The Corning announcement gave impetus to the study of the semiconductor laser, which in turn accelerated research on optical fibers. An outstanding invention or development usually has an impact on technological progress. In 1966, C. K. Kao and G. A. Hockham published their report of a concept for a transmission medium. This was the first report of optical communications, in which they pointed out the possibility of information transmission by optical fibers. Telecommunications has developed through the repeated encountering of such problems and their subsequent resolution. The greatest leap in wire transmission technology, which holds the potential for telecommunications, is the development of the optical fiber and semiconductor laser. The use of optical fiber cable is conceivable, for instance, when cable ducts in urban areas are all filled and additional cable installation is needed. Replacement of conventional communication cables in the ducts with optical fiber cables would increase the information-transmitting capacity more than 10 times without installation of additional ducts.