Multiparameter Measurements for Bending, Torsion, and Temperature by Long-Period Gratings in Three-Core Fiber

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
$\text{m}^{-{1}}$
. 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/
$\text{m}^{-{1}}$
, 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.