Multiparameter sensor based on long-period grating in few-mode ring-core fiber for vector curvature and torsion measurement
Yunhe Zhao, Shiqi Chen, Yutao Guo, Yan Jiang, Siyu Chen, Chengbo Mou, Yunqi Liu, Zuyuan He
Abstract
With the rapid development of optical fiber sensor in physical measurement, it is of practical significant to realize multi-parameter measurement. In this work, we proposed and demonstrated a multiparameter sensor for curvature, torsion and temperature. The sensor is formed from CO 2 laser-inscribed long-period grating (LPG) in few-mode ring-core fiber (RCF), which can convert fundamental mode to LP 11 mode. One-side inscription enhances asymmetric index modulation in fiber, resulting in directionally sensitive to bend by intensity interrogation. The curvature sensitivities in various bending directions perform linearity in curvature range of 5–9.466 m −1 . Curvature sensitivities are related to the bending directions. The intensity sensitivity achieves − 0.584 dB/m −1 , 0.879 dB/m −1 , and − 0.735 dB/m −1 , respectively. And torsion sensitivity from - 6.98 rad/m to 6.98 rad/m displays linearity with −0.554 dB/(rad/m). The measured influence of temperature can be negligible. The proposed RCF-LPG could not only be used as high-efficiency mode converter in mode division multiplexing systems but also be potential in few-mode fiber based multiparameter sensing fields.