Spatial resolution analysis for discrete Fourier transform-based Brillouin optical time domain reflectometry

Discrete Fourier transform (DFT) requires many sampled points for a spectrum. We find that the spatial resolution of the DFT-based Brillouin optical time domain reflectometry (BOTDR) is determined by the pulse width of the probe light and the time length of the sampling data used to perform the DFT. The best spatial resolution is limited by the pulse width. At a certain sampling rate, the spatial resolution increases linearly with the number of points in DFT. The frequency uncertainty improves with the increased number. Window function restrains the spectral leakage significantly and can improve the spatial resolution. But when the influence of the spectral leakage can be neglected, the frequency uncertainty without a window function is better than that with a window function for the same spatial resolution.