The Furukawa Electric Co., Ltd.

Yukio Koumura

Yasuhiro Naka

Nobuaki Orita

Kazuto Hirabayashi

Masahide Kuwabara

An optical fiber preform () serving as a material of an optical fiber has a shoulder portion () thrusting beyond a middle portion (M) in a base end region (K) which is on the upper side when the optical fiber preform is suspended for a drawing process. The optical fiber preform () of this configuration can be easily produced by appropriately setting the heating condition, etc. for the sintering step in the production process. Thus, it is possible to omit the elongating step after the sintering step, thereby simplifying the production process. Further, in the prior-art technique, turbulence is generated in the gas flow in the furnace of the drawing apparatus toward the end of the drawing step, making it impossible to draw in a stable manner. In contrast, in this embodiment, due to the shoulder portion (), there is a small gap between the inner wall surface of the furnace and the optical fiber preform; due to this small gap, the gas flow is regulated, and the drawing can be conducted in a stable manner even toward the end of the drawing step.

Optical fiber preform and the method of producing the same

An optical fiber preform ( ) serving as a material of an optical fiber has a shoulder portion ( ) thrusting beyond a middle portion (M) in a base end region (K) which is on the upper side when the optical fiber preform is suspended for a drawing process. The optical fiber preform ( ) of this configuration can be easily produced by appropriately setting the heating condition, etc. for the sintering step in the production process. Thus, it is possible to omit the elongating step after the sintering step, thereby simplifying the production process. Further, in the prior-art technique, turbulence is generated in the gas flow in the furnace of the drawing apparatus toward the end of the drawing step, making it impossible to draw in a stable manner. In contrast, in this embodiment, due to the shoulder portion ( ), there is a small gap between the inner wall surface of the furnace and the optical fiber preform; due to this small gap, the gas flow is regulated, and the drawing can be conducted in a stable manner even toward the end of the drawing step.

A porous glass intermediate body constructed by a core original layer formed as a core portion of an optical fiber, and a first clad original layer formed as a first clad portion of the optical fiber is formed. Thereafter, a transparent glass intermediate body is made by consolidating the porous glass intermediate body within an atmospheric gas with a chlorine-based gas with no fluorine compound. Thereafter, a porous optical fiber base material is made by forming a second clad original layer as a second clad portion of the optical fiber on the circumferential surface of the transparent glass intermediate body. When a porous state is then maintained, the porous optical fiber base material is dehydrated within the atmospheric gas with a chlorine concentration higher than that during the consolidation of the porous glass intermediate body. Thereafter, an optical fiber base material is manufactured by consolidating the porous optical fiber base material within a similar atmospheric gas. The optical fiber is made by wire-drawing this optical fiber base material.

Optical fiber base material, its manufacturing method and optical fiber

An optical fiber preform is a material used for fabricating optical fibers. The optical fiber preform has a target rod which will be the core for optical fibers and a glass layer formed around the outside thereof. A mass W (kg) of the optical fiber preform and a diameter D (cm) of the target rod satisfy a relational expression 0.4&middot;(W) <D. Satisfying this relational expression can prevent the optical fiber preform from being deformed and to have uneven diameters due to the weight thereof in the dehydrating and consolidating process in fabricating the optical fiber preform, even though it is a large-sized optical fiber preform having a diameter of 10 cm or more.

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Tokyo, Japan

Yukio Koumura