Abstract

A $1\times N$ interferometer–based router with single-stage all-pass filters in the arms has low loss, a flat passband, and low cross talk. However, we show that the router has substantial cubic dispersion over the channel passband, which is identical from channel to channel. For a $1\times 4$ router with a free spectral range of 100 GHz, the average dispersion slope over a 60% passband is $-8\times {10}^3 \mathrm{ps}/{\mathrm{nm}}^2$, and thus a cascade of four routers incurs 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.

© 2002 Optical Society of America

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