ROADM technologies and ROADM-enabled Wavelength Division Multiplexing (WDM) systems have come a long way, and are on the verge of becoming commonplace in the networks of service providers around the world. ROADMs are here to stay as an integral part of WDM networks, since they reduce the costs of networks and open the opportunity for service providers to build a versatile, agile, easily-manageable optical transport layer.