Two-Axis Bending Sensor Based on Asymmetric Grid Long-Period Fiber Grating
Ming-Wei Lai, Yanxin Zhang, Weigang Zhang, Han Gao, Liang Ma, Huizi Ma, Tieyi Yan
Abstract
A novel bidirectional high-sensitivity bending sensor based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\upsilon $ </tex-math></inline-formula> -shaped long-period fiber grating (LPFG) is designed and demonstrated. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\upsilon $ </tex-math></inline-formula> -shaped LPFG is composed of an array of asymmetrical <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\upsilon $ </tex-math></inline-formula> -shaped grating planes, which can provide stronger refractive index modulation than conventional planar grids. Therefore, the proposed sensor provides a more sensitive result. The experimental results show that the maximum bending sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\upsilon $ </tex-math></inline-formula> -shaped LPFG reaches −24.08 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> within the bending range of 0.22 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{-{1}}\,\,\sim \,\,2.21\,\,\text{m}^{-{1}}$ </tex-math></inline-formula> , enhancing the bending sensitivity while improving sensitivity to the micro-bending area. The sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\upsilon $ </tex-math></inline-formula> -shaped LPFG can be potentially improved by optimizing the structural parameters of the grid.