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Americas Issue: January 2007
Feature
There’s Still Gold In That Copper
DSL: The Ever Evolving Pipe
by Sean Buckley
At one time, the notion of delivering 1.5 Mbps over a copper line over ISDN — the precursor to what we now know as DSL—was a pipe dream.
When John Cioffi, now Hitachi America Professor of Engineering at Stanford University, suggested such an idea when he was a young Bell Labs engineer in 1979, many scoffed at the idea.
“Was it possible to design stuff to run that fast on the copper twisted pair, which had been long perceived as being only for voice, and only able to carry speeds of a few 10s of kilobits per second?” asked Cioffi. “If you put a piece of equipment in the CO that talks to the modem, the speeds are much higher, and 1.5 Mbps on a four mile loop is pretty easy to compute as the practical upper limit on what you might be able to achieve.”
Fast forward to 2006. According to Point Topic, there are 173 million subscribers and counting served by DSL, but service providers are not resting on their laurels.
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