JPS58161936A - Method and device for production of preform for optical fiber by external cvd method - Google Patents

Abstract

PURPOSE:To form a preform for optical fiber at high yields of raw materials in the stage of forming the preform on the outside of a target made of a quartz tube by an external CVD method, by providing movable electrodes on the inside and outside of the target and forming an electric field. CONSTITUTION:A target 2 made of quartz glass is held freely rotatably by the chucks 5 of a glass lathe 1, and an electrodes 6 of a platinum wire is disposed in the target 2 and is connected to a pulling wire 10 through an insulator 9. A sprayer 3 consisting of a burner 3 of a traversing mechanism provided with an electrode 7 is installed on the outside of the target 2. DC voltage is applied to both electrodes 6, 7, and particulate oxides SiO2, GeO2, etc. 8 of SiCl4 and GeCl4 which are gaseous raw materials are sprayed from the burner 3 to form a porous base material for the optical fiber. The electrode 6 is moved in the target 2 in this case to move the electric field by both electrodes, whereby the preform is formed uniformly on the surface of the target 2 in high yields.

Description

DETAILED DESCRIPTION OF THE INVENTION The object of the present invention is to improve the yield of sooting by external CVD.

The external chemical vapor deposition method (abbreviated as CVD method) for producing the base material of optical fibers is a method that uses 5I, which is the raw material for glass.
CI4, GeCl4, POCl3, BBr3
5i02, GeO2, which can be produced by reaction of raw material gases such as oxyhydrogen burner flame or plasma flame.
This method involves depositing particulate oxides such as B2O3 (commonly referred to as soot) onto a target such as a quartz rod.

According to this method, a porous base material is obtained.

Embodiments of the present invention shown in FIGS. 1 and 2 will be described below. FIG. 1 is a side view showing an embodiment of the present invention, including a partial cross section.

1 is a glass lathe, 2 is a target material such as a quartz glass tube, which is rotatably held by the rotating shaft of the glass lathe 1 and detachably held by the chuck part 5; A blast burner coupled to a traversing mechanism (not shown) capable of traversing parallel to the axis. Reference numeral 4 indicates a porous base material that is in the process of being manufactured and deposited on the target material 2 due to the progress of the reaction.

In the structure as described above, the electrode 6 is passed through and stretched inside the quartz glass tube which is the target material 2. Platinum wire is preferred as the electrode material. Further, the other electrode 7 is attached so as to be on the outside of the porous base material 4.

In the figure, the sprayer is attached to burner 3.

Reference numeral 13 denotes a DC power supply, which is of a variable voltage type whose polarity can be switched and whose voltage value can be adjusted.

When this DC power source 13 is connected to the electrodes 6 and 7, an electrostatic field is generated between the electrodes. For example, as shown in the figure, the electrode 6 on the inside of the target material 2 is used as a negative electrode, and the electrode 7 on the outside is used as a positive electrode. At this time, the outer electrode 7 and the inner electrode 6 are arranged so that the electric field spreads soot and covers the surface.

Therefore, the spraying is performed on the raw material gas emitted from the burner 3, such as fine oxide particles 5 of gases such as S+CI4 and GeCl4.
i02. When GeO2 or the like is positively charged, it is attracted to the inner electrode 6 side. If the fine oxide particles 8 are negatively charged, the polarity of the power source 11 can be changed, and in this way, the fine oxide particles 8 sprayed while traversing the target material 2 and the top thereof. It is deposited on the porous base material 4 to be deposited.

The inner electrode 6 may be a movable electrode in which a platinum wire, for example, is connected to the tip of the electrode 6 through an insulator 9 as a pull wire 1O. The tension line IO beyond the insulator 9 is used for the purpose of moving the electrode 6 within the quartz glass tube. No voltage is applied to this part due to the application of the power supply voltage, and the electric field is created between this tension line IO and the electrode 7. does not occur.

By pulling this movable electrode 6 in one direction while holding down the end of the pull wire 10 and the other end of the electrode 6, the tip of the electrode 6 can be moved within the quartz glass tube. Depending on the degree of growth of porous base material 4, the yield in porous base material 4 increases if the growth surface is always maintained to be included.

In particular, when doping with fluorine, the fluorine component tends to scatter and is difficult to dope, but according to the above-mentioned moving electrode configuration,
It is possible to prevent the diffusion of fluorine content and improve the yield of sooting. In this case, the burner 8 used for spraying is plasma flame, which will be described later.

FIG. 2 is an enlarged view of a part of the spraying device shown in FIG. 1, including the burner 3.

As shown in the figure, the surfaces of the outer electrodes 7 are oriented to be equidistant from the tip of the inner electrode 6, that is, near the connection of the insulator 9. The electrode 7 can have various shapes.

As in the embodiment already described, when the blowing is performed by moving the burner 3 in the axial direction of the quartz glass tube, the electrode 7 also moves at the same time, so that the inner electrode 6 is moved accordingly. The tip only needs to be moved so as to maintain the relationship with the aforementioned electrode 7;
Even in the case of a type in which the electrode 7 is fixed and the quartz glass tube moves in the direction of the rotation axis, a similar configuration is adopted.

The burner 3 is an oxyhydrogen burner with a multi-centre structure that uses gaseous materials such as S+C14, GeCl4, oxygen, and hydroxyl (hydrolysis method), and a nozzle with a multi-centre structure that uses 5i (I4.GeCl4. An oxidation device (non-hydrolysis method) using a plasma flame using oxygen etc. may also be used. 11 in Fig. 2 is a plasma generation coil;
12 is provided near the outer periphery of the plasma generating coil 11,
This is a shield intended to avoid electrical interference with the outer electrode 7 that is placed close to it. For spraying, the burner 3 may be integrally combined with the outer electrode 7, or may be configured independently.

The inner electrode 6 is removed from the porous base material 4 preformed according to the present invention as described above, and the next step is carried out.

According to the present invention, it is possible to improve the yield of sooting compared to the conventional external CVD method, and the amount of sooting can be controlled by adjusting the electric field. Accordingly, the amount of discarded soot such as 5i02 can be reduced by 1.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, including a partial cross section, and FIG. 2 is a partially enlarged view of the embodiment in FIG. ]...Glass lathe, 2...Target material, 3...
Spraying is performed using a burner, 4... porous base material, 5... chuck part, 6... inner electrode, 7... outer electrode, 8...
Fine grain oxide, 9... Insulator, 10... Tensile wire, 1
1... Coil for plasma generation, 12... Shield,
1B...DC power supply. π1 flash

Claims (1)

[Claims] (υ In the production of optical fiber preforms by the external CVD method, Si
When depositing fine grain oxides such as O2, the growth surface of the porous base material in the target material is placed in an electric field formed by electrodes installed on the inside and outside of the target material, and the fine grain oxide such as 5i02 is deposited. A method for producing an optical fiber preform by an external CVD method, which is characterized by attaching a material onto a target material and a porous material. (2) A lathe that removably and rotatably holds the target material, and S r 02 on the surface of the target material, etc.
For spraying fine oxide particles such as soot, a burner etc. should be installed, and electrodes should be installed inside and outside the target material to generate an electric field during the process of applying soot onto the target material, and these should be connected to all power sources. Optical fiber preform manufacturing equipment using external CVD method with all the features. (3) The electrode placed inside the turcut material consists of a moving electrode with a tension wire connected to its tip, and during the sooting process, the tip of the moving electrode moves according to the degree of growth of the porous base material. 3. The apparatus for producing an optical fiber preform by an external CVD method according to claim 2, wherein the apparatus is configured to move the preform to the growth surface.