套管辅助法测量异型预制棒折射率分布

Measurement of refractive index profile of special-shaped preform by sleeve-assistant method

基于光束扫描法的光纤预制棒折射率测试仪主要适用于直径和长度在一定范围内的圆柱形样品折射率分布的测试。提出一种套管辅助法可实现更短长度、更细直径和变直径样品的折射率测试。该方法将待测样品居中放置于一个尺寸符合测试要求的圆柱形套管内,并在套管内注入折射率匹配油,使其没过待测样品后按常规步骤进行测试。对比实验结果表明,套管辅助法与直接测量法的偏差与仪器的测量误差相当。采用套管法,获得了预制棒拉丝终止后变径区不同位置折射率的径向分布,可为拉丝过程的研究提供参考。

The refractive index profile of optical fiber preform can be measured by beam scanning method.Due to the requirements of the refractometer for the length,diameter and shape of preforms,the refractive index profile of special-shaped preforms cannot be measured directly.Thus the sleeve-assistant method is produced.A quarts sleeve is needed to expand the measuring range of the refractometer.The refractive index profile of the same round preform is measured directly by refractometer and by sleeve-assistant method respectively.And the results obtained are consistent,confirming the accuracy of the sleeve-assistant method.The refractive index profiles of the neck-down region of the preform measured confirm that the sleeve-assistant method can improve the test ability of refractometer.