In Japan, fiber-optic transmission systems were in the experimental stages in the early 1970's. By the end of the decade, the technology had entered the era of practical use in various fields. Today, there is a dramatic increase in the number of optical fiber transmission systems installed in Japan each year. From 1977 through 1982, each year has witnessed the installation of more than 50 new systems. By late 1982, more than 500 systems were in use across the country. At the present stage of development, the major users of optical fiber transmission systems are: the electric power industry with 116 systems; the steel making industry with 70 systems; railroads and highways with 56 systems; building management and office automation systems with 27 systems; the public sector including CATV with 24 systems. Following an overview of the current status of optical fiber transmission systems in Japan, future developments and possible new applications will be discussed.