Fast demodulated white-light interferometry-based fiber-optic Fabry–Perot cantilever microphone

We demonstrate a highly sensitive and stable fiber-optic Fabry–Perot cantilever microphone based on fast demodulated white-light interferometry. The cavity length of the low-finesse Fabry–Perot interferometry is absolutely measured by realizing a high-speed demodulation method utilizing a full spectrum, with the advantages of both high resolution and large dynamic range. An acoustic test demonstrates high sensitivities and linear responsivities at frequencies below 2 kHz. The pressure responsivity and the noise-limited minimum detectable acoustic pressure level are measured to be 211.2 nm/Pa and 5 μPa/Hz1/2, respectively, at the frequency of 1 kHz. Comparative experimental results show that the signal-to-noise ratio is over 10 times higher than a reference condenser microphone.