| 摘要 |
PURPOSE:To prepare a parent material for optical fiber glass contg. no fluorine in the core part by heating a deposited body of fine glass particles having a part corresponding to the core having high concentration of dopant in the outermost peripheral part in gaseous atmosphere contg. fluorine-contg. gas. CONSTITUTION:The concn. of dopant in the outermost peripheral part, and pref. the bulk density, of a part corresponding to the core of a deposited glass body of optical fiber glass, are adjusted to a higher value than those of the internal part. Then, a part corresponding to the clad is formed, and the deposited body is made transparent by heating in a sintering furnace. In the stage of this heat- treatment, the profile of the deposited body is heat-treated to adjust the profile in the atmosphere contg. pref. chlorine-contg. gas, then it is further heated in the atmosphere contg. fluorine-contg. gas at pref. 1,150+ or -150 deg.C. By this treatment, a parent material for optical fiber glass having large difference of specific refractive index between the core and the clad comprising a core contg. no fluorine and a clad contg. fluorine is obtd. |
