SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
X	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* SUMMIT PARTNERS L P (Last) (First) (Middle) 222 BERKELEY STREET 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Acacia Communications, Inc. [ ACIA ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) X Other (specify below) Manager of GP of 10% owner
	3. Date of Earliest Transaction (Month/Day/Year) 05/18/2016
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	05/18/2016		C		2,896,329	A	(1)	2,896,329(2)	I	See Footnotes.(3)(4)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series D Convertible Preferred Stock	(1)	05/18/2016		C		2,896,329		(1)	(1)	Common Stock	2,896,329(2)	$0(1)	0	I	See Footnotes(3)(4)

1. Name and Address of Reporting Person* SUMMIT PARTNERS L P (Last) (First) (Middle) 222 BERKELEY STREET 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) X Other (specify below) Manager of GP of 10% owner

1. Name and Address of Reporting Person* SUMMIT PARTNERS VC III, LP (Last) (First) (Middle) 222 BERKELEY STREET, 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director 10% Owner Officer (give title below) X Other (specify below) GP of 10% owner

1. Name and Address of Reporting Person* SUMMIT PARTNERS VC III, LLC (Last) (First) (Middle) 222 BERKELEY STREET, 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director 10% Owner Officer (give title below) X Other (specify below) Manager of GP of 10% owner

1. Name and Address of Reporting Person* SUMMIT MASTER COMPANY, LLC (Last) (First) (Middle) 222 BERKELEY STREET, 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director 10% Owner Officer (give title below) X Other (specify below) Manager of Manager of 10% owne

1. Name and Address of Reporting Person* Summit Investors Management, LLC (Last) (First) (Middle) 222 BERKELEY STREET, 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director 10% Owner Officer (give title below) X Other (specify below) Manager and GP of 10% Owner

1. Name and Address of Reporting Person* Summit Partners Venture Capital Fund III-A, L.P. (Last) (First) (Middle) 222 BERKELEY STREET, 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Summit Partners Venture Capital Fund III-B, L.P. (Last) (First) (Middle) 222 BERKELEY STREET, 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Summit Investors I, LLC (Last) (First) (Middle) 222 BERKELEY STREET, 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Summit Investors I (UK), L.P. (Last) (First) (Middle) 222 BERKELEY STREET, 18TH FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. The Series D Convertible Preferred Stock converted into common stock on a one-for-one basis upon the closing of Acacia Communications, Inc.'s (the "Issuer") initial public offering without payment of consideration. The Series D Convertible Preferred Stock had no expiration date.

2. Consists of 2,198,853 shares held by Summit Partners Venture Capital Fund III-A. L.P., 666,442 shares held by Summit Partners Venture Capital Fund III-B, L.P., 28,648 shares held by Summit Investors I, LLC and 2,386 shares held by Summit Investors I (UK), L.P.

3. Summit Partners, L.P. is the managing member of Summit Partners VC III, LLC, which is the general partner of Summit Partners VC III, L.P., which is the general partner of each of Summit Partners Venture Capital Fund III-A. L.P. and Summit Partners Venture Capital Fund III-B, L.P. Summit Master Company, LLC is the managing member of Summit Investors Management, LLC, which is the manager of Summit Investors I, LLC, and the general partner of Summit Investors I (UK), L.P. Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated investment decisions, including voting and dispositive power, to Summit Partners, L.P. and its investment committee responsible for voting and investment decisions with respect to the Issuer.

4. Summit Partners, L.P., through a three-person investment committee responsible for voting and investment decisions with respect to the Issuer, currently comprised of Martin J. Mannion, Bruce R. Evans and Peter Y. Chung, has voting and dispositive power over the shares held by each of these entities and therefore may be deemed to beneficially own such shares. Each of the Summit entities mentioned herein and Messrs. Mannion, Evans and Chung disclaims beneficial ownership of the shares, except, in each case, to the extent of each such person's pecuniary interest therein.

	Summit Partners, L.P., by Summit Master Company, LLC, its GP, by /s/ Robin W. Devereux, Member	05/20/2016
	Summit Partners VC III, L.P., by Summit Partners VC III, LLC, its GP, by Summit Partners, L.P., its Managing Member, by Summit Master Company, LLC, its GP, by /s/ Robin W. Devereux, Member	05/20/2016
	Summit Partners VC III, LLC, by Summit Partners, L.P., its Managing Member, by Summit Master Company, LLC, its GP, by /s/ Robin W. Devereux, Member	05/20/2016
	Summit Master Company, LLC, by /s/ Robin W. Devereux, Member	05/20/2016
	Summit Investors Management, LLC, by Summit Master Company, LLC, its Managing Member, by /s/ Robin W. Devereux, Member	05/20/2016
	Summit Partners Venture Capital Fund III-A, L.P., by Summit Partners VC III, L.P., its GP, by Summit Partners VC III, LLC, its GP, by Summit Partners, L.P., its Managing Member, by Summit Master Company, LLC, its GP, by /s/ Robin W. Devereux, Member	05/20/2016
	Summit Partners Venture Capital Fund III-B, L.P., by Summit Partners VC III, L.P., its GP, by Summit Partners VC III, LLC, its GP, by Summit Partners, L.P., its Managing Member, by Summit Master Company, LLC, its GP, by /s/ Robin W. Devereux, Member	05/20/2016
	Summit Investors I, LLC, by Summit Investors Management, LLC, its Manager, by Summit Master Company, LLC, its Managing Member, by /s/ Robin W. Devereux, Member	05/20/2016
	Summit Investors I (UK), L.P., by Summit Investors Management, LLC, its General Partner, by Summit Master Company, LLC, its Managing Member, by /s/ Robin W. Devereux, Member	05/20/2016
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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