Fig. 1. Structure diagram of Φ-OTDR system

Fig. 2. Normalized disturbance signal. (a) Mechanical excavation; (b) human beating

Fig. 3. Flow chart of proposed algorithm

Fig. 4. First to third order IMF components generated by EMD decomposition of vibration signals. (a) (b) (c) Mechanical excavation; (d) (e) (f) human beating

Fig. 5. First to third order IMF components after Butterworth filtering. (a) (b) (c) Mechanical excavation; (d) (e) (f) human beating

Fig. 6. The SNR of the original signal. (a) Mechanical excavation; (b) human beating

Fig. 7. The SNR of signal processed by the denoising method. (a) Mechanical excavation; (b) human beating