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Exhibit 99.4

AMENDMENT TO AGREEMENT AND PLAN OF MERGER AND REORGANIZATION

This Amendment to the Agreement and Plan of Merger and Reorganization
(this Amendment) is made effective as of June 17, 2003, by and between
Tellabs, Inc., a Delaware corporation (Parent), and Vivace Networks, Inc., a
Delaware corporation (the Company). Capitalized terms not otherwise defined
herein shall have the meanings ascribed to them in the Merger Agreement (as
defined below).

RECITALS

A.     Reference is made to that certain Agreement and Plan of Merger and
Reorganization (the Merger Agreement) dated as of May 12, 2003, by and among
Parent, Venice Acquisition Corp., a Delaware corporation and a wholly-owned
subsidiary of Parent, the Company, Kenneth Koenig, as Stockholder
Representative, and LaSalle Bank National Association, as Escrow Agent.

B.     Pursuant to Section 5.1(a) of the Merger Agreement, each Lower-Priced
Company Stock Option, whether or not vested, was to be replaced by Parent and
substituted with a Replacement Option as of the Effective Time, and each
Company Warrant was to be assumed and converted into a warrant to acquire
Parent Common Stock as of the Effective Time.

C.     The parties hereto desire to amend the Merger Agreement so that each
Lower-Priced Company Stock Option will be assumed by Parent as of the Effective
Time, and each Company Warrant will be assumed and converted into a warrant to
acquire cash representing the same per-share amount of cash payable to holders
of Company Common Stock in the Merger as of the Effective Time.

D.     Pursuant to Section 8.3 of the Merger Agreement, prior to the Closing
and the adoption of the Merger Agreement by the Company Stockholders, the
Merger Agreement may be amended at any time by Parent and the Company, provided
that such an amendment does not affect the rights, duties or responsibilities
of the Escrow Agent as set forth in Section 7.2 of the Merger Agreement or the
Stockholder Representative as set forth in Section 7.3 of the Merger Agreement,
and provided further that no such amendment may be made which reduces the
Merger Cash or which effects any changes which would materially adversely
affect the Company Stockholders without the further approval of the Company
Stockholders.

E.     This Amendment does not affect the rights, duties or responsibilities
of the Escrow Agent as set forth in Section 7.2 of the Merger Agreement or the
Stockholder Representative as set forth in Section 7.3 of the Merger Agreement,
does not reduce the Merger Cash and does not effect any changes which would
materially adversely affect the Company Stockholders.

AGREEMENT

NOW THEREFORE, in consideration for and of the mutual promises, covenants
and conditions hereinafter set forth and other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, pursuant to
Section 8.3 of the Merger Agreement, Parent and the Company, hereby agree as
follows:

1.     Definitions.

(a) The definitions of Replacement Option and Converted Warrant in
Section 1.1(a) of the Merger Agreement are replaced as follows:

Assumed Option                                   5.1(a)

Assumed Warrant                                   5.1(b).





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(b) The definition of Option Shares in Section 1.1(b) of the Merger
Agreement is amended and restated in its entirety as follows:



| |                                                                                                                                                  
| | -------------------------------------------------------------------------------------------------------------------------------------------------
| | Option Shares means the shares of Parent Common Stock
issued or issuable pursuant to the exercise of Assumed
Options under Section 5.1(a)(i).

2.     Assumption of Options and Warrants.

(a) Section 1.7(e) of the Merger Agreement is amended and restated in its
entirety as follows:



| |                                                                                                                                                                                                                                                                                                       
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | At the Effective Time, each outstanding Lower-Priced
Company Stock Option and outstanding Company Warrant shall
be assumed by Parent in accordance with Section 5.1. At the
Effective Time, all Company Stock Options that are not
Lower-Priced Company Stock Options will not be assumed by
Parent.

(b) Section 5.1
of the Merger Agreement is amended and restated in its entirety as
follows:



| |                                
| | -------------------------------
| | 5.1 Stock Options and Warrants



| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
| | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (a) Stock Options. Effective as of the Effective Time,
each Lower-Priced Company Stock Option outstanding
immediately prior to the Effective Time, whether or not
Vested, shall be assumed by Parent (an Assumed Option).
Each Assumed Option will continue to have, and be subject
to, substantially equivalent principal terms and conditions
as provided in the Company Stock Option Plan and the option
agreements relating thereto, as in effect immediately prior
to the Effective Time (including vesting schedules and
vesting commencement dates), except that:



| |                                                                                                                                                                                                                                                                                                                                                                                                                                   
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (i) Shares Issuable Upon Exercise. Each Assumed Option
will be exercisable for that number of whole shares of
Parent Common Stock equal to the product (rounded down to
the nearest whole share) of (1) the number of shares of
Company Common Stock that were issuable upon exercise of
such Lower-Priced Company Stock Option immediately prior to
the Effective Time, and (2) the Option Exchange Ratio.                       
|
| | (ii) Option Per Share Exercise Price. The per share
exercise price for the shares of Parent Common Stock
issuable upon exercise of each Assumed Option will be equal
to the quotient (rounded up to the nearest whole cent)
determined by dividing (X) the exercise price per share of
Company Common Stock at which such Assumed Option was
exercisable immediately prior to the Effective Time by (Y)
the Option Exchange Ratio.



| |                                                                                                                                                                                                                                                                                                              
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (iii) Compliance with Section 424 of the Code. In the
case of any Lower-Priced Company Stock Option to which
Section 421 of the Code applies by reason of its
qualification under Section 422 of the Code, the exercise
price of the option, the number of shares purchasable
pursuant to such option and the

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| |                                                                                                                     
| | --------------------------------------------------------------------------------------------------------------------
| | terms and conditions of exercise of such option shall be
determined in order to comply with Section 424 of the Code.



| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (b) Warrants. Effective as of the Effective Time, each
Company Warrant whether or not Vested, shall be assumed by Parent
(an Assumed Warrant). Each Assumed Warrant will continue to
have, and be subject to, the same terms and conditions as provided
in the respective warrant agreement governing such Company Warrant
immediately prior to the Effective Time, except that each such
Company Warrant shall be converted into and exchanged for the right
to receive a dollar amount equal to the excess (if any) of (A) the
dollar amount that would otherwise be payable pursuant to Section
1.7(a)(iv) with respect to all shares of Company Common Stock
issuable upon exercise of such Company Warrant over (B) the
aggregate exercise price of all shares of Company Common Stock
issuable upon exercise of such Company Warrant.

3.     Integration Clause. Section 9.5 of the Merger Agreement is amended and
restated in its entirety as follows:



| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | Entire Agreement; Third Party Beneficiaries. This
Agreement, as it may be amended from time to time in
accordance with its terms, and the documents and instruments
and other agreements among the Parties hereto as
contemplated by or referred to herein, including the Company
(a) constitute the entire agreement among the parties with
respect to the subject matter hereof and supersede all prior
agreements and understandings, both written and oral, among
the parties with respect to the subject matter hereof, it
being understood that the Confidentiality Agreement shall
continue in full force and effect until the Closing and
shall survive any termination of this Agreement; and (b) are
not intended to confer upon any other Person (including any
of the Company Stockholders or Company Rightholders) any
rights or remedies hereunder; provided, however, that the
provisions of Section 7.2are intended for the benefit of
the Covered Parties.

4.     Modification; Waiver. Except as set forth herein, the terms and
conditions of the Merger Agreement shall remain in full force and
effect.

5.      Governing Law. This Amendment shall be governed by and construed in
accordance with the laws of the State of Delaware, regardless of the laws that
might otherwise govern under applicable principles of conflicts of law thereof.
Each of Parent and the Company hereto irrevocably consents to the exclusive
jurisdiction and venue of any court within DuPage County, State of Illinois in
connection with any matter based upon or arising out of this Amendment or the
matters contemplated herein, agrees that process may be served upon them in any
manner authorized by the laws of the State of Illinois for such Persons and
waives and covenants not to assert or plead any objection that they might
otherwise have to such jurisdiction, venue and process.

6.     Counterparts. This Amendment may be executed in one or more
counterparts, all of which shall be considered one and the same agreement and
shall become effective when one or more counterparts
have been signed by each of the parties and delivered to the other party,
it being understood that all parties need not sign the same counterpart.

[Remainder of this Page Intentionally Left Blank]

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IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed by their duly authorized respective officers as of the date first
written above.

TELLABS, INC.

By:______________________

Name: James M. Sheehan

Title: Executive Vice President and General
Counsel.

VIVACE NETWORKS, INC.

By:______________________

Name: Kenneth Koenig

Title: President & Chief Executive Officer

Signature page to Amendment to
Agreement and Plan of Merger and Reorganization