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Spatial resolution improvement based on intensity modulation in measurement of Brillouin dynamic grating localized by correlation domain technique

We demonstrated that intensity modulation synchronized with laser frequency modulation enhances the spatial resolution in the measurement of Brillouin dynamic grating (BDG) spectrum localized by the correlation domain technique. Following the correlation domain principle, the stimulated Brillouin scattering is localized in so-called correlation peak, but the peak actually has side lobes which excite the BDG out of the peak region. To overcome this, we applied intensity modulation and apodize the optical spectrum of the participating waves to suppress the side lobes. We confirmed spatial resolution improvement from 75 cm to 17 cm in a measurement fiber of 500 m.