Fig. 1. Brillouin splicing spectrum

Fig. 2. Brillouin gain spectrum

Fig. 3. Schematic of quick positioning

Fig. 4. Device diagram of BOTDR system based on STFT

Fig. 5. Optical fiber to be tested in experiment 1

Fig. 6. Frequency spectra constructed by equal division FFT. (a) Frequency spectra by FFT processing of 0-1250 m and 1250-2500 m time domain signals; (b) frequency spectra by FFT processing of 1563-1719 m and 1719-1875 m time domain signals; (c) frequency spectra by FFT processing of 1641-1680 m and 1680-1719 m time domain signals; (d) frequency spectra by FFT processing of 1719-1758 m and 1758-1797 m time domain signals

Fig. 7. Optical fiber to be tested in experiment 2

Fig. 8. Brillouin gain spectra of tested optical fiber at different temperatures. (a) Keep the optical fiber at room temperature; (b) heat to 40 ℃; (c) heat to 50 ℃

Fig. 9. Brillouin frequency shift distribution at different conditions. (a) Traditional peak searching algorithm & 40 ℃ optical fiber; (b) traditional peak searching algorithm & 50 ℃ optical fiber; (c) maximum-seeking method & 40 ℃ optical fiber; (d) maximum-seeking method & 50 ℃ optical fiber