Optical filtering of RF signals through contrasting fiber dispersion slopes

The authors present a photonic filter that uses a difference in dispersion slopes in different fiber lengths to create a tunable notch filter. The use of differing dispersion slopes allows for a relative propagation delay in one output of a dual output Mach-Zehnder modulator.The performance of this filter has been simulated and shown to reduce co-site interference. Fibers or other optical waveguides with large dispersion slopes can be used to reduce the length of fiber necessary to achieve wide tuning ranges. Filters with wider pass bands and deeper nulls can be achieved by increasing the number of delay paths through the use of multiple optical splitters and combiners. Future work implementing photonic crystals or waveguides may be used in order to generate this filter structure over shorter physical path lengths, further reducing the size and weight of the system.