Design of an All-POF-Fiber Smartphone Multichannel Breathing Sensor With Camera-Division Multiplexing

We report the design and prototyping of an all-fiber-smartphone multiplexed sensor, with the purpose of breathing rate analysis. The architecture is based on a multichannel extrinsic sensor based on intensity modulation. The sensing system is entirely based on plastic optical fiber (POF). The optical hardware is entirely based on the smartphone, using the flashlight LED as the source and the camera as the pixel-based detector. A 3-D printed connector has been fabricated to facilitate light coupling to and from the POF links. A multiplexing concept labeled “camera-division multiplexing” has been implemented and is reported for a three-fiber system: The camera is spatially tessellated, dividing the contribution of each fiber with crosstalk 8.2-15.3 dB. The application for breathing rate detection, with camera ISO set to 800, is proposed and implemented, visualizing the power spectral density of the respiration pattern.