High-Precision OEO-Based Respiratory Monitoring System With Agarose-Coated FBG Sensor

In this paper, a respiration monitoring sensor based on an Agarose-coated fiber Bragg grating (AC-FBG) and an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated, which achieves high sensitivity and high-speed respiration signal detection by combining fiber optic sensing and OEO-based demodulating technology. The proposed sensor captures subtle respiratory variations with exceptional precision. The experimental investigation reveals that the absolute sensitivity of the proposed sensor reaches 0.07391%RH, which is 19.9 times higher than that measured with the optical method. The response frequency of the proposed OEO-based demodulation system is more than 6.69 Hz. Owing to its excellent sensing performance, the sensor not only monitors the human body's regular breathing mode and special breathing modes (e.g., rapid respiration, deep respiration, and apnea), but also realizes the monitoring of the weak respiratory signals at a distance. The measured data from the respiratory monitoring system proposed in this paper show a high level of agreement with the ground-truth breathing data, which provides new technological means for the evaluation of respiratory function in a variety of key medical scenarios.