MANUFACTURE OF GLASS PROFORM FOR OPTICAL FIBER

摘要

PURPOSE:To facilitate the control of the profile of a glass perform, by placing a preliminary heating furnace controlled at a temperature range to effect the incomplete solidification of the porous perform between the growing point of the porous perform and the main furnace for converting the preform to a transparent glass. CONSTITUTION:A porous preform for an optical fiber is grown longitudinally, and converted to a transparent glass continuously by using a main furnace 28 placed coaxially with the preform. A preliminary heating furnace 36 controlled to a temperature to effect the incomplete solidification of the porous preform is placed between the growing point of the preform and the main furnace 38. The preform is dehydrated and its refractive index is controlled by the dissipation of the dopant in the preliminary heating furnace 36 in an atmosphere containing an inert gas and a dehydration agent to reduce and dissipate the dopant. Thereafter, the preform is converted to transparent glass by the main furnace 38 in an atmosphere containing an inert gas and the dehydration agent.