Method for manufacturing an optical fiber preform by MCVD

PURPOSE: A method for manufacturing an optical fiber preform is provided to minimize or even prevent the index dip phenomenon generated in the center of an optical fiber core, thereby providing optical fiber with improved optical properties such as bandwidth or polarization mode dispersion by conducting an etching process together with a condensation process, then conducting a closing process. CONSTITUTION: The method for manufacturing an optical fiber preform by means of modified chemical vapor deposition method comprises: a deposition process which forms clad(9)/core(8) deposition layers on the inside wall of a quartz tube; a condensation process in which condensation of the resulted quartz tube is carried out by heating the tube to the softening temperature or more; an etching-condensation process in which the quartz tube is heated to the softening temperature or more while feeding reaction gas for etching into the tube in order to optimize the inner diameter of the tube; a closing process in which the quartz tube of which inner diameter is optimized, is heated to the softening temperature or more to form an optical fiber preform having no inner hole.