| 摘要 |
PURPOSE:To obtain the titled preform with high reliability by forming a circular tube with plural glass rods having a sectorial cross section, inserting the circular tube between a fiber preform and a glass tube to be coated on the preform, collapsing the material, and preventing the irregular deformation when collapsed. CONSTITUTION:The glass tube 3 consisting of quartz, etc., is put on the outside of the fiber preform 1 consisting of a core and a clad. A circular tube is formed with plural glass rods 4 having a sectorial cross section, and inserted between the preform 1 and the glass tube 3. the material is then collapsed. At this time, a glass rod 4' doped with a material such as boron for nonuniformly providing stress in the glass rod 4 is incorporated, and stress is imparted to the fiber when the preform is spinned. Consequently, the stress-imparted polarized wave maintaining fiber preform thus obtained has the above-mentioned characteristics, and is effectively used for improving the transmission characteristic of an optical fiber. |
