Fig. 1. Experimental systems of fast BOTDR based on Raman amplification. (a) Experiment setup; (b) data processing module

Fig. 2. Center frequency as a function of sensing distance after Lorentzian fitting. (a) With Raman amplification; (b) without Raman amplification

Fig. 3. Frequency spectra along fiber. (a) Frequency spectrum of whole fiber; (b) frequency spectrum around 95 km

Fig. 4. Long-distance temperature sensing experiment. (a) Center frequency; (b) center frequency in heated section

Fig. 5. Brillouin center frequency as a function of temperature

Fig. 6. Frequency spectra along fiber under different pulsed optical powers

Fig. 7. Center frequency as a function of sensing distance after Lorentzian fitting under different pulsed optical powers. (a) P=5 mW; (b) P=10 mW; (c) P=15 mW

Fig. 8. Standard deviation along fiber under different pulsed optical powers