Efficient Microwave Photonic Bandpass Filter With Large Out-of-Band Rejection, High-Resolution and Low Loss up to 40 GHz

Stimulated Brillouin scattering (SBS) based microwave photonic bandpass filters (MPBFs) provide wideband tunability, high-resolution, and bandwidth reconfigurability, which are critical for radio frequency systems. However, it is difficult to optimize all these performance parameters while maintaining low negative RF link gain and large out-of-band rejection over a wide frequency range. Here we present a novel MPBF design that harnesses the polarization dependence of the SBS gain and RF interference between the orthogonally polarized components of a probe, which consists of a carrier and single modulation sideband. We demonstrate an efficient MPBF with large out-of-band rejection (> 50 dB) up to 40 GHz using a SBS gain of only \sim 22 dB. Over the tuning range of 4.5 GHz to 40 GHz, we keep the RF link gain to > −10 dB while achieving a RF link gain of 0.147 dB at 10 GHz. The MPBF exhibits narrow 3 dB and 40 dB bandwidths of 14 \pm 1.5 MHz and 444 \pm 60 MHz, respectively, up to 40 GHz. Using the MPBF, we demonstrate signal recovery by suppressing a strong interferer, placed 250 MHz away from the signal, by 48 dB while observing an increase in the signal power due to SBS gain. By tailoring the Brillouin pump profile, we reconfigure the 3 dB bandwidth of the MPBF from 14 MHz to 59 MHz while achieving a maximum RF link gain of 5 dB and a shape factor of \sim 1.9.