Research On Optical Fiber Sagnac Interferometric Sensing System And Its Applications In Impact Monitoring

With the advantages of excellent electric insulation performance,light weight,fast response,high sensitivity,strong resistance to electromagnetic interference and resistance to corrosion,fiber sensors are gradually applied to the field of structural health monitoring and material damage detection.Fiber Sagnac interferometer has the advantages of zero optical path difference,no noise caused by the inconsistence of two sensing arms and suitable for distributed detection.It's a research hotspot in the field of AE testing.Based on the Sagnac interference principle,this paper constructed the fiber Sagnac interferometric sensing system,and studied the influence factors of the system sensitivity,temperature characteristic of the system and its application in the field of impact location.The main work includes the following aspects:Firstly,this paper designed the fiber Sagnac interferometric sensing system and wrote the graphical data acquisition and analysis software based on LabVIEW.On this basis,this paper researched the fiber Sagnac interferometric sensor system's response characteristics of the continuous excitation signal and the transient impact signal on four edges clamped aluminum alloy plate.Secondly,from the aspect of theoretical model,numerical simulation and experiment validation,this paper investigated how the factors such as initial phase of the sensing system,the length of the delaying coil,the structure and installation way of the sensor probe affect the sensitivity of fiber Sagnac interferometric sensing system.And put forward the corresponding sensitivity optimization schemes.Thirdly,this paper established the theory model that temperature how to influence the output of fiber Sagnac interferometric sensor system.Then,this paper studied temperature response characteristics of the optical fiber Sagnac interferometric sensor system by the test method.Finally,based on the fiber Sagnac interferometric sensor system,this paper studied a set of impact localization algorithm.Then,the impact area localization system based on the fiber Sagnac sensing technology was established on a steel pipe and an aluminum alloy plate.On the basis of the wavelet analysis and time difference positioning principle,this paper realized the impact location on different structures.