| 摘要 |
A fabrication method of optical fiber basic material, an optical fiber basic material manufactured by the method and an optical fiber drawn from the basic material are provided to reduce polarization mode dispersion, to simplify optical fiber drawing process and to improve the mechanical strength of optical fiber by modifying refractive index on the outer layer of the core. A fabrication method of optical fiber basic material comprises a step of carrying out a vapor deposition process comprising forming, lamination and calcination of soot particles in the thermal oxidation of reactant gas and oxygen gas on the surface of an substrate repeatedly depending on the refractive index profile in order to form core layer and clad layer, wherein fluorine gas is diffused locally into the core layer for forming outer layer of the core while the diffuse point of the fluorine gas varies randomly along the longitudinal direction of the basic material. In modified chemical vapor deposition, the reaction gas(50') from the reaction gas supply part(50) is put into the quartz tube(10) which rotates in a direction, the quartz tube is heated with high temperature furnace(60) which is transported to-and-fro along the outer respect of the quartz tube, and then preparing the optical fiber basic material by depositing a glass film which is a clad layer(20) and a core layer(30) repeatedly inside the quartz tube and making the quartz tube solid. When the reaction gas is provided from the reaction gas supply part, a little fluorine gas(40') is provided irregularly from the fluorine gas supply part(40) at the same time. The fluorine gas which is supplied irregularly is diffused to the core layer, and the refractive index in the part having the fluorine gas is locally lowered. |
