Abstract An optical fiber crack sensor based on macro-bending loss for detecting the crack opening displacement (COD) is developed in this paper. The sensor incorporates an extremely simple design, light source and detector. The decrease of the light intensity with displacement variation was reported. The verification experiments to the sensing principle were conducted. The sensor shows a response over a wide range of 212.1 and 87.9 mm in shrinkage and elongation, respectively. The response has two distinct nonlinear regions. A slab cracking model was established and random COD conditions were simulated. It is found that the predicted displacements of the sensor are nearly identical to the measured COD, and both relative errors are basically within 10%. Additionally, the sensor can be connected in series on one optical link to realized quasi-distributed monitoring; if crack shrinkage or elongation can be known in advance, the sensor by designed properly has a larger range of 300 mm. This optical fiber crack sensor is characterized by large measurement range, simple design, high flexibility and low economic cost, which shows a promising application in the field of displacement monitoring.

中文翻译：

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一种用于大位移范围的简单宏弯损耗光纤裂纹传感器

摘要 本文研制了一种基于宏弯损耗的用于检测裂纹张开位移（COD）的光纤裂纹传感器。该传感器采用极其简单的设计、光源和检测器。报告了随着位移变化的光强度降低。对传感原理进行了验证实验。该传感器在收缩率和伸长率方面分别在 212.1 和 87.9 毫米的宽范围内显示出响应。响应具有两个不同的非线性区域。建立板坯开裂模型并模拟随机COD条件。发现传感器的预测位移与实测COD几乎一致，两者的相对误差基本在10%以内。此外，传感器可串联在一条光链路上，实现准分布式监测；如果可以提前知道裂纹收缩率或伸长率，则设计合理的传感器的范围更大，为 300 mm。该光纤裂纹传感器具有测量范围大、设计简单、灵活性高、经济成本低等特点，在位移监测领域具有广阔的应用前景。