Fragmentation-aware routing and spectrum allocation algorithm in mixed-grid optical networks

The flex-grid technology is recognized as a promising solution to improve flexibility and scalability in optical networks. A gradual migrating process from the conventional fixed-grid to flex-grid networks is considered as a practical upgrading strategy, during which period the mixed-grid networks will emerge having both kinds of fixed/flex-grid nodes coexisting. Owing to different spectrum allocation constraints, conventional algorithms on fragmentation problem amelioration suited for pure flex-grid networks may not be feasible. In this work, a new fragmentation metric is proposed to ameliorate the fragmentation effects in mixed-grid networks and applied in a fragmentation-aware routing and spectrum allocation algorithm for spectrum efficiency improvement. Simulation on a representative network shows the bandwidth blocking ratio is reduced compared to the first fit policy in specific network scenarios.