— Assume the reliability of a connection is determined by the number of distinct risks associated with the path. We study the most reliable routing for WDM networks with arbitrary risk distribution in this paper. We first focus on the min-risk single path (MRSP) problem, in which a single most reliable path is to be established between a given source-destination pair. To solve MRSP, a simple label-setting (Simple-LS) algorithm is proposed by iteratively setting every node with a diminishing path-risk set (i.e. the label of a node). We then extend Simple-LS to find up to K lowest risk paths in each iteration, called K-path LS algorithm. Comparing to existing algorithms, we show that K-path LS can find paths with much fewer risks. We then define the original most reliable path pair (MRPP) problem. In MRPP, a pair of risk-disjoint paths must be established for each connection request. Unlike existing path pair routing problems, absolute priority is given to minimizing the risk number on...