Fig. 1. Block diagram of a three-wavelength adaptive intensity demodulation system

Fig. 2. Schematic diagram of principle of three wavelength selection. (a) Schematic diagram of absolute value curve of the first derivative of reflected light intensity; (b) normalization curve of working wavelength intensity

Fig. 3. Flowchart of three-wavelength adaptive intensity demodulation

Fig. 4. White light interference spectrum for fiber optic sensors

Fig. 5. Acoustic detection in temperature fluctuation environments. (a)-(d) Interference spectrum at different times and actual working wavelength; (e)-(h) corresponding response for measuring a 1 kHz standard sine signal

Fig. 6. Frequency response calibration. (a) Schematic diagram for frequency response calibration; (b) frequency response diagram of diaphragm sensor to 1 kHz to 20 kHz

Fig. 7. Performance test experiment of three-wavelength adaptive intensity demodulation system. (a) Light intensity alternating current (AC) detected by system under different sound pressure conditions at a sound signal frequency of 3 kHz; (b)-(d) waveform monitored by system at different frequencies when sound signal pressure is 0.09 Pa

Fig. 8. Audio signals received by electrical sensors and membrane sensors

Fig. 9. Amplitude variation over time of a sine signal demodulated by the system at 2 kHz of frequency and 0.09 Pa of sound pressure