Unconstrained pulse pressure sensing for health management based on a hetero-core fiber optic sensor

In this paper, we proposed a hetero-core fiber optic pulse sensor made by softly silicone rubber. In addition to the feature of fiber optics, a hetero-core fiber sensor is only sensitive to be bending action of the sensing portion and the transmission line is unaffected to temperature fluctuation with single-mode stable propagation. Therefore, the hetero-core fiber sensor is suitable for the pulse pressure sensing be placed in various sites, and wearable device at the wrist. The proposed pulse sensor was devised to have high sensitivity by adding two spacers to the both ends of a hetero-core portion. We estimated that the sensitivity was adjustable by the hetero-core position and combination between core diameters of transmission line and inserted fiber. The proposed pulse sensors were successfully demonstrated by setting at the chair arm and being arranged as the wearable application. 9 and 6 participants could be successfully tested for the pulse detection using proposed unconscious construction and downsized wearable sensor module using a hetero-core fiber sensor.