Routing, wavelength assignment and spectrum allocation for reconfigurable optical mesh networks having a combination of fixed and flexible spectrum ROADM nodes

Next generation of optical networks will witness the advent of flexible spectrum/grid reconfigurable optical add drop multiplexers (ROADMs). The pass band of these next generation ROADMs can be varied depending on the spectral width of the incoming signal. With the pass band becoming a variable, spectrum allocation becomes an added constraint to the currently employed routing and wavelength assignment (RWA) algorithm and hence turns it into a routing, wavelength assignment and spectrum allocation (RWSA) problem. In reality, the future networks will be a mix of “Fixed Spectrum” and “Flexible Spectrum” ROADM nodes. Considering this fact, the paper presents a novel RWSA algorithm. The proposed algorithm is applied on NSFNET and two sample networks—11 nodes, 30 node and the results are presented.