Reflecting on the Origins of Fiberoptic Communication
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Reflecting on the Origins of Fiberoptic Communication "Imagine what .the keen minds of our entertainment industry could do if they realized they had a hundred million channels into which they could funnel new and undreamed varieties of trash," wrote Isaac Asimov in 1962. The first working laser had been demonstrated just two years earlier and Asimov was contemplating what the new optical technology might mean for communications. "Maybe we should stop right now," he quipped. No chance. The laser had inflamed the long-thwarted lust for optical communications systems. Within a decade, researchers at Bell Telephone Laboratories, Corning Glass, and elsewhere had invented the kinds of solid state lasers and photodetectors and glass fibers needed to build workable optical communications systems. In 1976, the first experimental optical fiber links were going on-line in offices. Since then, the frenetic wiring of the world with high capacity optical fibers has even brought a portion of Asimov's nightmare to near reality. There could well be a day in the near future when viewers will be able to choose from 500 channels of trash. But long before the laser was invented, optical communication had racked up a lineage. In the ancient world large torches and sunlight reflectors served as optical signals that could be seen for miles. Flags served similar purposes since ancient times. In the 1790s, an optical telegraph using movable arms atop towers was designed in France. In 1840, the Prussian General Joseph Jakob Baeyer suggested that the heliotrope—an instrument that focuses sunlight into a narrow beam that Karl Friedrich Gauss had invented twenty years earlier for making land measurements—could serve well for transmitting messages. British and American military forces used a variation on that theme, called a heliograph, as an alternative to the electric telegraph. The inventor of the telephone himself, Alexander Graham Bell, filed a patent in August of 1880, for a "photophone," which he demonstrated between a couple of rooftops along 14th Street in Washington, DC. A human voice caused a thin mirror to vibrate. A beam of sunlight reflecting from that mirror onto a selenium pickup altered the pickup's
MRS BULLETIN/SEPTEMBER 1995
resistance in accordance with the changing light. This, in turn, modulated the amount of current going into a receiver. The result: a voice transmitted by light. The telephone changed the world and the photophone did not because the photophone had a fatal flaw. A passing cloud could interrupt an act of communication and bad weather muted the gadget altogether. Nothing short of enclosing the beam of light could solve this problem. An initial move in that direction occurred in 1854 when John Tyndall demonstrated to a gathering of the Royal Society how a bending stream of water could effectively trap light inside of it. He shined a beam of light through a glass wall of a water-filled tank and on through a tube fitted into the opposite wall of the tank. The light emerged as a white disk. But when Tyndall ope
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