As filed with the Securities and Exchange Commission on August 1, 2013

Registration No. 333-        

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

SONUS NETWORKS, INC.

(Exact name of registrant as specified in its charter)

2007 Stock Incentive Plan, As Amended

(Full title of the plan)

Jeffrey M. Snider
Senior Vice President, Chief Administrative Officer and General Counsel
Sonus Networks, Inc.
4 Technology Park Drive
Westford, Massachusetts 01886

(Name and address of agent for service)

(978) 614-8100

(Telephone number, including area code, of agent for service)

Copies to:

Jonathan Wolfman

Wilmer Cutler Pickering Hale and Dorr LLP

60 State Street

Boston, Massachusetts 02109

(617) 526-6833

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

CALCULATION OF REGISTRATION FEE

EXPLANATORY NOTE

This Registration Statement on Form S-8 is filed to register the offer and sale of an additional 21,000,000 shares of the registrant’s common stock, $0.001 par value per share, to be issued under the registrant’s 2007 Stock Incentive Plan, as amended, and is submitted in accordance with General Instruction E to Form S-8 regarding Registration of Additional Securities. Pursuant to General Instruction E to Form S-8, this Registration Statement on Form S-8 incorporates by reference the contents of the following Registration Statements on Form S-8 previously filed by the registrant with the Securities and Exchange Commission:

(1) Registration Statement on Form S-8 (File No. 333-150022), filed on April 1, 2008, relating to 9,500,000 shares of common stock to be offered and sold under the registrant’s 2007 Stock Incentive Plan;

(2) Registration Statement on Form S-8 (File No. 333-163684), filed on December 11, 2009, relating to an additional 5,402,701 shares of common stock to be offered and sold under the registrant’s 2007 Stock Incentive Plan, as amended; and

(3) Registration Statement on Form S-8 (File No. 333-170285), filed on November 2, 2010, relating to an additional 20,000,000 shares of common stock to be offered and sold under the registrant’s 2007 Stock Incentive Plan, as amended.

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 and 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:

(a)         The registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2012;

(b)         The registrant’s Quarterly Reports on Form 10-Q for the fiscal quarterly periods ended March 29, 2013 and June 28, 2013;

(c)          The registrant’s Current Reports on Form 8-K filed with the Commission on February 19, 2013, April 1, 2013, June 13, 2013, June 18, 2013, and June 24, 2013 and Item 5.02 of, and Exhibits 10.1 and 10.2 to, the registrant’s Current Report on Form 8-K filed with the Commission on July 29, 2013;

(d)         All other reports filed pursuant to Section 13(a) or 15(d) of the Exchange Act since the end of the fiscal year covered by the registrant’s Annual Report referred to in (a) above; and

(e)          The descriptions of the registrant’s common stock contained in the registrant’s Registration Statement on Form 8-A filed with the Commission on April 5, 2000 pursuant to Section 12(g) of the Exchange Act, including any amendment or report filed for the purpose of updating such descriptions.

All documents subsequently filed pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act after

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the date of this Registration Statement and prior to the filing of a post-effective amendment which indicates that all securities offered hereby have been sold or which deregisters all securities then remaining unsold shall be deemed to be incorporated by reference into this Registration Statement and to be a part hereof from the date of filing of such documents.  Unless expressly incorporated into this Registration Statement, a report furnished but not filed on Form 8-K shall not be incorporated by reference into this Registration Statement.  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 subsequently filed document which also is deemed to be incorporated by reference herein modifies or supersedes such statement.  Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this Registration Statement.

Item 8.   Exhibits.

The Exhibit Index immediately following the signature page is incorporated herein by reference.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, 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 Westford, the Commonwealth of Massachusetts, on August 1, 2013.

POWER OF ATTORNEY

We, the undersigned officers and directors of Sonus Networks, Inc., hereby severally constitute and appoint Maurice Castonguay and Jeffrey Snider, each of them singly, 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 on our behalf in our capacities as officers and directors to enable Sonus Networks, Inc. t  o comply with the provisions of the Securities Act of 1933, as amended, and all requirements of the Securities and Exchange Commission, hereby ratifying and confirming our signatures as they may be signed by our said attorneys, or any of them, to said registration statement and any and all amendments thereto.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates indicated.

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EXHIBIT INDEX

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Exhibit 5.1

Re:                             2007 Stock Incentive Plan, as amended

Ladies and Gentlemen:

We have assisted in the preparation of a Registration Statement on Form S-8 (the “Registration Statement”) to be filed with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), relating to an aggregate of 21,000,000 shares of common stock, $0.001 par value per share (the “Shares”), of Sonus Networks, Inc., a Delaware corporation (the “Company”), issuable under the Company’s 2007 Stock Incentive Plan, as amended (the “Plan”).

We have examined the Certificate of Incorporation and By-Laws of the Company, each as amended and restated to date, and originals, or copies certified to our satisfaction, of all pertinent records of the meetings of the directors and stockholders of the Company, the Registration Statement and such other documents relating to the Company as we have deemed material for the purposes of this opinion.

In our examination of the foregoing documents, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as certified, photostatic or other copies, the authenticity of the originals of any such documents and the legal competence of all signatories to such documents.

We assume that the appropriate action will be taken, prior to the offer and sale of the Shares in accordance with the Plan, to register and qualify the Shares for sale under all applicable state securities or “blue sky” laws.

We express no opinion herein as to the laws of any state or jurisdiction other than the state laws of The Commonwealth of Massachusetts, the General Corporation Law of the State of Delaware and the federal laws of the United States of America.

It is understood that this opinion is to be used only in connection with the offer and sale of the Shares while the Registration Statement is in effect.

Please note that we are opining only as to the matters expressly set forth herein, and no opinion should be inferred as to any other matters.

Based on the foregoing, we are of the opinion that the Shares have been duly authorized for issuance and, when the Shares are issued and paid for in accordance with the terms and conditions of the Plan, the Shares will be validly issued, fully paid and nonassessable.

We hereby consent to the filing of this opinion with the Commission in connection with the Registration Statement in accordance with the requirements of Item 601(b)(5) of Regulation S-K under

the Securities Act.  In giving such consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.

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Exhibit 23.2

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement on Form S-8 of our reports dated March 6, 2013, relating to the financial statements of Sonus Networks, Inc. (which report expresses an unqualified opinion and includes an explanatory paragraph regarding the Company’s change in its method of recognizing revenue for multiple-element arrangements), and the effectiveness of Sonus Networks, Inc.’s internal control over financial reporting, appearing in the Annual Report on Form 10-K of Sonus Networks, Inc. for the year ended December 31, 2012.

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