A novel photonic microwave notch filter with negative coefficient based on cross polarization modulation in a highly nonlinear fiber

摘要

A novel photonic microwave notch filter with both negative and positive coefficients is proposed and demonstrated using a single optical source as a probe beam. Due to the change in birefringence induced by another modulated pump beam, both non-inverted and inverted signals are generated in a highly nonlinear fiber. These are separated by using a polarization beam splitter and recombined with optical time delay given to one of them. From the generation of both coefficients and the orthogonal property between them, no resonance peaks were observed at baseband and the optical coherence could be avoided independently of the source coherence length. The experimental results show a stable transfer response with the free spectral range of 65 MHz and 1.32 GHz when the optical path difference is given to 3.19 m and 0.19 m, respectively.