Smart optical fiber fabric based on side-emitting and side-coupling for pulse and blood oxygen measurement

Monitoring pulse and arterial oxygen saturation (SpO2) continuously and in real-time is conducive to the prevention and monitoring of cardiovascular disease. The reported optical fiber fabrics have the shortcomings of low side-emitting and side-coupling efficiency of a single fiber, and more optical fibers were used. In this paper, we propose a micro-bending bulge structure based on side-emitting and side-coupling of the polymer optical fiber (POF), and a small number of the POFs are woven into the fabric as weft yarns to measure pulse and SpO2 using a simple plain weave. The experiments investigated the effect of the different micro-bending bulge structures on the side-emitting and side-coupling efficiencies by means of the ray tracing method, explored the feasibility to measure pulse waves and SpO2 on the fingertip, brachial artery, and forehead ophryon, and evaluated the accuracy of the measurements in the static, dynamic, and sweating states. The results show that the side-emitting and side-coupling efficiencies of the POF are optimal by adopting a 1 mm micro-bending bulge height and a 3 mm micro-bending bulge width. The fabric sensor with three side-emitting POFs and two side-coupling POFs is capable of monitoring pulse and SpO2 on the forehead. In addition, the maximum error is 1 bpm for the pulse and within 2% for SpO2 on the forehead.