Mitigation of Dispersion Induced Impairments in Brillouin-Based Microwave Photonic Bandpass Filter

Interference based microwave photonic bandpass filters (MPBF) form an important component of modern RF signal processing. Presence of multiple optical components in an RF photonic system e.g. fiber amplifiers, waveguides, cause a degradation in the MPBF profile and the out-of-band rejection due to the dispersion induced phase shift. Here, we compare the performance, using simulations and experiments, of two interference based MPBF configurations: (i) double-sideband phase modulation (DSB-PM) and (ii) double-sideband intensity modulation (DSB-IM), which exploit stimulated Brillouin scattering (SBS) for sideband processing, under different dispersion conditions. While the profile and out-of-band rejection for the DSB-PM based MPBF degrade drastically under the effect of dispersion, DSB-IM based MPBF achieves an out-of-band rejection of >40 dB and maintain the 3 dB and 20 dB bandwidths of 16.7 \pm 0.4 MHz and 104.5 \pm 5.4 MHz, respectively, under different dispersion conditions. The DSB-IM based MPBF exploits the bias dependent phase of the modulation sidebands of a z-cut intensity modulator to mitigate the dispersion induced impairment. The use of an intensity modulator for dispersion compensation makes our approach dynamic and compatible with integrated microwave photonic systems.