JPS593037A - Apparatus for manufacturing glass rod as base material for optical fiber - Google Patents

Abstract

PURPOSE:To manufacture the titled long-sized rod contg. no impurities and having a controlled diameter by enclosing a burner, a soot rod forming section and a sintering section with a cylindrical container and by installing a gaseous curtain structure at the top opening of the container through which a glass rod is passed. CONSTITUTION:Gaseous starting materials for glass in a holder 11 are introduced into a burner 14 together with gaseous oxygen and hydrogen from an oxygen cylinder 12 and a hydrogen cylinder 13, the materials are hydrolyzed in a flame 15 to form glass soot, and the soot is deposited and grown on the lower end of a quartz seed rod. The resulting soot rod 16 is converted into transparent glass by sintering in an electric furnace 17 to form a glass rod 18 as a base material for an optical fiber. Said hydrolysis and sintering are carried out in a reactor 19, and high-purity gas is introduced from the gas introducing inlet 21 of a gas curtain structure 20 installed around the top outlet of the reactor 19 for pulling out the rod 18. The introduced gas is spouted toward the inside and outside of the reactor 19.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for manufacturing a base material glass rod for optical fiber.

VA is one of the manufacturing methods of base material glass rod for optical fiber.
D method (Vapour Phase Ax
ialDeposition Method). In this method, glass raw materials such as 5iCA4 and GeCl4 are placed together with an oxyhydrogen flame at the lower end of a rotating starting quartz rod.
etc. is sprayed in a vapor phase to deposit glass fine powder (glass soot) produced by a flame hydrolysis reaction on the lower end of a quartz rod, thereby growing a porous soot rod in the length direction. The soot rod is pulled upward in accordance with the growth rate of the soot rod, and the soot rod is heated and sintered in an electric furnace installed above to make it transparent, thereby producing a base material glass rod. Thereafter, this base material glass rod is usually coated with quartz to produce a preform rod, which is then heated, melted, and drawn to form an optical fiber.

Since optical fibers must have extremely low transmission loss, it is necessary to minimize the introduction of impurities during manufacturing. However, the above method requires a space at the top to pull up the prepared base material glass rod, so both the part where the glass soot is generated by reaction and the part where the soot rod is sintered and vitrified have a sealed structure. It is difficult to avoid contamination with external impurities.

Furthermore, with the above method, it is also difficult to control the diameter of the soot rod, which is an aggregate of glass soot, to be constant.

As a method for solving this problem, a method as shown in FIG. 1 has been proposed. That is, when producing the soot rod 1 by blowing a flame 6 containing a reactive gas from an oxy-hydrogen burner 7 onto the lower end of the rotating quartz rod, the rod 1 is surrounded by an opening at the lower end and a burning hole at the upper end. The rod is surrounded by a circular tubular container 4 having a draw-out opening for the tied rod, and a highly pure gas is flowed downward from the side pipe 2 provided in the container 4 into the gap 5 between the rod 1 and the container 4, and this gas flow causes the rod to be drawn out. The diameter of the rod 1 is controlled by restricting the adhesion of glass soot to the side surface of the rod 1. This method is effective in controlling the diameter of the soot rod 1, but since the soot rod is generated inside the cylindrical container 4, the length of the soot rod is equal to the length of the cylindrical container 4. It is difficult to install an electric furnace above the soot rod without affecting the gas flow, so the formation of the soot rod and its sintering must be performed continuously. It has drawbacks such as being difficult to implement.

The present invention has been made in order to eliminate the following drawbacks of the prior art, and the first purpose is to provide an apparatus for manufacturing a base material glass rod for optical fiber without contamination with impurities. In addition to this, the second purpose is to provide an apparatus that has the function of controlling the diameter of the soot rod and can continuously manufacture, sinter, and vitrify long soot rods. be.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 FIG. 2 is a schematic diagram of one embodiment of the present invention.

The raw material gas in the glass raw material reservoir 11 is guided to the burner 14 together with the oxyhydrogen gas discharged from the oxygen cylinder 12 and hydrogen cylinder 13, where it undergoes a hydrolysis reaction in the flame 15 and becomes glass soot, which is pulled in one direction. ” - deposits and grows on the lower end of the quartz seed rod to form the soot rod 16.

This is sintered in an electric furnace 17 and made into transparent glass to obtain a glass rod 18 that will serve as a base material for optical fiber.

In this case, in the present invention, the above-mentioned reaction and sintering are performed in the reaction vessel 19. An oxyhydrogen burner 14 is airtightly attached to the bottom of the container 19, and a gas curtain structure 20 is provided around the outlet of the rod 18 at one end of the container 19. ing.

This gas curtain structure 20 is such that the gas introduced from the gas inlet 21 is blown out at the rod outlet in two directions, up and down, inside the container and outside. If a highly purified gas is introduced from the gas inlet 21, only the highly purified gas will be sent into the container 19, and the outside air will not be able to enter and will be completely shut off. The gas in the container 19 is discharged through the exhaust port 22.
The gas is exhausted from the container 19 at an amount corresponding to the amount of gas sent into the container 19.

If reaction and sintering are carried out in such a container to produce the glass rod that is the base material for optical fibers, the container will be completely isolated from the outside air and will be clean, even though it has an opening at the top. A glass base material for optical fibers with low loss can be produced in an atmosphere.

A specific example of producing an optical fiber base material glass rod using the apparatus described above will be described below.

The burner 14 uses a concentric quadruple burner, and 5iCA4, a small amount of dopant gas and Ar gas are flowed from the center nozzle, and a small amount of Ar gas is flowed from the outer nozzles to prevent wear of the nozzles. Furthermore, from the outer nozzle H2 and 0
2 dregs are poured and burned.

The flow rates of these gases were as follows when the nozzles were numbered 1 to 4 in order from the inside.

Nozzle l5iCt4200~500CC/m1nGeC
L4 20~80 cc/min +! j Aga x
(Ar) 1000cc/m1n) Su/
l/2Ar 1000cc/m
in nozzle/L/ 3 H22~5 A/min nozzle 4 02 5i02 produced by the flame hydrolysis reaction under conditions of 3~6 t/min or more
A soot rod 16 was grown by depositing fine powder of GeO2 and GeO2 on the lower end surface of a rotating quartz rod placed on one side. In this case, the gas curtain structure 20 has a gas inlet 21
High purity Ar gas was flowed from. The Ar gas flow rate at this time was adjusted so that the differential pressure between the container 19 and the outside was constant. As the soot rod 16 grows, it is pulled upward and heated in an electric furnace 17 to a temperature of approximately 1,300 to 1,600° C., and is vitrified by sintering to form a glass rod 18.

The glass rod produced as described above was placed in a commercially available quartz tube, and the tip was heated, melted, and drawn to produce an optical fiber, and the loss was measured. It wasn't much different than what I did.

From the above explanation, according to the above method, it is possible to completely block impurities from entering the container from the outside world. Therefore, if an optical fiber is manufactured using the obtained glass rod as a base material,
An optical fiber with low loss can be obtained.

Example 2 FIG. 3 is a schematic explanatory diagram of another embodiment of the present invention.

The apparatus of this embodiment is the apparatus shown in FIG. 2 with a soot rod diameter control mechanism added. Therefore, this device has the same structure as the device shown in FIG. 2 except for the soot rod control mechanism, and the same parts are indicated by the same symbols.

The soot rod diameter control mechanism consists of a gas curtain structure 30 and is provided near the growth part of the soot rod 16 in the reaction vessel 19. This gas curtain structure 30 is an annular container having an inner diameter slightly larger than the outer diameter of the soot rod 16, and has a gas outlet 31 facing downward in the middle of the inside, and a gas introduction port leading to the outside of the container 19 on the outside. tube 32
is provided. A high-purity gas such as Ar sent from the gas introduction pipe 32 is blown out from the gas outlet 31 and flows downward along the soot rod 16 to prevent excess soot from adhering to the side surface of the soot rod 16. By appropriately adjusting this gas flow rate, the soot rod 1
6 diameter can be controlled. Furthermore, since this cast curtain structure 30 does not impose any restriction on the upper part of the soot rod, it is possible to easily lengthen the soot rod and make it continuous up to sintering.

In the method explained above, the collection efficiency of glass soot attached to and collected at the end of the soot rod is as low as 50 to 70%.
This is a major drawback.

A method for producing a glass base material rond for optical fibers that eliminates the following two drawbacks will be described below.

FIG. 4 is a schematic explanatory diagram of this manufacturing method.

Source scum (for example, 5iCA4) is formed on the edge of the cup-shaped part 41 of the rotary spring bar 42 which has a cup-shaped part 41 at the lower end.

A flame 43 containing BBr3) is blown by an oxyhydrogen burner 44, and 5i02 or 5i02-B203 based crow soot is deposited thereon to form a soot pipe 45. At this time, the tip of the soot pipe 45 and the burner 44
Gradually pull up the rotating spring bar 42 so as to maintain a constant distance between the two. Once the soot pipe 45 has grown to a certain extent,
While growing the soot pipe 45,
The soot pipe 4 is heated using another burner 46 placed inside the soot pipe 4.
(P, Ge in Si02)

doped silica soot containing at least one type of Sn)
is deposited to form a core glass soot layer 47 on the inner wall surface of the soot pipe 45. In this case, in order to prevent the exhaust gas path 48 of the burner 46 from being clogged with glass soot, the path 48 is irradiated with a hot ray (for example, by a CO2 laser) while being forcibly exhausted from the upper end.

Depending on the amount of this exhaust gas and the composition of the soot formed by the burners 44 and 16, the soot formed by the burner 44 is mixed into the core soot layer 47, giving an appropriate composition distribution in the radial direction of the core soot layer 47. You can also do that. Note that clogging of the path 48 can be prevented by the hot wire 49 by utilizing the phenomenon that soot does not accumulate in the high temperature portion.

The soot collection efficiency when producing the above-mentioned core clad soot pipe was found to be approximately 90%, which was found to be considerably better than conventional methods. It has also been found that when a preform is made by vitrifying this soot pipe, the soot pipe is hollow so that it can be easily degassed.

Example 3 Burner 44 with 5i02 and dopant B2o
,.

source gases 5iC74 and BBr3 respectively.
Approximately 35g/h and approximately 4 in terms of Oz and B2O3
g/h, outer diameter 83 mm, inner diameter approx. 5
A soot pipe 45 of Q mm was formed. The outer diameter and inner diameter of this soot pipe are strongly related to the soot deposition conditions and are determined by the soot deposition conditions including the structure of the burner 44.
The distance up to 4 was several cm. When the length of the soot pipe 45 reaches 53 mm, 5i02 and the dopant GeO2Jp react with the burner 46.
Source gas BiCt4, GeCA forming o,
4, PO(J3-5i02, GeO2, P2
Approximately 35 g/h each in terms of O5.

The core soot layer 47 was grown at approximately the same growth rate of about 59 mm/h in the rotational axis direction as the soot pipe 45 on the outer periphery. At this time, the diameter of the CO2 laser beam used to form the exhaust path 48 was approximately 3 mm, but in reality, a somewhat smaller hole of 2 mm was formed.

After sintering the soot pipe with a compositional double structure formed by the method described in 1 above and making it transparent, the weight was measured. It had been made. This value is approximately 90% of the feedstock
The collection rate was higher than that of the conventional method. Furthermore, since it was a soot pipe, bubbles were successfully removed from the surface and inner surface of the pipe during transparent vitrification, and a preform rod with few optical defects was obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing a conventional method for manufacturing a glass preform for optical fibers, and FIGS. 2, 3, and 4 are schematic explanatory diagrams of embodiments of the present invention. In the figure, 11... Glass raw material reservoir 12... Oxygen cylinder 1
3...Hydrogen pump 14...Burner 15.
・・Flame 16−・・Soot mouth・Sodo 17・・Electric furnace
18...Glass lot 19...Reaction container 20...Gas curtain structure 21...Gas inlet 22...Exhaust port 30...Gas curtain structure 31...Gas outlet 32...Gas Introductory tube
41...Cup-shaped part 42...Rotating spring bar
43...Flame 44, 46...Burner 45
... Soot pipe 47 ... Glass soot layer for core 48 ... Exhaust gas path 49 ... Heat ray agent patent attorney Junnosuke Nakamura Continuation of page 1 @ Inventor Toshio Katsuyama 280 Higashi Koigakubo-chome, Kokubunji City Stock Company Hitachi, Ltd. Central Research Laboratory Applicant Hitachi Cable Co., Ltd. 2-1-2 Marunouchi, Chiyoda-ku, Tokyo

Claims (1)

[Claims] (1) A burner sprays an oxyhydrogen flame containing the glass material gas onto the lower end of the seed rod, which is rotated around a vertical axis by a rotating and moving mechanism and pulled upward, and generated by flame hydrolysis. depositing the glass fine powder on the lower end surface of the seed rod in the direction of the rotation axis of the seed rod;
At the same time, the soot rod is heated and sintered from the top end through a heating means provided at the top to form a soot rod, which is an aggregate of the fine glass powder, and is vitrified to form a long transparent glass rod. The apparatus for producing a base material glass rod for optical fiber, wherein the burner, the soot rod forming part, and the soot rod sintering part are surrounded by a cylindrical container coaxial with the seed rod rotation axis, A burner is installed at the bottom of the container so that gas supply to the burner does not break the airtightness of the container, and a hole is provided at the upper end of the container for passing the transparent glass rod that is pulled up. A gas curtain structure consisting of an annular container having a gas outlet for blowing out gas in the vertical direction on the inner surface thereof and a gas introduction pipe on the outer surface thereof is provided, and further, the heating means is provided at the lower part of the gas curtain structure. An apparatus for manufacturing a base material glass rod for optical fiber, characterized in that the soot rod sintered portion is provided at a position corresponding to the soot rod sintered portion so as not to break the airtightness of the container. (2. In the apparatus for manufacturing a base material glass rod for optical fiber according to claim 1, there is a hole for passing the rod through the soot rod in the vicinity of the forming part thereof, and an outlet for blowing gas downward on the inner surface. and a gas curtain structure consisting of an annular container having a gas introduction pipe drawn out from the outer surface of the container so as not to break the airtightness of the container. Equipment for manufacturing glass rods.