Overview of optical switching technologies in Japan

Optical Switching Systems can be divided into three groups-space division, time division, and wavelength division. This article describes each in detail and gives the present status and projects the future of each M any studies on ISDN are being made in a number of countries in an attempt to provide enhanced services that integrate voicr, data, and video. In order to provide high-speed, broadband services, a new network, consisting of high-speed transmission lines and highspeed, broadband switching systems, must be constructed. Currently, cost-effective transmission systems are being developed, due to remarkable progress in optical fiber transmission technologies. The penetration of optical fiber into the subscriber loop network f copper wires is expected soon. High-speed, broadband switching systems require high-speed operation, in which electronic circuits have many problems, such as high power consumption and low isolation. Optical switching technology is a highly promising candidate for solving these problems. It may be said that switching systems, using optical switching technologies, will most likely provide the future highspeed, broadband services. In view of the non-inductiveness and broad bandwidth of optical devices, studies on optical switches have been conducted in Japan with stress placed upon mechanical switches. However, recent technological progress, based on the electro-optic effect, has accelerated the development of true optical switches, and the application of these devices to optical switching systems is now being considered. In this article, we classify optical switching systems into three categories. The present status and'the future of each optical switching, system and optical device technologies in Japan are then described. It describes only optical devices, without using electronic-optical and optical-electronic onverters. Therefore,'optoelectronic integrated circuits (OEIC's), which are believed a principal candidate for constructing optical switching systems in the near future, are not discussed.