Improvement of spatial resolution of Brillouin optical time domain reflectometer using spectral decomposition

Brillouin optical time domain reflectometer (BOTDR) has been used for strain and temperature measurement and health monitoring in infrastructural systems. However, the spatial measurement resolution of BOTDR cannot yet meet the measuring needs of some specific local strains, such as the strain caused by a narrow crack or fissure in structures. In this paper, a spectral decomposition method is proposed and used for improving the spatial resolution. Based on the proportion of the strain length within the spatial resolution, taking the spectrum of the strain section from the measured spectrum, and fitting the decomposed Brillouin gain spectrum with the Lorentzian curve, the actual strain within a spatial resolution along optical fibers can be obtained. The experimental results demonstrate that this method is applicable to the modification of the measured strain whether its strained length is less or greater than the spatial resolution without considering the installation method of the optical fiber.