Brillouin Rectangular Optical Filter with Improved Selectivity and Noise Performance

We demonstrate a high selectivity rectangular optical filter based on stimulated Brillouin scattering (SBS) effect in fiber with bandwidth from 1 to 3 GHz. By using pump-splitting dual-stage configuration, the filter selectivity has been improved by more than 16 dB and exceeded 40 dB within 2-GHz bandwidth. The filter shape is well controlled by using precise digital feedback compensation and nonlinearity management. We also analyze the noise performance of both the single-stage and dual-stage filters by evaluating the signal-to-noise ratio of the amplified signal using coherent detection. The results show that the dual-stage approach performs better than the single-stage architecture in achieving higher selectivity and improving noise performance. The inherent tuning flexibility with improved performance makes the proposed SBS filter one of the best candidates for microwave photonic applications.