Fig. 1. The experiment setup

Fig. 2. Sequence diagram of double square waves reflected by WFBGs

Fig. 3. The 5-WFBG array setup

Fig. 4. The reflected signal of 5-WFBG array

Fig. 5. The detected intensity and extracted interference signal

Fig. 6. Detection of sine wave signal by four kinds of double square waves with different duty cycles

Fig. 7. The interferometric phase signals and their frequency information

Fig. 8. The interferometric intensity signals and their phase signals

Fig. 9. The phase signals of the interference signals in Area 2 under different amplitudes of sinusoidal sounds