High-Performance Extrinsic Fabry-Perot Fiber Optic Acoustic Sensor Based on Au/PI Composite Film

This paper reports a novel Fabry-Perot fiber optic microphone device based on Au/PI composite film, with an optimal F-P cavity length of approximately 500 μm, and the maximum extinction ratio (ER) obtained is about 12 dB. Besides, the sensor has flat response performance in the audio frequency range of 200-10 kHz, with a maximum signal-to-noise ratio (SNR) of 76 dB and a sensitivity of approximately 170 mV/Pa at the sound pressure level of 1000 Hz/94 dB, which is much higher than Brüel &? Kjær’s electric microphone 4939. Within a certain range of sound pressure, there is a fine linear relationship between the output response of the sensor and the input sound pressure, with a fitting coefficient of 0.9987. The new diaphragm-type fiber optic microphone proposed in our work has superb economy, sensitivity, frequency response and linearity within the audible sound range, which is expected to achieve large-scale, low-cost fabrication and long-term stable application in audio detection and other fields.