OVER CLADDING APPARATUS USING HEATING FURNACE AND PURGING METHOD IN OVER CLADDING

摘要

Provided are an overcladding apparatus, which prevents the oxidation by influx of exterior air and the attachment of foreign matters, and a purging method for effectively purging a gap between a heating furnace and a glass tube upon overcladding. The overcladding apparatus comprises an optical fiber preform rod(20), which includes a core and a clad, and substantially extends in a straight line to a longitudinal axis; a glass tube(10) having an inner diameter greater than an outer diameter of the preform rod in order to accommodate the preform rod; a cylindrical heating furnace(100) for surrounding the glass tube at a certain gap and heating an outer surface of the glass tube while relatively shifting along the longitudinal axis of the glass tube; a purging gas supply unit(130) for supplying purging gas into a gap between the heating furnace and the glass tube toward a rear end of the relative shift direction; and a sealing unit(140) for sealing a gap between a front end of the relative shift direction and the glass tube.