Optical Fiber Sensor Based on Plastic Optical Fiber and Smartphone for Measurement of the Breathing Rate

In the diagnosis of respiratory diseases, it is necessary to have a wearable device capable of measuring the breathing rate. We propose a sensor based on the integration of a smartphone with a plastic optical fiber (POF); the system behaves as an all-fiber sensor, using the flashlight as the source and the camera as a photodetector, and a 3D-printed connector to perform light coupling. The method of intensity modulation is used to detect the breathing rate. The ubiquitousness of smartphones and the low cost of POF make the proposed sensor a viable alternative to standard devices. The proposed configuration has been calibrated and then experimentally validated. The results are displayed in both the time and frequency domains to extract the information about the periodicity of breathing.