METHOD FOR IMPROVING THE SEALING INTERFACE IN PROCESS OF OVERCLADDING AND APPARATUS FOR THE SAME

摘要

A method and a device for improving a joined interface in an overcladding process are provided to reduce foreign matter or the residual bubbles on the joined interface by cleaning and drying an inner peripheral surface of a quartz tube before inserting a base metal rod into the quartz tube joined with an auxiliary tube. An overcladding process for producing an optical fiber preform of a large diameter by inserting a quartz tube(10) into an optical fiber base metal rod of a small diameter is composed of steps for preparing the quartz tube with an inner diameter larger than an outer diameter of a base metal rod to contain the optical fiber base metal rod; joining an auxiliary tube(20) with the thickness larger than or the same as the inner diameter of the quartz tube and smaller than the outer diameter of the quartz tube, to one longitudinal end of the quartz tube; etching the inner peripheral surface of the quartz tube by cleaning the peripheral surface of the quartz tube joined with the auxiliary tube, with HF(Hydrofluoric acid) aqueous solution; removing the residual HF aqueous solution by cleaning the etched inner peripheral surface of the quartz tube with the distilled water; vertically fixing one end of the quartz tube joined with the auxiliary tube on a support unit(80) and sealing the other end of the quartz tube with a sealing unit(50) having a gas injection port(52); and drying the inner peripheral surface of the quartz tube by injecting inert gas through the gas injection port for the predetermined time.