Optical Strain Gauge-Based on a Hetero-Core Fiber Macro-Bending Sensor

Abstract

This paper describes a novel approach for optical strain sensing based on a hetero-core fiber optic macro-bending sensor. A gauge substrate for the proposed sensor was designed to transduce the tensile and compression strain by changing to a gentle bending curvature on the fiber; thus, the hetero-core fiber detects the strain on the substrate as the transmitted light lost. Because optical fibers perform as a flexible structure in a buckling scheme owing to their slenderness, the mechanical properties of the proposed sensor can be widely tuned by the shape and mechanical properties of the gauge substrate. Experiments demonstrated that the proposed strain gauge with a spring-structured substrate made of SUS304 showed a strain applied within $\pm 3100~\mu \epsilon $ with a sensitivity of up to $- 9.14\times 10^{-4}$ dB/ $\mu \epsilon $ , and responded to temperature changes from 0 °C to 60 °C with $- 1.10\times 10^{-2}$ dB/°C owing to the thermal expansion of the substrate. Furthermore, both the strain and temperature sensitivities are tunable by changing the geometrical parameters of the gauge substrate.