Abstract A low-cost liquid level sensor capable of continuous liquid level sensing is proposed in this work. The sensor is based on twisted tapered plastic optical fibers (POFs) which is fabricated by twisting the tapered POFs around each other. The tapered structure could enhance the evanescent field and the light transmission from one POF to the other. The changes of liquid level can lead to the variations of light intensity at two output ends of the probe and by monitoring the changes of the coupling ratio, the liquid level can be measured. Experimental results show that a linear response with the sensitivity of 0.65%/mm and response time of 3.2 s is obtained when the probe is with active fiber diameter of 150 µm and the passive fiber diameter of 250 µm. In addition, the influences of tapered POFs diameters, the liquid refractive index and the temperature on the sensing performance are investigated, and the repeatability and the dynamic performance for the probe are also tested.

中文翻译：

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用于连续液位传感的扭曲锥形塑料光纤

摘要 本文提出了一种能够连续感测液位的低成本液位传感器。该传感器基于扭曲的锥形塑料光纤 (POF)，它是通过将锥形 POF 相互缠绕而制成的。锥形结构可以增强渐逝场和从一个 POF 到另一个 POF 的光传输。液位的变化会导致探头两个输出端光强的变化，通过监测耦合比的变化可以测量液位。实验结果表明，当探头的有源光纤直径为150 µm，无源光纤直径为250 µm时，获得了灵敏度为0.65%/mm、响应时间为3.2 s的线性响应。此外，锥形 POF 直径的影响，