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Note One: Fiber Optic Bugs
The cinder block, painted a symbolic red, sits on a rubber tube in a Virginia university lab. It’s part of an experiment by several electrical engineering students who were intrigued by a news report that fiber optic bugging devices may have been planted in the new U.S. embassy in Moscow.
Though little is known publicly about this technology, experts in electronic surveillance have said that it’s possible to put optical fibers - flexible, hair-like glass fibers that transmit light - in the mortar or plaster of buildings, allowing conversations within to be heard and taped. The fibers can transmit without emitting tell-tale frequency signals.
“We wanted to see if we could use optical fibers to do that,” says Joseph A. Wiencko Jr., associate director of the Virginia Center for Innovative Technology’s fiber and electro-optics research facility in Blacksburg. The research center’s focus, however, is not on electronic surveillance, but on designing and using optical fibers for communications, and for detecting stresses in materials that make up airplanes, bridges, buildings and other structures.
In the experiment, optical fibers were attached to a cinder block and to a laser that sent light through the fiber. The other end of the fiber was connected to a machine that changes light signals to electrical ones. The light-to-electricity converter was in turn linked to a machine called a digital storage oscilloscope. Another machine makes sound waves that reverberate through the block and flex the fibers, affecting the way light passes through them. (The rubber tube that the block rests on helps eliminate the effect of other vibrations in the room.)
In the oscilloscope, the light signals that have been converted into electrical signals are displayed as waves on a tiny TV screen, and stored on a computer disk for analysis. When amplifiers and filters are connected to the fibers, the original sound waves may be recreated and heard, whether they’re from a clandestine conversation or, in this case, a high-pitched monotonous whine. How accurately the sound is transmitted depends on how the fiber is designed and made.
The aim of the experiment is to study how light traveling through the fiber changes with respect to the sound that causes the fiber to vibrate, Mr. Wiencko said. While research at the fiber optics center isn’t aimed at embassy eavesdropping devices, much of the basic work could conceivably be applied to their development, he added.
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