Fig. 1. Influence of an external sound field on the optical fiberl fiber

Fig. 2. Hilbert transform demodulation process

Fig. 3. IQ demodulation flow chart

Fig. 4. Relationship between sampling period and sampling point

Fig. 5. Icing diagram of overhead power transmission line

Fig. 6. Sag model of overhead transmission line

Fig. 7. (a) Comparison between measured value and estimated value of sag; (b) Displacement of relative equilibrium position at the lowest point of overhead transmission line during vibration; (c) Ice thickness estimation

Fig. 8. Accident site of external damage of buried cable

Fig. 9. Schematic diagram of TDOA

Fig. 10. Outfield experiment. (a) Two dimensional Gaussian distribution of confidence interval; (b) Contour plot of confidence interval

Fig. 11. Position estimation error. (a) Single array; (b) Vertical orthogonal array