METHOD FOR MANUFACTURING OPTICAL FIBER PREFORM

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PROBLEM TO BE SOLVED : To provide a method for manufacturing an optical fiber preform, capable of preventing the core central part of an optical fiber from being a high refractive index in order to prevent deterioration of the effective core cross section of the optical fiber. SOLUTION : The method for manufacturing an optical fiber preform comprises the steps of : supplying at least SiCl4 and O2 into a quartz tube by a CVD method and depositing glass fine particles in the quartz tube while heating the outside of the quartz tube by a heat source; exhausting a solution including at least a rare earth element from the inside of the quartz tube and drying the glass fine particles after impregnating the glass fine particles with the solution; increasing a heat source temperature to sinter the glass fine particles and transparently vitrifying the sintered product; supplying at least O2 and SiCl4 in the quartz tube, further increasing the heat source temperature while controlling internal pressure in the quartz tube and crushing one end of the quartz tube; and supplying at least O2 into the quartz tube, venting it in the vicinity of the open end of the quartz tube, traversing the heat source in an axial direction of the quartz tube while controlling the internal pressure of the quartz tube and solidifying the quartz tube by reducing the diameter of the quartz tube. COPYRIGHT : (C)2014, JPO&INPIT