National Geographic : 1979 Oct
4 The coded pulses of light can flash through the fiber at a rate of 44.7 bits, or pieces of information, per millionth of a second. The signals may come from several hundred conversations, a few of which are represented by the blue frames at upper left. At the other end, a decoder translates the pulses back into electrical signals, which are fed into the receiving telephones and heard as human voices. IOTOGRAPHERBRUCEDALE 525 Talking on alight beam IIGHTING THE WAY for communications in the future, fiber-optic technology makes it possible to transmit 10,000 simultaneous con versationsthrougha single pairof glass "wires." Since infraredlight vibrates thousands to mil lions of times faster than microwaves or radio waves, it can accommodate more information thaneither.In practice,the sound waves arecon verted to an electrical signal, which is encoded and transmittedas light pulses. Many conversationscan be stacked along the same fiber and unscrambled at the other end. This process, called time-division multiplexing, is comparable to merging cars on a freeway ac cess roadinto a line of moving carsalreadyon the freeway. The possibility of using opticalfibers in com munications was first proposed in 1966 by CharlesKao (below), a vice-president and chief scientist for InternationalTelephone and Tele graph."Opticalcommunicationsmakes a whole range of new services economical for the first time," he says. Eventually, low-cost light-wave communica tions may be used to: receive and print out a newspaper over a home telecopier,shop by tele vision in your home, have the bill automatically charged to your credit card and deducted from your bank account,and remotely climate-control your home.