Fig. 1. KSVD algorithmic flow

Fig. 2. Principle of improve the performance of BOTDR system based on IFSBL-KSVD algorithm

Fig. 3. Installation diagram of BOTDR system based on short-time Fourier transform

Fig. 4. Temperature configuration on the sensing fiber

Fig. 5. 3D-BGS images and their top views before and after noise reduction. (a)(b) Before noise reduction; (c)(d) after noise reduction

Fig. 6. BGS curves before and after noise reduction at a certain position in the non-temperature-change region

Fig. 7. Power and Brillouin frequency shift distributions before and after noise reduction by different noise reduction methods. (a) Power distribution; (b) Brillouin frequency shift distribution

Fig. 8. Power and Brillouin frequency shift distributions after denoising by the IFSBL-KSVD algorithm for different pulse widths. (a) Power distribution; (b) Brillouin frequency shift distribution