Word: fibers
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Dates: during 1970-1979
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...demonstrate a century of progress, the teen-age descendants of Bell and Watson who re-enacted the historic moment then placed a call that was transmitted between two modern telephones not by electrical current or radio waves but by a beam of light passing through a hair-thin glass fiber. Proclaimed
Morse Code. The idea of using light to convey information far predates the new fiber-optics technology demonstrated so dramatically by AT&T. Primitive man sent signals by building fires or waving torches; ships still use shuttered signal lamps to flash messages to each other. Proof that light could be sent along a curved "pipe"-like electricity flowing through a wire-was provided by British Physicist John Tyndall in 1870. He showed that light shining down on a tank of water could be carried by a stream pouring from a hole in the side of the tank to illuminate...
...optical wires a reality. One development was the invention in 1960 of the laser, a device capable of generating an intense narrow beam of light that, for all practical purposes, did not diverge. Miniaturized lasers make it possible to couple powerful light beams accurately with hair-fine glass fibers. Another was the perfection, by Corning Glass Works, of a fiber of glass so pure that it could transmit light long distances. The third accomplishment was the devising, by engineers at Bell Labs and elsewhere, of methods of integrating fiber optics into modern telephone systems...
...waves. In a typical optical arrangement (see diagram), sound waves entering a telephone microphone are converted into electrical signals. These signals pass through an encoder, which converts them into electrical pulses that switch a laser on and off, interrupting a light beam being sent into the end of a fiber. The light thus travels in a series of pulses, not unlike Morse code, that race along the glass "wire." At the end of their journey, these light pulses are picked up by a photodetector, which converts them back to electrical pulses. These, in turn, are fed into a decoder...
...Fibers have enormous advantages over wires. Because they do not "leak" light as copper wires "leak" electricity, fibers should eliminate the cross talk and static that can occur when one telephone wire spills some of its signal into a neighboring line. Measuring as little as one-thousandth of an inch in diameter, the fibers are also far less bulky than wires -an important consideration in cities, where underground cable conduits are already overcrowded. Eventually, the fibers may also prove cheaper. Supplies of copper are limited; silicon, the chief ingredient of glass fiber, is one of the most plentiful materials...