Polarisation-independent bidirectional triplexer using grating-assisted multimode interference coupler in silica-on-silicon platform

A bidirectional triplexer based on a Bragg grating assisted multimode interference (MMI) coupler has been designed and fabricated. The MMI coupler can multiplex/demultiplex the 1310 nm wavelength (i.e. upload data) and the 1490 nm wavelength (i.e. download data). Moreover, the grating written in the waveguide of the MMI can reflect the 1550 nm wavelength (i.e. download video signals) to the other download port. Using a polarised UV ArF excimer laser irradiation, intrinsic waveguide birefringence can be compensated. Therefore, the fabricated device is polarasation insensitive. The working bandwidths of the final triplexer for 1310, 1490, and 1550 nm are about 110, 50, and 15 nm, respectively.