Fiber-optic based wearables for the continuous monitoring of respiratory rate

Fiber optic sensor technology is considered as a promising candidate for the monitoring of biophysical parameters due to its sensitivity to strain and temperature, immunity to electromagnetic interference, lightweight and opportunity to be mounted on the textiles. Therefore, this paper suggests using one of the fiber optic technologies, namely Fiber Bragg Grating (FBG) sensors, for the respiratory rate monitoring of the hospital patients or sportsmen. Two FBG arrays consisting of 5 sensors each have been sewed to two elastic belts. The belts have been put on volunteer‘s chest and abdomen because the expansion of those regions causes the elastic belts to elongate and, as a result, FBG arrays experience strain changes. The use of ten FBGs located in different regions is required to use the diversity technique, which allows increasing the accuracy of the result by combining output from multiple sensing points. Therefore, a special algorithm has been used to analyze the strain pattern detected by all ten FBGs and to reconstruct the respiratory rate based on them. The obtained breathing rate of the volunteer has been compared with the reference rate measured by a mobile application. Several sets of experiments have been performed in order to identify the influence of the volunteer‘s position and speed of breathing on the accuracy of the measurements.