All-optical microwave filters based on optical phase modulation

Abstract

In this thesis three different microwave filter architectures based on optical phase modulation are proposed and demonstrated. The first photonic microwave filter consists of an electro-optic phase modulator (EOPM), a length of high birefringence (Hi-Bi) fiber, a 25-km single-mode fiber and a narrow linewidth laser source. In the second and the third photonic microwave filters, we focus on the technique to obtain bipolar coefficients based on phase modulation to intensity modulation (PM-IM) conversion. In the second filter, chirped fiber Bragg gratings (CFBGs) are used as PM-IM conversion devices. In the third filter, the negative coefficients are obtained by locating the optical carriers at the opposite slopes of the transfer function of an optical filter, to convert the phase-modulated signals to intensity-modulated signals, with phase inversion of the RF modulating signals. Based on this scheme, a two-tap microwave bandpass filter with one negative coefficient is demonstrated. (Abstract shortened by UMI.)