Based On Optical Fiber Brillouin And Grating Multi-scale Sensor Network Technology

With large infrastructure facilities are continuously build, the construction of the project under construction quality monitoring and on existing engineering of health diagnosis technology demand is higher and higher. How to effective monitoring, identification, positioning and calibration of structural system is a key problem to Structural health monitoring. Brillouin Optical time-domain Analysis technology (BOTDA) is a kind of stimulated brillouin backscattering principle of distributed Optical Fiber strain sensor technology; it has broken the traditional point sensing concept and could achieve real sense of continuous distributed monitoring, its temperature and strain measurement to achieve the monitoring accuracy, sensing the length and the spatial resolution higher than other sensing technology. Therefore BOTDA has become the international developed countries developed large civil engineering health diagnosis of high-end sensing technology. FBG (Bragg grating Gating) is a new kind of Optical element, due to itself monitoring accurate and mature, which has been widely used in large structures. This paper, mainly focusing on monitoring of BOTDA technique, does a series of research work on the following:Firstly introduce the detail of the basic principle of distributed optical fiber sensing and BOTDA basic principle, BOTDA of distributed optical fiber strain and temperature sensing properties have been studied, analyzing brillouin frequency shift relation with temperature and strain. Working out the naked single-mode optical fiber temperature/strain sensitivity coefficient and encapsulates a kind of optical fiber temperature sensor.Distributed optical fiber sensors compared to traditional sensing methods have more advantages, main Performances can obtain the measured spatial distribution of the Status and information over time.It's could continuously measure environmental parameters throughout the entire fiber length distribution along the fiber.In theory, it can see measured result as a function of the length of fiber position, which can get any size resolution. One fiber can be used to replace the traditional form of hundreds of dot-matrix array of sensors, greatly reducing the monitoring costs; FBG monitoring is precision, but monitoring cost is expensive, relatively independent of measurement points, it is difficult to grasp the overall structure of variation. Two monitoring means can be considered to use, exceed and give full play to their advantages. Distributed fiber and FBG can be used in structure simultaneously. In the structure of key parts install distributed fiber optic sensors and FBG at the same time. In the structure of non-critical positions layout distributed fiber optic sensors only to monitor the general trend, the results show that the joint monitoring between the two are good.Finally, combining a real project "Development of bridge construction-fabricated continuous prestressed concrete box beam" unites using of distributed BOTDA and large-scale FBG monitoring and take the numerical simulation analysis of prestressed box beam. Experimental results show that the FBG used in large-scale monitoring of large-scale structure still has a very good accuracy; Joint use of both can be better monitored structure. Finally, based on the distributed strain derived the theoretical formula for solving structural deflection, the experimental results show that the formula can effectively solve the structural deformation.