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


                                  SCHEDULE 13G
                                 (RULE 13d-102)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
           TO RULES 13D-1 (b) (c) AND (d) AND AMENDMENTS THERETO FILED
                            PURSUANT TO RULE 13D-2(b)


                                 Amendment No. 1


                              Sonus Networks, Inc.
--------------------------------------------------------------------------------
                                (Name of Issuer)

                     Common Stock, $.001 par value per share
--------------------------------------------------------------------------------

                                   835916 10 7
                                   -----------
                                 (CUSIP Number)


                                December 31, 2001
--------------------------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

         [ ]  Rule 13d-1(b)

         [ ]  Rule 13d-1(c)

         [X]  Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).


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CUSIP No. 835916 10 7                13G                    PAGE  2  OF  9 PAGES
         ------------                                            ---    ---

(1)      NAMES OF REPORTING PERSONS.
         I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY).

         MATRIX PARTNERS V, L.P.

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

(2)      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*        (A)   [  ]
                                                                  (B)   [  ] 

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

(3)      SEC USE ONLY

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

(4)      CITIZENSHIP OR PLACE OF ORGANIZATION

         DELAWARE

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

                        (5)   SOLE VOTING POWER

                              SEE ITEM 5
     NUMBER OF          --------------------------------------------------------
       SHARES           (6)   SHARED VOTING POWER 
    BENEFICIALLY 
      OWNED BY                SEE ITEM 5
        EACH            --------------------------------------------------------
     REPORTING          (7)   SOLE DISPOSITIVE POWER
    PERSON WITH
                              SEE ITEM 5
                        --------------------------------------------------------
                        (8)   SHARED DISPOSITIVE POWER

                              SEE ITEM 5
--------------------------------------------------------------------------------

(9)      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

         SEE ITEM 5
--------------------------------------------------------------------------------

(10)     CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN 
         SHARES*                                                         [  ]

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

(11)     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

         SEE ITEM 5

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

(12)     TYPE OF REPORTING PERSON*

         PN

--------------------------------------------------------------------------------
                      *SEE INSTRUCTIONS BEFORE FILLING OUT!




<PAGE>

CUSIP No. 835916 10 7                13G                    PAGE  3  OF  9 PAGES
         ------------                                            ---    ---

(1)      NAMES OF REPORTING PERSONS.
         I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY).

         MATRIX V ENTREPRENEURS FUND, L.P.

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

(2)      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*        (A)   [  ]
                                                                  (B)   [  ] 

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

(3)      SEC USE ONLY

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

(4)      CITIZENSHIP OR PLACE OF ORGANIZATION

         DELAWARE

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

                        (5)   SOLE VOTING POWER

                              SEE ITEM 5
     NUMBER OF          --------------------------------------------------------
       SHARES           (6)   SHARED VOTING POWER 
    BENEFICIALLY 
      OWNED BY                SEE ITEM 5
        EACH            --------------------------------------------------------
     REPORTING          (7)   SOLE DISPOSITIVE POWER
    PERSON WITH
                              SEE ITEM 5
                        --------------------------------------------------------
                        (8)   SHARED DISPOSITIVE POWER

                              SEE ITEM 5
--------------------------------------------------------------------------------

(9)      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

         SEE ITEM 5
--------------------------------------------------------------------------------

(10)     CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN 
         SHARES*                                                         [  ]

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

(11)     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

         SEE ITEM 5

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

(12)     TYPE OF REPORTING PERSON*

         PN

--------------------------------------------------------------------------------
                      *SEE INSTRUCTIONS BEFORE FILLING OUT!


<PAGE>
CUSIP No. 835916 10 7                13G                    PAGE  4  OF  9 PAGES
         ------------                                            ---    ---

(1)      NAMES OF REPORTING PERSONS.
         I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY).

         MATRIX V MANAGEMENT CO., L.L.C.

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

(2)      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*        (A)   [  ]
                                                                  (B)   [  ] 

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

(3)      SEC USE ONLY

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

(4)      CITIZENSHIP OR PLACE OF ORGANIZATION

         DELAWARE

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

                        (5)   SOLE VOTING POWER

                              SEE ITEM 5
     NUMBER OF          --------------------------------------------------------
       SHARES           (6)   SHARED VOTING POWER 
    BENEFICIALLY 
      OWNED BY                SEE ITEM 5
        EACH            --------------------------------------------------------
     REPORTING          (7)   SOLE DISPOSITIVE POWER
    PERSON WITH
                              SEE ITEM 5
                        --------------------------------------------------------
                        (8)   SHARED DISPOSITIVE POWER

                              SEE ITEM 5
--------------------------------------------------------------------------------

(9)      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

         SEE ITEM 5
--------------------------------------------------------------------------------

(10)     CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN 
         SHARES*                                                         [  ]

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

(11)     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

         SEE ITEM 5

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

(12)     TYPE OF REPORTING PERSON*

         PN

--------------------------------------------------------------------------------
                      *SEE INSTRUCTIONS BEFORE FILLING OUT!

<PAGE>

CUSIP No. 835916 10 7                13G                    PAGE  5  OF  9 PAGES
         ------------                                            ---    ---

(1)      NAMES OF REPORTING PERSONS.
         I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY).

         PAUL J. FERRI

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

(2)      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*        (A)   [  ]
                                                                  (B)   [  ] 

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

(3)      SEC USE ONLY

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

(4)      CITIZENSHIP OR PLACE OF ORGANIZATION

         UNITED STATES

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

                        (5)   SOLE VOTING POWER

                              SEE ITEM 5
     NUMBER OF          --------------------------------------------------------
       SHARES           (6)   SHARED VOTING POWER 
    BENEFICIALLY 
      OWNED BY                SEE ITEM 5
        EACH            --------------------------------------------------------
     REPORTING          (7)   SOLE DISPOSITIVE POWER
    PERSON WITH
                              SEE ITEM 5
                        --------------------------------------------------------
                        (8)   SHARED DISPOSITIVE POWER

                              SEE ITEM 5
--------------------------------------------------------------------------------

(9)      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

         SEE ITEM 5
--------------------------------------------------------------------------------

(10)     CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN 
         SHARES*                                                         [  ]

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

(11)     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

         SEE ITEM 5

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

(12)     TYPE OF REPORTING PERSON*

         IN

--------------------------------------------------------------------------------
                      *SEE INSTRUCTIONS BEFORE FILLING OUT!

<PAGE>

CUSIP No. 835916 10 7                13G                    PAGE  6  OF  9 PAGES
         ------------                                            ---    ---

ITEM 1(a)                  NAME OF ISSUER:

                           Sonus Networks, Inc.

ITEM 1(b)                  ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES:

                           5 Carlisle Road
                           Westford, MA 01886

ITEM 2(a)                  NAME OF PERSONS FILING:

                           Matrix Partners V, L.P. ("Matrix V"); Matrix V 
                           Entrepreneurs Fund, L.P. ("Entrepreneurs", and 
                           together with Matrix V, the "Partnerships"); Matrix 
                           V Management Co., L.L.C. ("Management"), the general 
                           partner of each of  the Partnerships; and Paul J.
                           Ferri ("Ferri"), the managing member of Management, 
                           who has sole voting and  dispositive authority with 
                           respect to the shares of Sonus Networks, Inc. held 
                           of record by the Partnerships.

ITEM 2(b)                  ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, 
                           RESIDENCE:

                           The address of the reporting persons is:

                           1000 Winter Street, Suite 4500
                           Waltham, Massachusetts  02451

ITEM 2(c)                  CITIZENSHIP:

                           Matrix V is a limited partnership organized under the
                           laws of the State of Delaware. Entrepreneurs is a
                           limited partnership organized under the laws of the
                           State of Delaware. Management is a limited liability
                           company organized under the laws of the State of
                           Delaware. Mr. Ferri is a citizen of the United
                           States.

ITEM 2(d)                  TITLE OF CLASS OF SECURITIES:

                           Common Stock, par value $.001 per share (the "Common
                           Stock").


ITEM 2(e)                  CUSIP NUMBER:

                           835916 10 7


ITEM 3                     DESCRIPTION OF PERSON FILING:

                           Not applicable.




<PAGE>

CUSIP No. 835916 10 7                13G                    PAGE  7  OF  9 PAGES
         ------------                                            ---    ---


ITEM 4                     OWNERSHIP:

                           (a)      AMOUNT BENEFICIALLY OWNED:

                                    See Item 5

                           (b)      PERCENT OF CLASS:

                                    Matrix V:                 See Item 5
                                    Entrepreneurs:            See Item 5
                                    Management:               See Item 5
                                    Mr. Ferri:                See Item 5


                           (c)      NUMBER OF SHARES AS TO WHICH THE PERSON HAS:

                                    (i) sole voting power; (ii) shared voting
                                    power; (iii) sole dispositive power; (iv) 
                                    shared dispositive power:

                                    See Item 5


ITEM 5                     OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS:

                           If this statement is being filed to report the fact
                           that as of the date hereof the reporting person has
                           ceased to be the beneficial owner of more than five
                           percent of the class of securities, check the
                           following [X]

ITEM 6                     OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF 
                           ANOTHER PERSON:

                           Not applicable.

ITEM 7                     IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY 
                           WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE 
                           PARENT HOLDING COMPANY:

                           Not applicable.

ITEM 8                     IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE 
                           GROUP:

                           Not applicable.

ITEM 9                     NOTICE OF DISSOLUTION OF GROUP:

                           Not applicable.

ITEM 10                    CERTIFICATION:

                           Not applicable.



<PAGE>

CUSIP No. 835916 10 7                13G                    PAGE  8  OF  9 PAGES
         ------------                                            ---    ---

                                    SIGNATURE

         After reasonable inquiry and to the best of the knowledge and belief of
each of the undersigned, each of the undersigned hereby certifies that the
information set forth in this statement is true, complete and correct.

DATED:  February 13, 2002


                                            MATRIX PARTNERS V, L.P.


                                            By:  Matrix V Management Co., L.L.C.
                                                 General Partner


                                                 By: /s/ Paul J. Ferri
                                                    ----------------------------
                                                     Paul J. Ferri
                                                     Managing Member


                                            MATRIX V ENTREPRENEURS FUND, L.P.


                                            By:  Matrix V Management Co., L.L.C.
                                                    General Partner


                                                 By: /s/ Paul J. Ferri
                                                    ----------------------------
                                                    Paul J. Ferri
                                                    Managing Member


                                            MATRIX V MANAGEMENT CO., L.L.C.


                                            By: /s/ Paul J. Ferri
                                               ---------------------------------
                                               Paul J. Ferri
                                               Managing Member

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






<PAGE>

                                                                       Exhibit I

                                    AGREEMENT

         Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934,
as amended, the undersigned hereby agree that only one statement containing the
information required by Schedule 13G need be filed with respect to the ownership
by each of the undersigned of the shares of Common Stock of Sonus Networks, Inc.

         EXECUTED as a sealed instrument this 13th day of February, 2002.


                                            MATRIX PARTNERS V, L.P.

                                            By:  Matrix V Management Co., L.L.C.
                                                 General Partner


                                                 By: /s/ Paul J. Ferri    
                                                    ----------------------------
                                                    Paul J. Ferri
                                                    Managing Member

                                            MATRIX V ENTREPRENEURS FUND, L.P.

                                            By:  Matrix V Management Co., L.L.C.
                                                 General Partner


                                                 By: /s/ Paul J. Ferri   
                                                    ----------------------------
                                                    Paul J. Ferri
                                                    Managing Member


                                            MATRIX V MANAGEMENT CO., L.L.C.


                                                 By: /s/ Paul J. Ferri        
                                                    ----------------------------
                                                    Paul J. Ferri
                                                    Managing Member

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