| 摘要 |
PURPOSE:To obtain a base material, having the distribution coefficient (ag) of refractive index controllable at a desired value with a high accuracy, and capable of giving optical fibers having stable band characteristics, by changing the flow rate of hydrogen gas flowing through a burner to give the given shape to the bottom of a porous base material. CONSTITUTION:A raw material and a fuel are fed into a vertically fixed burner 1 to form fine oxide particles by the hydrolytic reaction, and the fine oxide particles are then deposited on the tip of an upper rodlike material 20 to form a porous base material 15. In the process, the burner 1 is supported on a fine adjustment table 2 for supporting the burner 1, and a gas introductory pipe 3 is provided. The burner 1 and glass tubes 6, 7 and 8 surrounding a flame 5 are fixed on a glass vessel table 4, and N2 gas is passed through gaps between them and applied to the porous base material 15 and the flame 5 to give the given shape to the bottom of the base material 15. The flow rate of H2 gas flowing through the burner 1 is changed to control the outside diameter of the porous base material 15, and therefore the distribution coefficient (ag) of the refractive index can be controlled with a high accuracy. Thus, the aimed base material for optical fibers capable of preparing the optical fibers having stable band characteristics is obtained. |
