Deep lateral displacement sensing experiment for rod–fiber coupling structure based on macrobending loss

Abstract

Deep lateral displacement is an important index for evaluating the safety of geological bodies. The short range and low resolution of sensor monitoring often lead to large errors and inaccurate positioning in monitoring deep lateral displacement of geological bodies. Based on the principle of macrobending loss of a single-mode fiber, a rod–fiber coupling structure is designed in this study using a single-mode fiber and a highly elastic rubber rod to measure a large lateral displacement of a geological body. By analyzing the dispersion degree of the macrobending loss caused by loading displacement, the effects of pitch, diameter, and loading position on the measuring sensitivity and axial resolution of the rod–fiber coupling structure are investigated. Through a comparative experiment, the stability and measurement accuracy of the rod–fiber coupling structure are studied. The experimental results show that the lateral displacement of the rod–fiber coupling structure corresponds to the macrobending loss of the single-mode fiber; the relative measurement error of lateral displacement is within 10% for different lateral deformations. The proposed rod–fiber coupling structure provides powerful support for efficient, high-resolution monitoring of large lateral displacements of geological bodies.