介绍了用准相干干涉法测量光纤群折射率的方法。通过准相干干涉定位 ,用精密光栅数显系统测长 ,由计算机采集并处理数据获得一段短光纤的光学长度 ,然后利用常规精密测长手段测得其几何长度 ,从而得到光纤的群折射率。实验结果及误差分析得出 :测量不确定度优于 7× 10 -5(2σ)。 The method to measure the refractive index of optical fiber group by quasi-coherent interferometry is introduced. By means of quasi-coherent interferometric positioning, the length of the optical fiber is measured by a precision grating digital display system. The optical length of a short optical fiber is acquired and processed by the computer. Then, the geometric length of the optical fiber is measured by a conventional precision length measuring method to obtain the group refractive index of the optical fiber. The experimental results and error analysis show that the measurement uncertainty is better than 7 × 10 -5 (2σ).