JPH0627624Y2 - Optical fiber base material manufacturing burner - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a burner for manufacturing a base material for an optical fiber, which includes a VAD method (gas phase axis method) and an OVPO method (external gas phase oxidation). Method) to improve the burner for efficiently producing soot (glass particles) at a high speed.

[Conventional technology]

As one method for producing a porous glass preform for optical fibers, a combustion gas and a glass raw material are mixed and jetted from a combustion burner to generate glass particles by a hydrolysis reaction or an oxidation reaction in a flame, and the glass particles are rotated. There is a VAD method in which a porous glass base material is manufactured by depositing the starting material on the tip of the starting material and moving the starting material relative to the burner as the deposit grows.

There is also an OVPO method in which glass particles produced by an oxidation reaction in the flame of a combustion burner are deposited on the outer periphery of the starting material and the starting material or the combustion burner is traversed multiple times to produce a porous glass preform. (JP-A-48-73
No. 522) [Problems to be solved by the invention] The combustion burner conventionally used in the VAD method is shown in FIG. 6 (a).
A concentric multi-tube burner, whose radial and axial sectional views are shown in (b) and (b), is common, and the jet port of this burner has a straight shape as shown in Fig. 6 (b). ing. In FIGS. 6 (a) and 6 (b), reference numerals 1, 2, 3 and 4 indicate jet ports of each layer from the central portion toward the outer periphery. From each layer of the burner, for example, gas is flowed from the center in the order of glass raw material, hydrogen, argon and oxygen. Further, the glass raw material may be added to the second layer.

By the way, when the raw material flow rate is increased for the purpose of increasing the synthesis rate of the optical fiber base material (base material weight synthesized per unit time), the flow rate increases as the flow rate increases,
As a result, there is a problem that the reaction reaches the surface of the base material before the reaction proceeds sufficiently, and most of the raw materials are exhausted without reacting. On the other hand, if the diameter of the ejection port of the raw material of the burner is increased in order to reduce the flow velocity, it takes time for the raw material and H ₂ and O ₂ flowing in the outer layer to diffuse, and the reaction also does not proceed. At the same time, when the port diameter becomes large, the reacted glass fine particles are dispersed in the outer peripheral direction from the center of the flame, and the space number density of the glass fine particles becomes thin. As a result, the efficiency with which the glass particles adhere to the surface of the base material also deteriorates, making it difficult to increase the synthesis rate. That is, in order to increase the synthesis rate, it is necessary to reduce the flow rate of the raw material and increase the space number density of the glass particles produced to increase the deposition rate of the glass particles.

The present invention is intended to solve these problems and to provide a burner for producing an optical fiber preform having a novel structure that increases the preform synthesis rate.

[Means for solving problems]

The present invention comprises four or more concentric multi-tubes, a central portion of which is a raw material ejection port for a gaseous glass raw material or a mixed gas of a gaseous glass raw material and a fuel gas, and the outer periphery of the raw material ejection port is provided with a fuel gas and a supporting gas. It is a port that flows and forms a flame,
A multi-tube combustion burner for producing a porous glass preform, in which a gaseous glass raw material is jetted to cause flame hydrolysis and the glass particles produced thereby are deposited around a rotating starting material or mandrel. The raw material jetting port located in the section is a burner for producing an optical fiber preform, which is provided without a step with other ports and is tapered so that the tip of the raw material jetting port becomes thin.

FIG. 1 (a) is a radial sectional view of an embodiment of a burner for manufacturing an optical fiber preform according to the present invention, and FIG. 1 is an axial sectional view thereof.
Shown in (b). This example is a concentric quadruple burner. Except for the central port 11 that ejects the source gas, the other ports 1, 2, 3 and 4 are straight in the longitudinal direction as shown in Fig. 1 (b). It has a shape. On the other hand, the central port 11 for ejecting the raw material has a tapered taper 11 'at the tip.

The burner of the present invention has a taper at the tip of the port for injecting the raw material gas, and therefore has a disadvantage caused by increasing the diameter of the raw material port, that is, it takes time to mix with the gas in the outer layer and the reaction It is possible to prevent the space number density of the glass fine particles generated as a result from decreasing. That is, the raw material gas that has flowed out of the raw material port is subjected to a velocity toward the central axis direction of the burner at the tapered portion at the tip, as indicated by the arrow in FIG. 1 (b). Therefore, the raw material gas does not disperse even if the diameter of the port increases, and the number density of the glass fine particles at the center does not decrease. In addition, since the central port is tapered, the gas flowing immediately outside the central port is also easily diffused in the central axis direction of the burner, and diffusion with the raw material is promoted.

As described above, the burner of the present invention does not hinder the diffusion even if the raw material port diameter is increased in order to slow down the flow velocity, and further, does not reduce the number density of the glass fine particles produced. It becomes easy to increase the synthesis speed of.

In the above description, only the central port is tapered, but when the source gas is supplied to the second and third layers, the respective ports may be tapered, and the same effect can be obtained. . Further, a multi-tube burner may be used instead of the quadruple tube, and if the multi-tube is used, the same effect can be obtained without using the concentric burner.

FIG. 3 is an axial sectional view of another embodiment of the 8-tube burner of the present invention, wherein 31 to 34 and 5 to 8 are from the center to the eighth.
The jetting ports up to the third layer, in this example the third layer 3
Up to three taper portions 31 ', 32', and 33 'are provided. 4 (a) and 4 (b) are a horizontal sectional view and a vertical sectional view of the square quadruple tube burner of the present invention, wherein 41 to 44 are respective ejection ports,
Reference numeral 41 'indicates a taper portion of the center port. Fig. 5
(a) and (b) are a radial sectional view and an axial sectional view of the eccentric multi-tube burner of the present invention, wherein 51, 52, 3 and 4 are respective ports, and 51 'is an eccentric center port 51. The taper part provided in FIG.

〔Example〕

Comparative Example An optical fiber preform was manufactured using a straight type octotube burner as shown in FIG. The glass raw material gas was flowed only from the central port. Center port diameter is 6 mm
It was. SiC ₄ was used as the glass raw material, hydrogen was used as the fuel, oxygen was used as the combustion supporting gas, and argon was used as the combustion adjusting gas. Each flow rate is SiC ₄
3 / min, hydrogen 45 / min, oxygen 46 / min, and argon 11 / min.

As a result, the synthesis rate was 4.2 g / min, and the raw material yield was 52.
It was in%. Here, the raw material yield indicates the ratio of the weight deposited on the base material to the weight of the raw material charged into the burner.

EXAMPLE An optical fiber preform was synthesized by using an octotube burner of the present invention having a tapered portion 21 'only at the center port 21 of the burner as shown in the axial sectional view in FIG. The diameter of the tip of the center port is 6mm, and it is 10mm at 20mm toward the upper gas side.
It has a taper of mm. The gas flow rate was set to be the same as that of the comparative example.

As a result, the synthesis rate was improved to 5.0 g / min, and the raw material yield was 63%, which was good.

[Effect of device]

The burner for producing optical fiber preform of the present invention promotes mixing of the raw material gas with the outer layer and makes the concentration of the raw material gas on the central axis of the burner by forming the tip of the raw material ejection port into a tapered shape. It can be improved, and the number density of the glass fine particles produced thereby can be increased to improve the raw material yield in the base material synthesis and the synthesis rate, which is highly effective for the production of optical fiber base material.

[Brief description of drawings]

1 (a) and (b) to FIGS. 5 (a) and (b) are sectional views showing various embodiments of a burner for manufacturing an optical fiber preform according to the present invention. 1 (a) and 1 (b) are radial and axial sectional views of an example in which a tapered portion is provided in the center port, 11, 12, 3 and 4: each port from the center to the fourth layer, 1
1 ': Taper part Fig. 2 is a sectional view of an octuple burner in which a taper part is provided in the center port used in the embodiment, 21, 22 and 3 to 8: each port from the center to the 8th layer, 2
1 ': Taper part Fig. 3 is a sectional view of an octuple burner provided with a taper part up to the third layer, 31 to 34 and 5 to 8: each port from the center to the eighth layer, 31', 32 'and 33 ': Taper part Fig. 4 (a) and (b) are horizontal and vertical cross-sectional views of the square quadruple burner, 41 to 44: Ports from the center to the fourth layer, 41': Tapered part 5 (a) and 5 (b) are radial and vertical cross-sectional views of an eccentric quadruple tube burner, 51, 52, 3 and 4: each port from the center to the fourth layer, 5
1 ': Taper part FIGS. 6 (a) and 6 (b) are a radial sectional view and an axial sectional view of a conventional straight burner, and FIG. 7 is a conventional straight octave pipe used in a comparative example. It is an axial sectional view of a burner. 1-8: Each port from the center to the 8th layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP 54-20024 (JP, A) JP 58-213639 (JP, A) JP 55-23066 (JP, A)

Claims (2)

[Scope of utility model registration request] 1. A raw material injection port for a gas glass raw material or a mixed gas of a gas glass raw material and a fuel gas, comprising a concentric multi-tube of four or more layers, the outer periphery of the raw material injection port being a fuel gas and an auxiliary burner. It is a port that flows gas to form a flame, and a porous glass base material that ejects a gaseous glass raw material and undergoes flame hydrolysis to deposit the fine glass particles thus produced around a rotating starting material or mandrel. In a multi-tube combustion burner for production, an optical fiber preform in which a raw material ejection port located at the center is provided without a step with other ports and the tip of the raw material ejection port is tapered to be thin. Burner for manufacturing. 2. A burner for manufacturing an optical fiber preform according to claim (1), characterized in that the raw material ejection port located at the center is provided at an eccentric position.