Ultrahigh-Speed Demodulation for Fabry-Pérot Sensors Based on Spatio-Temporal Features of Sparse Spectra

Fiber optic Fabry-Pérot (F-P) interferometric sensors have been widely applied in various industries, because it can sense multiple physical quantities such as pressure, vibration, and refractive index by changing its cavity length. Therefore, it is very important to get the accurate and effective cavity length information. Traditional demodulation techniques for F-P cavity suffer from low speed, high cost, and poor robustness. Here, we propose a novel ultrahigh-speed demodulation system for F-P interferometric sensors based on the spatio-temporal features of sparse spectra. This system employs a combination of a dense wavelength division multiplexer, multi-channel photodetector, and analog-to-digital converter to acquire sparse spectra at high speed. Two neural network models are trained to extract the spectral temporal and spatial features, enabling ultrahigh-speed high-resolution demodulation for the changes of the cavity length and wide-range stable demodulation for absolute cavity length. The system has a demodulation rate of up to 500 kHz and a cavity length change resolution at the nm scale. It also supports the demodulation for absolute cavity length over a wide range of 15–950 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula>m. And it remains stable after six hours of continuous testing. Therefore, the ultrahigh-speed wide-range demodulation system offers a novel, cost-effective, and reliable solution for engineering field, showcasing significant potential for applications in high-speed fiber optic sensing.