Dispersion compensation of a 1 x N passive optical router with low loss, flat passband and low crosstalk

Abstract: 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 -8·103 ps/nm2 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.