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Optical/IP

Telecom Bides Time on XFP

In the move to XFP modules for 10-Gbit/s Ethernet, datacom vendors appear to be ahead of telecom vendors for the moment.

What's the difference? XFP modules for short distances are available. But the varieties interesting to telecom aren't: 40km models are more scarce, and 80km and DWDM varieties haven't hit volume production yet.

"XFP doesn't support every flavor that they need. They can't see a path to getting to DWDM or 80km," says Ed Cornejo, director of applications marketing at Opnext Inc.

Not that this changes the XFP roadmap. XFP is the endgame in a series of multisource agreements (MSAs) for pluggable 10-Gbit/s optical modules. Because it keeps data as a serial 10-Gbit/s stream, it's not expected to hit mainstream use for several more years. In the meantime, vendors can use the Xenpak, XPAK, and X2 MSAs, which split the 10-Gbit/s signal into four lanes of 3.125 Gbit/s, a speed more palatable to today's chip buses.

Foundry Networks Inc. (Nasdaq: FDRY) has even announced product using XFP modules (see 10-GigE Price Drops Continue). But for most OEMs, XFP remains an eventuality more than an immediate necessity. XFP "will probably start to be a volume play around mid-to-late next year," says Claude Denton, vice president of marketing for Network Elements Inc.

For a while, XFP was expected to get a headstart from storage applications, but that prospect fizzled out (see XFP No Longer a BFD). Most of the early interest in XFP now comes from enterprise circles, with telecom still waiting for those two key advances: longer reach and Tunable Lasers.

At OFC in February, telecom OEMs got a sneak preview of what they want, as Bookham Technology plc (Nasdaq: BKHM; London: BHM) and Finisar Corp. (Nasdaq: FNSR) demonstrated 80km modules, with Finisar's model even claiming DWDM support. Other vendors don't think either advance is all that close, though. Tunable lasers for DWDM, in particular, will have a hard time fitting into the XFP power budget, Cornejo says.

XFP would offer the benefit of greater density than Xenpak and its ilk, but with 10-Gbit/s ports still a high-end play, that's not so important yet. A spokesman for Extreme Networks Inc. (Nasdaq: EXTR) notes his company has a blade carrying six Xenpak connectors, and the company thinks that's plenty for now.

Chip and module vendors are spurring some XFP interest by lowering prices (see Vitesse Softens XFP Prices and XFP Prices Plummet). But most of the products shipping are using Xenpak or the even older 300-pin MSA, and it's going to take some time for newer products to take their place, says Tom Hausken, analyst with Strategies Unlimited.

"Our forecasts have that whole category [Xenpak, XPAK, and X2] peaking in 2006," he says. "It's not because you have this world of converts to XFP in 2006. They were converted earlier -- last year or this year -- but their [old products'] momentum pulls along to 2005 or 2006."

It's worth noting that some products will skip from Xenpak to XFP, ignoring the intermediate stage of XPAK or X2.

"Certainly for the larger enterprise servers, they're considering staying with Xenpak for three to five years, and after that going to XFP," Cornejo says. But for mid-range servers and pizza-box appliances, most enterprise OEMs are including X2 modules in their next designs, with system announcments possible before the end of this year, he says.

XPAK and X2 are nearly equivalent but, in the end, incompatible. Because Cisco Systems Inc. (Nasdaq: CSCO) appears to be ignoring XPAK, that MSA has been relegated to designs based on Peripheral Component Interconnect (PCI), with XPAK instigator Intel Corp. (Nasdaq: INTC) among the top users.

— Craig Matsumoto, Senior Editor, Light Reading
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