| 摘要 |
<p>In accordance with a first method of the present invention, doping is conducted by forming two constricted portions (28) in a quartz reaction tube (4) and charging a solution containing a rare earth element compound as a solute between the constricted portions (28). Accordingly, a dope concentration becomes uniform in a longitudinal direction of an optical fiber base material (30) and moreover, defects are difficult to occur. Furthermore, complicated works are not necessary. In accordance with a second method of the present invention, a soot-like core glass (26) is impregnated with mist-like solution and high-precision control of a dope concentration becomes possible. In accordance with a third embodiment ot the present invention, the concentration is controlled in accordance with quantity of a laser beam passing through the soot-like core glass (26) and impregnation of the solution is carried out. In this manner a dope concentration not depending on the density of the soot-like core glass can be obtained. In accordance with a fourth method of the present invention, shaping of the soot-like core glass (26) is repeated several times at different temperatures, so that a dope concentration distribution in a core diameter direction can be set arbitrarily.</p> |
