IEEE P802.3ae Task Force settles multimode-fiber PMD debate

Meeting in New Orleans last month, the IEEE P802.3ae Task Force charged with establishing the 10-Gigabit Ethernet standard reached a conclusion on the contentious issue of multimode physical-media-dependent (PMD) interfaces for multimode optical fiber.

Having settled on 1,550- and 1,300-nm PMDs for singlemode applications involving distances of 40, 10, and 2 km in a meeting last July, the task force faced the prospect of choosing among three options for the remaining two PMDs on its plate: interfaces for 300-m and 100-m multimode applications. The group debated three options-a 1,300-nm wide WDM (WWDM) proposal, an 850-nm coarse WDM (CWDM) offering, and an 850-nm serial option.

While details were scarce at press time, it appears that proponents of the 1,300-nm WWDM and 850-nm serial options succeeded in banding together to galvanize support for their positions. The two options were joined in a single proposal, which achieved the 75% approval necessary to remain in the standards discussion.

In addition, the 100-m distance specification was shortened to 65 m, which more closely matched the capabilities of 850-nm serial devices. The CWDM option failed to receive the necessary 75% approval and is currently no longer part of the 10-Gigabit Ethernet standard discussions.

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