| 摘要 |
PURPOSE:To minimize the structural scattering of an optical fiber, by regulating the rate and temperature of vitrification within specific ranges in the thermal vitrification of a porous cylindrical preform deposited by VAD process. CONSTITUTION:The porous cylindrical preform 2 is manufactured by depositing SiO2, GeO2, P2O5, etc. by flame hydrolysis. The obtained porous preform 2 is passed downward through the heating zone 3 in the furnace 1 at a rate of >=1.5mm./min and <=2.5mm./min, and at the same time, the furnace is controlled to regulate the temperature of the point B of the surface of the preform at the center of the heating zone to >=1,600 deg.C and <=1,650 deg.C. The vitrification of the porous preform 2 begins at the point A or there-about by this process, the vitrification conditions are controlled at the point B, and the preform is cooled and solidified successively between the point B and the point C to complete the vitrification of the porous preform 2. |
