50 ms optical-layer failure recovery via fast-switching wavelength-selective switches and segment-based shared protection

Indeed, network protection is a well-established topic. However, achieving 50 ms failure recovery in the optical layer using shared protection capacity has long been an aspiration in the telecommunications community. This objective has remained elusive due to the limited reconfiguration speed of wavelength-selective switches (WSSs). Recent advancements in WSS technology, however, which enable fast switching on the order of 10–20 ms, have renewed optimism regarding the feasibility of achieving this aspiration. To make this vision a reality, we consider a segment-based protection scheme—termed shared backup segment protection (SBSP)—that leverages fast-switching WSSs. To efficiently allocate protection resources under the proposed SBSP framework, we first formulate an integer linear programming (ILP) model that jointly minimizes both the required spare capacity and the maximum failure recovery time. Additionally, we design a heuristic algorithm, virtual graph-based SBSP (VG-SBSP), to support time-constrained resource allocation for protected services. Simulation results demonstrate that VG-SBSP significantly outperforms traditional approaches by requiring fewer protection resources while satisfying stringent recovery time constraints. In the small-scale network, VG-SBSP achieves near-optimal results closely matching those of the ILP model. In large-scale topologies, VG-SBSP successfully accommodates the highest number of services while maintaining low spare capacity redundancy. Furthermore, we analyze the impact of WSS switching speed on the resource allocation and service establishment performance of SBSP.