Optical birefringent 90° hybrid for coherent receiver in free-space optical communication system

摘要

The design of an optical birefringent 90° hybrid for coherent receiver in free-space optical communication system is presented. The bulk optical design of 2×4 90° hybrid is a six-port device with two inputs and four outputs. For the balanced receiver configuration two pairs of 180° phase shifted outputs are obtained and one pair has a phase shift of 90°with respect to the other. The optical birefringent 90° hybrid includes two pairs of birefringent plates, an analyser plate and a λ/8 wave plate. The scheme of phase compensation is also presented.