firm retained by the Company. The
Optionee acknowledges that there is no guarantee in either case that the Internal Revenue Service will agree with the valuation, and the Optionee shall not make any claim against the Company or its Board of Directors, officers or employees in the
event that the Internal Revenue Service asserts that the valuation was too low. 
 (b) Electronic Delivery of Documents. The Optionee
agrees to accept by email all documents relating to the Company, the Plan or this option 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 Optionee 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 Optionee by email of their availability. The Optionee 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 this option expires or until the Optionee gives the Company written notice that it should deliver paper
documents. 
 (c) No Notice of Expiration Date. The Optionee agrees that the Company and its officers, employees, attorneys and
agents do not have any obligation to notify him or her prior to the expiration of this option pursuant to Section 6, regardless of whether this option will expire at the end of its full term or on an earlier date related to the termination of
the Optionee’s Service. The Optionee further agrees that he or she has the sole responsibility for monitoring the 

  
 9 

 
expiration of this option and for exercising this option, if at all, before it expires. This Subsection (c) shall supersede any contrary representation that may have been made, orally or in
writing, by the Company or by an officer, employee, attorney or agent of the Company. 
 SECTION 14. DEFINITIONS. 

(a) “Agreement” shall mean this Stock Option 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. 
 (g) “Date of Grant” shall mean the date of grant
specified in the Notice of Stock Option Grant, which date shall be the later of (i) the date on which the Board of Directors resolved to grant this option or (ii) the first day of the Optionee’s Service. 

(h) “Disability” shall mean that the Optionee is unable to engage in any substantial gainful activity by reason of any
medically determinable physical or mental impairment. 
 (i) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (j) “Exercise Price”
shall mean the amount for which one Share may be purchased upon exercise of this option, as specified in the Notice of Stock Option Grant. 

(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) “ISO” shall mean an employee incentive stock option described in Section 422(b) of the Code. 

  
 10 

 (n) “Notice of Stock Option Grant” shall mean the document so entitled to which
this Agreement is attached. 
 (o) “NSO” shall mean a stock option not described in Section 422(b) or 423(b) of
the Code. 
 (p) “Optionee” shall mean the person named in the Notice of Stock Option Grant. 

(q) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(r) “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. 

(s) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as in effect on the Date of Grant. 

(t) “Purchase Price” shall mean the Exercise Price multiplied by the number of Shares with respect to which this option is
being exercised. 
 (u) “Right of First Refusal” shall mean the Company’s right of first refusal described in
Section 7. 
 (v) “Securities Act” shall mean the Securities Act of 1933, as amended. 

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

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

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

(z) “Subsidiary” shall mean any corporation (other than the Company) in an unbroken chain of 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. 

(aa) “Transferee” shall mean any person to whom the Optionee has directly or indirectly transferred any Share acquired under
this Agreement. 
 (bb) “Transfer Notice” shall mean the notice of a proposed transfer of Shares described in
Section 7. 

  
 11 

 ACACIA COMMUNICATIONS, INC. 2009
STOCK PLAN 
 NOTICE OF STOCK OPTION
GRANT 
 (INSTALLMENT VESTING, ACCELERATION) 

The Optionee has been granted the following option to purchase shares of the Common Stock of Acacia Communications, Inc.: 

 

			
	Name of Optionee:	 	«Name»
		
	Total Number of Shares:	 	«TotalShares»
		
	Type of Option:	 	«ISO» Incentive Stock Option (ISO)
		
		 	«NSO» Nonstatutory Stock Option (NSO)
		
	Exercise Price per Share:	 	$«PricePerShare»
		
	Date of Grant:	 	«DateGrant»
		
	Date Exercisable:	 	This option may be exercised with respect to the first 20% of the Shares subject to this option when the Optionee completes 12 months of continuous Service beginning with the Vesting Commencement Date set forth below. This option
may be exercised with respect to an additional 1/60th of the Shares subject to this option when the Optionee completes each month of continuous Service thereafter. This option may become exercisable on an accelerated basis under Section 2(a) of
the Stock Option Agreement.
		
	Vesting Commencement Date:	 	«VestComDate»
		
	Expiration Date:	 	«ExpDate». This option expires earlier if the Optionee’s Service terminates earlier, as provided in Section 6 of the Stock Option Agreement.

 By signing below, the Optionee and the Company agree that this option is granted under, and governed by the terms and
conditions of, the 2009 Stock Plan and the Stock Option Agreement. Both of these documents are attached to, and made a part of, this Notice of Stock Option Grant. Section 13 of the Stock Option Agreement includes important acknowledgements
of the Optionee. 
  

							
	OPTIONEE:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

		 		 	Title:	 	  

 THE OPTION GRANTED PURSUANT TO THIS AGREEMENT AND THE SHARES ISSUABLE UPON THE EXERCISE THEREOF 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. 
 ACACIA COMMUNICATIONS, INC. 2009 STOCK
PLAN: 
 STOCK OPTION AGREEMENT (INSTALLMENT
VESTING) 
 SECTION 1. GRANT OF OPTION. 

(a) Option. On the terms and conditions set forth in the Notice of Stock Option Grant and this Agreement, the Company grants to the
Optionee on the Date of Grant the option to purchase at the Exercise Price the number of Shares set forth in the Notice of Stock Option Grant. The Exercise Price is agreed to be at least 100% of the Fair Market Value per Share on the Date of Grant
(110% of Fair Market Value if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). This option is intended to be an ISO or an NSO, as provided in the Notice of Stock Option Grant. 

(b) $100,000 Limitation. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it shall be deemed to be an
NSO to the extent (and only to the extent) required by the $100,000 annual limitation under Section 422(d) of the Code. 
 (c) Stock
Plan and Defined Terms. This option is granted pursuant to the Plan, a copy of which the Optionee acknowledges having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 14 of this Agreement. 
 SECTION 2. RIGHT TO EXERCISE. 

(a) Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or part of this
option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, if the Company is subject to a Change in Control before the Optionee’s Service terminates, then at all times after
the Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service. 

(b) Stockholder Approval. Any other provision of this Agreement notwithstanding, no portion of this option shall be exercisable at any
time prior to the approval of the Plan by the Company’s stockholders. 

 SECTION 3. NO TRANSFER OR ASSIGNMENT OF OPTION. 

Except as otherwise provided in this Agreement, this option and the rights and privileges conferred hereby shall not be sold, pledged or
otherwise transferred (whether by operation of law or otherwise) and shall not be subject to sale under execution, attachment, levy or similar process. 

SECTION 4. EXERCISE PROCEDURES. 
 (a)
Notice of Exercise. The Optionee or the Optionee’s representative may exercise this option by giving written notice to the Company pursuant to Section 12(c). The notice shall specify the election to exercise this option, the number
of Shares for which it is being exercised and the form of payment. The person exercising this option shall sign the notice. In the event that this option is being exercised by the representative of the Optionee, the notice shall be accompanied by
proof (satisfactory to the Company) of the representative’s right to exercise this option. The Optionee or the Optionee’s representative shall deliver to the Company, at the time of giving the notice, payment in a form permissible under
Section 5 for the full amount of the Purchase Price. 
 (b) Issuance of Shares. After receiving a proper notice of exercise, the
Company shall cause to be issued one or more certificates evidencing the Shares for which this option has been exercised. Such Shares shall be registered (i) in the name of the person exercising this option, (ii) in the names of such
person and his or her spouse as community property or as joint tenants with the right of survivorship or (iii) with the Company’s consent, in the name of a revocable trust. The Company shall cause such certificates to be delivered to or
upon the order of the person exercising this option. 
 (c) Withholding Taxes. In the event that the Company determines that it is
required to withhold any tax as a result of the exercise of this option, the Optionee, as a condition to the exercise of this option, shall make arrangements satisfactory to the Company to enable it to satisfy all withholding requirements. The
Optionee shall also make arrangements satisfactory to the Company to enable it to satisfy any withholding requirements that may arise in connection with the disposition of Shares purchased by exercising this option. 

SECTION 5. PAYMENT FOR STOCK. 
 (a)
Cash. All or part of the Purchase Price may be paid in cash or cash equivalents. 
 (b) Surrender of Stock. At the discretion
of the Board of Directors, all or any part of the Purchase Price may be paid by surrendering, or attesting to the ownership of, Shares that are already owned by the Optionee. Such Shares shall be surrendered to the Company in good form for transfer
and shall be valued at their Fair Market Value as of the date when this option is exercised. 
 (c) Exercise/Sale. All or part of the
Purchase Price and any withholding taxes may be paid by the delivery (on a form prescribed by the Company) of an irrevocable direction to a securities broker approved by the Company to sell Shares and to deliver all or part

  
 2 

 
of the sales proceeds to the Company. However, payment pursuant to this Subsection (c) shall be permitted only if (i) Stock then is publicly traded and (ii) such payment does not
violate applicable law. 
 SECTION 6. TERM AND EXPIRATION. 

(a) Basic Term. This option shall in any event expire on the expiration date set forth in the Notice of Stock Option Grant, which date
is 10 years after the Date of Grant (five years after the Date of Grant if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). 

(b) Termination of Service (Except by Death). If the Optionee’s Service terminates for any reason other than death, then this
option shall expire on the earliest of the following occasions: 
 (i) The expiration date determined pursuant to
Subsection (a) above; 
 (ii) The date three months after the termination of the Optionee’s Service for any reason
other than Disability; or 
 (iii) The date six months after the termination of the Optionee’s Service by reason of
Disability. 
 The Optionee may exercise all or part of this option at any time before its expiration under the preceding sentence, but only to the extent
that this option had become exercisable before the Optionee’s Service terminated. When the Optionee’s Service terminates, this option shall expire immediately with respect to the number of Shares for which this option is not yet
exercisable. In the event that the Optionee dies after termination of Service but before the expiration of this option, all or part of this option may be exercised (prior to expiration) by the executors or administrators of the Optionee’s
estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s Service terminated. 

(c) Death of the Optionee. If the Optionee dies while in Service, then this option shall expire on the earlier of the following dates:

 (i) The expiration date determined pursuant to Subsection (a) above; or 

(ii) The date 12 months after the Optionee’s death. 

All or part of this option may be exercised at any time before its expiration under the preceding sentence by the executors or administrators of the
Optionee’s estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s death. When
the Optionee dies, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. 

  
 3 

 (d) Part-Time Employment and Leaves of Absence. If the Optionee commences working on a
part-time basis, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option Grant. If the Optionee goes on a leave of absence, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option
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 for any purpose under this Agreement while the Optionee is 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 the Optionee immediately returns to active work. 
 (e)
Notice Concerning ISO Treatment. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it ceases to qualify for favorable tax treatment as an ISO to the extent that it is exercised: 

(i) More than three months after the date when the Optionee ceases to be an Employee for any reason other than death or
permanent and total disability (as defined in Section 22(e)(3) of the Code); 
 (ii) More than 12 months after the date
when the Optionee ceases to be an Employee by reason of permanent and total disability (as defined in Section 22(e)(3) of the Code); or 

(iii) More than three months after the date when the Optionee has been on a leave of absence for 90 days, unless the
Optionee’s reemployment rights following such leave were guaranteed by statute or by contract. 
 SECTION 7. RIGHT OF FIRST REFUSAL. 

(a) Right of First Refusal. In the event that the Optionee proposes 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 the Optionee desires to transfer Shares acquired under this Agreement,
the Optionee shall give a written Transfer Notice to the Company describing fully the proposed transfer, 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 the Optionee 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 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. 

  
 4 

 (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, the Optionee 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 the Optionee 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 Optionee, 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 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 7 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 7. 
 (d) Termination of Right of First Refusal. Any other provision
of this Section 7 notwithstanding, in the event that the Stock is readily tradable on an established securities market when the Optionee desires to transfer Shares, the Company shall have no Right of First Refusal, and the Optionee shall have
no obligation to comply with the procedures prescribed by Subsections (a) and (b) above. 
 (e) Permitted Transfers. This
Section 7 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 Optionee’s Immediate Family or to a trust established by the Optionee for the
benefit of the Optionee and/or one or more members of the Optionee’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
Optionee transfers any Shares acquired under this Agreement, 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 Transferee to the same extent as to the
Optionee. 
 (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 

  
 5 

 
for the Shares to be purchased in accordance with this Section 7, 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 7. 
 SECTION 8. LEGALITY OF INITIAL ISSUANCE. 

No Shares shall be issued upon the exercise of this option unless and until the Company has determined that: 

(a) It and the Optionee have taken any actions required to register the Shares under the Securities Act or to perfect an
exemption from the registration requirements thereof; 
 (b) Any applicable listing requirement of any stock exchange or
other securities market on which Stock is listed has been satisfied; and 
 (c) Any other applicable provision of federal,
State or foreign law has been satisfied. 
 SECTION 9. NO REGISTRATION RIGHTS. 

The Company may, but shall not be obligated to, register or qualify the sale of Shares under the Securities Act or any other applicable law.
The Company shall not be obligated to take any affirmative action in order to cause the sale of Shares under this Agreement to comply with any law. 

SECTION 10. RESTRICTIONS ON TRANSFER OF 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 such 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. 
 (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, the Optionee or a Transferee shall not directly or indirectly sell, make any
short sale of, loan, hypothecate, pledge, offer, grant 

  
 6 

 
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 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 Subsection (b). This Subsection (b) shall not apply to Shares registered in the public
offering under the Securities Act. 
 (c) Investment Intent at Grant. The Optionee represents and agrees that the Shares to be
acquired upon exercising this option will be acquired for investment, and not with a view to the sale or distribution thereof. 
 (d)
Investment Intent at Exercise. 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, the Optionee shall
represent and agree at the time of exercise that the Shares being acquired upon exercising this option 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) Legends. All certificates evidencing Shares purchased 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 purchased 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.” 

(f) Removal of Legends. If, in the opinion of the Company and its counsel, any legend placed on a stock certificate representing Shares
sold 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. 

(g) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth in this
Section 10 shall be conclusive and binding on the Optionee and all other persons. 
 SECTION 11. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 8(a) of the Plan, the terms of this option (including, without limitation, the number
and kind of Shares subject to this option and the Exercise Price) shall be adjusted as set forth in Section 8(a) of the Plan. In the event that the Company is a party to a merger or consolidation, this option shall be subject to the agreement
of merger or consolidation, as provided in Section 8(b) of the Plan. 
 SECTION 12. MISCELLANEOUS PROVISIONS. 

(a) Rights as a Stockholder. Neither the Optionee nor the Optionee’s representative shall have any rights as a stockholder with
respect to any Shares subject to this option until the Optionee or the Optionee’s representative becomes entitled to receive such Shares by filing a notice of exercise and paying the Purchase Price pursuant to Sections 4 and 5. 

(b) No Retention Rights. Nothing in this option or in the Plan shall confer upon the Optionee any right to continue in Service 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 the Optionee) or of the Optionee, 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. 
 (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 Federal Express Corporation, with shipping charges prepaid. Notice shall be addressed to the Company at its principal executive office and to the Optionee at the address that he or she most recently provided to the Company in accordance with
this Subsection (c). 

  
 8 

 (d) Modifications and Waivers. No provision of this Agreement shall be modified, waived or
discharged unless the modification, waiver or discharge is agreed to in writing and signed by the Optionee and by an authorized officer of the Company (other than the Optionee). No waiver by either party of any breach of, or of compliance with, any
condition or provision of this Agreement by the other party shall be considered a waiver of any other condition or provision or of the same condition or provision at another time. 

(e) Entire Agreement. The Notice of Stock Option 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. 

(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 13. ACKNOWLEDGEMENTS OF THE OPTIONEE. 

(a) Tax Consequences. The Optionee agrees that the Company does not have a duty to design or administer the Plan or its other
compensation programs in a manner that minimizes the Optionee’s tax liabilities. The Optionee shall not make any claim against the Company or its Board of Directors, officers or employees related to tax liabilities arising from this option or
the Optionee’s other compensation. In particular, the Optionee acknowledges that this option is exempt from Section 409A of the Code only if the Exercise Price is at least equal to the Fair Market Value per Share on the Date of Grant.
Since Shares are not traded on an established securities market, the determination of their Fair Market Value is made by the Board of Directors or by an independent valuation firm retained by the Company. The Optionee acknowledges that there is no
guarantee in either case that the Internal Revenue Service will agree with the valuation, and the Optionee shall not make any claim against the Company or its Board of Directors, officers or employees in the event that the Internal Revenue Service
asserts that the valuation was too low. 
 (b) Electronic Delivery of Documents. The Optionee agrees to accept by email all documents
relating to the Company, the Plan or this option 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
Optionee 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
Optionee by email of their availability. The Optionee 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 this option expires or until the Optionee gives the Company written notice that it should deliver paper documents. 

(c) No Notice of Expiration Date. The Optionee agrees that the Company and its officers, employees, attorneys and agents do not have
any obligation to notify him or her 

  
 9 

 
prior to the expiration of this option pursuant to Section 6, regardless of whether this option will expire at the end of its full term or on an earlier date related to the termination of
the Optionee’s Service. The Optionee further agrees that he or she has the sole responsibility for monitoring the expiration of this option and for exercising this option, if at all, before it expires. This Subsection (c) shall supersede
any contrary representation that may have been made, orally or in writing, by the Company or by an officer, employee, attorney or agent of the Company. 

SECTION 14. DEFINITIONS. 
 (a)
“Agreement” shall mean this Stock Option 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 Optionee of the Company’s confidential information or trade secrets, which use or disclosure causes material harm to the Company; 

(ii) A material breach by the Optionee of any material agreement between the Purchaser and the Company; 

(iii) A material failure by the Optionee to comply with the Company’s written policies or rules after receiving written
notification of such failure from the Board of Directors; 
 (iv) The Optionee’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 Optionee’s gross negligence or willful misconduct in the course of performing Service; 
 (vi) A continuing failure
by the Optionee to perform reasonably assigned duties after receiving written notification of such failure from the Board of Directors; or 

(vii) A failure by the Optionee 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 Purchaser’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 

  
 10 

 
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 a committee
of the Board of Directors, as described in Section 2 of the Plan. 
 (g) “Company” shall mean Acacia Communications,
Inc., a Delaware corporation. 
 (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) “Date of Grant” shall
mean the date of grant specified in the Notice of Stock Option Grant, which date shall be the later of (i) the date on which the Board of Directors resolved to grant this option or (ii) the first day of the Optionee’s Service. 

(j) “Disability” shall mean that the Optionee is unable to engage in any substantial gainful activity by reason of any
medically determinable physical or mental impairment. 
 (k) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (l) “Exercise Price”
shall mean the amount for which one Share may be purchased upon exercise of this option, as specified in the Notice of Stock Option Grant. 

(m) “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. 
 (n) “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. 

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

(i) The involuntary discharge of the Optionee by the Company (or the Parent or Subsidiary employing him) for reasons other than
Cause; or 
 (ii) The voluntary resignation of the Optionee following any of the following events, if such event occurs
without the consent of the Optionee: (A) a change in the Optionee’s position with the Company (or the Parent or 

  
 11 

 
Subsidiary employing him or her) that materially reduces his or her level of authority or responsibility (provided that the Optionee’s level of authority or responsibility shall not be
deemed to be reduced merely because there are additional employees more senior to the Optionee as a result of the Change in Control), (B) a reduction in the Optionee’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 Optionee’s principal workplace will be relocated more than 50 miles 

(p) “ISO” shall mean an employee incentive stock option described in Section 422(b) of the Code. 

(q) “Notice of Stock Option Grant” shall mean the document so entitled to which this Agreement is attached. 

(r) “NSO” shall mean a stock option not described in Section 422(b) or 423(b) of the Code. 

(s) “Optionee” shall mean the person named in the Notice of Stock Option Grant. 

(t) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(u) “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. 

(v) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as in effect on the Date of Grant. 

(w) “Purchase Price” shall mean the Exercise Price multiplied by the number of Shares with respect to which this option is
being exercised. 
 (x) “Right of First Refusal” shall mean the Company’s right of first refusal described in
Section 7. 
 (y) “Securities Act” shall mean the Securities Act of 1933, as amended. 

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

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

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

  
 12 

 (cc) “Subsidiary” shall mean any corporation (other than the Company) in an
unbroken chain of 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. 
 (dd) “Transferee” shall mean any person to whom the Optionee has directly or
indirectly transferred any Share acquired under this Agreement. 
 (ee) “Transfer Notice” shall mean the notice of a
proposed transfer of Shares described in Section 7. 

  
 13 

 ACACIA COMMUNICATIONS, INC. 2009
STOCK PLAN 
 NOTICE OF STOCK OPTION
GRANT 
 (INSTALLMENT VESTING, ACCELERATION) 

The Optionee has been granted the following option to purchase shares of the Common Stock of Acacia Communications, Inc.: 

 

			
	Name of Optionee:	  	«Name»
		
	Total Number of Shares:	  	«TotalShares»
		
	Type of Option:	  	«ISO» Incentive Stock Option (ISO)
		
		  	«NSO» Nonstatutory Stock Option (NSO)
		
	Exercise Price per Share:	  	$«PricePerShare»
		
	Date of Grant:	  	«DateGrant»
		
	Date Exercisable:	  	This option may be exercised with respect to the first 25% of the Shares subject to this option when the Optionee completes 12 months of continuous Service beginning with the Vesting Commencement Date set forth below. This option
may be exercised with respect to an additional 1/48th of the Shares subject to this option when the Optionee completes each month of continuous Service thereafter. This option may become exercisable on an accelerated basis under Section 2(a) of
the Stock Option Agreement.
		
	Vesting Commencement Date:	  	«VestComDate»
		
	Expiration Date:	  	«ExpDate». This option expires earlier if the Optionee’s Service terminates earlier, as provided in Section 6 of the Stock Option Agreement.

 By signing below, the Optionee and the Company agree that this option is granted under, and governed by the terms and
conditions of, the 2009 Stock Plan and the Stock Option Agreement. Both of these documents are attached to, and made a part of, this Notice of Stock Option Grant. Section 13 of the Stock Option Agreement includes important acknowledgements
of the Optionee. 
  

							
	OPTIONEE:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

		 		 	Title:	 	  

 THE OPTION GRANTED PURSUANT TO THIS AGREEMENT AND THE SHARES ISSUABLE UPON THE EXERCISE THEREOF 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. 
 ACACIA COMMUNICATIONS, INC. 2009 STOCK
PLAN: 
 STOCK OPTION AGREEMENT (INSTALLMENT
VESTING) 
 SECTION 1. GRANT OF OPTION. 

(a) Option. On the terms and conditions set forth in the Notice of Stock Option Grant and this Agreement, the Company grants to the
Optionee on the Date of Grant the option to purchase at the Exercise Price the number of Shares set forth in the Notice of Stock Option Grant. The Exercise Price is agreed to be at least 100% of the Fair Market Value per Share on the Date of Grant
(110% of Fair Market Value if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). This option is intended to be an ISO or an NSO, as provided in the Notice of Stock Option Grant. 

(b) $100,000 Limitation. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it shall be deemed to be an
NSO to the extent (and only to the extent) required by the $100,000 annual limitation under Section 422(d) of the Code. 
 (c) Stock
Plan and Defined Terms. This option is granted pursuant to the Plan, a copy of which the Optionee acknowledges having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 14 of this Agreement. 
 SECTION 2. RIGHT TO EXERCISE. 

(a) Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or part of this
option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, if the Company is subject to a Change in Control before the Optionee’s Service terminates, then at all times after
the Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service. 

(b) Stockholder Approval. Any other provision of this Agreement notwithstanding, no portion of this option shall be exercisable at any
time prior to the approval of the Plan by the Company’s stockholders. 

 SECTION 3. NO TRANSFER OR ASSIGNMENT OF OPTION. 

Except as otherwise provided in this Agreement, this option and the rights and privileges conferred hereby shall not be sold, pledged or
otherwise transferred (whether by operation of law or otherwise) and shall not be subject to sale under execution, attachment, levy or similar process. 

SECTION 4. EXERCISE PROCEDURES. 
 (a)
Notice of Exercise. The Optionee or the Optionee’s representative may exercise this option by giving written notice to the Company pursuant to Section 12(c). The notice shall specify the election to exercise this option, the number
of Shares for which it is being exercised and the form of payment. The person exercising this option shall sign the notice. In the event that this option is being exercised by the representative of the Optionee, the notice shall be accompanied by
proof (satisfactory to the Company) of the representative’s right to exercise this option. The Optionee or the Optionee’s representative shall deliver to the Company, at the time of giving the notice, payment in a form permissible under
Section 5 for the full amount of the Purchase Price. 
 (b) Issuance of Shares. After receiving a proper notice of exercise, the
Company shall cause to be issued one or more certificates evidencing the Shares for which this option has been exercised. Such Shares shall be registered (i) in the name of the person exercising this option, (ii) in the names of such
person and his or her spouse as community property or as joint tenants with the right of survivorship or (iii) with the Company’s consent, in the name of a revocable trust. The Company shall cause such certificates to be delivered to or
upon the order of the person exercising this option. 
 (c) Withholding Taxes. In the event that the Company determines that it is
required to withhold any tax as a result of the exercise of this option, the Optionee, as a condition to the exercise of this option, shall make arrangements satisfactory to the Company to enable it to satisfy all withholding requirements. The
Optionee shall also make arrangements satisfactory to the Company to enable it to satisfy any withholding requirements that may arise in connection with the disposition of Shares purchased by exercising this option. 

SECTION 5. PAYMENT FOR STOCK. 
 (a)
Cash. All or part of the Purchase Price may be paid in cash or cash equivalents. 
 (b) Surrender of Stock. At the discretion
of the Board of Directors, all or any part of the Purchase Price may be paid by surrendering, or attesting to the ownership of, Shares that are already owned by the Optionee. Such Shares shall be surrendered to the Company in good form for transfer
and shall be valued at their Fair Market Value as of the date when this option is exercised. 
 (c) Exercise/Sale. All or part of the
Purchase Price and any withholding taxes may be paid by the delivery (on a form prescribed by the Company) of an irrevocable direction to a securities broker approved by the Company to sell Shares and to deliver all or part

  
 2 

 
of the sales proceeds to the Company. However, payment pursuant to this Subsection (c) shall be permitted only if (i) Stock then is publicly traded and (ii) such payment does not
violate applicable law. 
 SECTION 6. TERM AND EXPIRATION. 

(a) Basic Term. This option shall in any event expire on the expiration date set forth in the Notice of Stock Option Grant, which date
is 10 years after the Date of Grant (five years after the Date of Grant if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). 

(b) Termination of Service (Except by Death). If the Optionee’s Service terminates for any reason other than death, then this
option shall expire on the earliest of the following occasions: 
 (i) The expiration date determined pursuant to
Subsection (a) above; 
 (ii) The date three months after the termination of the Optionee’s Service for any reason
other than Disability; or 
 (iii) The date six months after the termination of the Optionee’s Service by reason of
Disability. 
 The Optionee may exercise all or part of this option at any time before its expiration under the preceding sentence, but only to the extent
that this option had become exercisable before the Optionee’s Service terminated. When the Optionee’s Service terminates, this option shall expire immediately with respect to the number of Shares for which this option is not yet
exercisable. In the event that the Optionee dies after termination of Service but before the expiration of this option, all or part of this option may be exercised (prior to expiration) by the executors or administrators of the Optionee’s
estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s Service terminated. 

(c) Death of the Optionee. If the Optionee dies while in Service, then this option shall expire on the earlier of the following dates:

 (i) The expiration date determined pursuant to Subsection (a) above; or 

(ii) The date 12 months after the Optionee’s death. 

All or part of this option may be exercised at any time before its expiration under the preceding sentence by the executors or administrators of the
Optionee’s estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s death. When
the Optionee dies, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. 

  
 3 

 (d) Part-Time Employment and Leaves of Absence. If the Optionee commences working on a
part-time basis, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option Grant. If the Optionee goes on a leave of absence, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option
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 for any purpose under this Agreement while the Optionee is 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 the Optionee immediately returns to active work. 
 (e)
Notice Concerning ISO Treatment. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it ceases to qualify for favorable tax treatment as an ISO to the extent that it is exercised: 

(i) More than three months after the date when the Optionee ceases to be an Employee for any reason other than death or
permanent and total disability (as defined in Section 22(e)(3) of the Code); 
 (ii) More than 12 months after the date
when the Optionee ceases to be an Employee by reason of permanent and total disability (as defined in Section 22(e)(3) of the Code); or 

(iii) More than three months after the date when the Optionee has been on a leave of absence for 90 days, unless the
Optionee’s reemployment rights following such leave were guaranteed by statute or by contract. 
 SECTION 7. RIGHT OF FIRST REFUSAL. 

(a) Right of First Refusal. In the event that the Optionee proposes 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 the Optionee desires to transfer Shares acquired under this Agreement,
the Optionee shall give a written Transfer Notice to the Company describing fully the proposed transfer, 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 the Optionee 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 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. 

  
 4 

 (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, the Optionee 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 the Optionee 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 Optionee, 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 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 7 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 7. 
 (d) Termination of Right of First Refusal. Any other provision
of this Section 7 notwithstanding, in the event that the Stock is readily tradable on an established securities market when the Optionee desires to transfer Shares, the Company shall have no Right of First Refusal, and the Optionee shall have
no obligation to comply with the procedures prescribed by Subsections (a) and (b) above. 
 (e) Permitted Transfers. This
Section 7 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 Optionee’s Immediate Family or to a trust established by the Optionee for the
benefit of the Optionee and/or one or more members of the Optionee’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
Optionee transfers any Shares acquired under this Agreement, 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 Transferee to the same extent as to the
Optionee. 
 (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 

  
 5 

 
for the Shares to be purchased in accordance with this Section 7, 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 7. 
 SECTION 8. LEGALITY OF INITIAL ISSUANCE. 

No Shares shall be issued upon the exercise of this option unless and until the Company has determined that: 

(a) It and the Optionee have taken any actions required to register the Shares under the Securities Act or to perfect an
exemption from the registration requirements thereof; 
 (b) Any applicable listing requirement of any stock exchange or
other securities market on which Stock is listed has been satisfied; and 
 (c) Any other applicable provision of federal,
State or foreign law has been satisfied. 
 SECTION 9. NO REGISTRATION RIGHTS. 

The Company may, but shall not be obligated to, register or qualify the sale of Shares under the Securities Act or any other applicable law.
The Company shall not be obligated to take any affirmative action in order to cause the sale of Shares under this Agreement to comply with any law. 

SECTION 10. RESTRICTIONS ON TRANSFER OF 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 such 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. 
 (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, the Optionee or a Transferee shall not directly or indirectly sell, make any
short sale of, loan, hypothecate, pledge, offer, grant 

  
 6 

 
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 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 Subsection (b). This Subsection (b) shall not apply to Shares registered in the public
offering under the Securities Act. 
 (c) Investment Intent at Grant. The Optionee represents and agrees that the Shares to be
acquired upon exercising this option will be acquired for investment, and not with a view to the sale or distribution thereof. 
 (d)
Investment Intent at Exercise. 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, the Optionee shall
represent and agree at the time of exercise that the Shares being acquired upon exercising this option 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) Legends. All certificates evidencing Shares purchased 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 purchased 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.” 

(f) Removal of Legends. If, in the opinion of the Company and its counsel, any legend placed on a stock certificate representing Shares
sold 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. 

(g) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth in this
Section 10 shall be conclusive and binding on the Optionee and all other persons. 
 SECTION 11. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 8(a) of the Plan, the terms of this option (including, without limitation, the number
and kind of Shares subject to this option and the Exercise Price) shall be adjusted as set forth in Section 8(a) of the Plan. In the event that the Company is a party to a merger or consolidation, this option shall be subject to the agreement
of merger or consolidation, as provided in Section 8(b) of the Plan. 
 SECTION 12. MISCELLANEOUS PROVISIONS. 

(a) Rights as a Stockholder. Neither the Optionee nor the Optionee’s representative shall have any rights as a stockholder with
respect to any Shares subject to this option until the Optionee or the Optionee’s representative becomes entitled to receive such Shares by filing a notice of exercise and paying the Purchase Price pursuant to Sections 4 and 5. 

(b) No Retention Rights. Nothing in this option or in the Plan shall confer upon the Optionee any right to continue in Service 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 the Optionee) or of the Optionee, 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. 
 (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 Federal Express Corporation, with shipping charges prepaid. Notice shall be addressed to the Company at its principal executive office and to the Optionee at the address that he or she most recently provided to the Company in accordance with
this Subsection (c). 

  
 8 

 (d) Modifications and Waivers. No provision of this Agreement shall be modified, waived or
discharged unless the modification, waiver or discharge is agreed to in writing and signed by the Optionee and by an authorized officer of the Company (other than the Optionee). No waiver by either party of any breach of, or of compliance with, any
condition or provision of this Agreement by the other party shall be considered a waiver of any other condition or provision or of the same condition or provision at another time. 

(e) Entire Agreement. The Notice of Stock Option 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. 

(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 13. ACKNOWLEDGEMENTS OF THE OPTIONEE. 

(a) Tax Consequences. The Optionee agrees that the Company does not have a duty to design or administer the Plan or its other
compensation programs in a manner that minimizes the Optionee’s tax liabilities. The Optionee shall not make any claim against the Company or its Board of Directors, officers or employees related to tax liabilities arising from this option or
the Optionee’s other compensation. In particular, the Optionee acknowledges that this option is exempt from Section 409A of the Code only if the Exercise Price is at least equal to the Fair Market Value per Share on the Date of Grant.
Since Shares are not traded on an established securities market, the determination of their Fair Market Value is made by the Board of Directors or by an independent valuation firm retained by the Company. The Optionee acknowledges that there is no
guarantee in either case that the Internal Revenue Service will agree with the valuation, and the Optionee shall not make any claim against the Company or its Board of Directors, officers or employees in the event that the Internal Revenue Service
asserts that the valuation was too low. 
 (b) Electronic Delivery of Documents. The Optionee agrees to accept by email all documents
relating to the Company, the Plan or this option 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
Optionee 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
Optionee by email of their availability. The Optionee 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 this option expires or until the Optionee gives the Company written notice that it should deliver paper documents. 

(c) No Notice of Expiration Date. The Optionee agrees that the Company and its officers, employees, attorneys and agents do not have
any obligation to notify him or her 

  
 9 

 
prior to the expiration of this option pursuant to Section 6, regardless of whether this option will expire at the end of its full term or on an earlier date related to the termination of
the Optionee’s Service. The Optionee further agrees that he or she has the sole responsibility for monitoring the expiration of this option and for exercising this option, if at all, before it expires. This Subsection (c) shall supersede
any contrary representation that may have been made, orally or in writing, by the Company or by an officer, employee, attorney or agent of the Company. 

SECTION 14. DEFINITIONS. 
 (a)
“Agreement” shall mean this Stock Option 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 Optionee of the Company’s confidential information or trade secrets, which use or disclosure causes material harm to the Company; 

(ii) A material breach by the Optionee of any material agreement between the Purchaser and the Company; 

(iii) A material failure by the Optionee to comply with the Company’s written policies or rules after receiving written
notification of such failure from the Board of Directors; 
 (iv) The Optionee’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 Optionee’s gross negligence or willful misconduct in the course of performing Service; 
 (vi) A continuing failure
by the Optionee to perform reasonably assigned duties after receiving written notification of such failure from the Board of Directors; or 

(vii) A failure by the Optionee 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 Purchaser’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 

  
 10 

 
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 a committee
of the Board of Directors, as described in Section 2 of the Plan. 
 (g) “Company” shall mean Acacia Communications,
Inc., a Delaware corporation. 
 (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) “Date of Grant” shall
mean the date of grant specified in the Notice of Stock Option Grant, which date shall be the later of (i) the date on which the Board of Directors resolved to grant this option or (ii) the first day of the Optionee’s Service. 

(j) “Disability” shall mean that the Optionee is unable to engage in any substantial gainful activity by reason of any
medically determinable physical or mental impairment. 
 (k) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (l) “Exercise Price”
shall mean the amount for which one Share may be purchased upon exercise of this option, as specified in the Notice of Stock Option Grant. 

(m) “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. 
 (n) “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. 

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

(i) The involuntary discharge of the Optionee by the Company (or the Parent or Subsidiary employing him) for reasons other than
Cause; or 
 (ii) The voluntary resignation of the Optionee following any of the following events, if such event occurs
without the consent of the Optionee: (A) a change in the Optionee’s position with the Company (or the Parent or 

  
 11 

 
Subsidiary employing him or her) that materially reduces his or her level of authority or responsibility (provided that the Optionee’s level of authority or responsibility shall not be
deemed to be reduced merely because there are additional employees more senior to the Optionee as a result of the Change in Control), (B) a reduction in the Optionee’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 Optionee’s principal workplace will be relocated more than 50 miles 

(p) “ISO” shall mean an employee incentive stock option described in Section 422(b) of the Code. 

(q) “Notice of Stock Option Grant” shall mean the document so entitled to which this Agreement is attached. 

(r) “NSO” shall mean a stock option not described in Section 422(b) or 423(b) of the Code. 

(s) “Optionee” shall mean the person named in the Notice of Stock Option Grant. 

(t) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(u) “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. 

(v) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as in effect on the Date of Grant. 

(w) “Purchase Price” shall mean the Exercise Price multiplied by the number of Shares with respect to which this option is
being exercised. 
 (x) “Right of First Refusal” shall mean the Company’s right of first refusal described in
Section 7. 
 (y) “Securities Act” shall mean the Securities Act of 1933, as amended. 

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

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

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

  
 12 

 (cc) “Subsidiary” shall mean any corporation (other than the Company) in an
unbroken chain of 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. 
 (dd) “Transferee” shall mean any person to whom the Optionee has directly or
indirectly transferred any Share acquired under this Agreement. 
 (ee) “Transfer Notice” shall mean the notice of a
proposed transfer of Shares described in Section 7. 

  
 13 

 ACACIA COMMUNICATIONS, INC. 2009
STOCK PLAN 
 NOTICE OF STOCK OPTION
GRANT 
 (INSTALLMENT VESTING, ACCELERATION) 

The Optionee has been granted the following option to purchase shares of the Common Stock of Acacia Communications, Inc.: 

 

			
	Name of Optionee:	  	«Name»
		
	Total Number of Shares:	  	«TotalShares»
		
	Type of Option:	  	«ISO» Incentive Stock Option (ISO)
		
		  	«NSO» Nonstatutory Stock Option (NSO)
		
	Exercise Price per Share:	  	$«PricePerShare»
		
	Date of Grant:	  	«DateGrant»
		
	Date Exercisable:	  	This option may be exercised with respect to the first 25% of the Shares subject to this option when the Optionee completes 12 months of continuous Service beginning with the Vesting Commencement Date set forth below. This option
may be exercised with respect to an additional 1/48th of the Shares subject to this option when the Optionee completes each month of continuous Service thereafter. This option may become exercisable on an accelerated basis under Section 2(a) of
the Stock Option Agreement.
		
	Vesting Commencement Date:	  	«VestComDate»
		
	Expiration Date:	  	«ExpDate». This option expires earlier if the Optionee’s Service terminates earlier, as provided in Section 6 of the Stock Option Agreement.

 By signing below, the Optionee and the Company agree that this option is granted under, and governed by the terms and
conditions of, the 2009 Stock Plan and the Stock Option Agreement. Both of these documents are attached to, and made a part of, this Notice of Stock Option Grant. Section 13 of the Stock Option Agreement includes important acknowledgements
of the Optionee. 
  

							
	OPTIONEE:	 		 	ACACIA COMMUNICATIONS, INC.
				
	  
	 		 	By:	 	  

		 		 	Title:	 	  

 THE OPTION GRANTED PURSUANT TO THIS AGREEMENT AND THE SHARES ISSUABLE UPON THE EXERCISE THEREOF 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. 
 ACACIA COMMUNICATIONS, INC. 2009 STOCK
PLAN: 
 STOCK OPTION AGREEMENT (INSTALLMENT
VESTING) 
 SECTION 1. GRANT OF OPTION. 

(a) Option. On the terms and conditions set forth in the Notice of Stock Option Grant and this Agreement, the Company grants to the
Optionee on the Date of Grant the option to purchase at the Exercise Price the number of Shares set forth in the Notice of Stock Option Grant. The Exercise Price is agreed to be at least 100% of the Fair Market Value per Share on the Date of Grant
(110% of Fair Market Value if this option is designated as an ISO in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). This option is intended to be an ISO or an NSO, as provided in the Notice of Stock Option Grant. 

(b) $100,000 Limitation. Even if this option is designated as an ISO in the Notice of Stock Option Grant, it shall be deemed to be an
NSO to the extent (and only to the extent) required by the $100,000 annual limitation under Section 422(d) of the Code. 
 (c) Stock
Plan and Defined Terms. This option is granted pursuant to the Plan, a copy of which the Optionee acknowledges having received. The provisions of the Plan are incorporated into this Agreement by this reference. Capitalized terms are defined in
Section 14 of this Agreement. 
 SECTION 2. RIGHT TO EXERCISE. 

(a) Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or part of this
option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, the following rules shall apply if the Company is subject to a Change in Control before the Optionee’s Service
terminates: 
  

	 	i.	At all times after the Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service. 

	 	ii.	If the Optionee is subject to an Involuntary Termination upon or after the Change in Control, then this option shall vest in full and become immediately exercisable. 

(b) Stockholder Approval. Any other provision of this Agreement notwithstanding, no portion of this option shall be exercisable at any
time prior to the approval of the Plan by the Company’s stockholders. 
 SECTION 3. NO TRANSFER OR ASSIGNMENT OF OPTION. 

Except as otherwise provided in this Agreement, this option and the rights and privileges conferred hereby shall not be sold, pledged or
otherwise transferred (whether by operation of law or otherwise) and shall not be subject to sale under execution, attachment, levy or similar process. 

SECTION 4. EXERCISE PROCEDURES. 
 (a)
Notice of Exercise. The Optionee or the Optionee’s representative may exercise this option by giving written notice to the Company pursuant to Section 12(c). The notice shall specify the election to exercise this option, the number
of Shares for which it is being exercised and the form of payment. The person exercising this option shall sign the notice. In the event that this option is being exercised by the representative of the Optionee, the notice shall be accompanied by
proof (satisfactory to the Company) of the representative’s right to exercise this option. The Optionee or the Optionee’s representative shall deliver to the Company, at the time of giving the notice, payment in a form permissible under
Section 5 for the full amount of the Purchase Price. 
 (b) Issuance of Shares. After receiving a proper notice of exercise, the
Company shall cause to be issued one or more certificates evidencing the Shares for which this option has been exercised. Such Shares shall be registered (i) in the name of the person exercising this option, (ii) in the names of such
person and his or her spouse as community property or as joint tenants with the right of survivorship or (iii) with the Company’s consent, in the name of a revocable trust. The Company shall cause such certificates to be delivered to or
upon the order of the person exercising this option. 
 (c) Withholding Taxes. In the event that the Company determines that it is
required to withhold any tax as a result of the exercise of this option, the Optionee, as a condition to the exercise of this option, shall make arrangements satisfactory to the Company to enable it to satisfy all withholding requirements. The
Optionee shall also make arrangements satisfactory to the Company to enable it to satisfy any withholding requirements that may arise in connection with the disposition of Shares purchased by exercising this option. 

SECTION 5. PAYMENT FOR STOCK. 
 (a)
Cash. All or part of the Purchase Price may be paid in cash or cash equivalents. 

  
 2 

 (b) Surrender of Stock. At the discretion of the Board of Directors, all or any part of
the Purchase Price may be paid by surrendering, or attesting to the ownership of, Shares that are already owned by the Optionee. Such Shares shall be surrendered to the Company in good form for transfer and shall be valued at their Fair Market Value
as of the date when this option is exercised. 
 (c) Exercise/Sale. All or part of the Purchase Price and any withholding taxes may
be paid by the delivery (on a form prescribed by the Company) of an irrevocable direction to a securities broker approved by the Company to sell Shares and to deliver all or part of the sales proceeds to the Company. However, payment pursuant to
this Subsection (c) shall be permitted only if (i) Stock then is publicly traded and (ii) such payment does not violate applicable law. 

SECTION 6. TERM AND EXPIRATION. 
 (a)
Basic Term. This option shall in any event expire on the expiration date set forth in the Notice of Stock Option Grant, which date is 10 years after the Date of Grant (five years after the Date of Grant if this option is designated as an ISO
in the Notice of Stock Option Grant and Section 3(b) of the Plan applies). 
 (b) Termination of Service (Except by Death). If
the Optionee’s Service terminates for any reason other than death, then this option shall expire on the earliest of the following occasions: 

(i) The expiration date determined pursuant to Subsection (a) above; 

(ii) The date three months after the termination of the Optionee’s Service for any reason other than Disability; or 

(iii) The date six months after the termination of the Optionee’s Service by reason of Disability. 

The Optionee may exercise all or part of this option at any time before its expiration under the preceding sentence, but only to the extent that this option
had become exercisable before the Optionee’s Service terminated. When the Optionee’s Service terminates, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. In the event
that the Optionee dies after termination of Service but before the expiration of this option, all or part of this option may be exercised (prior to expiration) by the executors or administrators of the Optionee’s estate or by any person who has
acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s Service terminated. 

(c) Death of the Optionee. If the Optionee dies while in Service, then this option shall expire on the earlier of the following dates:

 (i) The expiration date determined pursuant to Subsection (a) above; or 

  
 3 

 (ii) The date 12 months after the Optionee’s death. 

All or part of this option may be exercised at any time before its expiration under the preceding sentence by the executors or administrators of the
Optionee’s estate or by any person who has acquired this option directly from the Optionee by beneficiary designation, bequest or inheritance, but only to the extent that this option had become exercisable before the Optionee’s death. When
the Optionee dies, this option shall expire immediately with respect to the number of Shares for which this option is not yet exercisable. 

(d) Part-Time Employment and Leaves of Absence. If the Optionee commences working on a part-time basis, then the Company may adjust the
vesting schedule set forth in the Notice of Stock Option Grant. If the Optionee goes on a leave of absence, then the Company may adjust the vesting schedule set forth in the Notice of Stock Option 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 for any purpose under this Agreement while the Optionee is 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 the Optionee immediately returns to active work. 
 (e) Notice Concerning ISO Treatment. Even if this option is
designated as an ISO in the Notice of Stock Option Grant, it ceases to qualify for favorable tax treatment as an ISO to the extent that it is exercised: 

(i) More than three months after the date when the Optionee ceases to be an Employee for any reason other than death or
permanent and total disability (as defined in Section 22(e)(3) of the Code); 
 (ii) More than 12 months after the date
when the Optionee ceases to be an Employee by reason of permanent and total disability (as defined in Section 22(e)(3) of the Code); or 

(iii) More than three months after the date when the Optionee has been on a leave of absence for 90 days, unless the
Optionee’s reemployment rights following such leave were guaranteed by statute or by contract. 
 SECTION 7. RIGHT OF FIRST REFUSAL. 

(a) Right of First Refusal. In the event that the Optionee proposes 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 the Optionee desires to transfer Shares acquired under this Agreement,
the Optionee shall give a written Transfer Notice to the Company describing fully the proposed transfer, 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 the Optionee and by the

  
 4 

 
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 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 the date when it received the Transfer Notice, the Optionee 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 the
Optionee 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 Optionee, 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 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 7 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 7. 
 (d) Termination of Right of First Refusal. Any other
provision of this Section 7 notwithstanding, in the event that the Stock is readily tradable on an established securities market when the Optionee desires to transfer Shares, the Company shall have no Right of First Refusal, and the Optionee
shall have no obligation to comply with the procedures prescribed by Subsections (a) and (b) above. 
 (e) Permitted
Transfers. This Section 7 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 Optionee’s Immediate Family or to a trust established by
the Optionee for the benefit of the Optionee and/or one or more members of the Optionee’s Immediate Family, provided in either case that the Transferee agrees in writing on a form prescribed by the Company to be bound by

  
 5 

 
all provisions of this Agreement. If the Optionee transfers any Shares acquired under this Agreement, 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 Transferee to the same extent as to the Optionee. 
 (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 7, 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 7. 

SECTION 8. LEGALITY OF INITIAL ISSUANCE. 

No Shares shall be issued upon the exercise of this option unless and until the Company has determined that: 

(a) It and the Optionee have taken any actions required to register the Shares under the Securities Act or to perfect an
exemption from the registration requirements thereof; 
 (b) Any applicable listing requirement of any stock exchange or
other securities market on which Stock is listed has been satisfied; and 
 (c) Any other applicable provision of federal,
State or foreign law has been satisfied. 
 SECTION 9. NO REGISTRATION RIGHTS. 

The Company may, but shall not be obligated to, register or qualify the sale of Shares under the Securities Act or any other applicable law.
The Company shall not be obligated to take any affirmative action in order to cause the sale of Shares under this Agreement to comply with any law. 

SECTION 10. RESTRICTIONS ON TRANSFER OF 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 such 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. 

  
 6 

 (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, the Optionee 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 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 Subsection (b). This Subsection (b) shall not apply to Shares registered in the public offering under the Securities
Act. 
 (c) Investment Intent at Grant. The Optionee represents and agrees that the Shares to be acquired upon exercising this option
will be acquired for investment, and not with a view to the sale or distribution thereof. 
 (d) Investment Intent at Exercise. 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, the Optionee shall represent and agree at the time of
exercise that the Shares being acquired upon exercising this option 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) Legends. All certificates evidencing Shares purchased 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 

  
 7 

 
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.” 

All certificates evidencing Shares purchased 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.” 
 (f) Removal of Legends. If, in the opinion of the Company and its counsel, any legend
placed on a stock certificate representing Shares sold 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. 
 (g) Administration. Any determination by the Company and its counsel in connection with any of the matters set forth
in this Section 10 shall be conclusive and binding on the Optionee and all other persons. 
 SECTION 11. ADJUSTMENT OF SHARES. 

In the event of any transaction described in Section 8(a) of the Plan, the terms of this option (including, without limitation, the number
and kind of Shares subject to this option and the Exercise Price) shall be adjusted as set forth in Section 8(a) of the Plan. In the event that the Company is a party to a merger or consolidation, this option shall be subject to the agreement
of merger or consolidation, as provided in Section 8(b) of the Plan. 
 SECTION 12. MISCELLANEOUS PROVISIONS. 

(a) Rights as a Stockholder. Neither the Optionee nor the Optionee’s representative shall have any rights as a stockholder with
respect to any Shares subject to this option until the Optionee or the Optionee’s representative becomes entitled to receive such Shares by filing a notice of exercise and paying the Purchase Price pursuant to Sections 4 and 5. 

(b) No Retention Rights. Nothing in this option or in the Plan shall confer upon the Optionee any right to continue in Service 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 the Optionee) or of the Optionee, 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. 

  
 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 Federal Express Corporation, with
shipping charges prepaid. Notice shall be addressed to the Company at its principal executive office and to the Optionee at the address that he or she most recently provided to the Company in accordance with this Subsection (c). 

(d) Modifications and Waivers. No provision of this Agreement shall be modified, waived or discharged unless the modification, waiver
or discharge is agreed to in writing and signed by the Optionee and by an authorized officer of the Company (other than the Optionee). No waiver by either party of any breach of, or of compliance with, any condition or provision of this Agreement by
the other party shall be considered a waiver of any other condition or provision or of the same condition or provision at another time. 

(e) Entire Agreement. The Notice of Stock Option 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. 

(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 13. ACKNOWLEDGEMENTS OF THE OPTIONEE. 

(a) Tax Consequences. The Optionee agrees that the Company does not have a duty to design or administer the Plan or its other
compensation programs in a manner that minimizes the Optionee’s tax liabilities. The Optionee shall not make any claim against the Company or its Board of Directors, officers or employees related to tax liabilities arising from this option or
the Optionee’s other compensation. In particular, the Optionee acknowledges that this option is exempt from Section 409A of the Code only if the Exercise Price is at least equal to the Fair Market Value per Share on the Date of Grant.
Since Shares are not traded on an established securities market, the determination of their Fair Market Value is made by the Board of Directors or by an independent valuation firm retained by the Company. The Optionee acknowledges that there is no
guarantee in either case that the Internal Revenue Service will agree with the valuation, and the Optionee shall not make any claim against the Company or its Board of Directors, officers or employees in the event that the Internal Revenue Service
asserts that the valuation was too low. 
 (b) Electronic Delivery of Documents. The Optionee agrees to accept by email all documents
relating to the Company, the Plan or this option 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
Optionee also agrees that the Company may deliver these documents by posting them on a website 

  
 9 

 
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 Optionee by email of their availability. The
Optionee 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 this option expires or until the Optionee gives the Company written notice that it should deliver paper documents. 

(c) No Notice of Expiration Date. The Optionee agrees that the Company and its officers, employees, attorneys and agents do not have
any obligation to notify him or her prior to the expiration of this option pursuant to Section 6, regardless of whether this option will expire at the end of its full term or on an earlier date related to the termination of the Optionee’s
Service. The Optionee further agrees that he or she has the sole responsibility for monitoring the expiration of this option and for exercising this option, if at all, before it expires. This Subsection (c) shall supersede any contrary
representation that may have been made, orally or in writing, by the Company or by an officer, employee, attorney or agent of the Company. 
 SECTION 14.
DEFINITIONS. 
 (a) “Agreement” shall mean this Stock Option 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 Optionee of the Company’s confidential information or trade secrets, which use or disclosure causes material harm to the Company; 

 

	 	ii.	A material breach by the Optionee of any material agreement between the Purchaser and the Company; 

  

	 	iii.	A material failure by the Optionee to comply with the Company’s written policies or rules after receiving written notification of such failure from the Board of Directors; 

 

	 	iv.	The Optionee’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 Optionee’s gross negligence or willful misconduct in the course of performing Service; 

  
 10 

	 	vi.	A continuing failure by the Optionee to perform reasonably assigned duties after receiving written notification of such failure from the Board of Directors; or 

 

	 	vii.	A failure by the Optionee 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 Optionee’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 a committee of the Board of Directors, as described in Section 2 of the Plan. 

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

(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) “Date of Grant” shall mean the date of grant
specified in the Notice of Stock Option Grant, which date shall be the later of (i) the date on which the Board of Directors resolved to grant this option or (ii) the first day of the Optionee’s Service. 

(j) “Disability” shall mean that the Optionee is unable to engage in any substantial gainful activity by reason of any
medically determinable physical or mental impairment. 
 (k) “Employee” shall mean any individual who is a common-law employee of the Company, a Parent or a Subsidiary. 
 (l) “Exercise Price”
shall mean the amount for which one Share may be purchased upon exercise of this option, as specified in the Notice of Stock Option Grant. 

  
 11 

 (m) “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. 
 (n)
“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. 
 (o) “Involuntary Termination” shall mean the termination of the Optionee’s Service by reason of:

  

	 	i.	The involuntary discharge of the Optionee by the Company (or the Parent or Subsidiary employing him) for reasons other than Cause; or 

 

	 	ii.	The voluntary resignation of the Optionee following any of the following events, if such event occurs without the consent of the Optionee (A) a change in the Optionee’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 Optionee’s level of authority or responsibility shall not be deemed to be reduced merely because there are additional
employees more senior to the Optionee as a result of the Change in Control), (B) a reduction in the Optionee’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 Optionee’s principal workplace will be relocated more than 50 miles. 

(p) “ISO” shall mean an employee incentive stock option described in Section 422(b) of the Code. 

(q) “Notice of Stock Option Grant” shall mean the document so entitled to which this Agreement is attached. 

(r) “NSO” shall mean a stock option not described in Section 422(b) or 423(b) of the Code. 

(s) “Optionee” shall mean the person named in the Notice of Stock Option Grant. 

(t) “Outside Director” shall mean a member of the Board of Directors who is not an Employee. 

(u) “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. 

  
 12 

 (v) “Plan” shall mean the Acacia Communications, Inc. 2009 Stock Plan, as in
effect on the Date of Grant. 
 (w) “Purchase Price” shall mean the Exercise Price multiplied by the number of Shares with
respect to which this option is being exercised. 
 (x) “Right of First Refusal” shall mean the Company’s right of
first refusal described in Section 7. 
 (y) “Securities Act” shall mean the Securities Act of 1933, as amended. 

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

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

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

(cc) “Subsidiary” shall mean any corporation (other than the Company) in an unbroken chain of 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. 

(dd) “Transferee” shall mean any person to whom the Optionee has directly or indirectly transferred any Share acquired under
this Agreement. 
 (ee) “Transfer Notice” shall mean the notice of a proposed transfer of Shares described in
Section 7. 

  
 13 

 STOCK OPTION AMENDMENT AGREEMENT 

This STOCK OPTION AMENDMENT AGREEMENT by and between Acacia Communications, Inc., a Delaware corporation (the “Company”) and
[                    ] (the “Optionee”) is made as of [            ],
2015 (this “Agreement”). 
 WHEREAS, the Company and the Optionee are parties to (i) a Notice of Grant and
Stock Option Agreement dated as of [            ] 2      , (“Option Agreement”), pursuant to which the Optionee was granted an option to
purchase [                ] shares of the Company’s Common Stock (the “Option”); 

WHEREAS, the Company seeks to provide certain accelerated vesting terms upon a change in control to the Optionee; and 

WHEREAS, the Optionee hereby agrees to amend the Option Agreement in order to modify the provisions regarding vesting as set forth
herein. 
 NOW, THEREFORE, in consideration of the foregoing, the parties hereby agree as follows: 

1. Amendment of Option Agreement. 

(a) Section 2(a) of the Option Agreement is hereby amended and restated in its entirety to read as follows: 

“Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or
part of this option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, if the Company is subject to a Change in Control before the Optionee’s Service terminates, then at all
times after the Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service.” 

 (b) Section [14] of the Option Agreement is hereby amended by inserting the following definitions
immediately after the definition of “Board of Directors”: 
 “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.” 
 (c) Section [14] of the Option
Agreement is hereby amended by renumbering the definitions listed therein to reflect the amendments set forth in Section 1(b) hereof. 

2. Effective Date. This Agreement will become effective as of the date set forth above. 

3. Counterparts. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument. 
 4. Effect of Amendment to the Option Agreement. Except as amended
hereby, all of the terms of the Option Agreement shall remain and continue in full force and effect. 
 (REMAINDER OF PAGE INTENTIONALLY
BLANK) 

 IN WITNESS WHEREOF, the parties have executed this Stock Option Amendment Agreement as of the
date first above written above. 
  

			
	ACACIA COMMUNICATIONS, INC.
		
	By:	 	  

	Name:	 	  

	Title:	 	  

 

			
	OPTIONEE
	
	  

	Printed Name:	 	  

 SIGNATURE PAGE 

TO STOCK OPTION AMENDMENT AGREEMENT 

 STOCK OPTION AMENDMENT AGREEMENT 

This STOCK OPTION AMENDMENT AGREEMENT by and between Acacia Communications, Inc., a Delaware corporation (the “Company”) and
[                    ] (the “Optionee”) is made as of [            ],
2015 (this “Agreement”). 
 WHEREAS, the Company and the Optionee are parties to (i) a Notice of Grant and
Stock Option Agreement dated as of [            ] 2      , (“Option Agreement”), pursuant to which the Optionee was granted an option to
purchase [                ] shares of the Company’s Common Stock (the “Option”); 

WHEREAS, the Company seeks to provide certain accelerated vesting terms upon a change in control to the Optionee; and 

WHEREAS, the Optionee hereby agrees to amend the Option Agreement in order to modify the provisions regarding vesting as set forth
herein. 
 NOW, THEREFORE, in consideration of the foregoing, the parties hereby agree as follows: 

1. Amendment of Option Agreement. 

(a) Section 2(a) of the Option Agreement is hereby amended and restated in its entirety to read as follows: 

“Exercisability. Subject to Subsection (b) below and the other conditions set forth in this Agreement, all or
part of this option may be exercised prior to its expiration at the time or times set forth in the Notice of Stock Option Grant. In addition, the following rules shall apply if the Company is subject to a Change in Control before the Optionee’s
Service terminates: 
  

	 	i.	At all times after a Change in Control the vested portion of the option shall be determined by adding six (6) months to the Optionee’s actual Service. 

 

	 	ii.	If the Optionee is subject to an Involuntary Termination upon or after the Change in Control, then this option shall vest in full and become immediately exercisable.” 

(b) Section [14] of the Option Agreement is hereby amended by inserting the following definitions immediately after the definition of
“Board of Directors”: 
 “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 Optionee of the Company’s confidential information or trade secrets, which use or disclosure causes material harm to the Company; 

	 	ii.	A material breach by the Optionee of any material agreement between the Purchaser and the Company; 

  

	 	iii.	A material failure by the Optionee to comply with the Company’s written policies or rules after receiving written notification of such failure from the Board of Directors; 

 

	 	iv.	The Optionee’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 Optionee’s gross negligence or willful misconduct in the course of performing Service; 

  

	 	vi.	A continuing failure by the Optionee to perform reasonably assigned duties after receiving written notification of such failure from the Board of Directors; or 

 

	 	vii.	A failure by the Optionee 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 Optionee’s cooperation.

 “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.” 
 (c) Section [14] of the Option Agreement is hereby amended by inserting the following
definitions immediately after the definition of “Immediate Family”: 
 “Involuntary Termination”
shall mean the termination of the Optionee’s Service by reason of: 
  

	 	i.	The involuntary discharge of the Optionee by the Company (or the Parent or Subsidiary employing him) for reasons other than Cause; or 

 

	 	ii.	 The voluntary resignation of the Optionee following any of the following events, if such event occurs without the consent of the Optionee (A) a
change in the Optionee’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 Optionee’s level of authority or responsibility shall not be deemed to be
reduced merely because there are additional employees more senior to the Optionee as a result of the Change in Control), (B) a reduction in the Optionee’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 Optionee’s principal workplace will be relocated more than 50 miles. 

(d) Section [14] of the Option Agreement is hereby amended by renumbering the definitions listed therein to reflect the amendments set forth
in Sections 1(b) through 1(c) hereof. 
 2. Effective Date. This Agreement will become effective as of the date set forth above. 

3. Counterparts. This Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument. 
 4. Effect of Amendment to the Option Agreement. Except as amended
hereby, all of the terms of the Option Agreement shall remain and continue in full force and effect. 
 (REMAINDER OF PAGE INTENTIONALLY
BLANK) 

 IN WITNESS WHEREOF, the parties have executed this Stock Option Amendment Agreement as of the
date first above written above. 
  

			
	ACACIA COMMUNICATIONS, INC.
		
	By:	 	  

	Name:	 	  

	Title:	 	  

	
	OPTIONEE

 
			
	
	  

	Printed Name:	 	  

 SIGNATURE PAGE 

TO STOCK OPTION AMENDMENT AGREEMENT

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