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                                  June 2, 2000





(650) 849-5318                                                     C 41507-00001


Harmonic Inc.
549 Baltic Way
Sunnyvale, CA 94089

         Re: Registration Statement on Form S-4

Gentlemen:

     We have acted as counsel for Harmonic, Inc., a Delaware corporation (the
"Company"), in connection with the preparation and filing with the Securities
and Exchange Commission (the "Commission") under Rule 462(b) of the Securities
Act of 1933, as amended (the "Act"), of the above-captioned Registration
Statement on Form S-4 (the "Registration Statement"), relating to the
registration of 1,628,775 shares of the Company's Common Stock, par value $.001
per share (the "Shares"). The Company proposes to issue the Shares in exchange
for shares of C-Cube Microsystems Inc.'s ("C-Cube Microsystems") Common Stock,
par value $0.001 per share. In connection therewith, we have examined, among
other things, the Registration Statement, as well as the proceedings and other
actions taken by the Company in connection with the authorization of the Shares
and such other matters as we deemed necessary for purposes of rendering this
opinion.

     Based on the foregoing, and in reliance thereon, we are of the opinion that
(i) the Shares have been duly authorized and (ii) upon issuance of the Shares in
connection with the merger of C-Cube Microsystems into the Company as described
in the Registration Statement and the Prospectus constituting a part thereof
(the "Prospectus"), the Shares will be validly issued, fully paid and
non-assessable.

     The Company is a Delaware corporation. We are not admitted to practice in
Delaware. However, we are familiar with the Delaware General Corporation Law and
have made such review thereof as we consider necessary for the purpose of this
opinion. Subject to the foregoing, this opinion is limited to the present laws
of the State of Delaware and to the present federal laws of the United States of
America.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to this firm under the heading
"Legal Matters" contained in the Prospectus. In giving this consent, we do not
admit that we are within the category of persons whose consent is required under
Section 7 of the Act or the General Rules and Regulations of the Securities and
Exchange Commission.

                                   Sincerely,

                                   /s/ Gibson, Dunn & Crutcher LLP

                                   Gibson, Dunn & Crutcher LLP

LC/SS/ss