| 摘要 |
PURPOSE:To efficiently minimize chlorine and obtain the titled fiber having low transmission loss, by thermally dechlorinating a porous glass preform in an atmosphere of a specific compound, dehydrating the resultant preform in an atmosphere containing a halogen other than the chlorine, transparently vitrifying the dehydrated preform and melt spinning the resultant preform. CONSTITUTION:A metallic chloride containing SiCl4, together with a gas, such as H2, O2 and Ar, etc., is fed into a multitubular burner and subjected to thermal oxidation or flame hydrolytic reaction by a VAD method to deposit fine glass particles on the tip or outer periphery of a starting member and provide a porous glass preform, which is then heat-treated and dechlorinated in an atmosphere of a compound, such as H2O, D2O, NH3 or SiH4, capable of reacting with Cl to form a chloride. The resultant dechlorinated preform is subsequently heated and subjected to dehydration treatment in an gaseous atmosphere, such as a mixed gas of SiF4 and He, containing a halogen except the Cl. The obtained dehydrated preform is then heat-treated in an atmosphere of only He gas to completely purge the SiF4, etc., and temperature is further increased to transparently vitrify the preform. The vitrified preform is subsequently melt spun to afford the titled fiber having <=0.5wt.% atomic ratio of Cl atoms within the light transmitting region. |
