| 摘要 |
PROBLEM TO BE SOLVED: To obtain a single-mode optical fiber excellent in wavelength dispersion characteristics, having a structure of refractive index distribution that keeps a step-like shoulder. SOLUTION: A method for manufacturing a porous glass preform is provided, comprising synthesizing soot corresponding to the core and the cladding of an optical fiber by a VAD (Vapor phase Axial Deposition) method from the respective burners. In the method, a concentric multi-pipe burner 100 is used; and the raw material for synthesizing the glass is introduced into the center layer, while a dopant giving a specific refractive index difference is supplied only to the second layer or further outer layers. Preferably, SiCl<SB>4</SB>mixed with H<SB>2</SB>is introduced into the center layer and GeCl<SB>4</SB>mixed with H<SB>2</SB>is introduced into the second layer 12a. COPYRIGHT: (C)2010,JPO&INPIT |
