Fig. 1. Experimental setup of φ-OTDR system

Fig. 2. Gray scale transformation and iterative operation of original signal. (a) Original gray image constructed via consecutive Rayleigh curves; denoised gray images with single bright line indicating position information obtained after different iteration times, (b) 10 iteration times, (c) 30 iteration times, (d) 50 iteration times

Fig. 3. Location of original signal and after different iteration times. (a) Original Rayleigh backscattering traces; position information obtained after different iteration times, (b) 10 iteration times, (c) 30 iteration times, (d) 50 iteration times

Fig. 4. Vibration detection of 300 Hz processed by different denoising methods. (a) Moving average and moving differential method; (b) nonlocal mean method; (c) total variation algorithm

Fig. 5. Spatial resolution of the three methods. (a) Moving average and moving differential method; (b) nonlocal mean method; (c) total variation method

Fig. 6. Frequency information of the vibration event at PZT1

Fig. 7. Location information for detection of two PZTs’ vibrations by different methods. (a) Moving average and moving differential method; (b) nonlocal mean method; (c) total variation algorithm

Fig. 8. Frequency information for the vibration events. (a) PZT1; (b) PZT2

Fig. 9. Results of total variation algorithm for wideband signal processing. (a) Location information of vibration; (b) information of wideband signal spectral