JPS58161935A - Method and device for production of preform for optical fiber by internal cvd method - Google Patents

Abstract

PURPOSE:To form a preform for optical fibers at high yields of raw materials in the stage of forming the preform on the inside of a target by an internal CVD method, by providing electrodes on the inside and outside of a target and forming an electric field. CONSTITUTION:A target material 1 made of a quartz glass tube is gripped freely rotatably by means of the chucks 5 of a glass lathe 2, and gaseous substances 4 such as SiCl4, GeCl4, BBr2, POCl3 and O2 are supplied as raw materials for the preform for optical fibers through an inlet 4 into a target 1. The target 1 is heated with a burner 3 to cause said gases to react, and to form particulate oxides 8 such as SiO2, GeO2, P2O5, B2O3 or the like. These oxides are stuck and melted on the inside wall of the quartz glass tube which is the target, thereby forming the preform for optical fibers. A platinum cathode 6 is disposed in the target 1 in this stage and the fine particles 8 of oxides are attracted forcibly to the inside wall of the tube 1 by the electric field formed when voltage is applied to the outside of the cathode with an anode 7 kept at the earth potential, whereby the preform is formed in high yields of raw materials.

Description

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

The encapsulated chemical vapor deposition method (abbreviated as the fleshed CVD method) for producing the base material of optical fibers uses 5I, which is the raw material for glass.
A gas such as C14, GeC14, POCl2, or BBrB is fed together with oxygen into a heated target material, such as a quartz glass tube, and a glass layer that will become the core of the optical fiber is deposited and synthesized on the inner wall surface of the quartz glass tube.

The present invention combines Cottrell's method with such a fleshy CVD method. That is, the present invention provides a method for applying soot by the above-mentioned CVD method under which electrodes are provided on the inside and outside of a quartz glass tube and a voltage is applied to the electrodes to generate an electric field, as well as an apparatus for applying soot. This is a book that tries to

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.

1 is a target material, for example, a quartz glass tube, and is held by a chuck portion 5 of the glass lathe 2 so as to be rotatable and mountable. 8 indicates a heating device, which is an oxyhydrogen burner in the figure. A raw material gas supply port 4 is provided through which the rotating shaft of the glass lathe 2 is inserted, and the waste gas and fine oxide particles 8 are passed through the held quartz glass tube 1 and left in the glass lathe 2.
The exhaust gas is configured to be exhausted from the other end of the rotating shaft.

Although the oxyhydrogen burner 8 is not shown, it is configured to be moved by a traverse 2 mechanism so that it can traverse left and right.

While holding the quartz glass tube 1, insert the electrode wire 6 inside it.
For example, a platinum wire is stretched and connected to a negative potential by a power source. On the other hand, the electrode 7 is located close to the outside of the quartz glass pipe l.
Connect this to the positive side of the power supply and set it to 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, an electric field is formed by the electrodes 6 and 7, and the quartz glass tube 1 is just inserted between the dust collection space of the Cottrell dust collector. While the electric field is formed in this manner and the quartz glass tube l is heated while being rotated by the heating device 8, a raw material gas, for example 5ICI4,
If GeCl4, BBrB, POCIB, oxygen, etc. are introduced, 5i0 is heated by the heating device 3.
2. Fine grain oxides such as GeO2, P2O6, B20B, etc.8
Tonashi, quartz glass tube summer? '3 I was drawn to the wall,
The attracted fine oxide particles 8 are melted and attached to the inner wall surface.

As explained above, in the device shown in FIG. 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 8 and its vicinity. In this case, as shown in FIG. 81d of the heating device, a slit is provided in a part of the plate-shaped electrode 7 having a curved surface, and the quartz glass tube l is attached so as to be oriented through the slit. With such a configuration, both the heating device 3 and the electrode 7 can be moved in the axial direction of the rotating quartz glass tube l, and the electric field can also be moved accordingly.In this way, the movement of the electric field and the heating device The movement of step 3 collects the raw material gas or particulate oxide, prevents most of it from flowing out to the exhaust side, and increases the yield. , it is possible to obtain a base material for an optical fiber in which homogeneous fine acid particles adhere to the inner wall surface of the quartz glass tube l.

Depending on the nature of the source gas, the gas atmosphere, etc., the polarities of the inner and outer electrodes relative to the quartz glass tube 1 may be reversed. Furthermore, an alternating voltage may be applied between the two electrodes to create an alternating electric field. In this case, it is preferable to use a power source whose frequency can be changed depending on the situation, and a power source whose voltage value can be changed is used for both DC and AC power supplies.

Even in the case of an alternating electric field, 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 glass tube 1.

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

However, compared to using electrodes containing nuclides in this way,
Needless to say, it is preferable to use a bare electrode without having an electrode, and one that does not affect the formed optical fiber preform is selected and used.

As explained above, according to the present invention, 5i02°Ge
The yield of O2, P2O3, etc. is improved, and the waste gas of the above-mentioned fine oxides is also reduced accordingly.

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 the drawing]

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 some parts.

Claims (3)

[Claims] (1) In the production of optical fiber preforms by the CVD method, when attaching fine grain oxides such as Sr02 to a heated and rotating target material, the inside and outside of the target material are 1. A method for producing an optical fiber preform by a thickened CVD method, characterized in that an electric field is applied by an electrode provided at the target material to cause the fine oxide particles to adhere to the inner wall of the target material. (2) A method for producing an optical fiber preform by the CVD method as set forth in claim 1, wherein an alternating electric field is used as the electric field. (3) A glass lathe that holds the target material in a removable and rotatable manner and is equipped with a supply port for supplying raw material gas, and a heating device that heats the surface of the target material, etc., to prevent soot from forming on the inner wall of the target material. An apparatus for producing an optical fiber preform by internal CVD, characterized in that electrodes are provided on the inside and outside of a target material and connected to a power source so as to generate an electric field during operation.