A new algorithm of route design against large-scale disasters

Due to the 2011 Great East Japan Earthquake, relay cables (physical routes) connecting telephone exchange offices (TEOs) were disconnected and communication between TEOs ceased. Routes compose a ring network using an optical add-drop multiplexer (OADM). Since large-scale earthquakes will likely occur in the future, we must design disaster-resistant routes, which are assumed to be short routes overlapping disaster areas. In addition to this resistance, route designer should also consider ease of accessing manholes, ease of pipelines maintenance, and cost. To do this, the route designer needs to select a route from a huge number of routes between TEOs that pass through a disaster area. Candidate routes, which are a set of routes satisfying the above conditions, all go through the upper, middle, and lower parts of a disaster area. The routes which go through the upper and lower parts of a disaster area become disaster- resistant routes, and the routes which go through the middle part become minimum-cost routes. The route designer needs to eliminate jumping routes, which bypass more than the length of the disaster which we focus on and similar routes, which pass through much of the same pipeline and are not the most disaster- resistant route. To calculate candidate routes, we proposed the algorithm that divides an area into smaller areas (meshes) and uses mesh combinations that are highly likely to contain disaster resistant routes. We report the effectiveness of our algorithm utilizing actual tsunami and liquefaction data.