光纤涂敷层对光纤裂缝传感器分布式监测能力的影响

Effects of optic fiber coatings on multiplexing capability of distributed fiber optic crack sensors

基于混凝土模型试验,对涂敷层的传感光纤的裂缝复用能力进行了定量分析,得到了传感光纤和工程结构裂缝夹角在30°,45°,60°时的复用能力与裂缝宽度的关系曲线。对由软性材料构成的光纤涂敷层来说,光纤的复用能力随涂敷层厚度的增加而增大,在与裂缝夹角成45°时,二次涂敷粗光纤的复用能力约为细光纤的5倍,表明光纤敷层对光纤裂缝监测的复用能力具有较大影响。对这种影响的机理进行了理论分析和试验研究,发现当混凝土开裂时,光纤沿混凝土界面的滑移是光纤涂敷层影响光纤裂缝复用能力的主要原因,在光纤与裂缝夹角成45°时,这一影响占60%以上。

Based on the experiments on concrete samples, the multiplexing capability of the sensing optic fibers with different coatings is analysed quantitatively. The relationships between the optic fiber＇s multiplexing capability and crack width at the crack orientation of 30°, 45° and 60° relative the optic fiber are obtained. For the coatings made of soft materials, the optic fiber＇s multiplexing capability increases with the enlargement of its coating＇s thickness. At the crack orientation of 45°, the thick optic fiber＇s multiplexing capability is about 5 times that of thin one, indicating the optic fiber coating has great effects on the multiplexing capability of the fiber optic crack sensing. The mechanical and optic mechanism of this effect is investigated through the theoretical analysis and experiments. It is found out that the optic fiber slides along the interface within concrete as a crack arises is the major cause of the optic fiber coating＇ s affecting the multiplexing capability of the fiber optic crack sensing, and at the crack orientation of 45°, this effect accounts for about more than 60%.