Routing problem for reducing significant outages in optical networks and its system analysis

Optical communication networks are operated with great care to avoid outages. In particular, significant outages having a devastating impact on society must be avoided, and several countries specify “significance standards” for network outages. Although the impact of possible outages strongly depends on routing methods for requested connections, there has been no research specifically on these standards. This paper for the first time, to the best of our knowledge, introduces a routing problem to minimize the impact of outages on a given significance standard. We have shown this problem to be non-deterministic polynomial-time hardness, and an efficient heuristic method is proposed. This method searches for a good solution by reducing the problem to a shortest-path search, where the significance of a link failure is regarded as the link weight, and suppresses outage impact compared with other routing methods. In addition, the analysis of the system dependence among a network model, mean time to repair (MTTR) of failure elements, and significance standards suggests that the total system design considering the MTTR, significance standards, and routing method could dramatically reduce the impact of significant outages on optical networks.