| 摘要 |
PROBLEM TO BE SOLVED: To produce a high-performance preform having complicated distribution of refractive index by using burners for synthesis of glass fine particles and successively synthesizing a glass porous body from a high fluorine concn. part by soot method to obtain an intermediate preform. SOLUTION: When an intermediate preform is produced by synthesizing a glass porous body by soot method using burners for synthesis of glass fine particles, for example, the flow rate of the source material is controlled in such a manner that the ratios of F atom/Si atom in the source material gas in first to fourth burners satisfy first burner > second burner > third burner > fourth burner so that the ratio decreases from the part to be first synthesized. Thus, the intermediate preform is produced in one process. Alternatively, an intermediate preform having the higher fluorine density near the center is synthesized in one process by soot method. Thereby, the fluorine concn. in the part previously produced can be selectively increased, and by changing the produced glass porous body into transparent, an optical fiber preform is obtd. |
