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.

I. INTRODUCTION

Fiber-optic sensors (FOS) [1] represent a valuable alternative to traditional sensors based on micro-electromechanical systems, electromechanical and electrochemical sensors, or free-space optical sensors and have attracted significant interest for industrial and biomedical applications [2]. FOS have some important advantages for these applications: miniature footprint and light weight, immunity to electromagnetic interference, safety as the fiber is a passive device, and miniature size of each sensing point.