Fig. 1. Vibration sensing system combined with TGD-OFDR and MZI

Fig. 2. Discrete Rayleigh scattering model of optical fiber

Fig. 3. Spatial resolution of system combining MZI and TGD-OFDR. (a) Shape of chirped pulse st after matched filtering;(b) relationship between sweep bandwidth and spatial resolution

Fig. 4. Time domain waveforms and spectra of original signal received by I/Q receiver. (a) (b) Time domain waveforms detected by I/Q receiver; (c) (d) spectra of channel I

Fig. 5. Flow chart of demodulation

Fig. 6. Single point vibration location. (a) Intensity trace; (b) standard deviation of intensity

Fig. 7. Phase demodulation of single point vibration. (a) Time domain phase demodulation results of TGD-OFDR at vibration position; (b) time domain phase demodulation results of MZI; (c) PSD of vibration signal obtained by demodulating TGD-OFDR phase; (d) PSD of vibration signal obtained by demodulating MZI phase

Fig. 8. Single point high frequency vibration PSD of phase demodulation. (a) PSD of vibration signal obtained by demodulating TGD-OFDR phase; (b) PSD of vibration signal obtained by demodulating MZI phase

Fig. 9. Two-point high frequency vibration location. (a)(b) Intensity traces of TGD-OFDR; (c)(d) standard deviation of TGD-OFDR intensity

Fig. 10. Phase demodulation of two-point vibration. (a) Time domain phase demodulation results of MZI; (b) time domain phase demodulation results of TGD-OFDR at vibration position; (c) PSD of vibration signal obtained by demodulating MZI phase; (d) PSD of vibration signal obtained by demodulating TGD-OFDR phase