Exhibit (a)(1)(D)

Offer to Purchase for Cash
All Outstanding Shares of Common Stock
of
Cartesian, Inc.
at
$0.40 Net Per Share
by
Cartesian Holdings, Inc.
a wholly owned direct subsidiary of
Cartesian Holdings, LLC

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT ONE MINUTE AFTER 11:59 P.M., NEW YORK CITY TIME, ON MAY 11, 2018, UNLESS THE OFFER IS EXTENDED OR EARLIER TERMINATED.

April 10, 2018

To Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees:

We have been engaged by Cartesian Holdings, Inc., a Delaware corporation (which we refer to as “Merger Sub”) and a wholly owned direct subsidiary of Cartesian Holdings, LLC, a Delaware limited liability company (which we refer to as “Parent”), to act as Information Agent in connection with Merger Sub’s offer to purchase all outstanding shares of common stock, par value $0.005 per share (which we refer to as “Shares”), of Cartesian, Inc., a Delaware corporation (which we refer to as “Cartesian”), at a purchase price of $0.40 per Share, net to the seller in cash, without interest thereon and less any applicable withholding taxes, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated April 10, 2018 (which we refer to as the “Offer to Purchase”), and the related Letter of Transmittal (which we refer to as the “Letter of Transmittal” and which, together with the Offer to Purchase, each as may be amended or supplemented from time to time, we refer to as the “Offer”) enclosed herewith. Please furnish copies of the enclosed materials to those of your clients for whom you hold Shares registered in your name or in the name of your nominee.

The conditions to the Offer are described in Section 15 of the Offer to Purchase.

For your information and for forwarding to your clients for whom you hold Shares registered in your name or in the name of your nominee, we are enclosing the following documents:

The Offer to Purchase;

The Letter of Transmittal for your use in accepting the Offer and tendering Shares and for the information of your clients;

Notice of Guaranteed Delivery to be used if the certificates representing the tendered Shares and all other required documents cannot be delivered to the Depositary by the Expiration Date the procedure for delivery by book-entry transfer cannot be completed on a timely basis;

A form of letter that may be sent to your clients for whose accounts you hold Shares registered in your name or in the name of your nominee, with space provided for obtaining such clients’ instructions with regard to the Offer; and

A return envelope addressed to Broadridge Corporate Issuer Solutions, Inc., in its capacity as depositary and paying agent for the Offer (which we refer to as the “Depositary”) for your use only.

We urge you to contact your clients as promptly as possible. Please note that the Offer and withdrawal rights will expire at one minute after 11:59 p.m., New York City time, on May 11, 2018, unless the Offer is extended or earlier terminated.

The Offer is being made pursuant to the Agreement and Plan of Merger, dated as of March 21, 2018 (which we refer to, together with any amendments thereto, as the “Merger Agreement”), by and among Parent, Merger Sub and Cartesian. The Merger Agreement provides, among other things, that following the consummation of the Offer and subject to the satisfaction or waiver of specified conditions, Merger Sub will be merged with and into Cartesian (the “Merger”) following approval of the Merger Agreement by the holders of a majority of the outstanding shares of Company Common Stock (the “Company Required Vote,” if needed), with Cartesian continuing as the surviving corporation in the Merger and thereby becoming a wholly owned direct subsidiary of

Parent. If 90% or more of the outstanding Shares are purchased in the Offer, the Merger may be affected under Section 253 of the Delaware General Corporation Law by a resolution adopted by the Parent's board of directors without the need for a Company Required Vote.

For Shares to be properly tendered pursuant to the Offer, (a) the share certificates or confirmation of receipt of such Shares under the procedure for book-entry transfer, together with a properly completed and duly executed Letter of Transmittal, including any required signature guarantees, or, in the case of book-entry transfer, either such Letter of Transmittal or an Agent’s Message (as defined in Section 2 of the Offer to Purchase) in lieu of such Letter of Transmittal, and any other documents required in the Letter of Transmittal, must be timely received by the Depositary or (b) the tendering stockholder must deliver a Notice of Guaranteed Delivery and comply with the guaranteed delivery procedures, all in accordance with the Offer to Purchase and the Letter of Transmittal.

Except as set forth in the Offer to Purchase, Merger Sub will not pay any fees or commissions to any broker or dealer or other person for soliciting tenders of Shares pursuant to the Offer. Merger Sub will, however, upon request, reimburse brokers, dealers, commercial banks, trust companies and other nominees for customary mailing and handling expenses incurred by them in forwarding the offering material to their customers. Merger Sub will pay all stock transfer taxes applicable to its purchase of Shares pursuant to the Offer, subject to Instruction 6 of the Letter of Transmittal.

Any inquiries you may have with respect to the Offer should be addressed to, and additional copies of the enclosed materials may be obtained from, the undersigned at the address, telephone numbers and email address set forth below.

Very truly yours,

Broadridge Corporate Issuer Solutions, Inc.

Nothing contained herein or in the enclosed documents shall render you the agent of Merger Sub, the Information Agent or the Depositary or any affiliate of any of them or authorize you or any other person to use any document or make any statement on behalf of any of them in connection with the Offer other than the enclosed documents and the statements contained therein.

The Depositary and Information Agent for the Offer is:

If delivering via a USPS Service:	If delivering via UPS, Fedex or Overnight Courier:

Broadridge Corporate Issuer Solutions, Inc. Attn: BCIS Re-Organization Dept. P.O. Box 1317 Brentwood, NY 11717-0693	Broadridge Corporate Issuer Solutions, Inc. Attn: BCIS IWS 51 Mercedes Way Edgewood, NY 11717

Questions:
Toll Free: (855) 793-5068
Email: shareholder@broadridge.com