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By Karen Brown
There's no doubt the Achilles heel of digital subscriber line technology is distance, and now Symmetricom Inc. says it has a partial cure.
The San Jose-based technology firm says it completed the first successful field trial for a scheme that doubles the distance for asymmetric digital subscriber line circuits, reaching into the 30,000-foot range.
The GoLong ADSL Loop Extender uses amplifiers placed along the twisted copper line to boost data signals in both directions. In a test with South Carolina's Chester Telephone, GoLong successfully delivered 3 megabits per second downstream at a distance of 24,000 feet with one amplifier, according to Barry Dropping, Symmetricom's director of engineering.
A two-amplifier test is in the works to extend the technology to 30,000 feet-and for now that is probably the limit. "Eventually, the noise buildup gets you and that's why we are limited to 30,000 feet," Dropping says.
The downside? The amplifier needs power, fed from a control card at the central office via the copper line. But that means the copper line can't support traditional voice service alongside the ADSL data. So customers will have to resort to a second line for traditional phone service.
Then there is the cost for amplifiers and control cards. "We're targeting an installation cost for telcos at the $500 per circuit range," Dropping acknowledges. That may be steep, but given the fierce competition from cable rivals, telcos may invest in GoLong to keep those customers, Dropping notes.
"And certainly we see long range that vast deployment will come down on a pretty steep cost slope," he adds.
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