Brillouin Microwave Filter With Enhanced Skirt Selectivity Using a Birefringent Fiber

A technique to enhance the slope of a photonic microwave filter based on the stimulated Brillouin scattering is proposed. It relies on exploiting the polarization dependence of Brillouin gain in birefringent fibers. The presence of two orthogonal Brillouin gains/loss in birefringent fibers results in two filter responses that can be subtracted in a balanced photodetector to remove the slow Lorentzian decay of the natural Brillouin gain response. The experimental results show that a filter slope of 8.3 dB/oct can be obtained.