Design of a Polarization Insensitive Triplexer Using Directional Couplers Based on Submicron Silicon Rib Waveguides

An ultracompact triplexer which could be used for both polarizations is designed by utilizing directional couplers based on submicron silicon rib waveguides. First, the polarization insensitive directional couplers are realized by carefully choosing cross-sectional geometry of the waveguide. The length of the coupling region in the first directional coupler is chosen to separate the three wavelengths (i.e., 1490 nm to one port, 1310 and 1550 nm to the other port). The second directional coupler separates the wavelengths of 1310 and 1550 nm. For the channel of 1490 nm, an additional directional coupler is used to reduce the crosstalk from the 1310 and 1550 nm channels. The total length of the present triplexer is only 400 $mu{rm m}$, and simulation with three-dimensional Beam Propagation Method shows good performances for both polarizations.