Capacity design of fast path restorable optical networks

Service restorability is a key requirement in optical networks. This means that when wavelength paths are established. both a primary path and a secondary disjoint path have to be set-up, with the secondary path being used for service restoration upon primary path failure. The secondary path may possibly be shared for efficiency. The need for secondary paths imposed by the restorability requirement has to be explicitly taken into consideration in the capacity design of optical networks. However, to our knowledge, there does not exist any algorithm for network capacity design that explicitly accounts for fast restoration requirements. The contribution of this paper is the development of algorithms for optical network capacity determination with restoration being directly taken into account. The problem is formulated as a generalization of the maximum concurrent flow problem that includes restoration requirements for the two different restoration models which are commonly used in optical networks with fast restoration requirements. We then develop fully polynomial approximation schemes that solve the restorable network capacity design problem.