Fig. 1. Diagram of pre-pump pulse

Fig. 2. Brillouin spectra of pre-pumping system at different length of heating optical fiber. (a) Schematic diagram of pre-pump pulse; (b) Brillouin spectrum for L_c>L_p; (c) Brillouin spectrum for L_c<L_p

Fig. 3. Brillouin interference spectra and Brillouin gain spectra. (a) Simulation results; (b) experimental results

Fig. 4. Diagram of experimental setup

Fig. 5. Pre-pumping temperature sensing experiment. (a) Diagram of optical fiber heating; (b) spectra of optical fiber heating section for double-sideband and single-sideband detections

Fig. 6. Results of temperature sensing. (a) Spectrum of optical fiber; (b) spectra of different heating sections

Fig. 7. Brillouin interference spectrum and traditional Brillouin gain spectrum varying with temperature, and time domain signal of heating section. (a) Brillouin interference spectrum; (b) traditional Brillouin gain spectrum; (c) time domain signal of heating section