Dispersion Compensation of a 1xN Passive Optical Router with Low Loss, Flat Passband and Low Crosstalk

A 1xN interferometer based router with single-stage all-pass filters in the arms has low loss, flat passbands and low crosstalk; however, we show that the router has substantial cubic dispersion over the channel passband, which is identical from channel-to-channel. For a 1x4 router with a FSR of 100GHz the average dispersion slope over a 60% passband is -8 dot 10 sup 3 ps/nm sup 2 whereby a cascade of 4 routers will incur a significant system power penalty. A three-stage all-pass filter placed on the input arm reduces the dispersion of all channels by a factor of 16. The router is quite insensitive to variations in the all-pass filter design parameters.