Using novel duobinary signaling architecture and FCI's AirMax VS^ò connector system, researchers at Lucent Technologies' Bell Labs have successfully demonstrated 25 Gbits per second (Gbps) data transmission over an electrical backplane. This is more than twice the highest transmission rates that have been demonstrated to date over electrical backplanes and is a significant step toward achieving 100 Gbps Ethernet over electrical backplanes. The team achieved error-free performance at 25 Gbps over electrical traces as long as 24 inches using a backplane made with FR4 laminate — an industry standard material.

“100 Gb/Ethernet over electrical backplanes is important because it will allow us to further scale today's data networks to support future high-bandwidth applications such as fast movie downloads, telemedicine and military communications,” said Martin Zirngibl, director, Photonic Networks Research, Bell Labs.

“We are extremely pleased that our AirMax VS^ò backplane Connector system turned out to be an enabler of this ultrahigh-speed technology,” said John Burkett, FCI product manager. “While the flexibility and cost of AirMax VS^ò has made it a winner at 2 Gbps, 3 Gbps and 6 Gbps, it is the connector's superior electrical performance that makes it the most attractive choice — and sometimes the only choice — at 10 Gbps and above.”

The new application of duobinary signaling, a technique that uses three electrical signal levels to represent binary code in a communications transmission, to high-speed electrical backplanes, was first documented by researchers Jeffrey Sinsky, Andrew Adamiecki and Marcus Duelk, of Bell Labs Photonic Networks Research group at the IEEE International Microwave Symposium in June 2004, and later in a paper published in the January 2005 issue of IEEE Transactions on Microwave Theory and Techniques.

“The group has demonstrated performance at 10 Gbps over several different legacy backplanes, and is supporting a movement to use this technique as part of the IEEE 802.3ap standard for 10G PHY (physical layer) Ethernet over backplane,” said Mary Mandich, a technical manager in Lucent's Network Hardware Integration Research Department.

The researchers attribute the performance to connector's carefully controlled impedance characteristics, plus low crosstalk. In addition, the AirMax VS connector achieves extremely low loss at frequencies up to 15 GHz by using air as a dielectric. Lucent's duobinary signaling architecture for electrical backplane systems takes advantage of the “natural rolloff” tendency of a backplane instead of fighting it like traditional approaches, and uses it to help shape the data bits and provide a clean signal at the receiver. “With a small amount of additional pre-emphasis and equalization to correct the frequency response — technologies that already are commonly used with today's communications transmitter and receivers — the output signal at the backplane requires only half the required bandwidth of traditional systems. And, we can convert the signal from duobinary format back to a traditional format using high-speed integrated circuit (IC) technology,” said Andrew Adamiecki, a researcher with Bell Labs.

For more information, visit www.bell-labs.com.