JPH04243929A - Production of matrix for optical fiber - Google Patents

Abstract

PURPOSE:To enlarge the deposition rate of glass fine particles and enable a sufficient reaction even when a raw material gas is supplied in a large volume. CONSTITUTION:In a state that a raw material gas flow layer blown from the second layer 92 is nipped with a combustible gas flow layer blown from the first layer 91 and with an oxidizing gas flow layer blown from the third layer 93, glass fine particles are synthesized from the gas layers in a flame to form a porous glass fine particle layer on the surface of a target article.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for manufacturing an optical fiber preform by a VAD method, an OVD method, or the like.

0002

2. Description of the Related Art Conventionally, when manufacturing an optical fiber preform by the VAD method, a core burner 3 makes a porous hole at the tip of a starting material rod 2a that is rotated and pulled up in a chamber 1, as shown in FIG. Core part 4 consisting of a layer of fine glass particles
A cladding part 6 made of a porous glass particle layer is formed on the outer periphery of the cladding part 6 using a cladding burner 5 to obtain an optical fiber preform 7. In this case, a plurality of cladding burners 5 are often used. Burners 3 and 5 used here
is a concentric four- or five-tube burner or a double flame burner.

On the other hand, when manufacturing an optical fiber base material by the OVD method, as shown in FIG. The optical fiber is traversed from side to side while being rotated in the same direction, and a cladding portion 6 made of glass fine particles is formed on the surface using an external burner 8, thereby obtaining a preform for an optical fiber. The external burner 8 used at this time is a concentric burner similar to the clad burner used in the VAD method.

As shown in FIG. 5, these concentric burners have a first layer 91 in the center where raw material gas flows, a second layer 92 where H2 gas or O2 gas flows, and a third layer 93 where an inert gas is passed. O2 gas or H2 gas is passed through the fourth layer 94.

[0005] As shown in FIG. 6, in the double flame burner, gas flows through the first layer 91 to the fourth layer 94 in the center to form the first flame, similar to the concentric burner, and the fifth layer forms the first flame. 95
Inert gas is flowed into the sixth layer 96, H2 gas or O2 gas is flowed into the seventh layer 97, inert gas is flowed into the seventh layer 97, and O2 gas or H2 gas is flowed into the eighth layer 98. A flame is formed.

[0006]

However, the concentric burners used in the conventional VAD method have a problem in that the deposition rate of glass particles is slow and a large number of burners must be used. Additionally, when multiple burners are used, there is a problem in that density changes occur between the layers of the porous optical fiber base material due to interference between the flames of adjacent burners, and the higher the density, the more difficult it is to dewater. .

[0007] In addition, in the case of a conventional external burner using the OVD method, if a large amount of raw material gas is supplied, the moisture generated by combustion will not be able to diffuse sufficiently to the center of the raw material layer, and the raw material gas will not be fully supplied. There was a problem that the hydrolysis reaction stopped.

On the other hand, in the case of a double flame burner, the deposition rate of glass particles is faster than in a four- or five-tube burner, but there is a problem in that the amount of combustion gas used increases. Furthermore, if a large amount of raw material gas is supplied, the same problem as in a four- or five-tube burner occurs, and there is a problem in that the raw material gas does not react sufficiently.

An object of the present invention is to provide a method for manufacturing an optical fiber base material that can increase the deposition rate of glass fine particles and can cause a sufficient reaction even when a large amount of raw material gas is supplied. be.

0010

[Means for Solving the Problems] To explain the means of the present invention for achieving the above object, the method for manufacturing an optical fiber preform according to the present invention comprises replacing a raw material gas flow layer with a combustion gas flow layer. It is characterized in that glass particles are synthesized within the flame by blowing out toward the object while being sandwiched between the oxidizing gas flow layer and forming a porous glass particle layer on the surface of the object.

[0011]

[Operation] When the raw material gas flow layer is sandwiched between the fuel gas flow layer and the oxidizing gas flow layer in this way, the combustion gas and the oxidizing gas diffuse into the raw material gas flow and react, producing H2O. The H2O thus formed immediately reacts with the source gas.

Therefore, even if the raw material gas is increased, glass fine particles can be sufficiently synthesized by correspondingly increasing the amounts of combustion gas and oxidizing gas.

[0013] Furthermore, since a synthesis reaction of glass particles occurs at the location where the combustion reaction is occurring, the temperature of the gas increases. For this reason, the particle size of the glass particles increases,
Deposition rate is increased.

Furthermore, in this method, since an inert gas flow layer is not flowed between the combustion gas flow layer and the oxidizing gas flow layer,
The raw material concentration can be increased accordingly, the particle density of the glass fine particle layer can be increased, and the deposition rate can be improved.

On the other hand, in the case of a double flame burner, for example, if the gas is passed through the inner flame as described above, and the gas is passed through the outer flame in the conventional manner, the deposition rate of glass particles increases. Of course, even if the amount of raw material gas supplied is increased, the glass particle synthesis reaction will still occur.

[0016]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a concentric burner 3, which is used in the present invention.
Examples 5 and 8 are shown. This burner 3, 5, 8
Then, a combustion gas such as H2 gas or methane gas is supplied to the first layer 91, a source gas such as SiCl4 gas is supplied to the second layer 92, an oxidizing gas such as O2 gas is supplied to the third layer 93, and a fourth layer 94 is supplied with a combustion gas such as H2 gas or methane gas. An inert gas such as Ar gas is flowed through.

That is, in the method for manufacturing an optical fiber base material of this embodiment, the material gas flow layer from the concentric burners 3, 5, and 8 is sandwiched between the combustion gas flow layer and the oxidizing gas flow layer, and the object is The starting material rod 2a or 2b is blown out to synthesize glass fine particles in the flame, and the starting material rod 2a or 2b is blown out.
A porous glass particle layer 4 or 6 is formed on the surface of b.

In this way, when the raw material gas flow layer is sandwiched between the combustion gas flow layer and the oxidizing gas flow layer, O2 is generated in the raw material gas flow layer.
An oxidizing gas such as 2 and a combustion gas such as H2 diffuse and react to form H2O. Thus formed H2
O immediately reacts with the source gas. Therefore, even if the amount of raw material gas is increased, glass fine particles can be synthesized sufficiently by increasing the corresponding amounts of oxidizing gas and combustion gas.

[0020] Since the synthesis reaction occurs where the combustion reaction occurs, the temperature of the gas is high. Therefore, the particle size of the glass fine particles becomes large, and the deposition rate of the glass fine particles on the starting material rod 2a or 2b can be improved. Furthermore, since no inert gas is flowed between the oxidizing gas flow layer and the combustion gas flow layer, the raw material gas concentration increases accordingly, the particle density can be increased, and the deposition rate of glass fine particles can be improved.

[0021] Also, in a double flame burner, the raw material gas flow layer is sandwiched between the combustion gas flow layer and the oxidizing gas flow layer and is supplied to the inner flame in the same manner as described above, and the conventional gas flow is supplied to the outer flame. Even if it is supplied, the deposition rate of glass fine particles can be improved.

Contrary to the above embodiment, the first layer 91 contains O.
An oxidizing gas such as H2 gas may be passed through the third layer 9, and a combustion gas such as H2 gas may be passed through the third layer 9. Of course, even if the amount of raw material gas supplied is increased, the glass particle synthesis reaction will still occur.

Next, a specific example in the case of the VAD method is as follows.

Core burner (quadruple tube burner) 1st layer
H2 gas 3 l/min 2nd layer
SiCl4 1 l/min, GeCl4
0.5 l/min 3rd layer O2 gas 4 l/min 4th layer Ar gas 1 l/min 2 cladding burners (seven-pipe burner) 1st layer H
2 Gas 10 l/min 2nd layer SiC
l4 3 l/min 3rd layer O2 gas 18 l/min 4th layer Ar gas
2 l/min 5th layer H2 gas
6 l/min 6th layer Ar gas 2.5
l/min 7th layer O2 gas 16
l/denominator material pulling speed 0.8 mm/min Conventionally, three cladding burners were required, but according to the present invention, the required amount of glass particles can be synthesized with two cladding burners. Ta.

FIG. 2 shows an example of a rectangular burner used in the present invention. This rectangular burner has a first layer 9 on top.
1, the second layer 92, the third layer 93, the fourth layer 9
4, five-layer structure up to the fifth layer 95, and further the second layer 92
and the third layer 93 on both sides in the width direction, side layers S1,
It has a structure in which one S2 is provided. In this case, O2 gas is passed through the first layer 91 and the second layer 92 is
SiCl4 gas is supplied to the third layer 93, and H2 gas is supplied to the third layer 93.
Ar gas is flowed into the fourth layer 94, O2 gas is flowed into the fifth layer 95, and both side layers S1 and S2 are
Flow Ar gas. The Ar gas flowing into the left and right side layers S1, S2 and the fourth layer 94 can be controlled independently.

[0026] When the raw material gas SiCl4 is sandwiched between the oxidizing gas O2 and the combustion gas H2 and sent out in this way, the reaction of the raw material gas can be caused quickly, and a large amount of the raw material gas can be introduced.

Furthermore, by aligning the width direction of the raw material gas flow layer with the longitudinal direction of the starting material rod, the deposition rate of glass fine particles can be increased compared to a concentric burner.

Furthermore, it goes without saying that the same effect can be obtained even if the top and bottom of FIG. 2 are reversed.

A specific example of carrying out the OVD method using such a rectangular burner is as follows.

[0030] First layer O2 gas 2
5 l/min 2nd layer SiCl4 20
g/min, GeCl4 0.5 l/min 3rd layer H2 gas 15 l/min 4th layer Ar gas 2 l/min 5th layer O2 gas 15 l/min Side layer Ar gas 4 l/min (
Total amount of left and right) Starting material rod outer diameter 20mm Rotation speed
20rpm Traverse speed 0.3m/
In this case, the deposition rate of glass particles is 3 to 5 g
/min to 7-10g/min.

[0031]

As explained above, according to the method for manufacturing an optical fiber preform according to the present invention, the following effects can be obtained.

(a) Since the raw material gas flow layer is sandwiched between the combustion gas flow layer and the oxidizing gas flow layer, the thickness of the raw material gas flow layer can be reduced, and therefore, the diffusion mixing of the combustion gas and the oxidizing gas with respect to the raw material gas is reduced. gets better. Therefore, in areas where the raw material concentration is high, a large amount of H2 O, which is the reaction between H2 and O2, reacts, so the reaction of the raw materials is rapid, the spatial distribution of glass fine particles becomes small, and a flame with a high density of glass fine particles is created.

(b) Since the raw material gas exists in a place where the reaction between H2 and O2 is intense, the temperature of the surrounding gas increases,
The outer diameter of the glass particles increases, and the deposition rate of the glass particles increases.

(c) Since a sealing gas for H2 and O2 is not used, a flame with a high concentration of raw material gas and a high density of glass particles can be produced.

[0035] For the above reasons, the glass particles can be sprayed onto the object without spreading much within the flame, and the deposition rate can be improved. Further, since the combustion gas and the oxidizing gas are made to easily diffuse, even if the input amount of the raw material gas increases, it can be sufficiently reacted with the combustion gas and the oxidizing gas.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a concentric burner used in the present invention.

FIG. 2 is a cross-sectional view showing an example of a square burner used in the present invention.

FIG. 3 is a longitudinal cross-sectional view of a conventional VAD device.

FIG. 4 is a longitudinal cross-sectional view of a conventional OVD device.

FIG. 5 is a cross-sectional view of a conventional concentric burner.

FIG. 6 is a longitudinal cross-sectional view of a conventional double flame burner.

[Explanation of symbols]

1 Chamber 2a, 2b
Starting material rod 3 Core burner 4
Core part 5 Burner 6 for cladding
Cladding part 7
Optical fiber base material 8 External burners 91 to 98 1st layer (center layer) to 8th layer S1, S2 Side layer

Claims (1)

[Claims] [Claim 1] Blowing out the raw material gas flow layer to the object side while sandwiching it between the combustion gas flow layer and the oxidizing gas flow layer,
A method for manufacturing an optical fiber preform, which comprises synthesizing glass particles in a flame to form a porous glass particle layer on the surface of the object.