Dual-Parameter Measurement System for Dynamic and Static Pressure Based on a Fiber-Optic FPE Sensor

This article proposes a sensing system that utilizes a fiber-optic Fabry-Perot etalon (FPE) interferometric sensor and a narrowband distributed feedback (DFB) laser for dual-parametric measurements of dynamic and static pressure. As the pressure signal passes through the central opening of the rigid FPE sensor, the pressure causes a change in the refractive index of the air in the sensor cavity, which in turn causes a change in the optical path difference (OPD) rather than the traditional pressure-induced mechanical displacement. Even though the wavelength tuning range of DFB lasers is only a few hundred pm, the appropriate cavity length of the FPE sensor ensures that it can always cover a complete spectral period. Ensuring that the wavelength of the DFB laser is fixed within the linear region of the sensor spectrum will lead to time-varying ac intensity signals caused by acoustic waves. The cross correlation algorithm is a high-precision method for absolute cavity length interrogation that can be used to obtain the OPD of the sensor and determine the static pressure parameters. The experimental results demonstrate a 53-dB signal-to-noise ratio (SNR) at 1-kHz acoustic pressure, along with an acoustic sensitivity of 4.025 V/Pa and a pressure sensitivity of 15.8 nm/kPa for static pressure ranging from 0 to 70 kPa. Additionally, the full-phase demodulation advantage of the cross correlation algorithm ensures an OPD resolution within 2.5 nm, even when the wavelength tuning range of the narrowband DFB laser used is less than 1 nm. The proposed dual-parameter measurement scheme relies solely on a single FPE sensor, simplifying the system structure and reducing costs, and offers a competitive solution for dual-parameter measurement of acoustic and static pressure in aerospace.