设计并研制了一种基于LP21模式的新型光纤弯曲传感器。该传感器通过检测敷设于弹性基片上的光纤所传输的LP21模式光斑图像的旋转，实现对弯曲值的高精度测量。运用光纤耦合模理论和弹光效应求解LP21的模方程，证明该模式具有弯曲无关和扭转线性的特性，并检验了光纤弯曲传感器对不同结构参数和环境温度下的性能。实验结果与理论分析相吻合，证实该传感器具有较大的线性动态范围，温度稳定性高，且能辨识弯曲方向。

A novel fiber optic bending sensor based on LP21 mode is developed. A fiber affixed onto an elastic substrate is used to sense bending angles in the real time by measuring rotation of LP21 mode spot image. Theoretical analysis is given by fiber coupled-mode theory combining with elastic-optic theory. Relation between spot-rotation angle and sensor bending angle for different structures and temperatures is tested. The experimental results agree with theoretical analysis and validate the accuracy of the sensor. The sensor is temperature-immune and can detect bending direction as well as bending angles with a large dynamic range.