Design of a wide upstream-bandwidth optical triplexer using three-waveguide interferometer

A novel planar lightwave circuit (PLC) triplexer is designed using a three-waveguide interferometer and Mach-Zehnder interferometers. We introduce a full-coupling scheme in the three-waveguide coupler for wide upstream-bandwidth characteristic. Transfer matrix forms for three-waveguide coupler and three-waveguide phase shifter are derived for numerical simulation. Simulation results show that the 1 dB- and 3 dB-bandwidth for the upstream channel are 115 nm and 200 nm, respectively. The proposed triplexer shows low insertion losses of less than 0.6 dB and low crosstalks of less than -28 dB for the two downstream bands, assuming that the waveguide width-error in the PLC fabrication is plusmn0.1 mum.