Compared with traditional WDM network, OFDMbased flexible optical networks are able to provide better spectral efficiency due to its flexible allocation of requests on fine granularity subcarriers. Survivability is a crucial issue in OFDMbased flexible optical networks. In this paper, we present a new survivable multipath provisioning scheme that provides flexible protection levels in OFDM-based flexible optical networks. We define the static Survivable Multipath Routing and Spectrum Allocation

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... (SM-RSA) problem which aims to accommodate a given set of demands with minimum utilized spectrum. We show that the static SM-RSA problem is NP-hard and provide an ILP formulation for it. Also, an efficient heuristic algorithm is given to solve the problem. Our simulation results show that the proposed multipath provisioning scheme achieves higher spectral efficiency than the traditional single-path provisioning scheme.