Investigation of phase-modulator-based all-optical bandpass microwave filter

Theoretical analysis and experimental implementation of an all-optical bandpass microwave filter are presented. Bandpass filtering is implemented using an electrooptic phase modulator combined with a dispersive device to eliminate the baseband resonance of a typical low-pass filter. In addition to bandpass operation, the proposed filter also provides an improved mainlobe-to-sidelobe ratio (MSR) and a reduced mainlobe bandwidth compared with those of the conventional microwave filters with windowing. A four-tap bandpass microwave filter with a 3-dB mainlobe bandwidth of 2.65 GHz and an MSR of 30 dB is demonstrated. The filter performances, including the reconfigurability, tunability, and the dynamic range, are also discussed.