JPS58181738A - Manufacture of base material for optical fiber of low oh content - Google Patents

Abstract

PURPOSE:To reduce the transmission loss of a base material for an optical fiber due to the absorption of light by OH groups by depositing transparent glass from a gaseous starting material while feeding gaseous CO as a dehydrating agent in the manufacture of the base material by a chemical vapor deposition method. CONSTITUTION:An SiCl4-base gaseous starting material mixed with a gas such as GeCl4, PCl3 or BBr3 is fed into a quartz glass pipe together with gaseous O2 as a carrier gas to deposit SiO2-base glass, thereby manufacturing a base material for an optical fiber consisting of a clad layer and a core layer. At this time, gaseous CO is added to the gaseous starting material as a dehydrating agent. Moisture contained in the gaseous starting material reacts with the gaseous CO, and they are discharged as gaseous CO2 and H2 to prevent the optical transmission loss of the transparent base material for an optical fiber deposited on the quartz pipe due to the absorption of light having specified wavelengths in OH groups.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is aimed at minimizing the increase in loss due to OH groups in the process of forming optical fiber preforms, and in particular suppressing the increase in loss due to OH groups to a minimum. Regarding manufacturing method:) Conventionally, as a method for manufacturing optical fiber base material,
The chemical vapor deposition method (hereinafter abbreviated as MCVD), which is commonly used, is a raw material quartz tube whose one end is connected to the raw material gas supply and the other end is connected to the atmosphere. In this case, using 81Cj4 as the raw material gas for the main component, GeCj,
PCl and BBr are used as the raw material gas for the additive oxide, and are distributed on a carrier gas of oxygen, and the outside of the quartz tube is scanned every ms with an oxyhydrogen burner.
The inner wall of the quartz tube is coated with a 5101 layer obtained as a result of a chemical reaction or ij neo, , P, 0. This is a method for manufacturing an optical fiber base material by depositing sio,@ containing additives such as 1 and B201, vitrifying it transparently, and solidifying it.

However, in such conventional methods, it is unavoidable that an acidic amount of moisture from the raw material and the spear is mixed in during the imitation process, which causes light absorption loss in the glass base material.

The basic absorption of water contained in the glass matrix is 2.72.
64) at 11 m of μm, its harmonic is 1.39
Extremely large optical absorption losses occur at wavelengths such as μm and 195 μm (1/2 and 1/3 of the fundamental absorption wavelength, respectively), and this is a major problem in manufacturing optical fibers for optical transmission. It is between. In this way, in the conventional method, it is difficult to remove the OH groups in the optical 7-iper, and the loss increases by 1.39 μm.
Setting it to about dB/b is #! ! & not. This means that the wavelength division multiplexing transmission method t
-This is a fatal flaw when trying to manifest.

The object of the present invention is to solve the above-mentioned problem of melting by using a specific dehydrating agent during production of the optical fiber preform, and to minimize the increase in loss due to OH groups. The goal is to provide the following.

To summarize the present invention, the method for manufacturing the toak optical fiber preform of the present invention includes the steps of preparing a desired IA#rII in glass snow.
The present invention is a method for manufacturing an optical fiber base material in which a glass layer containing Ilct is deposited in the longitudinal direction, and is characterized in that reaction, deposition, and transparent vitrification are carried out while flowing a monomer gas.

It can be expressed by the following formula.

When Kuturad is deposited: 8iCj, + O, → S1o, +2C1* (1
) Also, during core deposition: 1111 of such a gaff base material! In addition to the reactions necessary for the production and Okazaki, the diffusion of OHJ from the raw quartz tube or the moisture (l(,
0) deteriorates the properties of the j lath base material.

In addition, in the method of the present invention, sulfur monoxide gas (hereinafter abbreviated as CO) is passed through the quartz glass tube as a dehydrating agent, so the moisture contained in the raw material gas and others is reduced by the following formula: % (%) The 8102 layer or Ge is transported to the outside of the quartz tube by the reaction of
By adding O□, the incorporation of OH groups into sio and m can be significantly reduced.

The flow rate of CO at this time is determined by the lineage of the raw materials, reaction conditions, etc., and is not particularly determined, but it is necessary to round the core part to complete dehydration, and to use CoO in the core part manufacturing process.
It is desirable that the distribution volume be somewhat uniform.

Next, the present invention and its effects will be clarified by examples.
The present invention is not limited thereto in any way.Example: Using CO as a dehydrating agent, a base material for optical fiber was prepared using conventional techniques, and a 90% dry layer was deposited. 81('j, tM
I, when depositing the core layer, 8℃ at 28℃ was used as a wA material.
Using 1Cj4 and Gec 14 at 15℃, and in both cases, *mOl was used as a carrier gas and electrolyte AlOCOt-m was used as a dehydrating agent. Heat it with a burner while putting it in, and inspect the inner reef of the quartz tube with Cuturad 1111 and the core layer. For comparison, an optical fiber base material was prepared under the same conditions without flowing CO.

The loss characteristics of optical fibers fabricated under these conditions, which are inferior to TM materials, are explained below. In other words, the compiled drawings show the excellent loss characteristics of optical fibers with and without COt in the relationship between wavelength (μm) (horizontal axis) and loss (dB/b) (vertical axis). It's gross. As is clear from Figure (2), in the case of the conventional method that does not use CO, the wavelength t3? The loss value in μll14C was 4 dB/b, compared to that of the itsu friend, but it was found that it was possible to significantly reduce the loss value to [1L5 dB/-] by using CO and using nine windings.

As explained above, according to the present invention, C as a dehydrating agent.
By using o, wrinkles of OH groups in the base material can be reduced, and as a result, the loss characteristics of the resulting optical fiber are α5dB in a wide wavelength range from 1.2μm to t7μm.
/b or less. 1 This 'R- is large and enables the Uecho-Tarashi method t4, which is considered to be a promising future optical communication method.

[Brief explanation of drawings]

The drawing is a graph showing the loss characteristics of optical fibers obtained with and without CO. Patent solicitation entered into Nippon Telegraph 1 as an agent for the public corporation Nakamoto Major procedural amendment (method) August 24, 1980 Director of the Licensing Agency blindly arrived Kazuo Sugi Tono t◆Displayed Patent Application No. 62475 No. 1 Name of the invention Low OH Party 7 Aino (Manufacturing method for base material for this amendment) Case and OII Section Tatami license applicant address 1-1-6-1 Uchira-cho, Chiyoda-ku, Tokyo
Name (422) Nippon Telegraph and Telephone Public Corporation Representative Mr. Makoto Tsuneishi Shinbashi Chuo Building 602 Telephone (457)-5467
Name: Patent Attorney (7850) Hirokan Nakamoto 8 Village of July 9, 1980 (Shipping date: July 27, 1981) Subject to this amendment O Full text of the specification

Claims (1)

[Claims] (1) In a method for manufacturing an optical fiber base material in which a glass layer having a desired refractive index is deposited in the length direction in a glass tube, reaction, deposition, and transparent vitrification are performed while circulating a secondary oxidation gas. A method for producing a base material for a low OH optical fiber, characterized by: