Researchers develop fiber-optic monitor

Turan Erdogan, professor of optics, and researchers in his laboratory at the Institute of Optics have developed a device smaller than an inchworm that clings to a single optical fiber and precisely measures how efficiently it's performing. If trouble strikes and the fiber loses a few bits of data, the device could instantly detect the problem and tell headquarters to reroute the signal. Traditionally, such devices are filled with lenses and motors and take up as much space as a toaster, severely limiting where they can operate. But the new device has no moving parts and could fit anywhere the fiber goes.

"It's like a line-tester for the fiber-optic age," said Erdogan, "except instead of pulling out an oscilloscope whenever you think there's a problem, each fiber would monitor itself and let you know when there's trouble."

Trouble on a network of fiber optics is much different from trouble on a conventional network. Copper lines transmit one signal at a time, while an optical fiber may transmit over a hundred wavelengths of light all at once, each one carrying more information than an entire copper line. Most fiber-optic lines are strung between phone-company "central offices," while the slower copper lines extend to the customers. Although faster, optical fibers are glass and are more prone to breaking, which could cut off your phone conversation or demolish your download.

Over the next several years, communication companies will replace the copper wires connecting businesses and eventually homes with fast fiber optics, demanding a complete change in how engineers sustain the network.

"Network monitoring is more important for fiber optics than it is for copper lines because there's not much you can do with copper besides send an electric signal down it," explained Erdogan. "It either works or it doesn't. But in four or five years when the next generation of fiber-optic communications hits, the complexity of the networks will make it much more important to know the exact condition of every line, everywhere, instantly."

Erdogan and graduate student Mark Froggatt presented the design for the device at the 1999 Optical Fiber Communications Conference in San Diego and have published the results in the journal Optics Letters (Vol. 24, 1999).

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