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Competing With Copper

These leading-edge systems are still rare. Most telephone and cable television companies rely on fiber only as a “backbone” technology for piping signals between their own facilities. In fact, fibers are the standard links to and from the switching offices serving each community, and often stretch from there to large business customers or neighborhood distribution nodes. A single pair of fibers now can carry up to hundreds of gigabits per second, with each fiber transmitting separate signals at dozens of wavelengths in one direction. Yet the rest of the distribution network is virtually all copper-that’s an investment worth well over $100 billion and phone and cable companies are not eager to abandon it. Late last year, regional telephone company SBC Communications announced a three-year, $6 billion fiber construction program in its service area in the western United States.

But conventional wisdom holds that running fiber all the way to a home is too costly, so SBC’s fibers will stop at distribution nodes that typically serve hundreds of customers. Data will still slog into the home itself on old-fashioned copper. It’s as if a relay team of Olympic-class sprinters had to rely on a geriatric patient for the final leg of the race-known in telecommunications lingo as “the last mile.”

Phone and cable companies each promise a different cure for the World Wide Wait suffered by home users of dialup modems (see table on last page “Battle of the Last Mile”). Cable systems deliver up to 36 megabits per second through the same coaxial cable that pipes CNN and HBO to the television set. The phone companies have devised DSL as a ploy to trick ordinary copper wire into behaving as if it were a fatter info-pipe, carrying up to several megabits per second.

People who switch from ordinary Net connections to cable modems typically traverse an arc of experience that begins with delight: The link is always on, just like electricity in a socket, and information flows at speeds that leave dialup modems in the dust. Then the drawbacks become apparent: cable bandwidth is shared among a group of users, so the lightning-fast connections experienced at first start to drag as more of your neighbors sign on. Security is another issue; if file sharing is enabled-a common default setting-everyone on a cable modem line can access your files. DSL has a different problem. The higher signal frequencies that carry DSL’s digital data fade as they travel through copper wire, restricting these connections to homes within about five kilometers of cable from a phone switching station. Wireless systems-an emerging high-bandwidth alternative-can suffer blockages from bad weather, trees and buildings.

If the past is any guideline, moreover, demand for bandwidth will soon outstrip the capacity of these jury-rigged alternatives. Already, today’s image-intense Web sites crawl when viewed at 56 kilobits/second. Full-motion video, for example, appears as a jerky, low-resolution picture in a corner of the screen. The need for higher capacity into the home is likely to intensify as companies roar ahead with e-commerce. Why show just a static picture and product specifications for a refrigerator if you can have a top salesman deliver a video pitch while demonstrating it on the screen? A reasonable target may be 100 megabits/second, which should enable full-screen, full-motion video and would probably satisfy the Gernsbacks. Then again, satisfaction is a moving target. Bandwidth is a drug; once you’re hooked, you only want more. A single optical fiber can easily carry more than 600 megabits/second to individual users-far beyond the capability of either DSL or cable lines. Indeed, DSL and cable modems would whet consumers’ appetites by giving them a taste of bandwidth plenty that only fiber can satisfy.

Now is the time to make that investment, at least for new installations, argues Asim Saber, president of Optical Solutions. Saber says that installing fiber will cost an extra 15 percent to 25 percent, but claims that the payoff will come in a few years as bandwidth demand soars. Better, he says, to spend more now than be forced to rip up the sidewalks in 8 or 10 years to add capacity.

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Tagged: Communications

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