A multiport frequency band selector with inherently low loss, flat passbands, and low crosstalk

Conventional waveguide grating routers trade loss for passband flatness and use many grating arms to reduce crosstalk. A frequency band selector with low loss, flat passbands, and low crosstalk is analyzed using multibranch interferometers having a small number of arms. An optical all-pass filter is added to each arm to flatten the phase response around each passband. The bandwidth over which the crosstalk loss is less than 30 dB is improved by an order of magnitude over conventional architectures. Simulations show that the design is quite insensitive to loss and variations in the all-pass filter design parameters.