Evolution of WDM optical networks

Implementation of wavelength division multiplexing (WDM) in optical networks increased the fiber bandwidth utilization and emerged from the use in point-to-point applications to its current position as the next optical networking technology. There are, as well, other competing network approaches, such as optical time division multiplexing (OTDM) and code division multiplexing (CDM), both suffering from severe limitations and still immature technology. This paper reviews some major technological developments in architectures, devices and systems involved in WDM optical network evolution and discusses issues dealing with optimal exploitation of fiber bandwidth for information transmission and processing.