A light intensity-modulated optical fiber sensor for continuous level measurement is proposed and demonstrated. The sensor is constructed by vertically arranging groups of fibers on the oblique surface which reflects all the incident light when the fibers are in the air but a small proportion of light when the fibers are immersed in the liquid. In order to implement easy modulation and detection, the angle of oblique surface is specially designed to get the maximum intensity modulation according to Fresnel reflection. The fiber groups consist of emitting and receiving fibers, which are tightly fixed to make it easy to detect reflected light based on side coupling effect. The calculation model of the oblique structure and the light path simulation by finite element analysis are used to optimize the oblique angle and prove the feasibility of the sensor. Gradient level experiments and stability tests in the laboratory indicate that the sensor has high sensitivity of 0.21mW/cm, superior resolution and good stability.

中文翻译：

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基于斜端面耦合光纤的反射光强调制连续液位传感器

提出并演示了一种用于连续物位测量的光强度调制光纤传感器。该传感器由垂直排列在斜面上的纤维组构成，当纤维在空气中时反射所有入射光，而当纤维浸入液体中时反射一小部分光。为了实现简单的调制和检测，斜面的角度经过特殊设计，根据菲涅耳反射得到最大的强度调制。光纤组由发射光纤和接收光纤组成，它们紧密固定在一起，利用侧耦合效应便于检测反射光。采用斜结构计算模型和有限元分析光路仿真，对斜角进行优化，证明了传感器的可行性。实验室梯度水平实验和稳定性测试表明，该传感器具有0.21mW/cm的高灵敏度、优越的分辨率和良好的稳定性。