Abstract:Domain decomposition method (DDM) based on the Schwarz alternating method is divergent when it is used to analyze waveguide problems. In the paper, an absorbing fictitious boundary condition (FBC) is presented to generate an iterative DDM for waveguide problems. The FBC which connects the subdomains on fictitious boundaries is developed according to the actual field distribution in the waveguide to ensure the propagation of waves between adjacent subdomains. And the relaxation algorithm is introduced to improve the speed of iterative subdomains. And the relaxation algorithm is introduced to improve the speed of iterative convergence. Finally, a number of numerical examples are given to demonstrate its efficiency.