A method for preparing an optical fiber preform

Abstract

The invention discloses a preparation method for an optical fiber preform. A vapor deposition method is employed for preparation of a core layer and a coating layer of the optical fiber preform. The preparation method is characterized in that an alkali metal raw material is added into SiCl4 used as a supply source for a deposition raw material of the core layer; and during deposition of the core layer, SiCl4 volatilizes to form gas and carries the alkali metal raw material to enter a deposition reaction area. According to the invention, since SiCl4 directly used as the supply source for the deposition raw material of the core layer contains the alkali metal raw material, an alkali metal doping agent is added from the source of raw materials; alkali metal is doped into the core layer by using the vapor deposition method; and compared with the means of adding alkali metal raw materials by using an in-glass-tube diffusing method, the method provided by the invention is simpler and easier to operate, does not need extra heat source for heating of the alkali metal raw material, greatly reduces energy consumption, overcomes the problem of nonuniform distribution of alkali metal of the in-glass-tube diffusing method, and obviously reduces optical attenuation.

Description

technical field [0001] The invention relates to a method for preparing an optical fiber preform, belonging to the technical field of optical fiber communication. Background technique [0002] Optical fiber communication has the characteristics of large transmission capacity, long transmission distance, and fast transmission speed, and is widely used in optical communication networks such as long-distance trunk networks, metropolitan area networks, and access networks. Reducing the optical fiber attenuation coefficient can effectively increase the transmission distance of the optical fiber communication system, greatly reduce the number and cost of relay stations, and is of great significance for optimizing the structure of the transmission system and reducing operating costs. How to reduce the optical fiber attenuation coefficient has become a hot research topic for major optical fiber manufacturers. [0003] The existing technologies for reducing the fiber attenuation coef...

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Problems solved by technology

[0005] Document US7088900B1 proposes a low-attenuation optical fiber containing alkali metal, the alkali metal content is not less than 20ppmwt%, the attenuation of the optical fiber at 1550nm wavelength is lower than 0.178dB / km, and the method of doping alkali metal is not involved in the document; documents US7524780B2, US20050063663A1 and US7469559B2, all put alkali metal raw materials in the inner wall of the glass tube, and dope the alkali metal to improve the optical fiber attenuation by the diffusion method in the tube; document US9250386B2 puts the alkali metal raw material in the inner wall of the glass tube, heats the outer wall of the glass tube, and diffuses in the glass Doped with alkali metal oxides, the attenuation of the prepared optical fiber at a wavelength of 1550nm can reach below 0.17dB / km. The alkali metal doped by this heating diffusion method forms a concentration gradient on the inner and outer walls of the glass, and the distribution is uneven; document US20140127507A1 , US9229160B2, CN102627400B, CN102603179A, CN102627398A, CN103502164A, CN104093674A, CN102617033A, CN103502164A and CN102730977A, are all mixed into the inner wall of the alkali metal tube in the alkali glass tube by a continuous moving heat source, which is heated by a complex diffusion process.

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