Compact double-layer waveguide grating triplexer based on silicon-on-insulator

A double-layer grating design particularly suitable for triplexers is presented. It consists of two silicon-on-insulator planar waveguide gratings, where the upper grating is used to couple and split 1310 and 1490 nm signal, and transmits along the opposite direction. The coupling efficiency is about 88 and 84 . The crosstalk can reach up to 21 and 11 dB. However, the 1550 nm signal light almost passes through the upper layer and then is coupled by the lower grating. The coupling efficiency is about 79 . The design is validated by simulation, which shows excellent performance in terms of wavelength bandwidth, crosstalk, coupling efficiency as well as incident angle and so on.