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OIF signs off on high-speed I/O implementations

By Jeff Berman, News Editor -- EDN, 4/28/2005

The Optical Internetworking Forum (OIF), an industry concern made up of component manufacturers and system vendors, said today it has finished two implementation agreements targeting the development of high-speed backplanes.

The first agreement, CEI (Common Electrical Implementation) 11G-LR, targeting 11- to 13-Gbps backplanes, focuses on an industry effort toward high-speed electrical signaling that will allow system vendors to quadruple bandwidth without increasing the number of backplane traces. The second agreement, CEI-P (CEI Protocol) defines a protocol designed for use with the fast electrical interfaces developed by the CEI project team.

The OIF began the CEI effort more than two years ago with the goal of developing specifications for higher-speed electrical signaling, according to Mike Lerer, a Xilinx consultant and the chairman of the OIF's physical and link-layer working group.

The project's specific initial goals, Lerer said, included:

• Achieving a short-reach link of 0 to 200 mm with up to one connector and a long-reach link of 0 to 1m with up to two connectors at bit rates from 4.976 to >6 Gbps over printed-circuit boards
• Achieving the same types of short- and long-reach links, but with data lanes that support bit rates from 9.95 to >11 Gbps.

The group completed and released specs for the two 6-Gbps links and the short-reach 11-Gbps link during the fourth quarter of last year. "The fourth and last goal [the 11-Gbps, long-reach link] is now complete," Lerer said. "And all four utilize NRZ [non-return-zero] signaling."

The 6-Gbps long-reach signaling, Lerer said, targets usage with legacy IEEE 802-3a XAUI (extended auxiliary unit interface) and TFI-5-compliant backplanes. The 11-Gbps long-reach signaling, he added, suits applications that do not need to support legacy technologies.

"At both 6- and 11-gigabit long reach, it is assumed that the signal eye is closed at the input to the receiver," Lerer said. "The receiver contains equalization, which opens the eye. It attempts to compensate for high-frequency losses in the channel, impedance discontinuities in the channel, and reflections in the channel."