An adaptive gain equalization filter is presented. The filter is based on t
he resonant coupler principle, a cascade of power couplers and delay lines.
Reconfigurability and tuning is achieved by varying coupling strength and
delay line length via the thermo optic effect. A device consisting of seven
delay line stages was realized in high-index-contrast silicon-oxynitride t
echnology. This device flattens the ASE spectrum of an EDFA to a ripple of
less than 0.5 dB over 35 nm. The on-chip losses are 2 dB.