Exhibit 32.2

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report on Form 10-Q of Acacia Communications, Inc. (the “Company”) for the period ended March 31, 2020 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), John F. Gavin, as Chief Financial Officer of the Company, hereby certifies, as of the date hereof, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that, the Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, and the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

	Acacia Communications, Inc.
Date: May 4, 2020	By:	/s/ John F. Gavin
		John F. Gavin
		Chief Financial Officer