| 摘要 |
PURPOSE:To improve bending characteristics of optical fiber preform by dehydrating a preform comprising a porous glass rod for core and a specific glass fine granule clad layer having reduced refractive index in the vicinity of outer periphery part of the porous glass rod and making the preform into transparent glass. CONSTITUTION:Glass fine granules of SiO2 obtained by sending a Si hydride or halide and a F-containing gas such as SiF4 into flame are deposited as a clad layer on the periphery of porous glass rod for core made of fine granules of SiO2 glass containing GeO2 formed by flame hydrolysis method or heat oxidation method. A porous glass preform for optical fiber having a refractive index of clad in the vicinity of the outer periphery of the rod reduced to that of SiO2 is dehydrated in a Cl2-containing gas flow at about 1,050 deg.C, heated to about 1,600 deg.C and made into transparent glass to give optical fiber having excellent bending characteristics, wavelength characteristics of zero dispersion and mode field diameter. |
