When OM3 almost didn't happen

While digging around for information on wideband multimode fiber (WBMMF) for an article in this issue, I was told a story I hadn't heard before concerning OM3 fiber and how it almost didn't come to be.

While digging around for information on wideband multimode fiber (WBMMF) for an article in this issue, I was told a story I hadn't heard before concerning OM3 fiber and how it almost didn't come to be.

When the IEEE's P802.3ae Task Force was in the throes of developing the 10-Gigabit Ethernet specifications more than a decade ago, a certain camp within the group advocated for singlemode fiber as the only optical media type to be recognized. These contributors didn't want there to be a short-wavelength, multimode-fiber-supported flavor of 10-Gbit Ethernet. And they almost got their wish based on the manner in which standards bodies like the IEEE and the INCITS (which develops Fibre Channel specifications) cooperate with other standards bodies like the IEC or the TIA.

In the WBMMF article elsewhere in this issue, Paul Kolesar explains that application-standards groups like IEEE and INCITS "require a specification that can be referenced before they will adopt the fiber ... By the time their drafts are nearing publication, they must either have a published ... specification in hand, or be confident that its publication will precede their own."

IEEE 802.3ae, 10-Gigabit Ethernet, was nearly all the way through its approval process while the OM3 fiber specification remained an unfinished project. By just about the width of a human hair, the producers of the OM3 fiber specification completed their project approximately one meeting cycle before the IEEE's "drop dead" date by which it was required in order to be referenced in 802.3ae.

Since being introduced to the marketplace, OM3 frequently has been called "laser-optimized multimode" because it is optimized to support the transmission of signals generated by vertical cavity surface emitting lasers (VCSELs) at and very near the 850-nanometer window of operation. The farther you move away from that 850-nm range, the less able OM3 is to support long-distance transmission. The same is true of the higher-bandwidth OM4 multimode. But that has never really been a problem for OM3 or OM4 because the VCSELs used in transceivers for Ethernet, Fibre Channel and others have always operated in that tight window. Until recently, that is. Wavelength-division multiplexing is coming to short-wave transmission and will operate roughly between 850 and 950 nm. It's why WBMMF is under development. This time, though, the creators of the fiber specification are ahead of the game, not playing catch-up.

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