Novel ultracompact triplexer based on photonic crystal waveguides

Two stages of directional couplers based on photonic crystal waveguides Are cascaded to form an ultracompact triplexer. The directional couplers are decoupled at the wavelength of 1310 rum. The length of the coupling region in the first directional coupler is chosen to separate the other two wavelengths (i.e., 1490 and 1550 nm), and the coupling region is tapered to improve the extinction ratios. The second directional coupler separates the wavelengths of 1490 and 1310 run. For the channel of 1550 nm, an additional directional coupler is used to reduce the crosstalk from the channels of 1490 and 1310 nm. The total size of the present triplexer is only 50 mu m x 20 mu m, and the good performance is verified with finite-difference time-domain simulation.