Fiber Optic Wearable Curvature Sensor Based on Taper-Assisted Microcavity

In this article, a novel fiber-optic curvature sensor is proposed and demonstrated based on the tapered micro-open-cavity (T-MOC) structure. The fabrication parameters are experimentally compared and optimized, and the comprehensive tests are performed in terms of curvature and temperature. The results show that the curvature response is effectively improved through reducing the diameter of taper waist. The maximum sensitivity reaches −7.92 nm/m−1 when the diameter is
$\sim 30~\mu $
m, with a cross-sensitivity of 0.0137 °C/m−1. Moreover, encapsulated by polydimethylsiloxane (PDMS), the T-MOC structure is used as a wearable point of care device to monitor the health status of human body. Owing to the ultralow threshold detection of 0.067 m−1, both large bending change and weak neck pulse can be precisely measured with high signal-to-noise ratio (SNR) and rapid time response. Index Terms— Curvature, fiber-optic sensor, microcavity, wearable devices.