Optical fiber preform and manufacturing method therefor

Abstract

A method for manufacturing an optical fiber preform includes a process A of applying flame polishing to a center glass rod, a process B of determining a ratio ra / rb, which is a ratio of a radius ra of the center glass rod expressed in millimeters with respect to a radius rb of a target optical fiber preform expressed in millimeters, based on a refractive index profile of a target optical fiber preform, and a process C of determining an amount of fine glass particles to be deposited on the center glass rod so that a ratio ra / rb / c falls within a range from 0.002 to 0.01, where 'c' is a maximum value of hydroxyl group concentration expressed in ppm in the vicinity of a boundary between the center glass rod and an outer layer, which is formed by depositing fine glass particles on the center rod and by being vitrified.

Description

technical field [0001] The present invention relates to an optical fiber preform for manufacturing a single-mode optical fiber and a method for manufacturing the optical fiber preform. Specifically, the present invention relates to an optical fiber preform for manufacturing a single-mode optical fiber capable of wavelength division multiplexing over a wide wavelength band, and to a method of manufacturing such an optical fiber preform. [0002] This application claims priority from the following Japanese patent applications: Japanese Patent Application No. 2003-131729 filed on May 9, 2003, Japanese Patent Application No. 2003-192934 filed on July 7, 2003, and Japanese Patent Application No. 2003-192934 filed on April 2, 2004. Japanese Patent Application No. 2004-109698 filed on Japan, the contents of which are cited herein by reference. Background technique [0003] In recent years, due to the rapid popularization of the international Internet and internal Internet, the dem...

AI Technical Summary

Problems solved by technology

However, in this case, since the content of hydroxyl groups in the central glass rod must be reduced as low as possible, the costs for the dehydration treatment of the central glass rod increase, and thus also the manufacturing costs of the optical fiber

[0016] In the method of reducing the hydroxyl group content in the outer cladding formed on the outer surface of the central glass rod, a problem encountered is an increase in the number of treatments such as etching to remove a part of the outer cladding where hydroxyl groups exist.

[0017] In addition, using the method of drawing the central glass rod in an electric furnace may encounter problems with air bubbles or foreign particles in the central glass rod unless the preform is fire polished before further fine glass particle external deposition process

[0018] As mentioned above, when using any of the conventional methods for reducing the hydroxyl content in the optical fiber preform, the problem encountered is that the manufacturing cost of the optical fiber preform increases due to the increase in the number of processes or the decrease in production capacity.

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