Subband All Pass Filter Architectures With Applications To Dispersion And Dispersion Slope Compensation And Continuously Variable Delay Lines

A new filter architecture is proposed which employs optical half-band and allpass filters but circumvents the typical tradeoff between passband width and peak delay inherent to allpass filters. A filter design for a dispersion compensator with a tuning range of +/-1000 ps/nm and 95 GHz passband width on a 100 GHz grid is presented. Compared to a cascade architecture, a lower core-to-cladding index contrast for planar waveguide ring resonator implementations can be used and lower filter losses are achieved since the signal propagates through fewer allpass filter stages for the same dispersion. A continuously variable delay line is designed with over 90% bandwidth utilization. For a 10-stage allpass filter with 25 GHz free spectral range (FSR) in a double-pass configuration, a 1000 ps tuning range can be achieved. Finally, a dispersion slope compensator design is presented with a change in dispersion of 700 ps/nm over a wavelength range determined by the filter free spectral range to channel spacing ratio.