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Optical components

DWDM Gets Smaller -- and Cheaper

At least two transceiver vendors are introducing dense wavelength-division multiplexing (DWDM) modules in the popular small-form pluggable (SFP) format.

LuminentOIC Inc. and TriQuint Semiconductor Inc. (Nasdaq: TQNT) both expect to demonstrate DWDM SFPs at the OFC conference in March. TriQuint had announced plans for such a product in September, although details aren't likely to surface until OFC (see TriQuint Touts Its Schnaeliteä). LuminentOIC, meanwhile, is planning to announce its modules later this week.

The SFP push defies the DWDM Pluggable Transceiver multisource agreement (MSA), a set of specifications intended to make vendors' optics interchangeable. The MSA was launched by Agilent Technologies Inc. (NYSE: A), Nortel Networks Corp. (NYSE/Toronto: NT), and Agere Systems Inc. (NYSE: AGR.A) in June 2002, with six other vendors joining shortly after October 2002. (See Sextet Joins DWDM MSA and Agilent Gets Hot-Pluggable).

Since then, SFPs have taken over, becoming ubiquitous on equipment in both the carrier and enterprise space. The smaller size of the module gives it advantages over the DWDM MSA. Luminent's DWDM module is one-sixth the size of the DWDM MSA and consumes roughly 1.3W of power rather than the 4W typically achieved by MSA modules, says Near Margalit, Luminent CEO.

Given SFP's popularity, Luminent didn't see much reason to go with the DWDM MSA. "It's unique only to DWDM capabilities. There are no other types of interfaces that use that form factor," Margalit says.

In fact, TriQuint believes the old MSA is dead. "That was an interim solution," says Stefan Rochus, TriQuint Optotelectronics director of marketing. "Datacom equipment -- like switches and routers -- is using SFP today. [Equipment vendors] have no interest in using this format that was announced two years ago."

Rochus says TriQuint is talking with other SFP vendors about extending the SFP MSA to include a DWDM variant. The job might be easy: "It's possible we won't have to do anything," he says.

Previously, DWDM was an expensive and complicated proposition. Older DWDM modules were soldered onto the line card, meaning different line cards had to be created for each DWDM wavelength. Tunable lasers offered the promise of one generic line card for all wavelengths, but the line card still had to be DWDM-specific.

Customers have shown interest in moving equipment to WDM, but rather than immediately bring DWDM into the SFP realm, most vendors concentrated on the less expensive coarse WDM (CWDM). Vendors providing CWDM SFP optics include Agere, Agilent, Bookham Technology plc (Nasdaq: BKHM; London: BHM), Fiberxon Inc., Finisar Corp. (Nasdaq: FNSR), Optical Communication Products Inc. (OCPI) (Nasdaq: OCPI), Sumitomo Corp., and TriQuint. (See CWDM Products Proliferate and CWDM On the Move.)

LuminentOIC plans to sell its DWDM modules for the same price as CWDM, erasing the cost factor and, the company hopes, driving a push to adopt DWDM. Officials were reluctant to specify the price of the DWDM modules, however. "In optical components, every time you print a number everyone comes in 10 percent lower," Margalit says.

No other vendors have announced plans for SFP DWDM transceivers. Finisar comes close, having announced a DWDM transceiver in the GBIC format, a larger predecessor to SFPs.

As with the DWDM MSA, LuminentOIC's DWDM modules target speeds up to 2.5 Gbit/s. They offer wavelengths conforming to 100GHz DWDM spacing, providing 44 channels across the C band. The modules are sampling, with production volumes expected in the second quarter of 2004.

(LuminentOIC is the combination of MRV Communications Inc. (Nasdaq: MRVC) subsidiaries Luminent Inc. and Optronics International Corp. -- see Luminent Becomes LuminentOIC).

— Craig Matsumoto, Senior Editor, Light Reading
MrLight 12/5/2012 | 2:37:24 AM
re: DWDM Gets Smaller -- and Cheaper It is good to see DWDM in the SFP form factor, however the devices as specified can't be used across all the applications of the current DWDM transport products, however they definitely can do the job for the router and switch products.

For example the launch power, Extinction ratio and receiver sensitivity need to be increased so these devices can be used as drop-in replacements for existing discrete solutions.

As well such vendor specific aspects as side-mode suppression, power control, power monitoring, operation below 100Mbps, bit disparity support, sub-carrier modulation support, wavelength tagging scheme support, OEM vendor branding, 3rd party blocking, future support for tunable units etc have to be considered.

Nevertheless, this is definitely going in the right direction - smaller and cheaper.

MrLight...
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