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用透射式微分干涉法测量光纤内部折射率分布,其原理是利用旋转检偏器对测量光束进行调制,从相位分布和光程分布中计算出折射率分布。其中,从光程分布中解算出折射率分布的算法是关键。讨论了该算法的数学模型,推导了测量公式,并对算法的稳定性和误差进行了分析。利用自行研制的系统对渐变折射率分布光纤进行实测,与在NR 9200光纤测量仪上的结果进行了比较,对主要误差源进行了分析和计算机模拟。实测和模拟计算结果表明,该算法原理正确,系统稳定,测量精度优于10-3,完全可以用来测量光纤折射率分布。
Transmission differential inference method is used to measure the internal refractive index distribution of optical fiber. The principle is that the measuring optical beam is modulated by a rotating analyzer, and the refractive index distribution is calculated from the phase distribution and optical path distribution. Among them, the algorithm of calculating the refractive index distribution from the optical path distribution is the key. The mathematical model of the algorithm is discussed, the measurement formula is deduced, and the stability and error of the algorithm are analyzed. The graded-index optical fiber was measured by a self-developed system and compared with the results obtained on the NR 9200 fiber optic measuring instrument. The main error sources were analyzed and the computer simulation was carried out. The measured and simulation results show that the algorithm is correct in principle, the system is stable and the measurement accuracy is better than 10-3, which can be used to measure the refractive index of fiber.