| 摘要 |
PURPOSE:To obtain a preform for optical fibers capable of readily giving a steep refractive index distribution in a short time, by diffusing a dopant solution from the inner wall surface side of a tube to the radial direction while rotating a tubular silica porous body, drying and sintering the porous body. CONSTITUTION:A dopant solution is diffused in a tubular silica porous body, dried and sintered to produce a preform for optical fibers. In the process, the dopant is diffused from the inner wall surface side to the radial outward direction while rotating the preform for the optical fibers with the symmetry axis of rotation as the center. A tubular porous body produced by a sol-gel method is preferred for the tubular silica porous body used. The dopant solution may be directly diffused in the tubular silica porous body in a dry state, but the diffusion is preferably carried out after certain heat treatment from aspects of optimizing microstructure for high strengthening and diffusion behavior of the porous body. The speed of the above-mentioned rotation may be >=1G at the minimum expressed in terms of centrifugal force acting on the inner wall surface side of the tube, but is preferably about >=5G for practical use. |
