A Highly Sensitive Curvature Sensor Based on Omega-Shaped Long-Period Fiber Grating
Yuanyuan Li, Yiwei Ma, Tian Tian, Haoyang Tan, Cuiting Sun, Tao Geng, Libo Yuan
Abstract
A compact omega-shaped long-period fiber grating (OS-LPFG) for vector bending measurement is proposed and investigated in this article. This sensor is fabricated by periodically splicing single-mode fiber (SMF) and multimode fiber (MMF) into omega shape to get the purpose of sensitivity enhancement. The proposed OS-LPFG can distinguish the bending direction and achieves the curvature sensitivities in X-, Y-, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- {X}$ </tex-math></inline-formula> -directions are 12.03, −69.95, and −19.84 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> at the range of 0–1.5 <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. Meanwhile, the sensor has a small temperature crosstalk of 0.0011 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{-{1}}/^{\circ }\text{C}$ </tex-math></inline-formula> at the temperature range of 20 °C–110 °C. In addition, the sensor features a compact structure with the length of 1.5 mm due to the strong refractive index (RI) modulation induced by fabricating method, which proposes a feasible idea for compact fiber curvature sensor design.