A High-Sensitivity and Wide-Range FBG-Based Flow Sensor for Pulmonary Function Tests

With the continuous increase in the incidence rate of respiratory diseases, the importance of pulmonary function tests (PFTs) in early diagnosis and disease monitoring has become increasingly prominent. This paper proposes a high-sensitivity, wide-range flow sensor based on Fiber Bragg Grating (FBG) for pulmonary function testing. The sensor consists of 2 cylindrical covers and an internal flexible differential lever structure. By replacing rigid hinges with flexible hinges, it achieves airflow thrust amplification and differential strain measurement, effectively enhancing sensitivity and suppressing temperature effects. The sensor structure has been verified through structural optimization and finite-element simulation, resulting in high sensitivity. Simulation results show that the sensor exhibits excellent static and dynamic performance within the range of 0–12 L/s, with an average sensitivity of 877.2 pm/(Lꞏs⁻¹) and a safety factor greater than 3. A calibration experiment was conducted, and a quartic polynomial fitting was applied, which reduced the maximum fitting error to 5% and yielded an average resolution of 1.4 mL/s. Dynamic performance testing and temperature-decoupling experiments further verify its dynamic accuracy and insensitivity to temperature. Finally, by comparing the pulmonary function test data from six healthy subjects with those from a commercial spirometer, the average errors for key parameters, including FVC, FEV₁, and PEF, were all below 3%, demonstrating the feasibility and accuracy of the sensor in clinical pulmonary function tests.