聚焦法是一种较为简单而通用的测试光纤和预制棒折射率分布的方法.参考Marouse等工作,组成本文的测试系统,具有一定特色.对多模、单模样品均进行了实测,取得了较满意的结果.聚焦法是在散射法的基础上提出的.由于光纤和预制棒的折射率在径向有微小的变化,因此将光横向投射在纤或棒上,纤或棒相当于有弱聚焦作用的透镜. Focused method is a relatively simple and general method for testing the refractive index distribution of optical fiber and preform rod.Referring to the work of Marouse and others, the test system which is composed of this paper has certain characteristics.All the multimode and single-mode samples were measured and obtained Satisfactory results. Focusing method is based on the scattering method based on the optical fiber and preform due to the refractive index changes slightly in the radial direction, so the light is projected laterally on the fiber or rod, fiber or rod equivalent to a Weak focusing lens.