| 摘要 |
PURPOSE:To prevent generation of bond defect between Si and O in the production of a preform using a plasma outer deposition process, by specifying the outer surface temperature of a target rod and a compositional ratio of Si to F in the raw material composition of optical fiber. CONSTITUTION:A plasma torch 1 is supplied with Ar and O2 gas and a high-frequency coil 2 is applied with high voltage to generate a plasma flame 3. The plasma torch 1 forming the plasma flame is supplied with SiCl4 as a glass- forming raw material and CCl2F2 as an additive for modifying refractive index at respective specific flow rates. An optical fiber preform is produced by horizontally transferring a target rod 4 at a specific speed to deposit glass soot on the outer circumference of the target rod 4 and form a clad part. In the above process, the temperature of the outer circumference of the target rod 4 is controlled to 1,600-1,900 deg.C and the ratio of numbers of Si atoms in the above glass-forming raw material to F atoms in the additive raw material is adjusted to 1:(1.8-2.4). |
