Cut Cost, Power While Delivering 10-Gbit/s Ethernet Over 30 m Of Copper

July 24, 2008
Designers can deliver up to 10 Gbits/s of Ethernet over 30 m of copper cable thanks to a pair of developments from Phyworks Ltd. The 24 AWG twin-ax cable is terminated in SFP+ connector assemblies that employ the company’s PHY2060 active

Designers can deliver up to 10 Gbits/s of Ethernet over 30 m of copper cable thanks to a pair of developments from Phyworks Ltd. The 24 AWG twin-ax cable is terminated in SFP+ connector assemblies that employ the company’s PHY2060 active equalizer, CDR, and retimer IC (see the figure).

The PHY2060 was originally developed for optical-fiber applications, but it adapts well to the copper medium. The complete assembly achieves error-free transmission with a latency of just 120 ns at 30 m.

This technology is ideal for interconnecting servers and other equipment in datacenters. With at least 80% of datacenter cables less than 30 m long, a copper interconnect approach offers great cost savings. Optical-fiber cables based on the Ethernet 10GBaseSR standard are the best for such high-speed connections, but they’re very expensive, ranging from $400 to $600. Designers can also use the 10GBaseCX4 copper cable standard, which transmits over four parallel 3.125-Gbit/s channels.

These cable assemblies are large, bulky, and heavy, though, and they consume considerable power. They also still cost more than $7 per meter. Furthermore, CX4 cable assemblies need line-card mounted quad retimers and quad preemphasis drivers as well as the printed-circuit board (PCB) space to support eight data lanes. The new Phyworksbased cable assemblies are 40% smaller, 30% lighter, and far less bulky than CX4 cable. A 30-m cable is expected to cost around $150.

While Phyworks doesn’t make the cable assemblies, the PHY2060 is being used in modules and cable assemblies currently in trials by cable and connector OEMs. It’s primarily a receiver chip, so two devices are used at each end of the cable. Phyworks expects a singlechip transceiver using the same effective equalization and retime capability in the near future.

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