How far can you push 100G Ethernet over copper?

Researchers look into 100G on 100m

The IEEE Higher Speed Study Group is looking to move both 40Gbps and 100Gbps Ethernet over a modest 10 meters of copper cabling. And then there are the folks talking about running 100G Ethernet over 10 times that distance, using Category-7A copper wiring.

Materials from the most recent group meeting earlier this month include a presentation from some representatives of Pennsylvania State University's Center for Information and Communications Technology Research, and Department of Electrical Engineering. In it, faculty investigator Dr. M. Kavehrad and graduate researchers A. Enteshari and J. Fadlullah reveal the results of their research into whether you could actually get 100Gbps over 100 meters.

They found that crosstalk was not a big factor on Category-7A cables in the scenarios they tested. Alien crosstalk (interference from other wires) is "negligible," because of the heavy shielding, and far-end crosstalk (FEXT) and near-end crosstalk (NEXT) are "well below the signal levels." The biggest interference problem is echo, and they applied a canceller to their model that corrected for it.

They concluded that the best you could probably get on 100 meters of cable is 70Gbps. If you had to have 100Gbps, the maximum length would probably be around 70 to 80 meters.

Meanwhile, they said, 40Gbps (the other speed that the group is working toward) ought to work just fine over 100 meters.

However, they also noted that they're still investigating 100G on 100m, and they may even recommend improvements to Cat-7A to push the envelope further.

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