Temperature-Insensitive Fiber Bragg Grating Sensing System for Curvature Measurement Based on Optoelectronic Oscillator With the Enhanced Vernier Effect

We propose and experimentally demonstrate a sensitivity-enhanced fiber Bragg grating (FBG) curvature sensing system based on optoelectronic oscillator (OEO) with the enhanced Vernier effect. In this article, two FBGs with opposite wavelength shift directions are constructed by using the silicon plate, and the time delay of the two loops of OEO changes in opposite, thus realizing OEO-based sensitivity enhanced FBG curvature sensing system with the enhanced Vernier effect. The experimental results show that the sensitivity of single FBG curvature sensing system based on single-loop OEO is about 0.067 MHz/m−1, while the sensitivity of two FBGs-based curvature sensing system employing dual-loop OEO with the enhanced Vernier effect is 40.89 MHz/m−1, which is 612 times that of a single-loop OEO-based FBG curvature sensing system. Moreover, the proposed FBG curvature sensing system shows great temperature insensitivity characteristics, in which temperature sensitivity of the proposed curvature sensing system is 5.57 kHz/°C, and the curvature error caused by the change of 1 °C is
$1.358\times 10^{-{4}}\,\,\text{m}^{-{1}}$
, which shows potential for realizing high sensitivity, fast, real-time demodulation in temperature-insensitive FBG curvature sensing system.