THERMAL TREATMENT OF BASE MATERIAL FOR DOPED QUARTZ SERIES POROUS GLASS

摘要

PURPOSE:To obtain a uniform clad layer of controlling the transferring velocity of a base material for the doped quartz series porous glass in the specified value in case of passing the base material through the inside of a furnace contg. a halogeno- compd. and He to make it transparent and forming a synthesized clad layer. CONSTITUTION:A base material 6 for the doped quartz porous glass is introduced into a furnace core pipe 2 of an electric furnace in the atmosphere contg. a halogeno- compd. (e.g. SOCl2) and He and heat-treated to vitrify it transparently and simultane ously a synthesized clad layer 9 is formed. In this case, while a tip of the base material 6 is held at approximately <=1,000 deg.C in the inside of the core pipe 2, the base material 6 is trnasferred in the high velocity toward the high-temp. part in the core pipe 2 and when the temp. of the tip of the base material 6 exceeds 1,000 deg.C, the transferring velocity of the base material 6 is made to the specified velocity of <=10cm/hr. The transparent vitrification of the base material 6 is performed and simultaneously the uniform synthetic clad layer 9 is formed by transferring the base material 6 in the transferring velocity and passing it through the high-temp. part of the inside of the furnace core pipe 2.