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Or Dig a Trench

All of these technological developments, of course, face this challenge: how to continue to improve performance over lines that were typically designed, manufactured and installed many years earlier. The first fiber-optic lines in a public network were installed under downtown Chicago in 1977. Today, most of the world’s long-distance traffic is carried by optical-fiber cables-more than 370 million kilometers of the stuff, all of it designed before today’s breakthroughs in the labs. Eventually there will be no avoiding the need to dig a new trench.

Once the decision is made to lay new fiber, though, new possibilities to increase its capacity emerge. The fiber strands themselves have evolved to handle ever larger capacities. Today, the state-of-the-art is “nonzero-dispersion fiber,” invented by Lucent Technologies and sold by both Lucent and Corning. This version of fiber widens the area through which a signal travels, giving it more room to spread and reducing overlap. “If you have a water pipe and you want to put more water down it, one of the ways to do that is to widen the area of the pipe, and that’s essentially what [this technology] does,” says Corning’s Antos.

Next-generation optics technology may get rid of the glass altogether. Several research groups are working on building a fiber out of new materials known as “photonic-band-gap crystals” (see “The Next Generation of Optical Fibers,” TR May 2001). Such crystals have an atomic structure that makes it physically impossible for light to pass through or be absorbed, so light striking the inside of a fiber would bounce back into the core. Doug Allen, a research associate at Cor-ning working on developing such a material, suggests that the core could be filled with air, or perhaps an inert gas. By eliminating glass and its distorting effects, he says, “you can send more wavelengths without worrying about them interfering with one another.”

All these new developments have thrust research in the lab far beyond what’s currently available in the ground. If the backbone were equipped only with developments being demonstrated in labs right now-able to carry 160 channels over each strand, at 40 gigabits per second-the bandwidth we currently use in a month could be carried over our networks in less than a second. That’s when far-flung ideas start to get real, from holographic, 3-D videoconferences that mimic real life, to long-distance surgery, to instantaneous access to books stored at any library in the world.

What remains to be solved, though, is the economics of such a network: when will it be cost-effective to put these developments in place? In something as vast as the public communications network, even small upgrades take decades to be universally deployed. Theodore Vail, first president of AT&T, succeeded in building the world’s first state-of-the-art public network only by getting Congress to declare his company a natural monopoly. That’s not going to happen this time.

Raj Reddy, professor of computer science at Carnegie Mellon University and director of the High Speed Connectivity Consortium, a program funded by the U.S. Department of Defense, nevertheless remains optimistic that a very high-bandwidth network is inevitable-that one day we’ll have always-on, all-you-can-eat bandwidth, as easily accessible as the phone system is today. “It’s definitely going to happen in 30 years,” he says. “[But] what do we have to do, and what do we have to spend, to do it in five?”

And that, in spite of the legions of fiber-optics engineers dedicated to discovering the technological miracles that will power our next-generation networks, is the question waiting to be answered. But given the remarkable spectrum of cutting-edge work being done on the backbone, it is undoubtedly there that capacity will continue to increase at the most rapid rate.

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