Twin-core fiber (TCF)-based sensor was proposed for non-invasive vitalsign monitoring, including respiration and heartbeat. The TCF washomemade and the corresponding sensor was fabricated by sandwichingsingle-mode fiber (SMF) on both ends. The offset distance between SMFand TCF was optimized while the length of TCF was identified frompreliminary vital sign measurement results. Then, the TCF-based sensorwas attached under a mattress to realize non-invasive vital signmonitoring. Both respiration and heartbeat signal can be obtainedsimultaneously, which is consistent with the reference signals. Forfurther application, post-exercise physiological activititycharacterization were realized based on this vital sign monitoringsystem. In discussion, mode coupling in TCF was analyzed and utilizedfor curvature sensing with achieved sensitivity as high as 18nm/m , which supported its excellent performancefor vital signs monitoring. In conclusion, the TCF-based vital signsmonitors can be a promising candidate for healthcare and biomedicalapplications.
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