Fig. 1. Schematic of enhanced ?-OTDR vibration sensing system based on weak fiber Bragg grating array

Fig. 2. Schematic of reflection light interference from fiber Bragg grating array

Fig. 3. Demodulation structure of enhanced ?-OTDR vibration sensing signals based on fiber Bragg grating array

Fig. 4. Spectra of demodulated signals at different frequencies when voltage of sinusoidal driving signal is 0.53 V. (a) Low frequency; (b) high frequency

Fig. 5. Relation between driving voltage amplitude and demodulated signal amplitude at different frequencies. (a) 20 Hz; (b) 40 Hz; (c) 80 Hz; (d) 100 Hz; (e) 200 Hz; (f) 400 Hz

Fig. 6. Comparison between demodulated signal of sensing system and test signal of geophone at different frequencies. (a) 10 Hz; (b) 20 Hz; (c) 60 Hz; (d) 80 Hz; (e) 200 Hz; (f) 500 Hz