Wavelength division
multiplexing (WDM) has enabled telecommunication service providers to fully
exploit the transmission capacity of optical fibers. State of the art systems in long-haul networks now have aggregated capacities of terabits per second. Moreover, by providing multiple independent multi-
gigabit channels, WDM technologies offer service providers with a straight forward way to build networks and expand networks to support multiple clients with different requirements. In order to reduce costs, enhance network flexibility, reduce spares, and provide re-configurability many service providers have migrated away from fixed
wavelength transmitters, receivers, and transceivers, to
wavelength tunable transmitters, receivers, and transceivers as well as
wavelength dependent add-drop
multiplexer, space switches etc. However, to meet the competing demands for
improved performance, increased integration, reduced
footprint, reduced
power consumption, increased flexibility, re-configurability, and lower cost it is desirable to
exploit / adopt monolithic optical circuit technologies,
hybrid optoelectronic integration, and
microelectromechanical systems (MEMS).