JPS61222935A - Burner for producing fine glass particle - Google Patents

Abstract

PURPOSE:To produce a glass preform having perfectly triangular refractive index distribution in high reproducibility, by using a burner for the formation of glass soot and composed of a plurality of concentric pipes wherein the tip of the innermost pipe is protruded from the tips of the other pipes. CONSTITUTION:A plurality of pipes made of quartz and having different diameters, i.e. the first pipe 11 placed at the center, the second pipe 12, the third pipe 13, the fourth pipe 14 and the outermost fifth pipe 15 are arranged concentrically to form a burner for the formation of glass soot. The tip of the first pipe 11 is protruded from the tips of the other pipes by a proper length (e.g. 3mm). The first channel 16 is supplied with GeCl4 and SiCl4, and the second channel 17, the third channel 18, the fourth channel 19 and the fifth channel 20 are supplied with SiCl4, H2, Ar and O2 respectively. Glass soot produced by the flame hydrolysis reaction is deposited in a prescribed form to obtain a porous glass preform, which is vitrified to a transparent glass. A glass preform having a triangular refractive index distribution free from the roundness at the center can be produced by this process.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 1 The present invention relates to a burner for producing glass fine particles for communication and optical applications.

rPrior Art J The WAD method is known as a means for producing porous glass preforms for various optical fibers and porous glass preforms for rod lenses.

In this 1/AD method, a porous glass base material is produced by depositing glass particles generated by, for example, a flame hydrolysis reaction in a predetermined shape.
A burner with a quadruple or single tube structure is used.

FIG. 4 shows a conventional example of a multi-tube structure burner.

In FIG. 4, l is the first pipe located at the center, 2 is the second pipe, 3 is the third pipe, 4 is the fourth pipe, and 5 is the fifth pipe located at the outermost periphery. 5, the first gas flow path (center gas flow path) 8, the second gas flow path 7, the third gas flow path 8. A fourth gas flow path 8 and a fifth gas flow path (outermost gas flow path) 10 are respectively formed.

When producing a porous glass base material by the WAD method using the burner described above, the first gas flow path B to the fifth gas flow path 10
The following gases were supplied respectively.

First gas flow path θ: GeGIa (100cc/wi
n, -28°C) SiC1n (100cc/sin, -
40°C) Second gas flow path 7: 5iC14 (200cc
/win, -23°C) Third gas flow path 8: H2 (4,2
sentence/sin) Fourth gas flow path 9: Ar (1,91/m
1re) Fifth gas flow path 10: 02 (9,81/5
in) The porous glass base material produced under the above conditions was made into transparent glass by a known method.

When the refractive index distribution of the glass base material after the transparent vitrification was measured using a non-destructive measuring means, it exhibited a profile as shown in FIG.

As is clear from FIG. 5, the refractive index profile of the base material produced through the conventional burner is a pseudo-triangle with a roundness in the center.

Problem 1 to be Solved by the Invention Incidentally, when manufacturing a glass base material with a triangular refractive index distribution for use in communications or optics, in conventional burners, the above-mentioned rounding of the center occurs, so the desired refractive index distribution cannot be achieved. However, since the burner itself was developed for a GI-type bottom refractive index distribution, if a triangular refractive index distribution was forcibly formed, it would be difficult to obtain a porous glass base material at the manufacturing stage. The central part of the base material becomes flat and glassy.

Therefore, with conventional burners, it is difficult to set conditions for forming a triangular refractive index distribution, and it is difficult to obtain reproducibility.

In view of the above-mentioned problems, the present invention aims to provide a novel burner in which a glass base material having a triangular refractive index distribution can be easily produced.

Means for Solving Problems j The present invention is characterized in that a plurality of pipes having different cross-sectional diameters are stacked concentrically, and a gas flow path is formed in the pipe at the center position and between adjacent parts of each pipe. The burner for producing glass particles is characterized in that the tip of the pipe located at the center is more protruding than the other pipe tips.

r Effect] When the burner of the present invention is used to generate glass fine particles and the glass fine particles are deposited to produce a porous glass base material, the first gas flow path located at the center of the burner is filled with gas phase glass raw material and gas. phase dope material (for increasing the refractive index), gas phase glass material in the second gas flow path, hydrogen gas in the third gas flow path, buffer gas in the fourth gas flow path, Oxygen gas is supplied to each of the five gas channels (outermost gas channel).

When these mixed gases are combusted to produce glass particles, it goes without saying that the amount of dope material supplied to the first gas flow path is appropriately set.

As described above, when the burner is in a combustion state and the burner flame is directed toward a predetermined deposition surface, glass fine particles containing a dopant are injected from the first gas flow path in the center of the burner.

Therefore, in the burner flame, the dopant concentration is highest at the center of the flame, but in this burner, the tip of the first gas flow path is more protruding than the other, so diffusion is suppressed, and the concentration of dopant at the center of the flame is suppressed. The dopant concentration is higher,
The dopant concentration decreases toward the outer periphery of the flame.

Therefore, when a porous glass rod is produced by injecting glass particles ejected from the burner onto a predetermined deposition surface, the dopant concentration in the base material, that is, the refractive index, is highest at the center and moves toward the outer periphery of the base material. This results in a so-called triangular profile in which the height decreases as the temperature decreases.Of course, in this triangular profile, the tip of the first gas flow path is more protruding than the other, so the center of the refractive index distribution does not become rounded.

In addition, since a desired refractive index distribution can be formed by means of protruding the tip of a predetermined pipe, complicated gas flow rate control is unnecessary and reproducibility is improved.

Embodiment 1 Hereinafter, embodiments of the burner according to the present invention will be described with reference to the drawings.

In FIG. 1 showing an embodiment of the burner of the present invention, 1
1 is the first pipe located in the center, 12 is the second pipe, 1
3 is a third pipe, 14 is a fourth pipe, and 15 is a fifth pipe located at the outermost periphery. Due to the superposition structure of each of these pipes 11 to 15, the first gas flow path (center gas flow path) IB, the second gas flow path gas flow path 17, third gas flow path 18, fourth gas flow path 18,
A fifth gas flow path (outermost gas flow path) 20 is formed, respectively.

In the burner of the present invention, in this configuration, the first pipe 1
The tip of pipe 1 has an appropriate size (for example, 3mm) than the other pipe tips.
Accordingly, the tip of the first gas flow path 16 also protrudes by the same dimension as above.

Note that quartz is usually employed as the material for each of the pipes 11 to 15.

When producing a porous glass base material by the VAD method using the burner of the above embodiment, as in the conventional example, the first gas flow path 1
The following gases were supplied to the 6th to 5th gas channels 20, respectively.

First gas flow path 18: GeCl4 (100cc/w
in, -28℃) SiC14 (100cc/sin, -
40℃) Second gas flow path 17: SiC 1m (200℃
c/sin, -23°C) Third gas flow path 18: H2(
4,2jL/gin) Fourth gas flow path 19: Ar(
1,9JL/5in) Fifth gas flow path 20: 02(9
, 81/win) The porous glass base material produced under the above conditions was made into transparent glass by known means.

When the refractive index distribution of the glass base material after the transparent vitrification was measured using a non-destructive measuring means, it exhibited a profile as shown in FIG.

As is clear from FIG. 2, in the case of the base material produced through the burner, the refractive index profile is triangular, and the center of the profile is not rounded.

Next, another embodiment of the burner of the present invention will be described with reference to FIG.

In the burner of this embodiment, the tip of the fourth pipe 14 protrudes with respect to the fifth pipe 15, the tip of the third pipe 13 protrudes with respect to the fourth pipe 14, and the tip of the second pipe 12 protrudes with respect to the fourth pipe 14. The tip and the tip of the first vibrator 11 are successively protruded, with the tip of the first vibrator 11 protruding the most.

In this case, the protruding length of the tip of one pipe relative to the other pipe may be about 3 mm as described above, but depending on the case, the protruding length of each pipe may be made different.

When producing a porous glass base material by the VAD method using the burner shown in FIG. 3, the first gas flow path 16 to the fifth gas flow path 2
0 was supplied with the same gas as in the case of FIG. 1, respectively.

When the porous glass base material produced under the above conditions was made into transparent vitrification by known means and the refractive index distribution of the transparent vitrified base material was measured, a profile similar to that shown in FIG. 2 was obtained.

In addition, when forming a porous glass base material using the burner of each of the above-mentioned Examples, it is desirable to supply the dope raw material transported by a gas having a density of 1 gz1 or more to the gas flow path for supplying the dope raw material.

At the base end of the burner (not shown), gas supply ports communicating with each of the first, second, third, fourth, and fifth gas flow paths 18 to 20 are independently provided.

In both the burners shown in FIGS. 1 and 3, the number of pipes, that is, the number of channels can be increased or decreased as necessary.

Although the cross-sectional shape of each pipe in the above-described embodiments is circular, in some cases, the cross-sectional shape of each pipe may be rectangular.

``Effects of the Inventionj'' As explained above, according to the burner for producing glass particles according to the present invention, since the tip of the pipe at the center position protrudes more than the other tips of the pipes, it is possible to obtain a completely triangular refractive index distribution. The glass base material can be manufactured without problems and with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts showing an embodiment of the burner of the present invention;
Fig. 2 is a refractive index distribution diagram of the glass base material produced using the burner of the present invention, Fig. 3 is a cross-sectional view of the main part showing another embodiment of the burner of the present invention, and Fig. 4 is a cross-section of the main part of the conventional burner. FIG. 5 is a refractive index distribution diagram of a glass base material produced using a conventional burner. 11-φ fist pipe 12 first/second pipe 13...third pipe 14...fourth pipe 15...fifth pipe 18 jar 011 first gas flow path 17...e second gas Flow path 18...-Third gas flow path 19...Fourth gas flow path 20...Fifth gas flow path Agent Patent attorney Yoshio Saito Ifr! lJ

Claims (1)

[Claims] In a glass particulate generation burner, multiple pipes with different cross-sectional diameters are stacked concentrically, and a gas flow path is formed in the pipe at the center and between adjacent parts of each pipe. A burner for producing glass fine particles characterized by the tip of one pipe protruding from the tip of another pipe.