Photonic RF Phase Shifter Based on a Vector-Sum Technique Using Stimulated Brillouin Scattering in Dispersion Shifted Fiber

A photonic RF phase shifter is proposed and demonstrated based on a vector-sum technique using stimulated Brillouin scattering (SBS) in dispersion shifted fiber (DSF). Two optical sidebands are generated and introduced to the Brillouin processing module when an RF signal is modulated on a continuous-wave carrier by an electrooptic phase modulator. SBS amplification/depletion, as well as nonlinear SBS phase, is induced to the selective optical sideband due to the interaction between the optical sidebands and the pump wave in the DSF, thus resulting in the phase-to-intensity modulation conversion. The Brillouin erbium-doped fiber laser is implemented to generate the pump wave to fix the frequency difference between pump wave and optical sideband, which can make the phase shifter broadband. By a vector-sum technique, the phase-shifted RF signal is obtained after heterodyne mixing at the photodetector and the magnitude of the phase shift is determined by the amplitude ratio and nonlinear phase from SBS.