JPH0717398B2 - Method for manufacturing base material for optical fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a base material for optical fibers.

[Conventional technology]

VAD method, MCVD method, O
There is VPO law.

OVPO method, while moving a cylindrical or cylindrical glass rod relative to the burner, blow a glass raw material such as SiCl _{4 with} respect to the glass rod from the burner together with the oxyhydrogen flame,
Glass fine particles produced by hydrolysis in a flame are deposited on the outer circumference of a glass rod.

The optical fiber base material thus externally attached is dehydrated and clarified, and then the optical fiber is manufactured by drawing.

In Japanese Patent Laid-Open No. 62-70243, the upper end of a glass rod is supported by a rotary chuck of a pulling shaft, and glass particles are deposited on the outer periphery of the glass rod while the glass rod is being pulled while rotating. Prior to that, a method of correcting the whirling amount at both ends or a portion close to both ends of an effective portion of the glass rod as an optical fiber is described. That is, a correction jig such as a chuck that is accurately aligned with the axis of the pulling shaft is arranged at the correction position,
A hand burner is placed immediately above the correction jig to heat and soften the glass rod, and the whirling amount of the glass rod is corrected to a small amount by the correction jig. After the correction, these are removed and glass fine particles are deposited.

[Problems to be solved by the invention]

The above method does not maintain the axis of the glass rod in the step of depositing the glass particles. If the glass rod is rotated while the correction jig is attached and glass particles are deposited while pulling it up, whirling of the shaft center can be prevented, but the effective portion of the optical fiber also directly contacts the correction jig. As a result, scratches and dust may be attached to the surface of the glass rod. Such scratches and dust cause defects in the optical fiber.

Therefore, the present invention solves the above-mentioned drawbacks, and prevents the whirling of the shaft core through mechanical contact below the glass rod, while cleaning the surface of the glass rod on which glass particles are deposited to clean the surface of the glass rod. An object of the present invention is to provide a method for producing a base material, which prevents scratches and dust from being introduced into the base material.

[Means for solving problems]

INDUSTRIAL APPLICABILITY The present invention manufactures a base material for optical fibers in which the upper end of a cylindrical or cylindrical glass rod is fixed on a rotating shaft and glass fine particles are deposited on the outer periphery of the glass rod while moving upward while rotating the glass rod. In the method, the lower part of the glass rod is rotatably and movably supported through mechanical contact, and the surface of the glass rod immediately above the supporting means is heated to remove scratches and the like caused by mechanical contact, A method for producing a base material for an optical fiber, which comprises depositing glass fine particles.

[Action]

FIG. 1 is a diagram for explaining the implementation situation of the present invention,
FIG. 2 is a cross-sectional view showing an example of mechanical support means below the glass rod.

In the apparatus shown in FIG. 1, the glass rod 1 has its upper end supported by a rotary chuck 2 connected to a pulling shaft, and is arranged so as to vertically penetrate a reaction vessel 3. A synthesis burner 4 for synthesizing glass fine particles by supplying a glass raw material and oxygen-hydrogen gas is provided below the reaction vessel 3, and an exhaust pipe 5 is provided at a position facing the burner 4. Below the outside of the reaction vessel 3,
A cleaning treatment chamber 6 for the surface of the glass rod 1 is attached, and the treatment chamber 6 is attached.
Is provided with a burner 7 for heating the surface of the glass rod 1 and an exhaust pipe 8 facing the burner 7. Outside the processing chamber 6, a mechanical supporting means 9 for preventing whirling of the glass rod is attached. A concrete example of the supporting means is shown in FIG. 2 (a) in which the glass rod 1 is supported by a split type chuck 11, and FIG. 2 (b) is similar in the case of two rollers 12. To support. These supporting means are fixed so as to be exactly aligned with the axis of the pulling shaft, and the glass rod 1 is rotated in the supporting means and slidably supported so as to be able to be pulled up. The supporting means is not limited to the one shown in FIG. 2 as long as it has the above-mentioned function. It is preferable that the surface of these supporting means that is in direct contact with the glass rod is made of a material such as Teflon or carbon to suppress the occurrence of scratches as much as possible.

Next, a procedure for manufacturing the porous base material will be described. Fig. 1 (a)
Shows the initial stage of production. While rotating the glass rod 1 by the rotary chuck 2, the synthetic gas is supplied from the burner 4 and the glass fine particles synthesized in the oxyhydrogen flame are fed into the glass rod 1.
Is deposited on the surface of to form the porous base material 10. Porous matrix
The glass rod 1 is gradually pulled upward while the 10 is grown to a predetermined diameter. By the way, the supporting means below the glass rod 1 is designed to avoid the occurrence of scratches as much as possible, but it is impossible to avoid it completely. Therefore, the glass rod contacting the supporting means is moved to the cleaning chamber 6 by the above-mentioned pulling, heated by the heating burner 7 to remove scratches and dust on the surface of the glass rod, and cleaned and then moved into the reaction vessel 3. Then, the glass fine particles are deposited.
FIG. 1 (b) shows the final stage of the deposition process, and shows the state in which the cylindrical porous base material 10 is formed on the outer periphery of the glass rod 1.

The fuel gas supplied to the heating burner is H ₂ , CH ₂ .
₄ , C ₂ H ₆ , C ₃ H _3, etc. can be used. Further, the temperature of the glass rod is usually heated to about 1800 ° C. by these gases, but it is necessary to heat the glass rod within a range in which the glass rod cannot be bent by heat.

〔Example〕

Glass fine particles were deposited on the surface of a quartz glass rod having a diameter of 15 mm by using the apparatus shown in FIG. For the lower support, a Teflon chuck of the two-divided type shown in FIG. 2 (a) was used. 1 / min of SiCl ₄ and H for the burner for synthesizing glass particles
₂ was supplied at 40 l / min and O ₂ was supplied at 40 l / min, and was pulled upward at a moving speed of 80 mm / hour. During this time, from the heating burner,
H ₂ was supplied at 30 l / min and O ₂ was supplied at 15 l / min. When the obtained porous base material was dehydrated and transparently integrated, high-quality glass without any bubbles could be obtained.

For comparison, except that the supply of combustion gas from the heating burner was stopped, a porous preform was made under the same manufacturing conditions as in the above example, and transparent integration was performed. Many minute bubbles were generated.

〔The invention's effect〕

The present invention, by adopting the above configuration, prevents whirling under the glass rod through mechanical contact, while removing scratches and the like on the surface of the glass rod due to the contact, and then the porous mother material in the reaction vessel. Since the material can be formed, it is possible to form a high-quality optical fiber preform without causing eccentricity of the glass rod and having no defects such as scratches on the surface of the glass rod.

[Brief description of drawings]

1 (a) and 1 (b) are views for explaining the procedure for carrying out the present invention, and FIGS. 2 (a) and 2 (b) are views showing an example of the glass rod supporting means used at that time. .

Claims (1)

[Claims] 1. A base material for an optical fiber, wherein the upper end of a cylindrical or cylindrical glass rod is fixed on a rotating shaft, and glass fine particles are deposited on the outer periphery of the glass rod while moving upward while rotating the glass rod. In the manufacturing method of 1., the lower part of the glass rod is rotatably and movably supported through mechanical contact, and the surface of the glass rod immediately above the supporting means is heated to remove scratches and the like caused by mechanical contact. A method of manufacturing a base material for an optical fiber, which comprises depositing glass fine particles later.