Spatial Resolution Improvement in Correlation Domain Distributed Measurement of Brillouin Grating

We have demonstrated that intensity modulation enhances the spatial resolution in the distributed measurement of Brillouin dynamic grating (BDG) spectrum by the Brillouin optical correlation domain analysis. According to the correlation domain principle, the stimulated Brillouin scattering is localized in so-called correlation peaks, but these peaks actually have side lobes, which excite the BDG out of the peak region, compromising the spatial resolution in the BDG spectrum measurement. To solve this, we applied intensity modulation to apodize the optical power spectrum of the input lightwave to the system, suppressing the side lobes. We experimentally confirmed about 4.5 times improvement in the spatial resolution. A 25-cm-long stressed segment in a 500-m-long fiber was successfully recognized in the proposed system, which could not be achieved by a system without the intensity modulation.