The huge bandwidth of optical fiber was recognized back in the 1970s during the early development of fiber optic technology. For the last two decades, the capacity of experimental and deployed systems has been increasing at a rate of 100-fold each decade-a rate exceeding the increase of integrated circuit speeds. Today, optical communication in the public communication networks has developed from the status of a curiosity into being the dominant technology. Various great challenges arising from the deployment of the wavelength division multiplexing (WDM) have attracted a lot of efforts from...