Blocking triggered multi-path routing with spectrum retuning in elastic optical networks

Spectrum fragmentation has a substantial impact on spectrum utilization, which lowers blocking performance in elastic optical networks (EONs). In this paper, we investigate the spectrum status when a connection request cannot be served via single-path routing and propose a spectrum retuning approach with multi-path routing to address spectrum fragmentation, thus mitigating blocking concerns in EONs. We divide the approach into five stages: Single path routing, Spectrum block selection, Process Mapping, Connection retuning, and Connection splitting. Initially, the connection request is attempted to be served using the k-shortest routing paths in the best possible way. If, the request cannot be served through this process, this approach will first choose the “largest spectrum block” along the shortest path and then employ the “Process Mapping” operation to that block. This process will be repeated for other shortest paths until the required number of frequency slots is obtained (when there are multiple largest spectrum blocks on the shortest path and the “Process Mapping” function returns zero, the system will then analyze the next largest spectrum block in the array for the “Process Mapping” operation). Once the desired number of frequency slots is achieved through “Process Mapping”, the movable connections will be relocated to new spectrum locations, subsequently leading to the division of connection requests along the respective paths. Conversely, if the requested number of frequency slots is not achieved, the request will be declined, and all temporarily reserved spectrum allocations will be released. The simulation results demonstrate that the proposed approach significantly reduces the number of generated spectrum fragments, simultaneously enhancing blocking performance.