LX4 Gets Another Chance
A 10-Gbit/s Ethernet standard called 10GBASE-LX4 is drawing renewed interest from the likes of Cisco Systems Inc. (Nasdaq: CSCO), which plans to ship LX4 modules as early as the first quarter of 2004.
Most vendors, meanwhile, gave up on LX4 or never even tried it; and there's reportedly an alternative format that's being prepared for consideration by the Institute of Electrical and Electronics Engineers Inc. (IEEE).
Cisco, being Cisco, is ready to forge ahead anyway. Bruce Tolley, Cisco senior manager of engineering technology, says the company has "three or four" transceiver vendors lined up as suppliers, although he wouldn't name names.
LX4 is intended to send 10-Gbit/s Ethernet across 300 meters of old multimode fiber -- in other words, it targets the installed base. "10-Gig on that kind of multimode fiber goes about 20 meters," says Bill Woodruff, vice president of marketing at BitBlitz Communications Inc.
LX4 has long been included in 10-Gbit/s Ethernet standards talks, but interest among vendors waned during the dotcom boom, as huge installations of singlemode fiber seemed imminent.
Of course, the boom ended. And, as 10-Gbit/s Ethernet begins its ramp-up, it's looking as if the most promising customers will have to run it over old cable. Suddenly, LX4 is interesting again.
"We expect half the 10-Gig market is going to be for multimode -- that's in risers and enterprise accounts," Tolley says.
Tolley's been pushing LX4 since at least 2001, so Cisco's interest is no secret. Still, LX4 is a bit weird -- it avoids some problems of multimode fiber by using four wavelengths in a kind of coarse WDM. As the 10-Gbit/s Ethernet standard jelled, only Blaze Network Products Inc. and Molex Inc. (Nasdaq: MOLX/MOLXA) seemed interested in announcing LX4 transceivers (see Molex Makes Muxlink).
Some, such as Picolight Inc., shunned LX4 entirely. "We have felt the economies of scale favored serial optics," says Warner Andrews, vice president of marketing at Picolight.
"Certainly you hear a call for the application, but I don't think people believe LX4 is going to make it in the market. There are too many people who have backed out," says Steve Joiner, director of marketing for transceiver maker Ignis Optics. "Bruce [Tolley] would tell you emphatically they need a solution for this space, but I'm not sure he would mind if it was LX4 or something else -- just get it out there."
"Something else" might be arriving soon. Reportedly, there's a proposal afoot to replace LX4 with a serial option that uses electronic dispersion compensation to overcome the handicaps of multimode fiber. The IEEE 802.3ae task force, which shepherds the 10-Gbit/s Ethernet standard, is expected to hear the proposal at its September meeting.
Still, there's no guarantee that the new proposal will work out, leaving transceiver vendors with few options for supporting older fiber. "If LX4 turns out to be the best way to do that, then we'll have to find a way to do that," says Picolight's Andrews.
— Craig Matsumoto, Senior Editor, Light Reading