| 摘要 |
PURPOSE:To obtain an optical fiber having high strength, by immersing an optical fiber containing univalent cation at the surface layer in a molten salt containing univalent cation having larger ionic radius than the cation in the fiber, thereby effecting the ion exchange. CONSTITUTION:A preform rod 4 composed of a core part 1 and a clad part 2, and having a glass layer 3 containing univalent cation (e.g. Li ion) at the surface of the clad 2, is prepared beforehand. The preform rod 4 is inserted into the furnace 5 and molten to obtain an optical fiber 6. The fiber is introduced into a bath 7 containing a molten salt containing univalent cation (e.g. Na ion) having larger ionic radius than the univalent cation in the optical fiber to effect the ion exchange. Compression stress is generated at the surface layer 3 of the clad 2 by the difference of the ionic radii, and the strength of the optical fiber 6 can be improved. The obtained optical fiber 6 is washed in the water tank 8. |
