Photonic microwave bandpass filter based on optical single-sideband polarization modulation for long-reach radio over fiber applications

A two-tap dispersion-insensitive photonic microwave bandpass filter based on optical single-sideband (SSB) polarization modulation is proposed for long-reach radio over fiber applications. The optical SSB polarization modulation, which generates two complementary intensity-modulated signals along two orthogonal polarization directions, is implemented by a polarization modulator (PolM) followed by an optical filter. With a polarization maintaining fiber (PMF) to introduce a time delay, a two-tap dispersion-insensitive photonic microwave bandpass filter is obtained. The proposed filter is used to shape a Gaussian pulse to an ultra-wideband (UWB) signal. After 40-km fiber transmission, no distortion in the waveform of the UWB signal is observed.