Characterization of phase-shifted Brillouin dynamic gratings in a polarization maintaining fiber

Abstract

We numerically calculate and experimentally investigate the characterization of phase-shifted Brillouin dynamic gratings (PS-BDGs) in a polarization maintaining fiber (PMF). A phase-shifted point is induced into the middle of a conventional BDG through phase-modulating one of the two pump pulse, generating a PS-BDG thanks to the stimulated Brillouin scattering (SBS). When the frequency difference between a high frequency pump1 pulse with 1ns and π-1ns and a low frequency pump2 pulse with 100ps is equal to the Brillouin frequency shift of the PMF, a transient PS-BDG with a 3dBbandwidth of 354MHz of the notch spectrum is simulated based on the coupled-wave equations of BDG. By increasing the repetition rate up to 250MHz, an enhanced PS-BDG with a deep notch depth is obtained since the residual acoustic wave of the former SBS process is enhanced by the optical waves of the latter SBS process. Then a proof-of-concept experiment is built to verify the transient PS-BDG and the results show that the notch feature is consistent with the simulation results and the notch frequency of the PS-BDG can be changed by tuning the phase shift Δϕ . The proposed PS-BDGs have important potential applications in optical fiber sensing, microwave photonics, all-optical signal processing and RoF (radio-over-fiber) networks.