All-Optical Time-Division Multiplexing Technology

Abstract

During the past two decades, great progress has been achieved in optical fibre communications technologies toward higher capacity and longer repeaterspan transmission, leading to very economical trunk transmission systems for public communications networks. In particular, newly evolved technologies including erbium-doped fibre amplifiers have made very-high-speed 10 Gbit/s optical transmission systems of practical use. However, because these transmission techniques still rely on electronics for processing the high-speed signals, it is anticipated that the operational speed and transmission bit rate will hit the upper limit in the near future. Moreover, to accommodate the coming broadband network (B-ISDN) era, very-high-speed technologies must be developed not only for transmission lines, but also transmission nodes. The goal is to handle signal rates of over ITbit/s, so that vast amounts of information, including data and pictures, can be provided to many subscribers through optical-fibre cables. To this end, novel all-optical signalprocessing technologies capable of superseding conventional electron-based technologies are urgently required.Figure 9.1 illustrates a future ultrafast optical time-division-multiplexing (OTDM) transmission system that fully utilises all-optical high-speed signal processing technology.