Design of an optical Butler matrix for beamforming in satellite communications

In this paper, we present the design of an optical Butler matrix architecture for beamforming in satellite communications. The architecture exploits the use of hybrid couplers and phase shifters inside symmetric 4x4 and 8x8 matrices operating at 1.55 mu m. The Silicon on Insulator (SOI) technology has been considered for the realization of the building blocks of the matrix, through simulations based on Beam Propagation Method. We validate the potential of the optical Butler matrix for multibeam operation and demonstrate the optimum performance of the matrices which show that the output powers reach 95% in the case of the 4x4 Butler matrix and 70% in the case of the 8x8 Butler matrix, being the performance degradation mainly due to the waveguide crossings. The obtained results are very significant considering the promising small size and mass saving of the optical component, indispensable for satellite applications.