Scalability analysis of WSS-based ROADMs

Reconfigurable Optical Add/Drop Multiplexers (ROADMs) are becoming the industry standard for optical transparent switching in long-haul networks. ROADMs introduce new flexibility features towards full dynamic networks. In this paper, we investigate the scalability limits of the ROADM. We introduce a method to compute the number of ROADM internal subsystems (namely the wavelength selective switches) for a given traffic request. We evaluate the working and the blocking states of the ROADM with relation to its features of colorless, directionless and contentionless. We propose a method to compute the node requirements for a given set of network parameters.