A scalable approach for computing distance-bounded node-disjoint paths in optical networks

Both access and core optical networks require connectivity between a given set of pairs of nodes under path-length constraints. In the context of Long Reach Passive Optical Networks (LR-PON) there is a limit on the length of the fibre between a local-exchange (LE) site and its metro-core (MC) node, and in the transparent optical core network the length of fibre between each pair of MC nodes must be within a given threshold. A failure in the network could affect hundreds of thousands of customers. Therefore, it is often important ensuring multiple connectivity between a given set of pair of nodes through at least two node-disjoint paths while respecting the path-length constraints. Node-disjointness allows switching to an alternative path whenever a link or a node fails. Minimising the cost associated with the fibre while maximising the disjointness for a given network is a very challenging task. In this paper, we develop and present a general approach that is scalable for solving very large instances of this problem.