Magazine article Science News

Harnessing Chaos for Optical Communications

Magazine article Science News

Harnessing Chaos for Optical Communications

Article excerpt

Police radio messages are vulnerable to interception. A wireless communication system based on the erratic, unpredictable output of an electronic circuit or a laser, however, offers the possibility of enhanced security. An eavesdropper would detect only static, even though an intelligible message rides atop the chaotic carrier.

Researchers have now shown that chaotic signals transmitted from one laser directly to another can be used to carry information. Such an optical scheme has the advantage of reducing the amount of power required and potentially increasing the number of signals that can be delivered along an optical fiber, says Henry D.I. Abarbanel of the University of California, San Diego.

Abarbanel and Matthew B. Kennel describe the principles underlying such a technique in a report scheduled for publication in Physical Review Letters. Gregory D. VanWiggeren and Rajarshi Roy of the Georgia Institute of Technology in Atlanta report in the Feb. 20 Science the first experimental demonstration of chaotic communication using an optical system.

"What we've done is learned how to attach a message -- it could be one voice, it could be hundreds of voices -- to a carrier that is very irregular," Abarbanel says.

"In an ordinary digital signal, the message can immediately be seen," Roy adds. "In our system, digital information is encoded in the chaos, so the message would not be obvious to a person who may intercept it."

Using chaotic signals for communication requires synchronization of two highly unpredictable, virtually identical -- but separate -- systems. In 1990, Louis M. Pecora and Thomas L. Carroll of the Naval Research Laboratory in Washington, D.C., showed that it is possible under the right conditions to synchronize the wildly fluctuating voltages of a pair of properly matched chaotic electronic circuits (SN: 3/24/90, p. …

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