JPS5899133A - Burner for production of base material for optical fiber - Google Patents

Abstract

PURPOSE:To obtain a base material for optical fibers which has high accuracy and is free from change in structure by constituting the preceding end parts in the outlet parts of the respective nozzles of a concentrical multitubular burner with quartz glass and forming the remaining parts by metals. CONSTITUTION:In the respective burners of concentrical multitubes for production of optical fibers using quartz glass, an inside pipe 21 which feeds glass raw materials with Ar as a carrier gas and the outermost pipe 24 which feeds O2 do not suffer damage by heat and therefore these pipes are manufactured with stainless steel pipe, etc. The parts 22'', 23'' of a pipe 22' for feeding gaseous Ar and a pipe 23' for feeding H2 which suffer damage by heat are manufactured of quartz glass and are connected to the preceding end parts of the pipes 22', 23'. The base material for optical fibers is manufactured roughly under the same conditions by such burner construction, and the yield of production of the base material for optical fibers having high quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a burner for producing an optical fiber base material, that is, a concentric multi-tube burner made of quartz glass in which glass raw materials, HtOlOt, inert gas, etc. are used separately or at least in a mixed state. It has a burner structure that introduces gas into each nozzle and generates a flame containing glass particles from the nozzle outlet.

One of the conventional methods for manufacturing an optical fiber base material is the method shown in FIG. In this process, a flame 5 containing glass particles is generated by a flame hydrolysis burner 1, and the flame 5 is
A rond-shaped porous glass base material 2 is grown by spraying the starting material 4 moving in the direction of the arrow 7 while rotating in the direction of the arrow 7. Thereafter, the material is sintered using a heat source 3 to form a transparent optical fiber base material 14. Although this method has the feature that a long, large-diameter, broadband, and low-loss optical 7-eyeper can be easily obtained, its manufacturing yield is poor. In particular, there are large variations in transmission band and core diameter. The present inventor conducted various experimental studies to investigate the cause of jin, and as a result, discovered the following problems.

(1) The flame hydrolysis burner 1 has a concentric quadruple tube structure as shown in Fig. 2(a), and is designed to mix and burn glass raw materials, A'% Ht, and O* at the burner nozzle outlet. It has become. However, if this burner is used for a long time, glass particles will adhere to the Ht nozzle and Ar nozzle exits, which will be damaged by the oxyhydrogen flame and the height and shape of the nozzles will gradually change. And Figure 2(b)
The shape changes significantly from its initial shape. (b)
In the case of , the shape is at the stage where about 30 optical fiber base materials have been created. It has been found that it is extremely difficult to obtain a base material with the same characteristics when the shape of the burner gradually deforms in this way.

(2) Burner IFi is made by hand by skilled craftsmen using a quartz glass tube, but it is extremely difficult to make identical pieces with an accuracy of several tens of μm or less. Therefore, it was found that the variation in properties of the optical fiber (base material) due to the burner was extremely large.

(3) Since the cost of the burner is high, it is expensive and uneconomical to replace the optical fiber base material every 20 to 30 pieces. Moreover, the deformed nine-piece has a complicated structure and many welded parts, making it impossible to repair.

As described above, in the conventional method, the characteristics of the optical fiber base material vary greatly due to momentary changes in the structure of the burner, and since it is made of quartz glass tube, it is possible to reproduce the same structure with an accuracy of several tens of μm or less. It is impossible to reproduce the same, and there are variations in the characteristics of the optical fiber base material between each burner.Furthermore, it has a structure that has little shape deformation over a long period of time and can be manufactured with good reproducibility. A low cost burner is desired.

Therefore, an object of the present invention is to reproduce the same structure with high precision, and to minimize structural changes due to use.
It is an object of the present invention to provide a burner for manufacturing Hikari 7 Aipah base material.

In order to achieve the above object, the present invention provides a flame hydrolysis burner in which the majority of the burner is made of metal (for example, stainless steel), and only the vicinity of the horizontal nozzle H3 and Ar nozzle exits are made of quartz glass tubes. It is designed to be connected to a manufactured burner. If the burner is made of metal, it can be made with precision on the micron order and with good reproducibility. Since only the H2 and Ar nozzle exit areas are made from quartz glass tubes with a length of several (7), such short glass tubes can be made with high precision and good reproducibility. Therefore, variations in characteristics due to replacement of these two nozzles are also eliminated. The burner of the present invention is economical because it can be used for a long time by simply replacing the two quartz nozzles.

Hereinafter, the present invention will be explained in detail using the drawings.

FIGS. 3(a), 3(b) and 3(c) are side sectional views of the components of one embodiment of a burner according to the invention. A burner assembled using these is shown in Figure 4. Figure 3 (a
) is made of stainless steel (material 8U8304, product name). We have experimentally found that this part has no horizontal distortion due to heat, and that the precision of the inner and outer diameters of tubes 21 and 24 is the main factor controlling the shape and refractive index distribution of the optical fiber base material. It is made of metal with high precision. Stainless steel was used for the glass raw material injected from inside the tube 21.
This is to prevent corrosion caused by the gas. Note that since the inside of the pipe 21 is normally purged with Ar gas, corrosion will not occur. When made from metal, the dimensions can be made with high precision, several tens to hundreds of times higher than when made from quartz glass, so the characteristics of the optical fiber base material can also be made with high precision. Figure 3(b), (
C) is the part where there is a horizontal ruler caused by heat, so it is made of quartz glass. These tubes 22' and 23' are 22' in FIG. 3(a).

23'. Therefore 2
Since only a few lengths of 2' and 23' are required, the inner and outer diameters of the tube can be made with high accuracy and reproducibility.

When the burner starts to straighten due to heat, it can be replaced with a new one, making it possible to create optical fiber preforms under almost the same conditions each time, compared to conventional burners. This can improve the production yield of high-quality optical fiber preforms.

Next, an example of a method for manufacturing an optical fiber base material using the burner shown in FIG. 4 will be described. Hikari 7 Aipa base material manufacturing equipment is the first
A diagram was used. In Figure 4, 24 has an outer diameter of 18 m, an inner diameter of 14.5 m, 23' and 231 have outer diameters of 1 & 3 mm,
Inner diameter 12■, 22' and 22# have outer diameter 9m and inner diameter 7
For 1111% 21 K, tubes with an outer diameter of 5.2 mm and an inner diameter of 6 m were used.

And 25 to 5iCL4 (0,517min
), G e C1m (0,1817mmmn), PO
Cls (0,1 t/m1n) was fed with At as a carrier gas, and Ar (127m1n) was introduced from 26 to 27.
From 28 to 01 (sz/
min ) were respectively applied to prepare optical fiber preforms. 221 in Figure 4 every time the optical fiber base material is created several times.
゜Remove only ゜231, clean it, measure the shape and dimensions, and if the shape and dimensions have deformed by a few percent from the initial value, #i22'
, 23' were replaced with new ones and the production of the optical fiber base material was repeated. As a result, when using a conventional burner, the variation in the outer diameter of the optical fiber base material and the transmission band of the optical fiber ranged from a few percent to more than 30% when 30 optical fiber base materials were made. In contrast, when 30 optical fiber base materials were made using the burner of the present invention, the amount of variation was less than 10%, indicating that the variation was significantly improved.

The invention is not limited to the above embodiments. For example, in FIG. 4, several hundred of the tips 21.24 may be made of quartz glass tubes, and the remaining portions may be made of metal. In addition, the burners are not only concentric quadruple tubes, but also quintuple tubes and six-layer tubes.
Multiple pipes such as double pipes and triple pipes may be used. Then, it can be made of a bar type that produces side parts due to heat. Methods for connecting metal tubes and quartz glass tubes include a simple fitting method that creates steps as shown in Figure 4, or a method in which 22', 23', 22', and 23' are each made into a tapered shape and fitted. But that's fine. A structure that is easy to attach and detach is preferable.

The size and shape of the tip of the burner tube, the flow rate and type of gas flowing into each tube, etc. are not limited to the above embodiments. For example, the glass raw material dopant may be introduced not only into one tube but also into a plurality of tubes. Also O3
A pipe for flowing a gas such as Aro or N for purging may be provided between and Hl. Furthermore, 0. A tube may be provided around the outer periphery of the optical fiber for controlling the atmosphere or controlling the shape of the optical fiber base material through which a gas (for example, N!, A') flows.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the conventional manufacturing method of optical fiber base material, and Figure 2 (a), Φ) shows deformation before using a conventional burner and after using several tens of optical fiber base materials. Figures 3 (1), (b), and (C) are schematic diagrams of the components of an embodiment of the burner according to the present invention, and Figure 4 is a diagram showing the state of the burner. 1 shows a sectional side view of an embodiment of a burner according to the invention; FIG. DESCRIPTION OF SYMBOLS 1... Bar, Su, 2... Porous base material, 3... Electric furnace, 4... Starting material, 5... Flame containing glass fine particles, 6... Reaction vessel, 7 ...The pulling direction of the starting material,
8... Rotation direction of starting material, 9.10... Gas introduction pipe, 11, 12° 12'... Gas flow direction, 13...
- Pulling device, 14... Transparent optical fiber base material, 15.
...Pressure detector, 16...Control circuit, 17...Internal pressure control, exhaust device, 18.19...Chuck, 20...
・Support device, 21-24.22', 22', 23'
, 23'... Burner container pipe, 25-28... Gas inflow direction. '￥J1 Figure (ku) (b) Name: Person who corrects burners for optical fiber base material manufacturing 2, I!l 'OIQ+ Co., Ltd. 1
1.Tate Seisakusho f' Table Old 2:, 111
Masatoshi Katsu Location: Tokyo, Tokyo, Tokyo, 1st Ward, Kutsunouchi, J'l11't, υ"Name (612)Hitachi Cable, Ltd. -Representative: Tokugobe Mizukami"Representative: Person drawings

Claims (1)

[Claims] 1. In a burner configuration in which gas is introduced into each nozzle of a concentric multi-tube burner made of quartz glass and a flame containing glass particles is generated from the nozzle outlet, at least a portion of the tip of each nozzle outlet is A burner for producing an optical fiber base material, characterized in that it is made of quartz glass and the remaining part is made of metal.