谐振式光纤陀螺空间光学谐振腔耦合效率分析与设计

Analysis and design of coupling efficiency in space coupling cavity for resonator fiber optic gyroscope

谐振式光纤陀螺中光纤谐振腔为关键敏感器件,新型空芯光子晶体光纤具有高环境适应性和小弯曲半径等特性,有利于陀螺降低寄生噪声及小型化。针对传统熔接耦合损耗大问题,提出了基于球透镜的空间耦合谐振腔方案,分析了该谐振腔方案精度的影响因素,并给出腔内光纤耦合效率要求。根据矩阵光学理论和高斯光束传输特性推导了系统传输矩阵,并基于模场匹配法给出了系统耦合效率模型。根据导航级陀螺腔内光纤耦合效率高于87%的要求,将系统装配误差分解,完成了系统参数对装配容差的影响分析以及系统参数设计、优化及装调建议。空芯光子晶体光纤耦合误差验证实验表明,参数设计优化前后耦合效率接近,优化使得光纤径向和倾斜容差提高了约16%和100%,从而降低了装配难度,提高了系统稳定性。理论分析与实验验证基本吻合,为其工程化应用奠定了基础。

The fiber cavity is the key sensitive device in the resonator fiber optic gyroscope(RFOG).The new hollow core photonic crystal fiber(HCPCF)has the characteristics of high environmental adaptability and small bending radius,which is conducive to reduce the parasitic noise and miniaturize the gyroscope.In order to solve the problem of large coupling loss in traditional fusion splices,a spatial coupling resonator based on spherical lens is proposed.The factors affecting the accuracy of the resonator are analyzed,and the coupling efficiency requirements are given.According to the theory of matrix optics and the Gaussian beam transmission characteristics,the transmission matrix of the system is derived,and the coupling efficiency formula is given based on the mode field matching model.According to the requirement that the fiber coupling efficiency of the fiber cavity in the navigation-grade gyro is higher than 87%,the system assembly errors are decomposed,and the influence analysis of system parameters on assembly tolerance is completed,as well as the suggestions for system parameter design,optimization and assembly adjustment.The coupling error verification experiment of hollow core photonic crystal fiber shows that the coupling efficiency before parameter design optimization is close to that after optimization,and the radial and tilt tolerances of fiber are increased by 16%and 100%by optimization,thus reducing the assembly difficulty and improving the system stability.The theoretical analysis is consistent with the experimental verification,which lays a foundation for its engineering application.