| 摘要 |
PURPOSE:To obtain uniform and flexible optical fibers efficiently, by packing and arranging triple optical fibers, which consist of a core glass, an acid-proof glass, and an acid soluble glass, most closely in a hexagonal cylinder-shaped glass overcoat tube, where six inside vertical angles are about 120 deg., and stretching them by heating and pressurizing. CONSTITUTION:Triple optical fibers 1 where a core glass 2 having a high refractive index is covered with an acid-proof glass 3 having a low refractive index and the glass 3 is covered with an acid soluble glass are packed most closely in a hexagonal cylinder-shaped glass overcoat tube 22 consisting of an acid soluble glass, a soda lime glass, or the like, where six inside vertical angles are about 120 deg., to produce an optical fiber bundle 27. The bundle 27 is heated and pressurized to be stretched, thereby obtaining an optical fiber bundle 17 having a prescribed diameter. After both end parts of the fiber bundle 17 are coated with acid-proof resin coatings 20, the bundle 17 is immersed in an acid processing liquid 19 to dissolve and remove the overcoat tube 22 (in case of the acid soluble glass) and acid soluble coatings 4. In case of the tube 22 consisting of a soda glass, the bundle 17 is immersed in the acid processing liquid 19 to remove coatings 4 after the tube 22 is removed mechanically. Thus, since optical fibers 4 are arranged without generating uneven gaps in the overcoat tube 22, the unevenness of the image transmission characteristics due to partial unevenness after stretching is prevented. |
