Multiparameter Measurements for Bending, Torsion, and Temperature by Long-Period Gratings in Three-Core Fiber
Yunhe Zhao, Xin Wang, Huiqin Peng, Mengjiao Ding, Siyu Chen, Yunqi Liu, Zuyuan He
Abstract
In this article, it is reported on a multiparameter sensor for measuring bending, torsion, and temperature. The sensor is formed from long-period gratings (LPGs) induced in a linearly arranged three-core fiber (TCF) using the electric arc-discharge technique. This sensor could realize the simultaneous measurement for curvature magnitudes and discriminate bending direction because of the linearly distributed fiber cores of TCF and high polarization-dependent loss (PDL) of TCF-LPGs. The bending reactions in various directions exhibit a high degree of linearity in the curvature region of 0.249–0.8731 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{-{1}}$ </tex-math></inline-formula> . The obtained bending sensitivities are noticeably distinct and adhere to sine function relationship with the bending direction. At the direction of 0°, the bending sensitivities of dual resonances in TCF-LPGs reach the highest value of −7.58 and −8.83 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{-{1}}$ </tex-math></inline-formula> , respectively, and the measured temperature sensitivities are 0.023 and 0.107 nm/°C, respectively. Considering dual resonances response different coefficients to different parameters, the simultaneous measurement of temperature and bending could be achieved. Moreover, the torsional characteristics of the TCF-LPGs adhere to sine function as well, which shows potential for directional torsion sensing. The suggested TCF-LPGs offer great deal of promise in the area of multiparameter sensing measurement.