A fiber-optic shape sensing based on 7-core fiber Bragg gratings (FBGs) is proposed and experimentally demonstrated. The investigations are presented for two-dimensional and three-dimensional shape reconstruction by distinguishing bending and twisting of 7-core optical fiber with FBGs. The curvature and bending orientation can be calculated by acquiring FBG wavelengths from any two side cores among the six outer cores. And the shape sensing in three-dimensional (3D) space is computed by analytic geometry theory. The experiments corresponding of two-dimensional (2D) and 3D shape sensing are demonstrated and conducted to verify the theoretical principles. The resolution of curvature is about 0.1m⁻¹ for 2D measuring. The error of angle in shape reconstruction is about 1.89° for 3D measuring. The proposed sensing technique based on 7-core FBGs is promising of high feasibility, stability, and repeatability, especially for the distinguishing ability on the bending orientation due to the six symmetrical cores on the cross-section.

提出并基于7芯光纤布拉格光栅（FBG）的光纤形状感测。通过区分7芯光纤和FBG的弯曲和扭曲，提出了二维和三维形状重构的研究。曲率和弯曲取向可以通过从六个外芯中的任意两个侧芯获取FBG波长来计算。并利用解析几何理论计算了三维空间中的形状感测。演示并进行了二维（2D）和3D形状感测相对应的实验，以验证理论原理。曲率分辨率约为0.1m ^-1用于2D测量。对于3D测量，形状重建中的角度误差约为1.89°。所提出的基于7芯FBG的传感技术具有很高的可行性，稳定性和可重复性，特别是由于截面上有六个对称的芯而在弯曲方向的识别能力方面。