Bell Labs pushes gigabit wireless link as a way to boost throughput fourfold

High-powered, fiber-optic amplifiers can transmit up to 2.5 Gbps over distances as far
as 1.5 miles without wires.


That is a fourfold throughput increase over current commercial wireless products, which
are limited to 622 Mbps and short wavelengths.


The new amplifiers boost power output tenfold, so that the longer wavelengths of
fiber-optic transmissions can also work for point-to-point wireless, said Jim Auborn, head
of communications technology for Bell Labs, the R&D arm of Lucent Technologies Inc. of
Murray Hill, N.J.


“We can blast through much more power,” Auborn said. “That means we can
overcome weather conditions better, we can go farther and most importantly, we can
transmit more data.”


Auborn said the transmission rate could in theory reach dozens of gigabits per second,
but it will take a couple of years for government applications to appear.


“I think it’s going to be government-friendly” for Defense Department
and NASA communications satellites, he said. On the ground, the military could use gigabit
wireless for rapid deployment of fast data links, he said.


Wireless optical links now use laser-generated light in the 800-nanometer range at 100
milliwatts of power or less, Auborn said. The new gigabit technology works in the
1.55-micrometer range, and its amplifiers generate up to 10 watts at the longer
wavelengths.


Bell Labs’ experimental transmissions used laser equipment from AstroTerra Corp.
of San Diego. The signals went across a 1.5-mile gap from a transmitting telescope to a
receiving telescope, which focused them onto fiber by coupling optics.


“We don’t see it as a replacement for fiber,” Auborn said. But gigabit
wireless could supplant other optical wireless links as well as radio and microwave in
campus and urban environments or in military situations where it would be impractical to
install temporary networks.


Because gigabit wireless uses the same wavelengths as fiber, it could take advantage of
fiber-optic techniques such as wavelength division multiplexing to increase capacity. But
it has the same drawbacks as other wireless links, Auborn said: It works only on line of
sight and is affected by snow, fog and rain.


At distances of a few hundred yards, availability runs about 99 percent. Over distances
of a mile or more, that drops into the 90 percent range. “It’s not 100 percent
available as fiber systems are,” Auborn said.


For satellites, which orbit above the weather, the high-powered optical links would be
an improvement over current radio bands, which are getting crowded, Auborn said.


“Optical communications are completely unregulated,” he said, and optical
links are point-to-point, not broadcast. “That’s a big advantage because you
won’t overcrowd the frequency spectrum.”  



About the Author

William Jackson is a Maryland-based freelance writer.

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