MURRAY HILL, NJ and ETTERS, PA - Lucent Technologies’ Bell Labs and FCI recently announced the successful demonstration of 25 Gbit/s data transmission over an electrical backplane using a Bell Labs signaling architecture and FCI’s AirMax VS connector system. The demonstration doubles previously demonstrated transmission rates over electrical backplanes and is a significant step towards achieving 100 Gbit/s Ethernet (4 x 25 Gbit/s) over electrical backplanes.
Martin Zirngibl, director, Photonic Networks Research, Bell Labs, commented, “The 100 Gbit/s 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.”
“We are extremely pleased that our AirMax VS backplane connector system turned out to be an enabler of this ultra-high-speed technology,” said John Burkett, FCI product manager. “While the flexibility and cost of AirMax VS has made it a winner at 2, 3, and 6 Gbit/s, it is the connector’s superior electrical performance that makes it the most attractive choice-and sometimes the only choice-at 10 Gbit/s and above.”
The Bell Labs duobinary signaling architecture is a technique that uses three electrical signal levels to represent binary code in a communications transmission. The application of duobinary signaling to high-speed electrical backplanes-circuit boards that act as a backbone to connect different elements in the electronic card cages used in network switches and computing platforms--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 Gbit/s 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.
“We are always looking one step beyond,” said Jeffrey Sinsky, lead researcher on the duobinary effort at Bell Labs. “To demonstrate 25 Gbit/s, we needed a connector with carefully controlled impedance characteristics, which prevents signals from bouncing back and forth, plus low crosstalk. We also need a signaling technique that can compress bandwidth without requiring excessively complex hardware. Our duobinary signaling technique combined with FCI’s AirMax VS connector proved to be a successful recipe for achieving 25 Gbit/s transmission speeds.”
The AirMax VS connector offers low insertion loss and crosstalk at frequencies up to 15 GHz by using air as a dielectric, an insulator that resists electrical current. “The connector’s novel design does not require metal shields, yet exhibits lower crosstalk than existing shielded high-speed connectors,” said Dana Bergey, manager of FCI’s signal integrity group.
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. Andrew Adamiecki, a researcher with Bell Labs, explained, “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.”
The team achieved error-free performance at 25 Gbit/s over electrical traces up to 24” using a backplane made with FR4 laminate, an industry standard material.
