Microwave and optical systems

Summary form only given, as follows. Since its introduction in the early 50s, the use of microwave radio for long distance transmission has grown, so that today it carries more telephone, television, and data communications than coaxial systems. The need for channel capacity is growing exponentially with time, and it is obvious that millimeter-wavelength communications will soon become a necessity. In the early 605, millimeter systems were considered impractical because they required closely-spaced high-cost repeaters using vacuum/tube amplifiers and oscillators. The discovery of IMPATT and Gunn diodes in the mid-60s made low-cost repeaters possible, and stimulated the development of practical millimeterwave systems. Japan has been particularly active in this area, and such systems are now in use. Even larger channel capacity is possible at optical frequencies. The discovery of low-loss optical fibers and solid-state optical sources and detectors makes optical communication systems economically feasible. Although the performance of experimental optical systems are presently inferior to millimeter systems, the technology is still in its infancy and significant progress is to be expected. increased activity is taking place in applying microwave techniques in non-military, non-communication systems.