Fig. 1. Frequency difference between multi-pulse Brillouin signal and local light caused by optical source frequency instability

Fig. 2. Simulation result of Brillouin center frequency deviation distribution due to frequency fluctuation of laser

Fig. 3. Measurement setup for frequency stability of optical source

Fig. 4. Frequency deviation of laser ITLA

Fig. 5. Setup of BOTDR sensing experiment

Fig. 6. Brillouin frequency spectra of sensing fiber at different positions

Fig. 7. Frequency deviation of laser DL-BF10

Fig. 8. Long-distance sensing experimental results of BOTDR system based on laser DL-BF10