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一、引言为了扩大通信容量,光纤设计者希望制造出具有最佳折射率分布的光纤。判断光纤的折射率分布是否最佳,必须从测得的折射率分布曲线计算出分布指数α的数值。α值对多模光纤传输带宽有着决定性的影响,同时光纤最大理论数值孔径与稳态有效数值孔径之间的比例系数K_α值仅取决于α,考虑到斜射光线时,斜射光线的数值孔径与子午光线数值孔径间的关系也与α有关。无论用反射法、近场法、干涉法还是别的什么方法测出的折射率分布,或是扫描
I. INTRODUCTION In order to expand the communication capacity, optical fiber designers want to create the optical fiber with the best refractive index distribution. Judging whether the refractive index distribution of the optical fiber is the best, the value of the distribution index α must be calculated from the measured refractive index distribution curve. The α value has a decisive influence on the transmission bandwidth of multimode fiber. Meanwhile, the ratio coefficient K_α between the theoretical maximum theoretical aperture and the steady-state effective numerical aperture depends only on α. Considering the oblique light, the numerical aperture of oblique light and the meridional The relationship between the numerical aperture of light is also related to α. Reflectance, near-field, interference or any other method of measuring the refractive index distribution, or scanning