Research On Relationship Between Losses Of Fiber Connector And Geometrical Parameters & Connection Force

With the development of optical fiber communication technology which has the characteristics of high bandwidth and ultra-high speed, the requirement for communication transmission quality will be more stringent in the future. As one of the optical passive components, the optical fiber connector has been widely used in the optical communication system to realize the connection between two fibers. However, the joint of the optical fiber connector is influenced by environment easily in optical network. Therefore, the optical transmission quality of optical fiber connector is mainly depended on the status of connection. In this paper, we have researched the mechanism and influence law of various factors on coupling loss in the optical network communication system by theoretical analysis, finite element simulation and experiment validation method.Firstly, based on the basic principle of optics, we have got some key factors about the ferrule which have been optimized by detailed theoretical analysis and deduction. The study shows show that when the transverse displacement of single mode fiber is less than 0.7 μm, the insertion loss will be in the range between 0 dB and 0.1 dB. Without considering the fiber end face grinding quality, only when the air-gap of end face appeared in fiber connector is less than 0.1 μm, the insertion loss will be under 0.13dB. Also the surface geometrical parameters (including the radius of curvature of end face, vertex offset etc) of ferrule need to meet some requests, just additional connection loss will be reduced. The curvature radius of ferrule should be controlled within the range of 17mm to 20mm and the vertex offset of end face for ferrule should be less than 50μm so that the insertion loss will be controlled within 0.13dB. Regardless of air-gap and lateral displacement, the influence of grinding metamorphic layer (damage layer of high refractive index) occurring in the process of end face grinding is the main factor which has a great effect on return loss of connector. We found that the refractive index of metamorphic layer compared with the refractive index of fiber core change smaller, the return loss is higher. Therefore, in order to achieve a return loss of 60dB, the refractive index and the thickness of metamorphic layer should be 0.01 μm and 1.475 respectively.Secondly, we study the compensation of axial force for the optical end face with air-gap by using ABAQUS finite element simulation software. Moreover, we have analyzed indirectly the influencing factors on joint loss of fiber connector through the relationship between geometrical parameters of end face and air-gap. The simulation results show that the axial force should be controlled in the range of 0.92N to 1.4N, the joint loss will be reduced by exerting axial force.Finally, we build a test system for researching on the insertion loss and return loss which are influenced by air-gap and axial force. The experiment results are well in accord with the results from finite element simulation by ABAQUS and theoretical analysis. Furthermore, it will provide some theory reference for optimization of optical fiber connection in the future.