Solar-outage-based SRLG and protection in optical satellite networks

Optical satellite networks (OSNs) are advancing at an impressive pace, but ensuring their reliability remains a significant challenge. Unlike terrestrial optical networks, many of the problems faced in optical satellite networks are unique. For example, in the case of a solar outage, some laser links will not be able to communicate. These events occur frequently and can vary on a minute-by-minute scale. Traditional 1+1 dedicated protection can effectively protect against single-link failures. However, sun outages simultaneously affect multiple links near the day–night terminator, which may cause protection failure. For regional failures under 1+1 protection, constructing shared risk link groups (SRLGs) is commonly used to avoid such failures. Unlike terrestrial networks, though, the failure regions in satellite networks are constantly shifting from the network’s perspective, which poses new challenges for survivability design. In this paper, we propose a shared risk link group (SRLG) model based on solar outage to define the joint risk caused by the sun outage region. Accordingly, we further propose an SRLG-constrained dedicated path protection (SRLG-DP) algorithm. SRLG-DP defines a protection window to avoid excessive detours and identifies SRLG-disjoint paths within the network. Simulation results demonstrate that SRLG-DP maintains high transmission success rates even under reduced prediction accuracy, along with relatively low path delay and delay jitter.