Brinkmeyer E
Appl Opt. 1979 Mar 15;18(6):932-7. doi: 10.1364/AO.18.000932.
A simple nondestructive method is described for determining the spot size omega(0) (width of the fundamental mode)-one of the most important quantities to characterize monomode optical fibers. The theory involves the definition of effective values of core radius and normalized frequency. Thereby, graded-index fibers can be replaced by equivalent step-index fibers. The experiment consists in illuminating the fiber perpendicularly to its axis and determining the position of the first minimum in the diffraction pattern. In this way, just one measurement yields omega(0) regardless of the index profile and for any operating wavelength, provided the cutoff wavelength is known.
本文描述了一种简单的无损方法，用于确定光斑尺寸ω(0)（基模宽度），这是表征单模光纤的最重要参数之一。该理论涉及芯半径和归一化频率有效值的定义。由此，渐变折射率光纤可以用等效的阶跃折射率光纤代替。实验包括垂直于光纤轴照射光纤，并确定衍射图样中第一个最小值的位置。这样，只要截止波长已知，无论折射率分布如何，对于任何工作波长，仅通过一次测量就能得出ω(0)。
