Photonic microwave filters with negative and complex coefficients

Abstract

Photonic microwave filter has been a topic of interest for over two decades because of the many advantageous features such as large time-bandwidth product, wide tunability, high Q-factor, low loss, light weight, and immunity to electromagnetic interference offered by photonics. Theoretical and experimental studies of photonic microwave filters are presented in this thesis. Three novel techniques to implement photonic microwave filters with negative coefficients and complex coefficients are proposed and experimentally demonstrated. In the first technique, the negative coefficients are generated based on cross-polarization-modulation (XPolM) in a semiconductor optical amplifier (SOA). In the second technique, negative coefficients are generated based on phase modulation and phase modulation to intensity modulation (PM-IM) conversion using linearly-chirped fiber Bragg gratings (LCNBGs) with positive and negative dispersions. In the third technique, a tunable photonic microwave filter with complex coefficients is implemented using a wideband tunable optical RF phase shifter. A technique to improve the dynamic range of a photonic microwave bandpass filter is also investigated.