绞合式光纤应变传感器

研究了一种可用于工程结构状态监测的本征型强度调制光纤应变传感器，由两根以上多模光纤相互绞合形成，分析了该传感器的应变传感原理，得到其既能测量拉应变，又有测定压应变的结论，传感器对应变的响应具有良好的线性和重复性、灵敏度高、无迟滞现象，对钢筋拉应变、混凝土压就矿业的实验结果与理论分析一致，表明该传感器是适合土木工程测量、结构状态监测等方面的较为理想的光纤传感器。

TWISTED OPTICAL FIBER STRAIN SENSOR

This paper presents a novel intrinsic optical fiber strain sensor based on intensity modulation for structural states monitoring in civil engineering, whose sensing element is formed directly on the multi-mode fibers by twisting two or more fibers together. Compared with conventional phase interferometric optical fiber sensor and intensity modulated optical fiber microbending sensors, the advantages of this kind of twisting optical fiber sensor is evident: its configuration is very simple and its operation is very facile, it is easy fabricated and it is much sturdy and portable. Based on the mechanism of optical loss in microbending fibers and analysis of Material Mechanics, this paper analyses in detail the sensing principle of this new class fiber optic sensor and gives the diagram of the relationship of the loss of optical power and the axial strain on the sensor. The analysis and calculation shows that this kind of sensor can detect both tensile and compressive strains and stresses, and the response of twisting optical fiber sensor is of excellent linearity, repeatability, sensitivity, cyclic endurance and no measurable hysteresis. Based on above theoretic analysis and calculation, several optical fiber strain sensors are manufactured by twisting three common multi-mode fibers together and tested in detail. The experimental results in testing steel tension and concrete compression are in good agreement with theoretical analysis, and at the same time, the experiment also shows the good thermal stability of this kind of sensor. This new class fiber optic sensor is ideal for measuring and monitoring mechanical structures in smart civil engineering material and structures.