Microwave Photonic Filter with Two Highly-Selective and Independently- Tunable Passbands

We propose and demonstrate an approach to realizing a highly-selective and freely-tunable dual-passband microwave photonic filter (MPF) based on phase-to-intensity modulation conversion by stimulated Brillouin scattering (SBS). In the proposed scheme, two passbands are obtained via a two-tone SBS pump which is generated by passing the optical carrier through two cascaded dual-parallel Mach-Zehnder modulators (DPMZMs) working at carrier-suppressed single-sideband modulation mode and carrier-suppressed double-sideband modulation mode, respectively. The frequencies of the two-tone pump are independently varied by adjusting the two single-tone signal frequencies applied to the two DPMZMs. Hence, two freely tunable and stable passbands are obtained. A proof-of-concept experiment is carried out, where the two passbands of the MPF can be freely tuned in the frequency range of 0-9.644 GHz. The out-of-band rejection ratio and the 3-dB bandwidth of the passbands are measured to be larger than 25 dB and smaller than 55 MHz, respectively.