Here we go again

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Th Acf893

It's déjà vu all over again in the fiber-optic standards community, as the IEEE P802.3ae Task Force meets this month to somehow strike a balance between technical and commercial interests in the matter of adopting one or more physical media-dependent interfaces (PMDs) for 10-Gigabit Ethernet over multimode fiber. The task force has already performed yeoman work, whittling more than 20 proposals to five-two of which have already been approved. These two PMDs meet three of the task force's five transmission benchmarks. However, nailing down the last two objectives, 100 m over "installed" multimode fiber and 300 m over other multimode fiber types, has proved to be something of a tangle. (For more details, see the lead news story on page 1.)

Much of the current wrangling echoes the politicking and finger-pointing that accompanied the discussions of a small-form-factor (SFF) connector standard a few years ago.

As you may recall, five alternatives were also under discussion in the Tele communications Industry Association's (TIA's) TR-41.8.1 Working Group-as was the question of whether SFF technology itself was ready for standardization. Naturally, voting members of the working group employed by companies that produced SFF connectors were happy to cooperate with each other to urge the inclusion of these devices in the TIA/EIA-568B wiring standard. That alliance proved temporary, however, when it came to determining which SFF connectors to add to the standard. If a member's favorite connector didn't make the cut, it apparently became that person's mission to ensure that no other option passed, either.

In the end, the working group agreed to disagree. Instead of selecting specific connectors, the group settled on a set of performance criteria; once an SFF connector met the criteria and acquired its FOCIS documentation, its manufacturer could claim the device complied with the new standard.

In essence, the burden of settling on one or more "standard" SFF connectors shifted to the marketplace, which is still making up its mind.

One might be tempted to predict a similar outcome over the question of the 10-Gigabit Ethernet PMDs. The three remaining proposals-1,300-nm and 850-nm approaches based on WDM, plus an 850-nm serial offering-each have powerful manufacturers behind them. The respective camps would be quite happy, one would think, to compromise in such a way that they could all approach the market with a standards-compliant offering.

Unfortunately for the 10-Gigabit Ethernet community, the political forces in this instance are more complex than the SFF fracas. For one thing, fiber manufacturers with new, high-bandwidth multimode fiber in the pipeline are very interested in the 850-nm serial PMD, which would appear to require such fiber to meet the task force's objectives at 300 m. This voting block could prove extremely influential.

Even more influential will be the voting members employed by the systems companies. Each PMD added to the standard will create two port types that users could potentially demand; if all five PMDs survive the standards process, systems vendors might have to provide 10 port types to fully cover the market. Not surprisingly, these companies have lobbied strongly for just one multimode-fiber PMD.

Personally, I think it will be difficult for the 10-Gigabit Ethernet task force to follow the example of the TIA TR-41.8.1 Working Group and agree to unleash all five PMDs on the market, unless the system houses roll over because they've grown tired of the standards-making process.

That said, they've had a few months to contemplate what will happen if this impasse continues. Adoption of two of the three multimode PMDs may begin to appear like a workable compromise.

Improvements in the performance of one or more of these multimode PMDs-and efforts along these lines are underway-may radically affect the popularity of the three proposals still under discussion. But barring such a technological factor, it would appear that the discussions this month will once again illustrate that business realities will continue to play a lead role in the standards arena.

Stephen M. Hardy
Editorial Director and Associate Publisher
stephenh@pennwell.com

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