Optimizing ROADM configuration in WDM networks

Wavelength Switched Optical Networks (WSONs) have been designed to take advantage of all optical switching fabrics with a high level of automation and efficiency. Therein, the Wavelength Selective Switches (WSS) represent the core switching elements with a technology enabling multi-degree Reconfigurable Optical Add/Drop Multiplexers (ROADM) architectures with colorless, directionless and contentionless (CDC) switching. With the use of CDC ROADMs, WSON nodes are asymmetrical with respect to their switching capabilities. Firstly, the selection of the restricted switching capabilities plays a critical role in order to maximize, e.g., the grade of service subject to a given number of ports. Secondly, the asymmetry depends on the port size of WSS. In this paper, we propose an optimization model in order to establish the best ROADM switching connectivity to maximize the grade of service, for a given number of ports. We show that the grade of service can vary significantly, up to 30%, depending on the switching connectivity.