This paper discusses a fault tolerant technique called redundant path design in wavelength division multiplexing networks, in which backup paths between source and destination nodes, such that when primary paths between them fail the primary paths are quickly switched to the backup paths, are prepared. Unlike the previous centralized approaches, this paper proposes two multiagent-based methods called Method 1 and Method 2, which is an improvement of Method 1, and evaluates optimality and efficiency of the proposed methods by simulation experiments. The simulation results show that, compared with Method 1, Method 2 has higher optimality with reasonable time.