An Defragmentation Scheme for Extending the Maximal Unoccupied Spectrum Block in Elastic Optical Networks

In Elastic Optical Networks (EONs), dynamic allocation and release of lightpaths will lead to frequency spectrum fragment issue which making the optical spectrum into non-aligned, isolated and small-sized spectrum segments. Defragmentation strategies are key issues to minimize this problem. In this paper, we investigate the states of spectrum when the bandwidth blocking probability (BBP) is high, and propose a modified defragmentation scheme to alleviate spectrum fragmentation in dynamic network environments by extending the maximal unoccupied spectrum blocks. Theoretical analysis and numerical simulations show that the proposed scheme can effectively reduce the degree of fragmentation of the network and extend the maximal unoccupied spectrum blocks.