镀膜长周期光纤光栅耦合系数的研究

The Study of Coupling Coefficient of Coated Long Period Fiber Grating

给出了镀膜长周期光纤光栅芯层模式和包层模式耦合的耦合系数的详细表达式,应用此表达式对镀膜长周期光纤光栅的耦合系数的特性进行了较为详细的研究。研究发现:1)同次模式的耦合系数随薄膜厚度变化而变化,在某些厚度下,奇次模式耦合的耦合系数与偶次模式耦合的耦合系数几乎相等;2)在某些厚度处,交流耦合系数会有跳变发生;3)交流耦合系数随环境折射率的变化而变化,并且当环境折射率靠近光纤包层折射率时交流耦合系数会有急剧跳变发生。

In this paper,the formula of coupling constant of coated long period fiber is given,and the characteristics of coupling constant of coated long period fiber grating was studied in details with this formula.The result shows：1） The coupling constant of the same mode changes with the change of film thickness,and the coupling constant of odd modes and even modes are almost equal in some thickness; 2） In some thickness,the exchange coupling constant will jump; 3） AC coupling constant changes with ambient refractive index changes,and the coupling constant will skip when the ambient refractive index close to the fiber cladding refractive index.