Dynamic Dispersion-Compensation for Wideband Microwave Photonic Notch Filter With High Rejection and High-Resolution

Interference-based microwave photonic notch filters (MPNFs) provide large rejection through destructive interference of radio frequency signals generated by beating a carrier with the upper and lower modulation sidebands. The two modulation sidebands are designed to have an amplitude imbalance and phase shift of $\pi$ between them. In many schemes, large rejection is achieved at the desired radio frequency by balancing the amplitudes of the modulation sidebands using stimulated Brillouin scattering (SBS) based gain or loss. However, the combined dispersion of the Brillouin active medium and other components detunes the phase difference between the sidebands away from pi, which causes a reduction in the notch depth. Dynamic dispersion control is, therefore, desirable for compensating dispersion-induced notch depth reduction. Here, we report dispersion-compensation exploiting bias-dependent phase of the modulation sidebands of a z-cut intensity modulator. We demonstrate a high-resolution (similar to 50 MHz) MPNF with a large rejection of >65 dB over 1-25 GHz. To demonstrate the applicability of our MPNF in the presence of radio frequency interference, we suppress an interferer by 49 dB without affecting the signal. Such dispersion-compensated MPNFs are of importance in the sphere of Industry 4.0 based applications such as frequency measurement.