WAVEGUIDE STAR COUPLER USING MULTIMODE INTERFERENCE

摘要

A radiation coupling device (10) incorporates a rectangular multimode beamsplitter waveguide (20) connected at one end to a set of input waveguides (18). The input waveguides (18) have inserted within them respective fibre optic waveguides (22). The input waveguides (18) are connected at periodic positions across the beamsplitter waveguide's transverse cross section. The beamsplitter waveguide (20) is also connected at its other end to retroreflecting mirror (24). Radiation propagating in fundamental mode in any one of the input waveguides (18) passes along the beamsplitter waveguide (20) and is retroreflected at the mirror (24). On return, it becomes divided between the input waveguides (18) by virtue of modal dispersion (multimode interference) in the beamsplitter waveguide (20). The device (10) therefore acts as a star coupler.