| 摘要 |
PURPOSE:To control a transmission loss and an absorption loss due to OH group by carrying out vitrification at a lower temp. at first when a clad layer is deposited and vitrifying a layer part close to a core at a higher temp. to change the vitrifying temp. in the through thickness direction of the deposited clad layer. CONSTITUTION:When a clad layer is formed, vitrification is carried out at 1,500- 1,550 deg.C in the first half and at 1,600-1,650 deg.C in the latter half. For example, oxygen gas is fed from starting material feed section 1 to preburn quartz pipe 3 with oxyhydrogen burner 5. SiCl4 of a fixed temp. is bubbled with carrier gas oxygen, introduced into rotating pipe 3 together with oxygen gas, heated and scanned with moving burner 5, and vitrified after vapor phase reaction of SiCl4 to deposite a clad layer. The vitrification is carried out at 1,500-1,550 deg.C in the first half and at 1,600-1,650 deg.C in the latter half. SiCl4 and GeCl4 are then introduced into pipe 5 after adjusting carrier gas so as to attain a desired refractive index, and a core is deposited on the inside of the clad layer. Finally, they are made solid to obtain an optical fiber base material. |
