A multi-channel and real-time demodulator for low-finesse FBG-FP atmospheric pressure sensors based on tunable laser scanning

Abstract

Fiber Bragg grating-Fabry-Perot (FBG-FP) sensor has attracted significant attention in the past decade as an effective measurement tool for multiple environmental parameters. We proposed a small-sized and real-time demodulator for low-finesse FBG-FP sensors based on tunable laser scanning and dedicated to atmospheric pressure measurement. With a compact size of 23.5 cm × 16.5 cm × 7.8 cm, the demodulator integrates a modulated grating Y-branch (MG-Y) tunable laser and a field-programmable gate array (FPGA)- controlled parallel acquisition module. The system enables 32-channel parallel spectral acquisition, with real-time demodulation and detailed characterization performed on four representative FBG-FP sensors. Atmospheric pressure measurement is realized by extracting the FP interference spectrum phase via the Carré algorithm, where the FBG-measured temperature values are used to decouple the FP phase from temperature cross-sensitivity. The Sensor 4 exhibits an excellent linear response (R² = 0.999) with a pressure sensitivity of −0.0052 rad/kPa. In addition, the impact of laser scanning errors on demodulation performance is investigated, and a temperature experiment confirms the system’s ability to distinguish pressure-induced spectral shifts from thermal effects. The results validate the effectiveness of the proposed demodulator in achieving real-time, stable demodulation for FBG-FP sensors, offering a reference for distributed atmospheric pressure monitoring and other fiber-optic sensing applications.