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Fibre-cable speeds travel through copper telephone wires

Posted: 14 Jul 2014     Print Version  Bookmark and Share

Keywords:Bell labs  fibre  broadband  copper  XG-FAST 

Bell Labs recently hit the headlines for stealing a 10Gbit/s world-record speed over existing copper wires—setting the benchmark for ultra-broadband applications and solving the fibre-to-residence problem. This was two months after it celebrated a return to its original R&D business model (see Bell Labs reverts to 'game-changing research' model).

Fibre cables for high-speed Internet services are being laid all throughout the country and world, but at a relatively slow rate due to the "curb-to-residence" problem. Many home owners are reluctant to let their lawns be dug up to lay fibre from the curb to the house, and many Internet providers are reluctant to incur the cost. Now Alcatel-Lucent's Bell Labs has invented a solution—a method of running 1Gbit/s to 10Gbit/s broadband signals from the curb to the residence using the existing copper telephone lines already there.

"Cost and time-to-market are the two of the biggest factors in bringing fibre to the home," Keith Russell, senior marketing manager for Alcatel-Lucent's Fixed Networks, told EE Times. "If you can imagine being an operator that is deploying and all fibre network they have to put new infrastructure into every unit. And as you put fibre into neighbourhoods there's a high cost to that, but when you get to the curb and try to get across their property—maybe digging up the lawn or going under the driveway—there is a lot of cost to that too. Even avoiding that last little bit by using copper deployment can save an operator a lot of time and money."

The Bell Labs inventors of XG-Fast discuss how they were inspired by Bell Labs' most famous member, Claude Shannon.

Bell Labs' broadband-over-copper technology, called XG-Fast, is an extension of the digital subscriber line (DSL) standard under development at the International Telegraph Union Telecommunication (ITU-T) standardisation group. Called G.fast, it is expected to deliver speeds of 200Mbit/s to 500Mbit/s. By the time G.fast is deployed circa 2015, Alcatel-Lucent hopes to have readied commercial versions of Bell Labs G.fast extension—XG-Fast—offering 1Gbit/s to 10Gbit/s speeds. Bell Labs also demonstrated the "holy grail" of broadband-over-copper—1Gbit/s symmetrical ultra-broadband access (allowing simultaneous uploads and downloads at 1Gbit/s per second).

The limitations of XG-Fast, however, are that the 10Gbit speed only for runs of 30m and requires bonding two copper pairs, whereas the 1Gbit/s speed requires only a single copper pair, but can provide symmetrical ultra-broadband access for over 70m, making it indistinguishable from Fibre-to-the-Home (FTTH).

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Bell Labs' new XG-Fast carries broadband frequencies over copper from the curb to the residence at 1Gbit/s to 10Gbit/s broadband speeds. Source: Alcatel-Lucent

XG-Fast offers its higher performance (over shorter distances) by upping the standard 106MHz frequency of G.fast, which gives it 500Mbit/s for 100m, to 500MHz, thus achieving 10Gbit/s speeds over 30m. The 1Gbit/s symmetrical speeds over 70m were achieved at a frequency of 350MHz.

- R. Colin Johnson
  EE Times





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