Spatial resolution enhancement of DFT-BOTDR with high-order self-convolution window

Brillouin optical time-domain reflectometer based on discrete Fourier transform has attracted interest for the simple structure, low cost, and fast data processing. In this paper, a 4th-order Hanning self-convolution window method is demonstrated to enhance the spatial resolution of DFT-BOTDR system. The Brillouin backscattering is profile-weighted by convolving with a 4th-order Hanning self-convolution window. The center frequency of the Brillouin spectrum is determined by the weighted function, where the spectrum power is concentrated in the main lobe, leading to an optimized spatial resolution. Experiments of strain sensing on a 5 km long sensing fiber with pulse width of 300 ns and sampling rate of 625 MS/s are carried out. The theoretical spatial resolution is 41m with traditional rectangular window. The experimental results show that the spatial resolution is improved by similar to 31m with the proposed 4th-order Hanning self-convolution window. The sensing system is promising in accurate location of distributed sensing.