Fig. 1. Experimental device diagram of the BOTDA sensing system

Fig. 2. Flow chart of the LMD noise reduction algorithm

Fig. 3. Decomposition results of the LMD algorithm

Fig. 4. Fourier transform spectra of different PF components

Fig. 5. Residual component decomposed by LMD algorithm

Fig. 6. Energy distributions of different PF components

Fig. 7. BOTDA signal before and after LMD algorithm noise reduction

Fig. 8. Flow chart of optimized LMD noise reduction algorithm

Fig. 9. Filter curve of the Chebyshev I digital bandpass filter

Fig. 10. Typical PF curves and spectra before and after filtering. (a) Timing curve before filtering; (b) spectrum curve before filtering; (c) timing curve after filtering; (d) spectrum curve after filtering

Fig. 11. Time domain curve of BOTDA signal before and after optimized LMD algorithm for noise reduction

Fig. 12. Noise reduction results of the optimized LMD algorithm for different pulse widths. (a) 50 ns; (b) 70 ns; (c) 100 ns

Fig. 13. Change curves of signal SNR before and after noise reduction with the frequency of the probe light

Fig. 14. SNR analysis at different probe light frequencies. (a) Signal amplitude; (b) noise variance; (c) SNR