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Show Light Beams Newest Method To Transmit Communication The world's first communication system using beams of light to transmit sounds will be evaluated this year and could benefit Utah telephone customers, according to Mountain Bell engineer George Hatch. The system is being developed by Bell Laboratories for AT&T. During the avaluation, a cable of hair-thin glass fibers, known as lightguides, will run under the streets of Chicago carrying voices, data and video signals on pulses of light. If successful, these cables will replace expensive copper wire which is now in common usage. Testing will begin by mid-year. "If the system proves economic and reliable, it may be used in areas .which have heavy communication needs and where there is a great demand for space under the streets," Hatch said. The hair-thin size of the fiber lightguides makes possible cables that are much smaller and lighter than copper cables, and that could make better use of available underground passageways. The basic material of the lightguides is silica, the most common form of which is sand one of the earth's most abundant materials. Because of the abundance of this raw material, lightguide cables may, in the future, cost less to manufacture than copper cables of equivalent capacity. Installation of the lightwave system is expected to begin shortly. A sinele half-inch diameter cable, 'containing 24 lightguides, will be installed under the streets of Chicago, connecting a modern office building with Bell offices in Chicago, a distance of approximately 1V4 miles. "The installation will help the Bell system further evaluate the potential of this new technology under actual operating conditions another step toward assuring that such systems will be economical and reliable," Hatch sasid. In the Chicago system, a single pair of lightguides in the cable will be able to carry 576 simultaneous conversations or an equivalent mix of voice and various types of data signals. "Amplifiers" such as those used on copper cables will not be needed to boost signals along the route. The planned system evaluation should be completed next year. Ultimately, lightwave communications systems may be used throughout the nation's telecommunications network for both local and long distance communications to provide a full range of Bell System services. |