Switchable microwave photonic filter between high Q bandpass filter and notch filter with flat passband based on phase modulation.

We propose and demonstrate a novel switchable microwave photonic filter based on phase modulation. Both a microwave high Q bandpass filter and a microwave notch filter with flat passband are achieved respectively. And the switchability between them by tuning the two tunable optical bandpass filters is demonstrated. We also present a theoretical model and analytical expression for the proposed scheme. A frequency response of a high Q bandpass filter with a Q factor of 327 and a rejection ratio of exceeding 42 dB, and a frequency response of a notch filter with flat passband with a rejection ratio exceeding 34 dB are experimentally obtained. The operation frequency of microwave photonic filter is around 20 GHz.