The clean-up crew

Even in the most remote areas, there are places where the noise just won't go away.

As vice president of engineering, Bill Doran had overseen an extensive network upgrade for the Ontario and Trumansburg Telephone companies (conjoined twin telcos in New York with about 14,000 customers). When it was done, 90% of the network was DSL-ready. It was that other 10% that posed a problem. Some of the lead cable in those areas might have been deployed as far back as the 1950s. And some of the local loops were upwards of 18,000 and 20,000 feet long. For customers there, DSL was plagued by sluggish speeds, service errors and noise pollution.

Earlier this year, Doran was approached by John Fortier, a longtime telecom consultant who now calls himself the chief technology officer of Communications Technology, an as-yet-unfunded zygote-stage equipment start-up with a headcount of four. The quartet was looking for telcos to test Nexus, their new device for cleaning up and smoothing out ADSL lines.

“We said, ‘Show us your worst lines, and let's see what we can do,’” Fortier said.

A 6-inch-high box housing 24 circuits, Nexus is deployed across the cable pair in central offices or cross-connect boxes. It sits in place of a module block on a main distribution frame, where operators can jumper a troubled pair to it. Without interrupting the signal, Nexus balances the line (equalizing the impedance in each of the two wires), thus protecting it from external interference, which can couple into unbalanced lines. The device also absorbs residual interference and prevents outside interference from reflecting off the line's end points. The end result is a 4 dB to 6 dB improvement in signal-to-noise ratio, Fortier said. His goal for the next-gen Nexus is 10 dB.

Doran tested Nexus on a dozen or so lines earlier this year and said it helped improve the noise margin on about eight of them. At $30 per circuit, the price tag wasn't bad, either.

“It's not a fix for bad cable,” Doran said. “It's a help when you've done all you can short of a construction project. If you've got a hum on a line, you need to find out where you're getting that hum and repair it.”

Nexus works particularly well fixing impedance mismatches that can't be pinpointed and reducing impulse noise, Doran said. For example, some of his lines were getting interference from a nearby Loran transmitter (a navigation device used by the U.S. Coast Guard), whose frequency was smack dab in the middle of the ADSL spectrum.

“It was breaking through so badly, you could hear it in the telephone,” Fortier said. With the Nexus installed, the noise went away, and the line's throughput jumped 50%, he said.

Fortier hopes to eventually sell the technology (which has also been tested by at least one other unnamed telco) to DSL equipment vendors as a chip in their systems. But for now, he's looking for about $5 million in funding to get the company going. In the meantime, he hopes to sell Nexus to more rural telcos by asking to see their longest, noisiest, old lines and showing what he can do about them.