Bending and rotation sensing based on high coherence interferometry in seven-core fiber (SCF) is proposed here for the first time. In the suggested scheme, distinct optical paths are formed from the selected cores, thus creating a very compact in-fiber Michelson interferometer. The interferometer consists of an in-line taper structure fabricated on the SCF for a light splitting/coupling element, and a Faraday rotating mirror used as a reflective element. Different strains are exerted on the reference and sensing cores because of the dissimilar distance from the neutral axis. The phase difference between these two interferometer arms resulting from the variations in strain is resolved using a fringe counting technique. The proposed sensor is revealed to be extremely sensitive for curvature and rotation measurement, with sensitivities of 629 fringe/m⁻¹ and 6.2 fringe/°, respectively. The sensor is capable of detecting the smallest curvature of 0.0032 m⁻¹ or radius of 312 m. The sensor also responds linearly to rotation, with a sensitivity of 6.2 fringe/°. This response is highly repeatable; linear; insensitive to slow-varying parameters, such as temperature; and promising for the detection of direction. The proposed sensor is particularly attractive for robotics, wearable medical devices, and structural health-monitoring applications.

本文首次提出了基于高相干干涉技术的七芯光纤（SCF）弯曲和旋转传感技术。在建议的方案中，从选定的纤芯形成了不同的光路，从而创建了一个非常紧凑的光纤迈克尔逊干涉仪。干涉仪由在SCF上制造的用于光束分离/耦合元件的直列锥形结构和用作反射元件的法拉第旋转镜组成。由于与中性轴的距离不同，因此在参考和传感磁芯上会施加不同的应变。使用条纹计数技术解决了由应变变化引起的这两个干涉仪臂之间的相位差。该传感器对曲率和旋转测量极为敏感，灵敏度为629条纹/米^-1和6.2条纹/°。该传感器能够检测0.0032 m ^-1的最小曲率或312 m的半径。该传感器还对旋转做出线性响应，灵敏度为6.2条纹/°。这种反应是高度可重复的。线性 对缓慢变化的参数（例如温度）不敏感；并有望发现方向。所提出的传感器对于机器人技术，可穿戴医疗设备和结构健康监测应用特别有吸引力。