Furnace for heating highly pure quartz preform for optical fiber.

摘要

The furnace comprises a cylindrical furnace body (5), a heater (4) installed in said furnace body (5) and a muffle tube (3) installed inside said heater (4) to separate a heating atmosphere from said heater (4). The muffle tube (3, 34, 35, 36) is made of highly pure carbon and coated with a gas impermeable carbon. In particular the highly pure carbon muffle tube may be coated on the outside with a gas impermeable pyrolytic or vitreous carbon layer. The furnace prevents contamination of the preform with impurities and has a long life.