<PAGE>

   As filed with the Securities and Exchange Commission on December 22, 2000
                                                       Registration No. 333-

                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                         -----------------------------

                                    FORM S-8
                         -----------------------------

                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933

                         -----------------------------

                            SYCAMORE NETWORKS, INC.
             (Exact name of registrant as specified in its charter)

           Delaware                                        04-3410558
 (State or other jurisdiction of                (I.R.S. Employer Identification
  incorporation or organization)                              No.)

               150 Apollo Drive, Chelmsford, Massachusetts 01824
              (Address of Principal Executive Offices) (Zip Code)

                           1999 Stock Incentive Plan
                            (Full title of the plan)

                                Daniel E. Smith
                     President and Chief Executive Officer
                            Sycamore Networks, Inc.
                                150 Apollo Drive
                              Chelmsford, MA 01824
                                 (978) 250-2900
                      (Name, Address and Telephone Number,
                   Including Area Code, of Agent for Service)

                                   Copies to:
                           Margaret A. Brown, Esquire
                    Skadden, Arps, Slate, Meagher & Flom LLP
                               One Beacon Street
                             Boston, MA 02108-3194



                        CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
<S>                                       <C>               <C>                          <C>                     <C>
 Title of securities to be registered      Amount to be     Proposed maximum offering     Proposed maximum          Amount of
                                          registered (1)       price per share (2)            aggregate          Registration fee
                                                                                          offering price (2)
---------------------------------------------------------------------------------------------------------------------------------

 1999 Stock Incentive Plan, Common
 Stock, $.001 par value (1)              25,000,000 shares               $31.31              $782,750,000          $195,687.50

---------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)  In accordance with Rule 416 of the Securities Act of 1933, as amended (the
     "Securities Act"), this Registration Statement also includes an
     indeterminate number of shares that may be subject to issuance as a result
     of anti-dilution and other provisions of the plan.
<PAGE>

(2)  Estimated solely for purposes of calculating the registration fee in
     accordance with Rule 457(h) under the Securities Act.  The computation is
     on the basis of the average of the bid and asked prices on December 21,
     2000.

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

     The documents containing the information specified in Part I will be sent
or given to employees as specified by Rule 428(b)(1). Such documents are not
being filed with the Securities and Exchange Commission (the "Commission")
either as part of this Registration Statement or as prospectuses or prospectus
supplements pursuant to Rule 424. Such documents and the documents incorporated
by reference in this Registration Statement pursuant to Item 3 of Part II of
this Form, taken together, constitute a prospectus that meets the requirements
of Section 10(a) of the Securities Act.


                                    PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE

     The Registrant is subject to the informational and reporting requirements
of Sections 13(a), 14 and 15(d) of the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), and in accordance therewith files reports, proxy
statements and other information with the Securities and Exchange Commission
(the "Commission"). The following documents, which are on file with the
Commission, are incorporated in this Registration Statement by reference:

     (1) Annual Report on Form 10-K for the year ended July 31, 2000;

     (2) Current Report on Form 8-K filed on September 11, 2000;

     (3) Quarterly Report on Form 10-Q for the quarter ended October 28, 2000;
         and

     (4) The description of Common Stock contained in the Rule 424(b)(3)
         Prospectus filed on  August 16, 2000.

     All documents subsequently filed by the Registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a post-
effective amendment which indicates that all shares of Common Stock offered
hereby have been sold or which deregisters all shares of Common Stock then
remaining unsold, shall be deemed to be incorporated by reference herein and to
be part hereof from the date of the filing of such documents. Any statement
contained in a document incorporated or deemed to be incorporated by reference
herein shall be deemed to be modified or superseded for purposes of this
Registration Statement to the extent that a statement contained herein or in any
other subsequently filed document which also is or is deemed to be incorporated
by reference herein modifies or supersedes such statement. Any statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part of this Registration Statement.

                                       2
<PAGE>

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

     Article SEVENTH of the Registrant's Amended and Restated Certificate of
Incorporation (the "Restated Certificate") provides that no director of the
Registrant shall be personally liable for any monetary damages for any breach of
fiduciary duty as a director, except to the extent that the Delaware General
Corporation Law prohibits the elimination or limitation of liability of
directors for breach of fiduciary duty.

     Article EIGHTH of the Restated Certificate provides that a director or
officer of the Registrant (a) shall be indemnified by the Registrant against all
expenses (including attorneys' fees), judgments, fines and amounts paid in
settlement incurred in connection with any litigation or other legal proceeding
(other than an action by or in the right of the Registrant) brought against him
by virtue of his position as a director or officer of the Registrant if he acted
in good faith and in a manner he reasonably believed to be in, or not opposed
to, the best interests of the Registrant, and, with respect to any criminal
action or proceeding, had no reasonable cause to believe his conduct was
unlawful and (b) shall be indemnified by the Registrant against all expenses
(including attorneys' fees) and amounts paid in settlement incurred in
connection with any action by or in the right of the Registrant brought against
him by virtue of his position as director or officer of the Registrant if he
acted in good faith and in a manner he reasonably believed to be in, or not
opposed to, the best interests of the Registrant, except that no indemnification
shall be made with respect to any matter as to which such person shall have been
adjudged to be liable to the Registrant, unless the Court of Chancery of
Delaware determines that, despite such adjudication but in view of all of the
circumstances, he is entitled to indemnification of such expenses.
Notwithstanding the foregoing, to the extent that a director or officer has been
successful, on the merits or otherwise, including, without limitation, the
dismissal of an action without prejudice, he is required to be indemnified by
the Registrant against all expenses (including attorneys' fees) incurred in
connection therewith. Expenses shall be advanced to a director or officer at his
request, unless it is determined that he did not act in good faith and in a
manner he reasonably believed to be in, or not opposed to, the best interests of
the Registrant, and, with respect to any criminal action or proceeding had
reasonable cause to believe that his conduct was unlawful, provided that he
undertakes to repay the amount advanced if it is ultimately determined that he
is not entitled to indemnification for such expenses.

     Indemnification is required to be made unless the Registrant determines
that the applicable standard of conduct required for indemnification has not
been met. In the event of a determination by the Registrant that the director or
officer did not meet the applicable standard of conduct required for
indemnification, or if the Registrant fails to make an indemnification payment
within 60 days after such payment is claimed by such person, such person is
permitted to petition the court to make an independent determination as to
whether such person is entitled to indemnification. As a condition precedent to
the right of indemnification, the director or officer must give the Registrant
notice of the action for which indemnity is sought and the Registrant has the
right to participate in such action or assume the defense thereof.

     Article EIGHTH of the Restated Certificate further provides that the
indemnification provided therein is not exclusive, and provides that in the
event that the Delaware General Corporation Law is amended to expand the
indemnification permitted to directors or officers, the Registrant must
indemnify those persons to the fullest extent permitted by such law as so
amended.

     Section 145 of the Delaware General Corporation Law provides that a
corporation has the power to indemnify a director, officer, employee or agent of
the corporation and certain other persons serving at the request of the

                                       3
<PAGE>

corporation in related capacities against amounts paid and expenses incurred in
connection with an action or proceeding to which he is a party or is threatened
to be made a party by reason of such position, if such person shall have acted
in good faith and in a manner he reasonably believed to be in or not opposed to
the best interests of the corporation, and, in any criminal proceeding, if such
person had no reasonable cause to believe his conduct was unlawful; provided
that, in the case of actions brought by or in the right of the corporation, no
indemnification shall be made with respect to any matter as to which such person
shall have been adjudged to be liable to the corporation unless and only to the
extent that the adjudicating court determines that such indemnification is
proper under the circumstances.

     The Registrant has entered into indemnification agreements with each of its
director and officers. These agreements may require the Registrant, among other
things, to indemnify directors and officers against certain liabilities that may
arise by reason of their status or service as directors and officers and to
advance their expenses incurred as a result of any proceeding against them as to
which they could be indemnified.

     The Registrant has obtained liability insurance for its officers and
directors, which insures such officers and directors against certain
liabilities.

ITEM 8.  EXHIBITS

The Exhibit Index immediately preceding the exhibits is incorporated herein by
reference.

ITEM 9.  UNDERTAKINGS

     a. The undersigned Registrant hereby undertakes:

        (1) To file, during any period in which offers or sales are being made,
            a post-effective amendment to this Registration Statement:

           (i)  To include any material information with respect to the plan of
                distribution not previously disclosed in the Registration
                Statement or any material change to such information in the
                Registration Statement.

        (2) That, for the purpose of determining any liability under the
            Securities Act of 1933, each such post-effective amendment shall be
            deemed to be a new Registration Statement relating to the securities
            offered therein, and the offering of such securities at that time
            shall be deemed to be the initial bona fide offering thereof.

        (3) To remove from registration by means of a post-effective amendment
            any of the securities being registered which remain unsold at the
            termination of the offering.

     b. The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
Registrant's annual report pursuant to Section 13(a) or 15(d) of the Securities
Exchange Act of 1934 (and, where applicable, each filing of an employee benefit
plan's annual report pursuant to Section 15(d) of the Securities Exchange Act of
1934) that is incorporated by reference in the Registration Statement shall be
deemed to be a new Registration Statement relating to the securities offered
therein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

                                       4
<PAGE>

     c.   Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, or otherwise,
the Registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.

                                       5
<PAGE>

                                   SIGNATURES

     Pursuant to the requirements of the Securities Act, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Chelmsford, Commonwealth of Massachusetts, on this
21st day of December, 2000.


                              SYCAMORE NETWORKS, INC.

                              By: /s/  Daniel E. Smith
                                 -------------------------------------------
                                 Daniel E. Smith
                                 President and Chief Executive Officer

                        POWER OF ATTORNEY AND SIGNATURES

     We, the undersigned officers and directors of Sycamore Networks, Inc.,
hereby severally constitute Gururaj Deshpande, Daniel E. Smith and Frances M.
Jewels, and each of them individually, our true and lawful attorneys with full
power to them, and each of them singly, to sign for us and in our names in the
capacities indicated below, the Registration Statement on Form S-8 filed
herewith and any and all subsequent amendments to said Registration Statement,
and generally to do all such things in our names and behalf in our capacities as
officers and directors to enable Sycamore Networks, Inc. to comply with all
requirements of the Securities and Exchange Commission, hereby ratifying and
confirming our signatures as they may be signed by said attorneys, or any of
them, to said Registration Statement and any and all amendments thereto.

     Pursuant to the requirements of the Securities Act, this Registration
Statement has been signed below by the following persons in the capacities
indicated on this 21st day of December, 2000.

   /s/ Gururaj Deshpande            Chairman of the Board of Directors
-----------------------------
     Gururaj Deshpande


     /s/ Daniel E. Smith            Chief Executive Officer and Director
-----------------------------
       Daniel E. Smith

    /s/ Frances M. Jewels           Chief Financial Officer, Vice President,
-----------------------------       Finance and Administration, Secretary and
      Frances M. Jewels             Treasurer


     /s/ Timothy Barrows            Director
-----------------------------
        Timothy Barrows

       /s/ Paul J. Ferri            Director
-----------------------------
         Paul J. Ferri

     /s/ John W. Gerdelman          Director
-----------------------------
        John W. Gerdelman

                                       6
<PAGE>

                                 EXHIBIT INDEX

<TABLE>
<CAPTION>

 EXHIBIT
 NUMBER                         DESCRIPTION
  ---------  -----------------------------------------------------------------------
<C>        <S>

   *4.1    Specimen Certificate of Common Stock, $.001 par value per share, of the
           Registrant is incorporated herein by reference to Exhibit 4(a) to the
           Registrant's Registration Statement on Form S-4 (Registration No.
           333-40146)

    5.1    Opinion of Skadden, Arps, Slate, Meagher & Flom LLP

   23.1    Consent of Skadden, Arps, Slate, Meagher & Flom LLP (included in Exhibit
           5.1)

   23.2    Consent of PricewaterhouseCoopers LLP (Boston, Massachusetts)

   24.1    Power of Attorney (included in the signature pages of this
           Registration Statement)
</TABLE>

------------------------------
*Incorporated by reference to Sycamore Networks, Inc.'s Registration Statement
on Form S-1 (Registration Statement No. 333-84635)
[{"type": "S-8", "sequence": "1", "filename": "0001.txt", "description": "FORM S-8", "secsgml_size_bytes": 18620}]
{"company-data": {"conformed-name": "SYCAMORE NETWORKS INC", "cik": "0001092367", "assigned-sic": "3661", "irs-number": "043410558", "state-of-incorporation": "DE", "fiscal-year-end": "0731"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-52562", "film-number": "794379"}, "business-address": {"street1": "10 ELIZABETH DRIVE", "city": "CHELMSFORD", "state": "MA", "zip": "01824", "phone": "9782502900"}, "mail-address": {"street1": "10 ELIZABETH DRIVE", "city": "CHELMSORD", "state": "MA", "zip": "01824"}}
As filed with the Securities and Exchange Commission on December 22, 2000
                                                       Registration No. 333-

                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                         -----------------------------

                                    FORM S-8
                         -----------------------------

                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933

                         -----------------------------

                            SYCAMORE NETWORKS, INC.
             (Exact name of registrant as specified in its charter)

           Delaware                                        04-3410558
 (State or other jurisdiction of                (I.R.S. Employer Identification
  incorporation or organization)                              No.)

               150 Apollo Drive, Chelmsford, Massachusetts 01824
              (Address of Principal Executive Offices) (Zip Code)

                           1999 Stock Incentive Plan
                            (Full title of the plan)

                                Daniel E. Smith
                     President and Chief Executive Officer
                            Sycamore Networks, Inc.
                                150 Apollo Drive
                              Chelmsford, MA 01824
                                 (978) 250-2900
                      (Name, Address and Telephone Number,
                   Including Area Code, of Agent for Service)

                                   Copies to:
                           Margaret A. Brown, Esquire
                    Skadden, Arps, Slate, Meagher & Flom LLP
                               One Beacon Street
                             Boston, MA 02108-3194

                        CALCULATION OF REGISTRATION FEE
Title of securities to be registered      Amount to be     Proposed maximum offering     Proposed maximum          Amount of
                                          registered (1)       price per share (2)            aggregate          Registration fee
                                                                                          offering price (2)
---------------------------------------------------------------------------------------------------------------------------------

 1999 Stock Incentive Plan, Common
 Stock, $.001 par value (1)              25,000,000 shares               $31.31              $782,750,000          $195,687.50

---------------------------------------------------------------------------------------------------------------------------------
(1)  In accordance with Rule 416 of the Securities Act of 1933, as amended (the
     "Securities Act"), this Registration Statement also includes an
     indeterminate number of shares that may be subject to issuance as a result
     of anti-dilution and other provisions of the plan.
(2)  Estimated solely for purposes of calculating the registration fee in
     accordance with Rule 457(h) under the Securities Act.  The computation is
     on the basis of the average of the bid and asked prices on December 21,
     2000.

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

     The documents containing the information specified in Part I will be sent
or given to employees as specified by Rule 428(b)(1). Such documents are not
being filed with the Securities and Exchange Commission (the "Commission")
either as part of this Registration Statement or as prospectuses or prospectus
supplements pursuant to Rule 424. Such documents and the documents incorporated
by reference in this Registration Statement pursuant to Item 3 of Part II of
this Form, taken together, constitute a prospectus that meets the requirements
of Section 10(a) of the Securities Act.

                                    PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE

     The Registrant is subject to the informational and reporting requirements
of Sections 13(a), 14 and 15(d) of the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), and in accordance therewith files reports, proxy
statements and other information with the Securities and Exchange Commission
(the "Commission"). The following documents, which are on file with the
Commission, are incorporated in this Registration Statement by reference:

     (1) Annual Report on Form 10-K for the year ended July 31, 2000;

     (2) Current Report on Form 8-K filed on September 11, 2000;

     (3) Quarterly Report on Form 10-Q for the quarter ended October 28, 2000;
         and

     (4) The description of Common Stock contained in the Rule 424(b)(3)
         Prospectus filed on  August 16, 2000.

     All documents subsequently filed by the Registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a post-
effective amendment which indicates that all shares of Common Stock offered
hereby have been sold or which deregisters all shares of Common Stock then
remaining unsold, shall be deemed to be incorporated by reference herein and to
be part hereof from the date of the filing of such documents. Any statement
contained in a document incorporated or deemed to be incorporated by reference
herein shall be deemed to be modified or superseded for purposes of this
Registration Statement to the extent that a statement contained herein or in any
other subsequently filed document which also is or is deemed to be incorporated
by reference herein modifies or supersedes such statement. Any statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part of this Registration Statement.

                                       2
ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

     Article SEVENTH of the Registrant's Amended and Restated Certificate of
Incorporation (the "Restated Certificate") provides that no director of the
Registrant shall be personally liable for any monetary damages for any breach of
fiduciary duty as a director, except to the extent that the Delaware General
Corporation Law prohibits the elimination or limitation of liability of
directors for breach of fiduciary duty.

     Article EIGHTH of the Restated Certificate provides that a director or
officer of the Registrant (a) shall be indemnified by the Registrant against all
expenses (including attorneys' fees), judgments, fines and amounts paid in
settlement incurred in connection with any litigation or other legal proceeding
(other than an action by or in the right of the Registrant) brought against him
by virtue of his position as a director or officer of the Registrant if he acted
in good faith and in a manner he reasonably believed to be in, or not opposed
to, the best interests of the Registrant, and, with respect to any criminal
action or proceeding, had no reasonable cause to believe his conduct was
unlawful and (b) shall be indemnified by the Registrant against all expenses
(including attorneys' fees) and amounts paid in settlement incurred in
connection with any action by or in the right of the Registrant brought against
him by virtue of his position as director or officer of the Registrant if he
acted in good faith and in a manner he reasonably believed to be in, or not
opposed to, the best interests of the Registrant, except that no indemnification
shall be made with respect to any matter as to which such person shall have been
adjudged to be liable to the Registrant, unless the Court of Chancery of
Delaware determines that, despite such adjudication but in view of all of the
circumstances, he is entitled to indemnification of such expenses.
Notwithstanding the foregoing, to the extent that a director or officer has been
successful, on the merits or otherwise, including, without limitation, the
dismissal of an action without prejudice, he is required to be indemnified by
the Registrant against all expenses (including attorneys' fees) incurred in
connection therewith. Expenses shall be advanced to a director or officer at his
request, unless it is determined that he did not act in good faith and in a
manner he reasonably believed to be in, or not opposed to, the best interests of
the Registrant, and, with respect to any criminal action or proceeding had
reasonable cause to believe that his conduct was unlawful, provided that he
undertakes to repay the amount advanced if it is ultimately determined that he
is not entitled to indemnification for such expenses.

     Indemnification is required to be made unless the Registrant determines
that the applicable standard of conduct required for indemnification has not
been met. In the event of a determination by the Registrant that the director or
officer did not meet the applicable standard of conduct required for
indemnification, or if the Registrant fails to make an indemnification payment
within 60 days after such payment is claimed by such person, such person is
permitted to petition the court to make an independent determination as to
whether such person is entitled to indemnification. As a condition precedent to
the right of indemnification, the director or officer must give the Registrant
notice of the action for which indemnity is sought and the Registrant has the
right to participate in such action or assume the defense thereof.

     Article EIGHTH of the Restated Certificate further provides that the
indemnification provided therein is not exclusive, and provides that in the
event that the Delaware General Corporation Law is amended to expand the
indemnification permitted to directors or officers, the Registrant must
indemnify those persons to the fullest extent permitted by such law as so
amended.

     Section 145 of the Delaware General Corporation Law provides that a
corporation has the power to indemnify a director, officer, employee or agent of
the corporation and certain other persons serving at the request of the

                                       3
corporation in related capacities against amounts paid and expenses incurred in
connection with an action or proceeding to which he is a party or is threatened
to be made a party by reason of such position, if such person shall have acted
in good faith and in a manner he reasonably believed to be in or not opposed to
the best interests of the corporation, and, in any criminal proceeding, if such
person had no reasonable cause to believe his conduct was unlawful; provided
that, in the case of actions brought by or in the right of the corporation, no
indemnification shall be made with respect to any matter as to which such person
shall have been adjudged to be liable to the corporation unless and only to the
extent that the adjudicating court determines that such indemnification is
proper under the circumstances.

     The Registrant has entered into indemnification agreements with each of its
director and officers. These agreements may require the Registrant, among other
things, to indemnify directors and officers against certain liabilities that may
arise by reason of their status or service as directors and officers and to
advance their expenses incurred as a result of any proceeding against them as to
which they could be indemnified.

     The Registrant has obtained liability insurance for its officers and
directors, which insures such officers and directors against certain
liabilities.

ITEM 8.  EXHIBITS

The Exhibit Index immediately preceding the exhibits is incorporated herein by
reference.

ITEM 9.  UNDERTAKINGS

     a. The undersigned Registrant hereby undertakes:

        (1) To file, during any period in which offers or sales are being made,
            a post-effective amendment to this Registration Statement:

           (i)  To include any material information with respect to the plan of
                distribution not previously disclosed in the Registration
                Statement or any material change to such information in the
                Registration Statement.

        (2) That, for the purpose of determining any liability under the
            Securities Act of 1933, each such post-effective amendment shall be
            deemed to be a new Registration Statement relating to the securities
            offered therein, and the offering of such securities at that time
            shall be deemed to be the initial bona fide offering thereof.

        (3) To remove from registration by means of a post-effective amendment
            any of the securities being registered which remain unsold at the
            termination of the offering.

     b. The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
Registrant's annual report pursuant to Section 13(a) or 15(d) of the Securities
Exchange Act of 1934 (and, where applicable, each filing of an employee benefit
plan's annual report pursuant to Section 15(d) of the Securities Exchange Act of
1934) that is incorporated by reference in the Registration Statement shall be
deemed to be a new Registration Statement relating to the securities offered
therein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

                                       4
c.   Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, or otherwise,
the Registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.

                                       5
SIGNATURES

     Pursuant to the requirements of the Securities Act, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Chelmsford, Commonwealth of Massachusetts, on this
21st day of December, 2000.

                              SYCAMORE NETWORKS, INC.

                              By: /s/  Daniel E. Smith
                                 -------------------------------------------
                                 Daniel E. Smith
                                 President and Chief Executive Officer

                        POWER OF ATTORNEY AND SIGNATURES

     We, the undersigned officers and directors of Sycamore Networks, Inc.,
hereby severally constitute Gururaj Deshpande, Daniel E. Smith and Frances M.
Jewels, and each of them individually, our true and lawful attorneys with full
power to them, and each of them singly, to sign for us and in our names in the
capacities indicated below, the Registration Statement on Form S-8 filed
herewith and any and all subsequent amendments to said Registration Statement,
and generally to do all such things in our names and behalf in our capacities as
officers and directors to enable Sycamore Networks, Inc. to comply with all
requirements of the Securities and Exchange Commission, hereby ratifying and
confirming our signatures as they may be signed by said attorneys, or any of
them, to said Registration Statement and any and all amendments thereto.

     Pursuant to the requirements of the Securities Act, this Registration
Statement has been signed below by the following persons in the capacities
indicated on this 21st day of December, 2000.

   /s/ Gururaj Deshpande            Chairman of the Board of Directors
-----------------------------
     Gururaj Deshpande

     /s/ Daniel E. Smith            Chief Executive Officer and Director
-----------------------------
       Daniel E. Smith

    /s/ Frances M. Jewels           Chief Financial Officer, Vice President,
-----------------------------       Finance and Administration, Secretary and
      Frances M. Jewels             Treasurer

     /s/ Timothy Barrows            Director
-----------------------------
        Timothy Barrows

       /s/ Paul J. Ferri            Director
-----------------------------
         Paul J. Ferri

     /s/ John W. Gerdelman          Director
-----------------------------
        John W. Gerdelman

                                       6
EXHIBIT INDEX
EXHIBIT
 NUMBER                         DESCRIPTION
  ---------  -----------------------------------------------------------------------
*4.1    Specimen Certificate of Common Stock, $.001 par value per share, of the
           Registrant is incorporated herein by reference to Exhibit 4(a) to the
           Registrant's Registration Statement on Form S-4 (Registration No.
           333-40146)

    5.1    Opinion of Skadden, Arps, Slate, Meagher & Flom LLP

   23.1    Consent of Skadden, Arps, Slate, Meagher & Flom LLP (included in Exhibit
           5.1)

   23.2    Consent of PricewaterhouseCoopers LLP (Boston, Massachusetts)

   24.1    Power of Attorney (included in the signature pages of this
           Registration Statement)
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*Incorporated by reference to Sycamore Networks, Inc.'s Registration Statement
on Form S-1 (Registration Statement No. 333-84635)