A distributed hydrostatic pressure sensor based on Brillouin dynamic gratings (BDGs) was proposed and demonstrated for the first time to the best of our knowledge. Through measuring the pressure-induced birefringence changes through exciting and probing the BDGs, the hydrostatic pressure sensing is realized. The thin-diameter PM-PCF is used as the fiber under test. The temperature can be compensated by measuring the temperature-induced Brillouin frequency shift (BFS) through differential pulse-width pair Brillouin optical time-domain analysis (DPP-BOTDA). A distributed measurement is reported with a 20-cm spatial resolution and measurement accuracy as high as 0.025 MPa.
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.
We report on a high-sensitive distributed transverse load sensing based on Brillouin dynamic gratings (BDGs) for the first time to the best of our knowledge. The sensing mechanism is to measure the transverse-load induced birefringence through exciting and probing a BDG in an elliptical-core polarization-maintaining fiber. A distributed measurement of transverse load is experimentally demonstrated with a 20-cm spatial resolution, and the measurement accuracy is as high as 4.8x10<sup>-4</sup>N/mm, which improves by three orders of magnitude compared with the prior techniques.