Nonlinear intermodulation distortion suppression in digital photonic link using polarization modulator

A novel approach to implementing high-linearity microwave photonic link based on in-phase/quadrature (I/Q)-demodulation is proposed and experimentally demonstrated. The simultaneous optical in-phase and quadrature signals are implemented using a single polarization modulator (PolM) in conjunction with two polarization beam splitters (PBS). Thanks to the phase-modulation to intensity-modulation conversion, the fluctuation of the phase noise of the laser have no impact on the coherent I/Q signals. In addition, the other major improvement is that only one polarization modulator is used here, which can realize easier distribution of RF signals over long distances. The linearization leads to suppression of the third order intermodulation (IMD3) by more than 40-dB for both back-to-back and after 10 km of fiber transmission, respectively, compared to the quadrature signal.