When the first 10-Gbit/s Ethernet switches were developed, the target customers were expected to be folk with new singlemode fiber installations. Now it’s turned out that there’s a lot of demand for running 10 Gbit/s over older, multimode fiber. As a result, vendors have been caught on the hop and are scrambling for suitable transceivers.

This state of affairs was underscored this week in a paper from Cisco Systems Inc. (Nasdaq: CSCO) at the Communications Design Conference (CDC).

The paper gave a status report on the two technologies being touted for transceivers for running 10-Gbit/s Ethernet over multimode fiber -- 10GBase-LX4 and electronic dispersion compensation (EDC) (see LX4 Gets Another Chance and IEEE Eyeballs Compensation).

Right now, LX4 is the only choice, according to Bruce Tolley, Cisco senior manager of emerging technologies. "There are no [EDC] products today that I can buy and ship to my customers," he says.

Neither LX4 nor EDC is exactly storming the industry, however. Molex Inc. (Nasdaq: MOLX/MOLXA) remains the only vendor actively committed to LX4, and that's based on a product line introduced in 2001. EDC, meanwhile, is only beginning its standardization effort in the Institute of Electrical and Electronics Engineers Inc. (IEEE) 802.3ae task force.

Better known for selling connectors, Molex hasn't been particularly vocal about its LX4 transceivers. But the company's been working on improving them.

As part of the CDC session, Molex group engineering manager John Dallesasse presented data showing that LX4 transceivers can reach even farther than expected, up to 1,400 meters on multimode fiber and 40 kilometers on singlemode, if the transceiver is properly tuned. (The LX4 standard calls for a 300 meter reach on multimode and 30 km on singlemode.)

Ben Willcocks, lead systems designer for Phyworks Ltd. delivered the case for EDC being cheaper and more compact. For example, an EDC chip could fit inside an XFP module, replacing the retimer chip that's required in there.

All that might be true, but Tolley says he'll remain skeptical until Cisco can look at the EDC devices in depth: "I've seen some of the demos, but I haven't seen parts in my lab, so I don't know how real they are."

Phyworks is expecting its first sample chips to complete manufacturing by the end of the year, Willcocks said. That puts it a step behind competitors such as startup Scintera Networks Inc., which is sampling now (see Scintera Networks Launches).

Separately, Tolley threw in a mention of the 10GBase-CX4 effort for standardizing 10-Gbit/s Ethernet over copper, a cheaper alternative to fiber. The CX4 standard is close to completion and chips are available -- and Cisco is interested. "I need to support legacy copper immediately," he says.

— Craig Matsumoto, Senior Editor, Light Reading