应用耦合模原理，用Ｍａｔｈｉｅｕ函数表示纤芯、包层为同心椭圆度的光纤中的电磁场，在适当近似条件下，求得了基模场中的偶模耦合系数表示式，并给出了截止条件下的离心率耦合系数，半长轴耦合系数曲线 The coupled-mode principle is used to represent the electromagnetic field in a fiber with concentric ellipticity by using the Mathieu function. Under proper approximation, the expression of even-mode coupling coefficients in the fundamental mode field is obtained and the cut-off conditions Under the centrifugal coupling coefficient, semi-major axis coupling coefficient curve