Vita P D, Vannucci R
Appl Opt. 1976 Nov 1;15(11):2765-72. doi: 10.1364/AO.15.002765.
The power launching into multimode optical fibers with any profile of refractive index is analyzed by means of the geometrical optics. First two formulas of the numerical aperture are obtained, one including and the other excluding the contribution of leaky skew rays. Each one of these two numerical apertures has a certain domain of application, and the launching efficiencies from incoherent sources into optical fibers are calculated in both cases. Useful formulas and plots of launching efficiency for a few refractive index profiles are given. Finally the power losses due to source-fiber coupling errors (separation, displacement, or misalignment) are evaluated, and an interesting effect of virtual lengthening of the fiber is found.
利用几何光学方法分析了以任意折射率分布发射到多模光纤中的光功率。首先得到了数值孔径的两个公式，一个包含泄漏斜光线的贡献，另一个不包含。这两个数值孔径中的每一个都有一定的应用范围，并分别计算了非相干光源向光纤的发射效率。给出了几种折射率分布的发射效率的实用公式和图表。最后评估了由于源 - 光纤耦合误差（分离、位移或未对准）引起的功率损耗，并发现了光纤虚拟延长的有趣效应。
