Leal-Junior Arnaldo, Frizera Anselmo, Marques Carlos
Graduate Program of Electrical Engineering, Federal University of Espirito Santo, Vitória 29075-910, Brazil.
I3N & Physics Department, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
Sensors (Basel). 2020 May 27;20(11):3026. doi: 10.3390/s20113026.
We report the development and characterizations of a fiber Bragg grating (FBG) sensor coated with different ultraviolet (UV) curable resins. The UV-curable resins were applied on the fiber after the FBG inscription and cured with an UV lamp. One set of samples used the NOA 68 resin and the other used NOA 88. The samples were characterized with respect to the temperature, moisture absorption and strain response. Furthermore, in order to understand the influence of the resin coating on the optical fiber's mechanical properties, tensile tests were performed with the samples. Results show that all samples presented negligible sensitivity to moisture absorption in the 50-min long tests with the fibers immersed in a container filled with distillated water. Regarding the temperature responses, the coated FBGs presented higher sensitivity (13.84 pm/°C for NOA 88 and 12.76 pm/°C for NOA 68) than the uncoated FBGs due to the thermal expansion of the coatings. In the strain tests, all coated and uncoated samples presented similar sensitivities, but with a larger strain range applied for the coated samples (strains higher than 5500 µε) when compared with the uncoated samples (3500 µε). Moreover, the stress-strain curves of the coated samples indicated a Young's modulus one order with magnitude lower than the one of the uncoated silica fiber, where the lowest Young's modulus is 3.84 GPa and was obtained with the NOA 68 coating, which indicates the possibility of obtaining highly sensitive pressure and force sensors.
我们报告了一种涂覆有不同紫外（UV）固化树脂的光纤布拉格光栅（FBG）传感器的研制与特性表征。在写入FBG之后，将UV固化树脂涂覆在光纤上，并用UV灯进行固化。一组样品使用NOA 68树脂，另一组使用NOA 88树脂。对样品进行了温度、吸湿和应变响应方面的特性表征。此外，为了了解树脂涂层对光纤机械性能的影响，对样品进行了拉伸试验。结果表明，在将光纤浸入装有蒸馏水的容器中进行的50分钟长时间测试中，所有样品对吸湿的敏感度都可忽略不计。关于温度响应，由于涂层的热膨胀，涂覆FBG的温度敏感度（NOA 88为13.84 pm/°C，NOA 68为12.76 pm/°C）高于未涂覆的FBG。在应变测试中，所有涂覆和未涂覆的样品呈现出相似的敏感度，但与未涂覆样品（3500 με）相比，涂覆样品的应变范围更大（应变高于5500 με）。此外，涂覆样品的应力-应变曲线表明，其杨氏模量比未涂覆的石英光纤低一个数量级，其中最低杨氏模量为3.84 GPa，是使用NOA 68涂层获得的，这表明有可能获得高灵敏度的压力和力传感器。
