Compared with traditional WDM network, OFDM-based flexible optical networks are able to provide better spectral efficiency due to its flexible allocation of requests on fine granularity subcarrirers. Survivability is a crucial issue in OFDM-based flexible optical networks. In [19], Ruan and Xiao propose a new survivable multipath provisioning scheme (MPP) that provides flexible protection levels in OFDM-based flexible optical networks. They also studies the static Survivable Multipath Routing and Spectrum Allocation (SM-RSA) problem which aims to accommodate a given set of demands with minimum utilized spectrum. It is shown that the MPP scheme achieves higher spectral efficiency than the traditional single-path provisioning (SPP) scheme. In this thesis, we study the dynamic SM-RSA problem, which allocates multiple routes and spectrum for a given demand as it arrives at the network. We develop an ILP model for the problem as well as a heuristic algorithm. We conduct simulations to study the advantage of MPP over SPP for dynamic traffic scenario in terms of blocking performance and fairness. We also compare the performance of the MPP heuristic algorithm and the ILP model.