JPH09142865A - Reactor forming porous preform for optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor capable of producing a high quality porous preform for optical fibers in a high yield. SOLUTION: In this reactor forming a porous preform for optical fibers, equipped with an apparatus for pulling up the porous preform for optical fibers while rotating, a burner 40 for attaching soot on the growth face of porous preform 20 for optical fiber, a discharge port 50, suction port 60 and airway 63 for suction gas, a blocking body 64 for blocking the flow of the suction gas to flame 41 is provided in the airway 63 for suction gas. Since the suction gas is blocked by the blocking body 64 provided in a prescribed place of the airway 63 for suction gas, the suction gas is not directly brought into contact with the flame 41. As a result, the porous preform 20 for optical fiber not causing fluctuation of the flame 41 and having good shape and free from crack is obtained in high yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reaction container in which a high quality porous preform for optical fibers can be obtained with a high yield.

[0002]

2. Description of the Related Art A porous base material for an optical fiber is a raw material gas such as SiCl ₄ or GeCl ₄ ejected from a burner, and the raw material gas is hydrolyzed in a flame of oxyhydrogen or hydrocarbon to form glass fine particles, It is manufactured by depositing the glass particles around a rotating starting material (quartz rod). The obtained porous preform for optical fibers is heated and softened after sintering, and one end of the porous preform is drawn at a constant speed to be drawn into an optical fiber having a required outer diameter. By the way, as illustrated in FIG. 3, the reaction container for producing such a porous base material for an optical fiber includes a device 30 for pulling up the porous base material for an optical fiber 20 while rotating the porous base material for an optical fiber, and a porous base material for an optical fiber. A burner 40 for sooting the growth surface of the material 20, an exhaust port 50 for exhausting by-products and unnecessary substances exhausted from the burner 40, an intake port 60 for sucking gas flowing in the reaction vessel 12, and the vicinity of the intake port 60. The intake air passage 63 is provided in an annular shape. still,
With the above-mentioned by-products, chlorine, hydrogen chloride, etc.
For example, glass fine particles not deposited on the porous preform for optical fibers. As described above, these by-products and unnecessary substances are carried to the intake gas flowing in the reaction container 12 and discharged from the exhaust port 50.

[0003]

However, the burner flame is fluctuated by being influenced by the surrounding airflow as seen in the candle flame. In particular, the flow of the intake gas after leaving the air passage was unstable, which caused large fluctuations in the flame, which could lead to uneven shapes and cracks in the porous preform for optical fibers. . Further, when the flow of the intake gas is disturbed, a large amount of glass particles that are not deposited will stay in the reaction container, and the stayed substances will be mixed in the porous preform for optical fiber to produce the above-mentioned porous glass for optical fiber. Bubbles were sometimes generated in the glass preform for optical fibers obtained by sintering the preform. Since the porous glass preform for optical fibers having a non-uniform shape or cracks and the glass preform for optical fibers having bubbles are defective products, a high production yield cannot be obtained. Against such a situation, the present inventors have conducted various researches on a method of preventing fluctuations of flames, and have found that fluctuations of flames can be reduced by controlling the flow of intake gas in the air passage, and further researches have been conducted. To complete the present invention. An object of the present invention is to provide a reaction container capable of producing a high-quality porous preform for optical fibers with a high yield.

[0004]

Means for Solving the Problems The present invention provides at least:
Device for pulling while rotating the porous preform for optical fiber,
In a reaction vessel for forming a porous base material for an optical fiber, which comprises a burner for sooting a growth surface of the porous base material for an optical fiber, an exhaust port, an intake port, and an air passage for the intake gas, A reactor for forming a porous preform for an optical fiber, characterized in that a shield for blocking the flow of intake gas to the burner portion is provided inside the passage.

In the present invention, various shapes such as a plate material, a block material, and a mesh material having a fine mesh are applied to the shield. The shape and mounting position of the shield are determined in consideration of the size of the air passage, the amount of intake gas, the position of the flame from the burner, and the like. In particular, it is important that the mounting position is such that the flow of the intake gas that bypasses the shield and flows out is symmetrical with respect to the flame emitted from the burner. As the intake gas, any gas such as an inert gas such as nitrogen gas or air that does not deteriorate the porous preform for optical fiber can be applied. The present invention can be applied to any reaction vessel having an air passage. Further, it is not particularly restricted by the shape and position of the air passage.

[0006]

The present invention will be described below in detail with reference to examples. (Embodiment 1) FIGS. 1A and 1B are a longitudinal sectional view and a plan perspective view showing a first embodiment of a reaction container of the present invention. 10 in the figure
Is a reaction vessel for forming a porous preform for optical fiber (hereinafter abbreviated as porous preform) 20, and a device 30 for pulling up while rotating the porous preform 20 is attached to the top of the reaction vessel 10. Has been. A burner 40 is installed below the porous base material 20, and soot generated by reaction by a flame 41 from the burner 40 is deposited on the lower surface of the porous base material 20. An exhaust port 50 is provided in front of the burner 40, and from this exhaust port 50,
By-products and unnecessary substances in the reaction vessel 10 are discharged. An intake port 60 is provided above the reaction container 10. This inlet
A cylindrical partition wall 61 is provided inside 60, and an annular space formed between this partition wall 61 and the inner wall surface 62 of the reaction vessel 10 serves as an intake gas air passage 63. The lower end of this air passage 63 is open, and the lower end of this open air passage 63
A plate-shaped shield 64 having a predetermined length is provided directly above the burner 40.

A porous base material 20 was manufactured using the reaction vessel 10 shown in FIG. A quartz rod 31 as a starting material is attached to a device 30 for pulling up while rotating the porous base material, and a flame 41 of oxyhydrogen from a burner 40 is applied to the tip end portion of the quartz rod 31, and the raw material (SiCl 4 ₄ , glass particles produced by hydrolysis of GeCl ₄ ) were deposited. Reaction vessel
The inside of 10 was degassed from the exhaust port 50 by a degassing pump (not shown), and at the same time, nitrogen gas was sucked from the intake port 60. By-products such as chlorine gas and unnecessary substances such as glass particles that did not deposit were discharged from the exhaust port 50 along with the nitrogen gas flow. The glass particles did not stay in the reaction vessel.

(Embodiment 2) FIGS. 2A and 2B are a longitudinal sectional view and a plan perspective view showing a second embodiment of the reaction container of the present invention. In the reaction container 11, the intake port 60 is at a position deviated from the disposition position of the burner 40 by 90 degrees in a plan perspective view. For this reason, the shield 64 is protected by the nitrogen gas that bypasses the shield 64.
It was installed at a position slightly offset from the position directly above the burner 40 toward the intake port 60 so that it would flow symmetrically to the flame 41 of the 40. Using this reaction vessel 11, a porous preform for optical fibers was manufactured in the same manner as in Example 1.

With respect to each of the obtained porous base materials for optical fibers, the uniformity of shape and the occurrence of cracks were investigated.
Further, with respect to the porous preform for optical fibers, which had no problem in shape uniformity and did not crack, the bubbles of the glass preform for optical fibers obtained by sintering were also investigated. And the yield was investigated based on these survey results. The same investigation was carried out by producing a porous preform for optical fibers by using the conventional reaction container shown in FIG. The results are shown in Table 1 together with the situation of flame fluctuation.

[0010]

[Table 1] ◯: All have good shape, no cracks, and no bubbles. Δ: Some shapes were defective, some were cracked, and some were foamed. *: The shape and cracks were evaluated as ○.

As can be seen from Table 1, the products of Examples of the present invention (Examples 1 and 2) were excellent in the shape of the porous base material for optical fiber over all, without cracking, and for optical fiber. No bubbles were generated in the glass base material, and as a result, the production yield was high. On the other hand, the conventional product (conventional example 1) had a large flame fluctuation, an uneven shape, and no cracking. Further, a large amount of glass microparticles stayed in the reaction container, which was mixed in the porous preform for optical fibers to generate bubbles in the sintered glass preform for optical fibers. Therefore, the production yield was remarkably reduced.

[0012]

As described above, in the reaction container of the present invention, since the shield is provided at a predetermined position of the intake air passage, the intake gas is shielded by the shield and does not directly hit the flame. ,
Therefore, the fluctuation of the flame becomes small, the shape is good, and a high-quality porous base material without cracks can be obtained with a high yield.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view showing a first embodiment of a reaction container of the present invention, and FIG. 1B is a plan perspective view showing a first embodiment of the reaction container of the present invention.

FIG. 2A is a vertical sectional view showing a second embodiment of the reaction container of the present invention, and FIG. 2B is a plan perspective view showing the second embodiment of the reaction container of the present invention.

FIG. 3 is a vertical cross-sectional view of a conventional reaction container.

[Explanation of symbols]

10,11,12… Reaction vessel 20 ………… Porous preform for optical fiber 30 ………… Device for pulling while rotating porous preform for optical fiber 31 ………… Quartz rod 40 ………… … Burner 41 ………… Flame 50 ………… Exhaust port 60 ………… Intake port 61 ………… Partition wall 62 ………… Upper inner wall of reaction vessel 63 ………… Intake gas air passage 64 ………… Shield

Claims (1)

[Claims] 1. At least an apparatus for pulling while rotating a porous preform for optical fiber, a burner for sooting a growth surface of the porous preform for optical fiber, an exhaust port, an intake port, and an air passage for intake gas. In a reaction container for forming a porous preform for optical fibers, the shield for blocking the flow of the intake gas to the burner portion is provided in the intake gas wind passage. A reaction vessel that forms a porous matrix.