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This paper proposes two lightpath-level active rerouting algorithms, namely, the least resources rerouting algorithm and the load balanced rerouting algorithm, in all-optical WDM networks with alternate routing and traffic grooming. The proposed algorithms consist of three major components to be determined: i) when the rerouting algorithm initiates, ii) which lightpath is rerouted, and iii) which routing path and wavelength for the rerouted lightpath is newly allocated. The proposed active rerouting algorithms initiate the rerouting procedure when a connection leaves and a lightpath is released. The lightpath to be rerouted is selected according to the objectives of two different algorithms. The routing path and wavelength allocated to the rerouted lightpath is that the departure connection released. Simulation results show that the proposed load-balanced active rerouting algorithm yields much lower connection blocking probability than the least resources rerouting algorithms. We also observe that the number of rerouted lightpaths is very small. This result implies that the overhead for rerouting a lightpath is small and the performance of the networks can be significantly improved.