Fig. 1. Diagram of distributed optical fiber micro-vibration sensor structure based on φ-OTDR

Fig. 2. Frequency response diagram of PZT vibration at 10 Hz, 50 Hz and 100 Hz

Fig. 3. Stable vibration RMS data of sensing fiber at static state and the 500 th monitoring point

Fig. 4. Train vibration signal monitoring system

Fig. 5. Diagram of original signal and differential signal of passing train

Fig. 6. Frequency spectrum space waterfall of passing train

Fig. 7. Diagram of original signal and differential signal of passing freight train

Fig. 8. Vibration time-domain signals and corresponding frequency spectrum waveform of trains at 5 590 m and 5 695 m

Fig. 9. Vibration time-domain signals and corresponding frequency spectrum waveform of passenger trains at 5 590 m and5 588 m in same spatial resolution

Fig. 10. Diagram of time-domain waterfall and frequency-domain waterfall of passing freight train

Fig. 11. Time-domain waterfall diagram of locomotive