MANUFACTURE OF OPTICAL FIBER BASE MATERIAL

摘要

PURPOSE:To improve the reproducibility of band characteristics of a multi-mold graded type optical fiber and the yield of broad band fiber by fluctuating periodically the flow rate of gaseous raw material in case of manufacturing the optical fiber base material by a gas phase axial accumulation method. CONSTITUTION:Gaseous raw material such as silicon chloride plus germanium chloride and gaseous fuel such as oxygen plus hydrogen are fed into a quartz pipe burner 8 and the gaseous raw material is allowed to react in the oxyhydrogen flame to produce the fine glass powder and the porous base material 3 is formed by accumulating it on a tip of a target 1. In this case, the flow rate of the gaseous raw material is periodically fluctuated while the accumulation of the fine glass powder is continued and the accumulating conditions of the glass powder of the tip of the target 1 are changed and thereby the distribution index alpha of refractive index of an optical fiber base material after the vitrification or the maximum specific refractive index variance is changed in the lengthwise direction. Thereafter, the obtained porous base material 3 is heated and vitrified to obtain the aimed optical fiber base material.