G.fast means fiber speeds over copper, up to a point


The point where the infrastructure collapses.

A short range, high speed technology standard for broadband over copper phone lines has been approved by the International Telecommunications Union. The G.fast standard is intended to make fiber-class speeds possible over legacy lines, with a maximum distance of 400 meters between the customer and the nearest fiber node.

Practical distances, though, are much shorter. “Service rate performance targets” – total bandwidth which can be split between up and down loads – are…

500-1000 Mb/s for FTTB deployments at less than 100m, straight loops
500 Mb/s at 100m
200 Mb/s at 200m
150 Mb/s at 250m

Bell Labs has succeeded in pushing a gigabit over 70 meters of pristine plant and 500 Mbps over 100 meters of lousy copper, using its implementation of an earlier version of the G.fast standard.

But it’s not just a transportation protocol. The G.fast standard is intended to fit typical telco provisioning processes, enabling consumer installation with shrink wrapped kit, just like DSL. It makes it easy for telcos to upgrade service levels.

With one big if.

Telcos have to be willing to extend fiber further into neighborhoods and install more nodes. In urban business districts and affluent suburbs – high potential areas, as AT&T puts it – that’s not such a big deal. Either the fiber is already built or the revenue is there for the taking, or both. With the typical AT&T node feeding 600 to 900 meters of copper, doubling fiber distances and quadrupling the number of nodes requires a very sweet business case, if AT&T is to make the investment.

Mass market deployment of G.fast technology is still a few years out. It’ll eventually be a boon to those on the high potential side of the digital divide: places where incumbents have already decided to invest. For people living where telcos let copper rot on the poles, it’s not much help.