by Academician Alexander PROKHOROV, Director of the Institute of General Physics of the USSR Academy of Sciences, Academician Secretary of the Department of General Physics and Astronomy of the USSR Academy of Sciences, Yevgeni DIANOV, Dr. Sc. (Phys. & Math.), now-Academician, Head of the Department of Fiber Optics at the same Institute The introduction of lasers* has triggered off numerous ideas on their application, one of the first being data transmission. Certain attempts had already been made to transmit data via the atmosphere with the aid of lasers; these experiments had been carried out during the 1960s all over the world, including the Soviet Union. The first optical communication link was established between Moscow State University on Lenin Hills and a building on Zubovskaya Square in Moscow which at that time was heralded as a miracle. Such links proved to be very inefficient and specialists discovered that the atmosphere was a highly unstable medium, far too unreliable for practical communications. Optical communications appeared to be faced by an insurmountable obstacle - the absence of a suitable transmission medium. Then the fiber light guides were recalled: thin glass fibers of special structure would, indeed, be suitable for this purpose, but those available at that time were very low-grade, with optical losses of about 1,000 dB/km. In other words, light was attenuated by a factor of two over a distance of but 1 m, while a system can operate efficiently only if such attenuation occurs over a distance of at least one kilometer. An impasse appeared to have been reached. The situation, however, quickly changed due to two circumstances. First of all, in 1966 the high optical losses in glass were shown to be determined by the production technology and not by fundamental effects. Improved technology reduces the losses to less than 20 dB/km, which is acceptable for practical use in data transmission systems. Secondly, in 1970 Academician Zhores A ... Read more