In future telecommunication systems, efforts will be made to exhaust the almost unlimited transmission capacity of optical fibers by applying optical frequency-division-multiplexing (OFDM) techniques. The switching elements of such networks must be able to process OFDM signals as well as time-division-multiplexing (TDM) signals. The extent to which optical signal processing can be brought into use instead of present-day electronic signal processing in such switching elements is examined. Several experiments involving OFDM technologies are described which are intended to underline the significance of those technologies for future telecommunication networks. Various techniques for and experiments on the optical switching of signals in the frequency, space, and time domain are described. Experiments dealing with optical signal regeneration are described.>

At present there are worldwide efforts directed towards a services-integrated broad-band network. The first section of this paper describes different solutions of broad-band network components such as subscriber premises networks, local loops, subscriber exchanges, and trunk networks. The design of these components was taken from various proposals and broad-band communication field trials carried out in several countries up to 1984. In the second section, we consider the possibilities and implications of integrated optical components and of optical coherent communication techniques for broad-band networks in the far future.