| 摘要 |
PURPOSE:To obtain an optical fiber which is suppressed in the increase of transmission loss at the time of radiation irradiation and has excellent radiation resistance by relieving the abrupt change in viscosity at the core-clad boundary, thereby averting the generation of strain at the boundary face. CONSTITUTION:A GeO2 concn. gradient layer in which the GeO2 concn. at the boundary face is maximized is provided near the core-clad boundary face between the core part consisting of quartz glass contg. GeO2 and the clad part consisting of pure quartz glass. While the boundary concn. of the GeO2 concn. gradient layer depends on the GeO2 concn. in the core part, said concn. is determined with the sufficient quantity to fill the defects in the pure quartz glass around the boundary face as a measure. The abrupt change in the viscosity at the boundary face is, therefore, relieved. The generation of the strain at the boundary face at the time of drawing is thereby suppressed and the optical fiber which is suppressed in the increase of the transmission loss even at the time of the radiation irradiation and has the excellent environmental resistance is obtd. |
