Fabrication and application of a grooved optical fiber respiratory sensor based on geometric parameter optimization by optical simulation

In this paper, a grooved polymer optical fiber (POF) sensor embedded in polyurethane is to monitor human respiratory rate. First, the luminescence characteristics of POFs with different numbers, depths, and lengths of grooves, and the coupling effect of fiber groups (one each for luminescent and receiving POFs) are investigated using geometric optical simulations. The results show that the luminescence characteristics of the groove fibers are proportional to the depth and number of grooves, and the coupling effect is related to the arrangement of the fiber groups. Then, the geometrically optimized fluted fibers are embedded in polyurethane in different arrangement groups to prepare fiber optic sensing elements, and tensile tests are performed to compare the coupling effects to verify the accuracy of the simulation conclusions. The optimal arrangement of the sensor fiber with the tensile region is also analyzed and positioned to significantly improve the tensile sensitivity of the sensor. Finally, the sensor device is introduced in the form of a belt for human respiratory monitoring, which can track the respiratory signal in real time under different motion states. Evaluation experiments on three subjects show that the device has a strong correlation with the simultaneous monitoring results of commercial respiratory sensors, with an accuracy of 69.4% for respiratory rate monitoring in different states and 83.3% for respiratory rate monitoring in sitting and standing states.