Exhibit 99.1

				Acacia Communications, Inc. 3 Mill and Main Place #400 Maynard, MA 01754   978-938-4896 www.acacia-inc.com

January 8, 2021

Cisco Systems, Inc.

170 West Tasman Drive

San Jose, California 95134

Attention: General Counsel

Facsimile No.: (408) 525-2912

Fenwick & West LLP

801 California Street

Mountain View, California 94041

Attention:     Douglas N. Cogen

                     Ken S. Myers

Facsimile No.: (650) 938-5200

Reference is hereby made to that certain Agreement and Plan of Merger (the “Merger Agreement”), dated as of July 8, 2019, by and among Cisco Systems, Inc., a California corporation (“Parent”), Amarone Acquisition Corp., a Delaware corporation and wholly owned subsidiary of Parent, and Acacia Communications, Inc., a Delaware corporation (the “Company”).

The Company, acting pursuant to Section 7.1(b) of the Merger Agreement, hereby exercises its right to terminate the Merger Agreement, effectively immediately.