40-Gig Gets Extended

Out of nowhere, components vendor Kailight Photonics Ltd. says it wants to be a transponder vendor, and it's going to be starting at the 40-Gbit/s level.

So kicks off another year of 40-Gbit/s talk at the OFC/NFOEC conference. 40-Gbit/s Sonet OC768 (or STM256) networking was a hot issue during the bubble, circa 2000, before many startups pursuing the technology shut such efforts down. But talk of a 40-gig revival started simmering at last year's conference. (See 40-Gig Begins Its Ramp.)

To be fair, Kailight shows no ambitions of wanting to be a transponder powerhouse. Rather, the company says it's responding to the vacancy it sees in the long-haul market.

That's the arena where Kailight makes its money. The company is best known for TASR, a line of wavelength converters and signal regenerators that target long-reach optical links, with distance being a key selling point. (See Wavelength Converters Go the Distance.)

The transponder came about after Kailight hired some engineers from TeraSea Inc. , another components startup aimed at long-reach optics. "TASR works in the midpoint of the network, anywhere you would do OEO [optical-electrical-optical] conversions. This extends us out to the endpoints," says Neil Salisbury, Kailight vice president of marketing. (See Kailight Preps for OFC.)

The OC768 modules on the market so far have targeted distances of 2 km or less. Kailight is going further than that by using what's called optical duobinary signaling (ODB), an alternative to the return-to-zero (RZ) and non-return-to-zero (NRZ) modulation normally associated with optical transponders. ODB can be found in places such as the early Bell Labs research on 100 Gbit/s Ethernet. (See Lucent Tries 100 GigE .)

Kailight claims its transponders, conforming to the 300-pin multisource agreement, will be the first ODB 40-Gbit/s option on the open market. Cisco Systems Inc. (Nasdaq: CSCO) is deploying duobinary 40-Gbit/s cards from StrataLight Communications , but Salisbury says those aren't available as merchant parts; equipment vendors would have to go to Cisco, essentially. (StrataLight didn't return a call for comment on Friday.)

Big whoop, competitors say. Longer distances for OC768 are nice but not yet necessary. "This is the first I'm hearing" of anyone building a duobinary 40-Gbit/s module, says Ed Cornejo, director of marketing for Opnext Inc. (Nasdaq: OPXT) "Nobody's pressing for it."

Some believe a more likely long-term answer is found in an even longer alphaglommeration: RZDPSK: return-to-zero differential phase-shift keying. "That gives you a very long reach, potentially 1,000 km to 1,500 km," compared with more like 600 km for ODB, says Saied Aramideh, vice president of marketing for CoreOptics Inc. , which plans to skip ahead to the RZDPSK step. "We will be out with customers in various stages of qualification [for RZDPSK 40-Gbit/s transponders] by the end of the year."

Kailight is set to begin sampling transponder modules this summer, Salisbury says, with general availability slated for the end of the year.

— Craig Matsumoto, Senior Editor, Light Reading

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