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                                                                     Exhibit 8.1

                  FORM OF OPINION OF GIBSON DUNN & CRUTCHER LLP




(213) 229-7000                                                    C  41507-00001


Harmonic Inc.
549 Baltic Way
Sunnyvale, California 94089

     Re:  Registration Statement on Form S-4

Ladies and Gentlemen:

     We have acted as counsel to Harmonic Inc., a Delaware corporation
("Harmonic"), in connection with the preparation and execution of the Amended
and Restated Agreement and Plan of Merger and Reorganization (the "Merger
Agreement"), dated as of December 9, 1999, by and between Harmonic and C-Cube
Microsystems Inc., a Delaware corporation ("C-Cube"). Pursuant to the Merger
Agreement, C-Cube will merge with and into Harmonic, with Harmonic surviving the
merger (the "Merger"). The Merger and certain proposed transactions incident
thereto are described in the Registration Statement on Form S-4 (the
"Registration Statement") of Harmonic, which includes the Joint Proxy
Statement/Prospectus/Information Statement of C-Cube and Harmonic ("Joint Proxy
Statement"), and which is to be filed with the U.S. Securities and Exchange
Commission under the Securities Act of 1933 on the date hereof.

     You have requested our opinion regarding certain federal income tax
consequences of the Merger. In connection with rendering this opinion, we have
assumed and relied upon (without any independent investigation):

     1.   The truth and accuracy of the statements, covenants, representations
and warranties contained in the Merger Agreement, in the representations
received from Harmonic and C-Cube (the "Tax Representation Letters") that have
been provided to us and that were issued in support of this opinion, and in the
Registration Statement;

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     2.   consummation of the Merger in accordance with the Merger Agreement,
without any waiver, breach or amendment of any material provisions of the Merger
Agreement, the effectiveness of the Merger under applicable state law, and the
performance of all covenants contained in the Merger Agreement and the Tax
Representation Letters without waiver or breach of any material provisions
thereof;

     3.   the accuracy of any representation or statement made "to the knowledge
of" or similarly qualified without such qualification, and as to all matters in
which a person or entity is making a representation, that such person or entity
is not a party to, does not have, or is not aware of, any plan, intention,
understanding or agreement inconsistent with such representation, and there is
no such plan, intention, understanding, or agreement inconsistent with such
representation;

     4.   the reporting of the Merger as a reorganization, within the meaning of
Section 368(a) of the Internal Revenue Code of 1986, as amended (the "Code"), by
Harmonic in its federal income return; and

     5.   the authenticity of original documents (including signatures),
conformity to the originals of documents submitted to us as copies, and due
execution and delivery of all documents where due execution and delivery are
prerequisites to effectiveness thereof.

     Based upon the foregoing, the discussion contained in the Joint Proxy
Statement under the caption "Material Federal Income Tax Consequences of the
Merger," subject to the limitations and qualifications described therein and
herein, is our opinion with respect to the material United States federal income
tax consequences generally applicable to the Merger.

     This opinion represents our best judgment regarding the application of
federal income tax laws under the Code, existing judicial decisions,
administrative regulations and published rulings and procedures. Because this
opinion is being delivered prior to the Effective Time of the Merger, it must be
considered prospective and dependent on future events. Our opinion is not
binding upon the Internal Revenue Service or the courts, and there is no
assurance that the Internal Revenue Service will not successfully assert a
contrary position. Furthermore, no assurance can be given that future
legislative, judicial or administrative changes, on either a prospective or
retroactive basis, would not adversely affect the accuracy of the conclusions
stated herein. We undertake no responsibility to advise you of any new
developments in the application or interpretation of the federal income tax
laws. Furthermore, in the event any one of the statements, covenants,
representations, warranties or assumptions upon which we have relied to issue
this opinion is incorrect, our opinion might be adversely affected and may not
be relied upon.

     This opinion addresses only the matters described above, and does not
address any other federal, state, local or foreign tax consequences that may
result from the Merger or any other transaction undertaken in connection with
the Merger.

     This opinion is rendered only to you and is solely for your benefit in
connection with filing the Registration Statement with the Securities and
Exchange Commission. This opinion may not be relied upon for any other purpose
or by any other person or entity, and may not be

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furnished to, quoted to or by or relied upon by any other person or entity,
without our prior written consent. We hereby consent to the use of this opinion
as an exhibit to the Registration Statement and to the use of our name under the
caption "Material Federal Income Tax Consequences" in the Joint Proxy Statement.
In giving such consent, we do not thereby admit that we are in the category of
persons whose consent is required under Section 7 of the Securities Act of 1933,
as amended, nor do we thereby admit that we are experts with respect to any part
of such Registration Statement within the meaning of the term "experts" as used
in the Securities Act of 1933, as amended.

                                       Very truly yours,



                                       Gibson, Dunn & Crutcher LLP



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