JPH0227291B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for improving the internal CVD method, and its main purpose is to improve the yield in soot deposition.

[Technical background] The internal chemical vapor deposition method (abbreviated as internal CVD method) for manufacturing the base material of optical fiber is the process of manufacturing glass raw materials such as SiCl ₄ , GeCl ₄ , POCl ₄ , BBr _{3 ,} etc. This is a widely used method in which gas is fed into a heated target material, such as a quartz glass tube, together with oxygen, and a glass layer, which will become the core of the optical fiber, is deposited and synthesized on the inner wall surface of the quartz glass tube.

[Structure of the Invention] The present invention provides a method for applying soot using the internal CVD method described above under an alternating electric field created by providing electrodes on the inside and outside of a quartz glass tube and applying an alternating voltage to the electrodes. The present invention aims to provide a device that implements the following.

The embodiments shown in the drawings will be described below.

FIG. 1 shows an embodiment of the present invention in a side view, including a partial cross section.

Reference numeral 1 designates a target material, for example a quartz glass tube, which is held by a chuck portion 5 of a glass lathe 2 so as to be rotatable and attachable. 3 indicates a heating device, which is an oxyhydrogen burner in the figure. A raw material gas supply port 4 is provided that passes through the rotating shaft of the glass lathe 2, and the remaining waste gas and fine oxide particles 8 pass through the held quartz glass tube 1 from the other end of the rotating shaft of the glass lathe 2. Configured to be evacuated.

Although not shown, the oxyhydrogen burner 3 is configured to be moved by a traverse mechanism so that it can traverse left and right.

While holding the quartz glass tube 1, an electrode wire 6 such as a platinum wire is stretched inside the tube and connected to one side of an alternating power source. On the other hand, an electrode 7 is provided close to the outside of the quartz glass tube 1 and connected to the other side of the alternating current power source to be at ground potential. This electrode 7 is plate-shaped and extends over a wide area along the outer diameter surface of the quartz glass tube 1. Therefore, the alternating power supply, electrode 6 and electrode 7
As a result, an alternating electric field is formed, and the quartz glass tube 1
enters between the electrodes. An electric field is formed in this manner, and while the quartz glass tube 1 is being rotated and heated by the heating device 3, a raw material gas such as SiCl ₄ , GeCl ₄ ,
If BBr ₃ , POCl ₃ , oxygen, etc. are introduced, SiO ₂ , GeO ₂ , P ₂ O ₅ ,
A fine oxide such as B ₂ O ₃ becomes 8, and the quartz glass tube 1
The fine oxide particles 8 are attracted to the inner wall surface, and the attracted fine oxide particles 8 are melted and uniformly adhered to the inner wall surface.

As explained above, in the apparatus shown in FIG. 1, the outer electrode 7 is configured to extend along the outer diameter of the quartz glass tube 1 over a relatively long range in the axial direction. As in the embodiment shown in the figure, the dimension in the axial direction can be reduced to a size that extends to the portion actually heated by the heating device 3 and its vicinity. In this case, the heating device 3 is provided with a slit in a part of a plate-shaped electrode 7 having a curved surface as shown in the figure, and is attached so that the quartz glass tube 1 is oriented through the slit. With such a configuration, the heating device 3 and the electrode 7 can be moved in the axial direction of the rotating quartz glass tube 1, and the electric field can also be moved accordingly.In this way, the movement of the electric field and the heating By moving the device 3, the raw material gas or particulate oxides can be collected, preventing most of them from flowing out to the exhaust side, increasing the yield, and by uniformly moving the concentrated electrostatic field, A base material for an optical fiber in which homogeneous fine oxide particles adhere to the inner wall surface of the quartz glass tube 1 can be obtained.

Depending on the nature of the raw material gas, the gas atmosphere, etc.
The applied alternating electric field is preferably one whose frequency can be changed depending on the situation, and one whose voltage value can be changed.

When an alternating electric field is applied, the fine oxide particles in the quartz glass tube 1 are excited and adhere to the inner wall surface of the quartz glass tube 1 during heating, and do not scatter even when a repulsive force is applied. A glass film layer grows on the inner wall surface of the tube 1.

As for the inner electrode 6, platinum wire can be used as explained in FIG. 1, but if it actually becomes long, it will be difficult to hold it without loosening, The sagging can be prevented by using a quartz glass tube or a Vycor glass pipe as shown in 9.
In this case, it is also preferable to confine the inner electrode 6 within the quartz glass pipe or Vycor glass pipe 9 to prevent foreign matter from the electrode material from entering the reaction space of the quartz glass tube 1. If this is adopted, it becomes possible to use copper, silver, carbon wire, etc. as the electrode material.

However, it goes without saying that it is more preferable to use a bare electrode without a coating than to use a coated electrode in this way, and it does not affect the formed optical fiber preform. Select and use things.

[Effects of the Invention] As explained above, according to the present invention, since electrodes are arranged inside and outside the quartz glass tube, SiO ₂ ,
The yields of GeO ₂ , P ₂ O ₃ and the like are improved, and the waste gas of the fine oxides is accordingly reduced.

Furthermore, by changing the voltage and frequency applied to the electrodes, the amount of soot adhering to the inner wall surface of the quartz glass tube can be controlled.

The completed preform is transferred to the next process.

[Brief explanation of drawings]

FIG. 1 is a side view showing an embodiment of the present invention, including a partial cross section. FIG. 2 is a side view showing another embodiment of the present invention, including a partial cross section. DESCRIPTION OF SYMBOLS 1...Quartz glass, 2...Glass lathe, 3...Heating device, 4...Material gas supply port, 5...Chuck part, 6
...inner electrode, 7...outer electrode, 8...fine oxide, 9...quartz glass tube or Vycor glass pipe.

Claims (1)

[Claims] 1. In the production of optical fiber preforms using the internal CVD method, when fine grain oxides such as SiO ₂ are attached to a heated and rotating quartz glass tube, the inside of the quartz glass tube and An internal attachment characterized in that an electrode is placed on the outside and an alternating electric field is applied to cause the fine oxide particles to adhere to the inner wall of the quartz glass tube.
A method for manufacturing optical fiber preforms using the CVD method. 2. A glass lathe that removably and rotatably holds a quartz glass tube and is equipped with a supply port for supplying raw material gas, and a heating device equipped with a traverse mechanism that heats the surface of the quartz glass tube, and the inner wall of the quartz glass tube. During the soot application process, electrodes were provided inside and outside the quartz glass tube to generate an alternating electric field.
Optical fiber preform manufacturing equipment using the internal CVD method, which is characterized by connecting this to a variable frequency, variable voltage alternating power supply.