| 摘要 |
PURPOSE:To obtain the titled preform having high refractive index difference between the core and clad, low transmission loss and high quality, by heating a specific porous preform in a gaseous atmosphere containing deuterium-based gas, and then heating in an atmosphere containing fluorine gas. CONSTITUTION:O2 and H2 are supplied as fuel gases to the upper burner 3A and the lower burner 3B of a multi-core burner through the inlet ports 4 and 5, and are made to react with SiCl4 and Ar supplied through the inlet port 7 of the upper burner 3A forming the part corresponding to the clad, and at the same time, made to react with POCl3 and SiCl4 supplied through the inlet port 7 of the lower burner 3B synthesizing the core part. Fine glass particles are deposited at the end of the starting rotary preform 8 along the axial direction to obtain a porous preform wherein the part 9 corresponding to the core is made of quartz containing P2O5 and the part 10 corresponding to the clad is made of pure quartz. The preform is heated in a gaseous atmosphere containing deuterium- containing gas and chlorine-containing gas, and then heated in a gaseous atmosphere containing a fluorine-containing gas to obtain the titled preform wherein 1-20ppm of OD group is added to the part corresponding to the core, and fluorine is added only to the clad part. |
