| 摘要 |
PURPOSE:To improve the dimensional stability of an axially asymmetrical optical fiber preform by placing a glass bar unit comprising plural mutually parallelly fixed transparent glass bars in a sealed cylindrical container, filling glass fine powder in the container and subsequently heating the container. CONSTITUTION:A transparent glass bar 2 for a core is fused to a supporting rod 5 of a supporting member 7 provided with a flange 6, the supporting rod 5 having a pin hole 5a at one end thereof and having a spherical portion 5b at the other end. The glass bar 2 is inserted into a penetrated hole 8 of a clamp member 10 and further transparent glass bars 3 for a stress-imparting material are inserted into right and left through holes 9, followed by fixing the glass bars to provide a glass bar unit 1. The unit 1 is placed in a cylindrical container 4 inserted into a cooling oven 14 except the upper portion of the container 4, and the container 4 is sealed with a cap 13. A raw material gas is fed from a glass fine powder-feeding system of a gas phase synthetic method connected to the upper end of the container 4 into a burner 18 connected to a raw material feed tube 17, and ignited. The produced glass fine powder 20 is deposited in the container 4 and subsequently heated to integrate the unit 1 with the glass powder 20. |
