Optical multiplexing in fiber networks: progress in WDM and OTDM

WDM systems are maturing and are in use in real point-to-point applications. The technology has also become of interest in the development of all-optical networks, and in this context the performance of WDM can be more critical. In some networks, multiple-access demands that a large number of channels be deployed over long distances, and in these cases the performance of WDM may be degraded by crosstalk arising from fiber nonlinearity. Other problems arise from non-ideal components such as optical amplifiers, switches, and multiplexers/demultiplexers, Much activity in WDM has been understanding its limitations and improving component performance, Some of the limitations imposed may be overcome by the use of OTDM, and research in this area continues to be of interest and importance. However, OTDM is less mature, and much activity is concerned with the realization of robust subsystems such as sources and demultiplexers. It is likely that in the longer term networks will employ a combination of WDM and OTDM.