MANUFACTURING METHOD FOR MULTI-MODE OPTICAL FIBER

PROBLEM TO BE SOLVED: To provide a multi-mode optical fiber manufacturing method capable of reducing the discrepancy of a refractive index distribution due to a residual stress after drawn.SOLUTION: A multi-mode optical fiber manufacturing method comprises: a step S1 of forming a first glass preform while controlling the feed rate of a refractive index adjusting additive so as to realize a desired refractive index distribution; a step S2 of drawing the first grass preform; a step S3 of measuring a residual stress distribution in the radial direction of a multi mode optical fiber 1A after drawn; a step S4 of reassessing the feed rate of the additive, in accordance with the deviation of the refractive index from a desired refractive index distribution, which is determined from the residual stress distribution measured; a step S5 of forming a second glass preform while feeding the additive in accordance with the feed rate reassessed; and a step S6 of drawing the second glass preform.SELECTED DRAWING: Figure 4 【課題】線引き後の残留応力による屈折率分布のずれを低減できるマルチモード光ファイバの製造方法の提供。【解決手段】所望の屈折率分布を実現するために屈折率調整用の添加材の供給速度を制御しつつ第１のガラス母材を形成する工程Ｓ１と、第１のガラス母材を線引きする工程Ｓ２と、線引き後のマルチモード光ファイバ1Ａの径方向における残留応力分布を測定する工程Ｓ３と、測定された残留応力分布から求められる、所望の屈折率分布からの屈折率のずれに応じて、添加材の供給速度の見直しを行う工程Ｓ４と、見直し後の供給速度に従って添加材を供給しながら第２のガラス母材を形成する工程Ｓ５と、第２のガラス母材を線引きする工程Ｓ６とを含むマルチモード光ファイバーの製造方法。【選択図】図４