| 摘要 |
Doping is conducted by forming two constricted portions (28) in a quartz reaction tube (4) and charging a soln. contg. a rare earth element cpd. as a solute between the constricted portions 828). Accordingly, the dope concn. becomes uniform in the longitudinal direction of an optical fibre base amterial (30) and moreover, defects are difficult to occur. Furthermore, complicated works are not necessary. In a second method of the present invention, a soot-like core glass (26) is impregnated with mist-like soln. and high-precision control of a dope concn. becomes possible. In accordance with a third embodiment, the concn. is controlled in accordance with quantity of a laser beam passing through the soot-like core glass (26) and impregnation of the soln. is carried out. In this manner a dope concn. not depending on the density of the soot-like core glass can be obtd. In accordance with a fourth method, shaping of the soot-like core glass (26) is repeated several times at different temps., so that a dope concn. distribution in the core dia. direction can be set arbitrarily. @(57pp Dwg.No.2/19)@. |
