Spectrum utilization maximization in coarse granular optical routing networks that employ fine granular shared protection

To offset the impairment caused by imperfect optical filtering at ROADMs/OXCs, guard bands must be inserted between optical channels. The resulting degradation in frequency utilization detracts from the benefit of next-generation elastic optical path networks. To overcome this problem and achieve an ICT infrastructure with the required level of resiliency, we add path-granularity-level shared protection to our coarse granular optical routing networks with fine granular add/drop. Optical paths are densely packed in coarse granular optical pipes, but the filtering impairment generated by the routing process is greatly mitigated, which results in enhanced fiber frequency utilization. The impairment caused by path dropping is carefully minimized for all possible backup paths, which is made possible by our newly developed network design algorithm. Numerical experiments show that the number of fibers in a network is substantially reduced over conventional shared protected networks.