Tunable Microwave Photonic Notch Filter and Bandpass Filter Based on High-Birefringence Fiber-Bragg-Grating-Based Fabry–Pérot Cavity

We propose and successfully demonstrate a microwave photonic filter based on phase modulation (PM) and a fiber-Bragg-grating-based Fabry-Pérot (FBG-FP) cavity etched in a high-birefringence fiber. It can switch between continuously tunable single notch filter and bandpass filter operation. The principle of the tunable notch filter is based on the reflection response of the FBG-FP to break the phase balance of PM sidebands and achieve effective phase modulation to amplitude modulation conversion, while the principle of the bandpass filter is based on the transmission response of the FBG-FP to break the amplitude balance of the PM sidebands. Both filters have narrow bandwidth and high side-mode suppression ratio.