Bell Labs test shows faster speeds on shorter copper

21 May 2016 by Steve Blum
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Next generation cable technology – DOCSIS 3.1 – can support symmetrical 10 Gbps speeds over hybrid fiber coax plant, according to a press release from Bell Labs, now known as Nokia Bell Labs. Nokia completed its purchase of Alcatel Lucent earlier this year and Bell Labs was part of the bargain.

Bell Labs is pitching its XG-Cable technology for integration into CableLabs’ DOCSIS 3.1 standard, which is undergoing field trials in a few U.S. markets. It’s essentially the same pitch that companies with gear are making to telcos: our stuff will dramatically boost broadband speeds on existing copper wire networks.

From everything I’ve seen, that’s true. At least as far as it goes. And that’s the catch. Both XG-Cable and are relatively short range technologies. Bell Labs’ says it simultaneously pushed 10 Gbps in both directions over 100 meters of coaxial cable on 1.2 GHz of bandwidth under laboratory conditions. The speed dropped to 7.5 Gbps symmetrical when a point-to-multipoint architecture was used. Ultimately, Bell Labs expects to get that level of performance at up to 200 meters., which is touted as an upgrade path for DSL networks, is limited to something like 250 meters to 500 meters of copper wire, with speeds ranging from 100 Mbps to 1 Gbps, again depending on how far it has to go (and who’s press release you’re reading). To get to the high end of the range, the distance needs to be less than 100 meters.

For either or XG-Cable to deliver promised speeds, the outside plant needs to be in good condition. Deteriorating lines will mean sharp drops in performance, to the point that older technologies will outperform it. With all due regard to the danger of taking an analogy too far, it’s not unlike trying to drive a Lamborghini on a dirt road.

But if you’re on a short, pristine track, a Lamborghini will fly.

It’s easy jump to the conclusion that technological advances such as these will render fiber unnecessary. That’s not true. The way you get short, final copper runs is to push more and more fiber, deeper and deeper into the network. At some point, it might not be necessary to go all the way to a home or business to get fiber-class broadband speeds, but you’ll have to extend the fiber portion of last mile networks much closer. And you’ll have to add fiber capacity – either more strands or better electronics – to handle the increased demand for bandwidth.

It’s still early days for this technology, but it’s good news that it might not be too far over the horizon.