JPS60239334A - Manufacture of base material for optical fiber - Google Patents

Abstract

PURPOSE:To manufacture a transparent base material for an optical fiber having a specified refractive index distribution by putting a porous glass rod of pure quartz in a pipe of quartz-base glass contg. fluorine and by heating the pipe from the outside. CONSTITUTION:A starting member 1 is attached to a support rod 3 provided with a pulling device 2, quratz glass powder is deposited with oxyhydrogen burner 4, and while pulling up the member 1, a porous glass body 5 is grown in the axial direction. After pulling out the member 1, the resulting pipe-shaped porous glass body 5 is slowly lowered in a vessel 7, and is heated with a carbon resistance furnace 6 while feeding a gaseous SF6-He mixture to form a pipe 5 of glass contg. enough flourine. At this time, OH groups in the glass pipe are removed by feeding gaseous chlorine or the like. A porous quartz glass rod is put in the glass pipe 5 and heated from the outside. By the heating, the quartz glass rod is made transparent and united with the glass pipe 5 to manufacture a base material for an optical fiber.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing an optical fiber base material, which has particularly excellent light transmission properties, in which the core is made of pure silica glass and the cladding is made of fluorine and quartz. The present invention relates to a method for manufacturing an optical fiber base material made of glass.

(Prior art) In order to increase the refractive index of the core in a silica-based optical fiber by increasing the refractive index of the cladding, there are cases where the core is made of silica glass containing germanium oxide, and other cases where the core is made of pure silica glass. In some cases, the cladding part is made of pure quartz glass made of quartz having a low refractive index and fluorine. Compared to the former, the latter has a core made of pure quartz, through which the light propagates, and can reduce the influence of Rayleigh scattering, which is one of the factors that reduce light transmittance. Excellent optical fiber can be obtained. In this case, in order to lower the refractive index of the cladding part, it may be possible to use glass made of boron oxide and quartz for the cladding part, but boron oxide has an absorption band around 1.5 μm, which is close to the wavelength band often used for optical communications. Therefore, in order to improve the light transmittance, it is desirable to use glass made of fluorine and quartz, which does not have an absorption band near the wavelength band used, for the cladding.

On the other hand, among the manufacturing methods for optical fiber base materials, the MAD method or ovpo method, which synthesizes a porous glass body using a flame hydrolysis reaction, is said to be a highly productive and economical method. . A method of synthesizing a porous glass body using such a flame hydrolysis reaction and producing a base material for a fiber whose constituent elements are glass containing fluorine and quartz is disclosed in Japanese Patent Application Laid-open No. Showa 55-67555
Another method described in the above publication is to heat-treat a porous glass body in an atmosphere containing fluorine. However, with this method, fluorine is often introduced almost uniformly into the entire region of the porous glass body, making it difficult to create a difference in refractive index between the cladding and the core.

Furthermore, as described in JP-A-55-15682, when a porous glass body is formed using a flame hydrolysis reaction, a fluorine compound is mixed with the raw material to form a porous glass body containing fluorine. There is also a method of forming a porous glass body and then converting the porous glass body into transparent vitrification in a high-temperature furnace.

However, with this method, it is difficult to sufficiently increase the amount of fluorine present in the glass, and the difference in refractive index caused by fluorine can only be about 0.2% at most, making it impractical.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the above-mentioned problems of the conventional method, and to ensure that the cladding portion contains sufficient fluorine and that there is no problem in practical use as a transmission line for optical communication. An object of the present invention is to provide a method for manufacturing an optical fiber base material having a refractive index distribution formed by using a highly productive flame hydrolysis reaction.

(Means for Solving the Problems) The method of the present invention consists of two separately manufactured quartz vibrators containing sufficient fluorine as a main component and corresponding to the cladding part, and a vibrator with a porous vibrator mainly composed of quartz corresponding to the core part. The problems of the conventional method were solved by heating and making the fiber transparent after combining it with high quality glass red, and the optical fiber was made with sufficient fluorine content in the cladding and a satisfactory refractive index difference between the core and cladding. This is to obtain the base material for use.

That is, the present invention involves inserting a porous glass red whose main component is quartz into a glass pipe whose main component is quartz, heating the glass pipe from the outside, and making the porous glass red transparent. The present invention also relates to a method for manufacturing an optical fiber base material, characterized in that the glass pipe and the glass red are integrated.

The present invention also relates to a method for producing an optical fiber base material in which the glass pipe is made of fluorine and quartz and the porous red is made of pure quartz.

Furthermore, the present invention relates to a method for manufacturing an optical fiber base material, in which a gas containing chlorine is passed through the gap between the glass pipe and the porous glass red in the above manufacturing method.

This will be explained in detail below.

A porous glass red whose main component is quartz, which corresponds to the core section, is inserted into a glass pipe whose main component is quartz, which corresponds to the cladding section, and when the glass pipe is heated from the outside, the glass pipe begins to shrink. Meanwhile, the porous glass red inserted into the glass pipe becomes transparent vitrified. If the heating is continued further, the porous glass red becomes transparent vitrified, and the transparent glass red and the glass pipe are integrated to form an optical fiber base material.

At this time, by using a quartz glass pipe containing sufficient fluorine and a porous glass red made of pure quartz, it is possible to create an optical fiber base material whose cladding part is made of fluorine and quartz and whose core part is made of pure quartz. can.

The method for producing a glass pipe equivalent to a cladding whose main component is quartz containing sufficient fluorine in the method of the present invention is carried out, for example, as follows. FIG. 1 is a diagram illustrating one embodiment of the apparatus for manufacturing a pipe-shaped porous glass body, in which a support rod 3, which is attached to a rotary pulling device 2 and whose tip is processed into a pipe shape, has a surface A smooth starting material 1 is attached.

Fine glass particles are deposited on the support rod 5 using an oxyhydrogen burner 4 in the same way as in the normal VAD method, and gradually deposited onto the starting material by pulling up the support rod 3 while rotating it. glass particles are also deposited. In this way, by growing the porous glass body 5 in the axial direction on the outer periphery of the starting material 1 and then pulling out the starting material 1, a pipe-shaped porous glass body 5 can be obtained. By heating and making the pipe-shaped porous glass body 5 transparent in an atmosphere containing fluorine, a glass pipe containing sufficient fluorine can be obtained. For example, in the apparatus shown in Fig. 2, the atmosphere gas is "Fi 100 cc/min, H
While feeding e5z/min, the pipe 1-shaped porous glass body 5 attached to the support rod 3 is moved downward and passed through a high temperature area (~165°C) near the carbon resistance furnace 6. As a result, a glass pipe containing fluorine whose refractive index is reduced by α3% can be obtained.

By the way, when a large amount of OH groups are contained in a silica-based optical fiber, absorption loss of propagating light increases, which impedes long-distance optical communication.

Therefore, it is necessary to sufficiently reduce the OH groups in the optical fiber base material. In order to prevent OH groups from being mixed into the optical fiber base material produced according to the present invention, when heating the glass pipe from the outside, it is necessary to use a chlorine-based gas that has a dehydrating effect, such as Ct or 5O, in the glass pipe when heating it from the outside.
cz.

It is effective to run the following. By doing so, it is possible to remove OH groups in the base material that are derived from moisture contained in the atmosphere within the glass pipe. moreover,
OH groups or water contained in the porous glass rod can also be removed.

Of course, by thoroughly dehydrating the porous glass iron used and by using a glass pipe with a sufficiently low OH group content, it is possible to
Needless to say, the number of groups can be reduced easily.

(Effect of the invention) In the conventional method, as already mentioned, the core is pure quartz and the cladding is mainly composed of quartz containing fluorine, and has a refractive index distribution structure with a sufficient refractive index difference due to fluorine to withstand practical use. However, the method of the present invention makes it possible to produce a glass base material having a refractive index in which the cladding part contains sufficient fluorine and can be used practically as a transmission line for optical communication. A glass base material having a rate distribution structure and excellent transmission loss characteristics can be manufactured using a highly productive flame hydrolysis reaction.

(Example) Example 1 A quartz glass pipe containing approximately 1% by weight of fluorine (outer diameter: 41mm)
, inner diameter 9cm, length 150mm. ) inside the porous quartz glass pipe (bulk density α55 f/err?, outer diameter 8tmφ,
By inserting a quartz pipe with a length of 150 m) and heating and integrating the quartz pipe from the outside using a carbon furnace, an optical fiber base material having a cross-sectional structure and refractive index distribution as shown in FIG. 6 was obtained.

Furthermore, after stretching this base material, it was inserted into a commercially available quartz pipe and integrated to produce a base material for a single mode optical fiber.

The quartz glass pipe containing about 1% by weight of fluorine is obtained by producing a pipe-shaped porous quartz glass body and then sintering it in an atmosphere containing fluorine. Further, the porous quartz rond was manufactured using the VAD method.

Figure 4 shows the transmission loss characteristics of a 5 km long single mode optical fiber obtained by drawing this base material. In Fig. 4, α95μm, 1.24μm, and 1.39μm bands, respectively.
Absorption loss originating from OH groups appears. This absorption by OH groups is thought to be due to moisture present in the atmosphere inside the quartz glass pipe entering the prepared base material when the quartz pipe and the porous glass iron were integrated.

Example 2 In the method of Example 1, quartz glass and porous glass iron were further integrated while supplying chlorine gas at a rate of 150 cc/min and helium gas at a rate of 511 min into the quartz glass pipe. FIG. 5 shows the transmission loss characteristics of the single mode optical fiber obtained by this method. Absorption due to OH groups has been reduced to a level that poses no practical problem.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating an embodiment of an apparatus for manufacturing a pipe-shaped porous glass body used in the method of the present invention. FIG. 2 is a diagram illustrating an embodiment of an apparatus for adding fluorine to a pipe-shaped porous glass body and making it transparent vitrified, which is used in the method of the present invention. Figure 6: Refractive index fraction of the base material obtained in Example 1.4: Transmission loss characteristics of the fiber obtained in Example 1.Figure 5: Transmission loss characteristics of the fiber obtained in Example 2. Figure 3 Figure 4 Figure 5 Procedural amendment January 30, 1985 Director General of the Temple Office Shiga Number of characters 1, case description 1988 Patent Application No. 92931 2° Invention 0 Name Hikari 7 Base material for Aipa Manufacturing method 3, relationship with the case of the person making the amendment Patent applicant address 4, Tetsube Kawakami, 5-15 Kitahama, Higashi-ku, Osaka, Agent f3- Address: 16-2-5, Toranomon-chome, Minato-ku, Tokyo Date of amendment order Number of inventions to be increased by amendment to spontaneous amendment 6 None l Subject of amendment (1) “Detailed explanation of the invention” column of specification (2) Drawings Contents of amendment (1) Specification No. On page 7, line 4, the description "the support rod" is corrected to "the support rod." (2)Amend Figure 1 of the attached drawings (as attached). Figure 1

Claims (1)

[Claims] (11) A porous glass rod mainly composed of quartz is inserted into a glass pipe mainly composed of quartz, and the porous glass rod is heated from the outside. A method for manufacturing an optical fiber base material, which is made transparent and is characterized by integrating the glass pipe and the glass rod. (2) The glass pipe is made of fluorine and quartz, and the porous glass rod is made of pure quartz. A method for manufacturing an optical fiber base material according to claim 1, which comprises: (3) a method of manufacturing a base material for optical fiber according to claim il+ or claim 2, which comprises flowing a gas containing chlorine into the gap between the glass pipe and the porous glass rod;
2) A method for manufacturing an optical fiber base material described in item 2).