PHOTONICS IN FUTURE TELECOMMUNICATIONS

In future telecommunication systems, efforts will be made to exhaust the almost unlimited transmission capacity of optical fibers by applying optical-frequency-division-multiplex (OFDM) techniques. The switching elements of such networks must be able to process optical-frequency-multiplex signals as well as time-division-multiplex signals. The question arises as to what extent optical signal processing can be brought into use instead of present-day electronic signal processing in such switching elements. In the last twenty years, research in optical communications was essentially focussed on the transmission of signals through optical fibers. Meanwhile, many questions relating to optical transmission have been answered, and the emphasis of research is increasingly shifting towards optical signal processing. One of the main areas of research at the Heinrich-Hertz-lnstitut is optical switching technology. In the introduction, several experiments involving OFDM technologies are described which are intended to underline the significance of those technologies for future telecommunication networks. In the main section, various techniques and experiments for the optical switching of signals in the frequency, space, and time domain are described. In the closing section, we describe experiments dealing with optical signal regeneration.