Fig. 1. Fiber-wrapped thin-walled cylinder. (a) Schematic diagram; (b) physical map

Fig. 2. Diagram of Michelson interference phase extraction calibration device based on 3×3 coupler. (a) Phase extraction calibration device; (b) schematic diagram of demodulation method

Fig. 3. Curves of relation between calculated value of sound pressure sensitivity and (a) material, (b) outer radius, and (c) wall thickness of thin-walled cylinder

Fig. 4. Phase of fiber wrapped on thin-walled cylinder with an outer radius of 25 mm and a wall thickness of 1 mm varies with sound pressure

Fig. 5. Research on acoustic response directivity of thin-walled cylinder. (a) Layout of incident azimuth of sound source in experiment; (b) sensitivity of sound pressure varies with azimuth

Fig. 6. Experimental measurement results of sound pressure sensitivity varies with (a) outer radius and (b) wall thickness of thin-walled cylinder

Fig. 7. Schematic of quasi-DAS system

Fig. 8. Original signals and demodulation results of quasi-DAS system. (a) Space-time diagram of detective signal; (b) time domain diagram and (c) spectrum diagram of demodulated signals in unsensitized sensing area; (d) time domain diagram and (e) spectrum diagram of demodulated signals in sensitized sensing area

Fig. 9. Sound pressure measured by microphone and DAS system