Design of an InGaAlAs/InP ‘3mi’ wavelength division demultiplexer employing a novel mode transformer

A wavelength demultiplexer based on a three moded optical waveguide is discussed. A novel solution is proposed to tackle the problem of obtaining the optimum mixture of fundamental and second order modes within the guide. The design is shown to be 40% more dispersive than two-mode interferometer devices, and the channel spacing is relatively insensitive to fabrication errors.