A fast dynamic cavity length demodulation technique for extrinsic Fabry-Perot interferometer sensor

This paper proposed a fast dynamic cavity length demodulation technique for signal demodulation of optical fiber Extrinsic Fabry-Perot Interferometer (EFPI) sensors. The proposed technique averages the five-step phase shift demodulation phase signals at multiple wavelengths to reduce noise and enhance signal demodulation stability. The reflected spectrum is obtained using white light interferometry (WLI) technology, and Ns sets of five-step phase shift signals are extracted from the reflected spectrum. The Ns sets of five-step phase shift signals are individually processed and their corresponding demodulated phase signals are averaged using FPGA, resulting in a dynamically demodulated cavity length signal. A corresponding testing system is established to analyze the noise characteristics of the demodulation technique. Experimental results demonstrate that compared to the traditional single-wavelength five-step phase shifting demodulation technique, the proposed demodulation technique effectively reduces noise, and improves noise stability. The demodulation scheme presented in this paper enables low-noise and high-precision signal demodulation in the weak signal detection field of EFPI sensors and holds significant value for the signal demodulation of EFPI sensor arrays.