| 摘要 |
PURPOSE:To obtain a flexible optical fiber with long life by providing acid-resistant coating on the edge of a bundle of threelayer optical fibers comprising core glass, acid-resistant glass and acid-soluble borosilicate glass and by treating, after bringing the whole into contact with acid, with an alkaline solution above specified pH. CONSTITUTION:In production of an optical fiber bundle where an edge 23 is adhered and the other part 25 is flexible, optical fibers 1 are bundled where glass 3 that is low in refractive index and is resistive to acid, is coated on the outer circumference of core glass 2 with a higher reflactive index, and further on the outer circumference, acid-soluble borosilicate glass 4 is coated. Acid-soluble glass 4 which is in the intermediate part is eluted and washed by immersing this fiber bundle 17 into a acid-eluting tank 21 and treating, for example, in 1 N nitric acie at 70 deg.C for about 2 hours. Next, the washed fiber bundle is treated in an alkaline solution of >=9 (for example, NaOH solution of 13.8pH) and the insoluble residue cinsisting essentially of silica gel remaining in the vicinity of the edge 20 is eluted to be removed. The edge 20 of a hard opeical fiber bundle 17 is coated with acid-resistive resin. The fiber bundle 17 is removed with elution. Thus a flexible optical fiber bundle that has good durability and is short in length of the adhered part 23 can be obtained. |
