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

This paper 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 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 alternating current (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 kPa 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.