Summary form only given. Shared protection aims to provide the same level of protection, against a single link failure, as the dedicated one while using less network resources. In this paper, we present the issue of survivability in a time slotted optical networks deploying DWDM. To guarantee the recovery and to maintain the performance of the service, sufficient resource needs to be available at the setup time of the protection. However it is possible to optimize the protection capacity. Indeed the primary traffic is composed of a set of flows, which may be going through different paths. Therefore a protection could be found using just enough resources by sharing the backup among many flows. We propose here a technique to identify and provision the protection using the minimum necessary resources. In particular, we present an algorithm that computes the optimal protection required for a primary traffic from a source to a destination, and the maximum capacity that could be used, on each link, for the protection. We prove through simulation results that this shared mesh protection scheme can significantly reduce the required network protection capacity.