Reconfigurable Microwave Photonic Filter Based on Dual-polarization Dual-parallel Mach-Zehnder Modulator and Phase-shifted Fiber Bragg Grating with Small Birefringence

A reconfigurable microwave photonic filter is proposed and experimentally demonstrated. The filter is based on a dual-polarization dual-parallel Mach-Zehnder modulator (DPol-DPMZM) and a phase-shifted fiber Bragg grating (PS-FBG) with small birefringence. The DPMZM is properly biased to serve as a carrier suppression single-sideband modulator or an equivalent phase modulator, a notch or a bandpasss frequency response is obtained after the PS-FBG. The central frequency of the filter can be tuned by adjusting the wavelength of the tunable laser. If only X-DPMZM is loaded, while the Y-DPMZM is unloaded, and the polarization state of the CS-SSB modulated signals is set to be 45° relative to one axis (fast) of the PS-FBG to equally enter fast and slow axes, and the axis (fast) of the PS-FBG has 135° relative to one principal axis of the polarization beam splitter (PBS) to subtract the signals in two axes of the PS-FBG at one output port, a bandpass filter with performance improvement can be obtained.