JPS60260437A - Manufacture of glass base material for optical fiber - Google Patents

Abstract

PURPOSE:To prevent the liquefaction or solidification of a gaseous starting material and to manufacture stably a glass base material for an optical fiber by feeding a heated gas for heating to the nozzle of a burner together with the gaseous starting material gasified by heating and by bringing the gaseous starting material into a vapor phase reaction. CONSTITUTION:A carrier gas such as Ar fed from a carrier gas feeding source 1a is sent to a starting material feeder 3 through a flow rate regulator 2, and a starting material for glass such as SiCl4 whose b.p. is above room temp. and additives are gasified by heating to produce a gaseous starting material. This gaseous starting material is regulated to a prescribed concn. with a concn. regulator 4 and introduced into a burner 6. A gas which is not degenerated by mixing with the gaseous starting material such as an inert gas is fed to a heater 10 from a heating gas feeding source 1b, heated, and allowed to join the gaseous starting material in a branch joint 82. The gaseous starting material is not liquefied or solidified in the nozzle of the burner 6 and piping, and a high quality glass base material 7 for an optical fiber can be obtd. continuously for a long time by a stable vapor phase reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a glass preform for optical fiber by a gas phase reaction using a multi-tube burner.

<Prior art> In recent years, the VAD method has been used as a method for manufacturing optical fibers as it is superior in terms of quality and manufacturing, and the manufacturing technology has also become more sophisticated.
However, due to the manufacturing process, a stable supply of raw materials over a long period of time has become an essential condition in order to obtain high-quality optical fiber for long-distance lines.

The VAD method uses a multi-tube burner to guide vaporized glass raw materials and glass additives together with combustion gas, inert gas, etc. to a designated nozzle of the multi-tube burner, and react in front of the nozzle to chemically convert glass particles. A porous glass base material is obtained by synthesizing and depositing it on a target in the axial direction. Glass raw material/glass additive 710 agent L-1j
5iCt4, GeC1,, POCt3. TiCz4
゜AICts etc. are used. These chemicals are usually liquid or solid at room temperature and cannot be fed directly to the burner. Conventionally, therefore, a method has been adopted in which the raw material gas is forcibly vaporized using another gas, and then the raw material gas is maintained at a constant concentration using a concentration control device before being supplied to the burner. The term "raw material glass" includes the vaporized glass raw materials and glass additives. FIG. 1 shows an example of a raw material supply device for supplying raw material gas to a gas burner in a conventional optical fiber manufacturing method using the VAD method.

Generally, the gases supplied to the gas burner in the VAD method are classified into the following three types.

(1) Raw material gas; silicon tetrachloride, germanium tetrachloride,
A gas for supplying vaporized glass raw materials such as phosphorus oxychloride and titanium tetrachloride or glass additives with a carrier gas such as argon, helium, or hydrogen that does not react with the above chlorides.

(2) Combustion/combustion auxiliary gas: A gas such as hydrogen or oxygen that generates glass particles by reacting with the raw material gas in (1) and at the same time generates HzO in the reaction.

(3) Seal gas: This is a gas that does not directly participate in the glass reaction, but is used to prevent the nozzle from deteriorating due to a reaction occurring in front of the burner nozzle, and argon, helium, nitrogen gas, etc. are used. The problem in the present invention is the method of supplying the raw material gas.

In FIG. 1, a carrier gas (inert gas) is supplied from a supply source 1, maintained at a predetermined flow rate by a flow rate adjustment device 2, and passed through a raw material supply tank 3 to add glass raw materials or glass additives. vaporize. Next, the vaporized raw material gas is controlled to a predetermined concentration by the raw material concentration adjusting device 4 and sent to the burner 6 via the pipe 5 heated by the n1 pipe heating device 9. In the case shown in Fig. 1, for simplicity, a raw material supply system is shown in which one raw material system feeds one type of raw material gas to one burner nozzle, but in reality it is much more complicated and involves multiple raw material gases. are often connected to one nozzle. Note that 81 is a joint.

In the conventional raw material supply device shown in Fig. 1, the raw material gas supply system piping from the burner section and the raw material gas generator to the burner is heated to a temperature at least higher than the saturation temperature of the raw material gas to prevent the raw material gas from liquefying and solidifying. It needs to be maintained. However, in the conventional method, the piping system is kept warm by wrapping tape-shaped heaters, nichrome wire, etc., and the heating effect is poor in thick parts of piping joints 81 and central nozzles of multi-pipe bars, etc. However, the raw material gas is often prone to liquefaction or assimilation, making it impossible to maintain and stably supply the raw material gas at a predetermined value, which has hindered production.

<Object of the Invention> The present invention has been developed in view of the drawbacks of the prior art, and provides a method for manufacturing a glass base material for optical fibers in which liquefaction and solidification of raw materials do not occur in the burner and the raw material supply system piping. The purpose is to provide.

Concrete Means for Solving Problems〉 The structure of the method for manufacturing a glass base material for optical fiber according to the present invention that achieves the above object is that the boiling point of the glass base material for optical fiber can be varied from room temperature to The glass raw material of the glass base material or the glass additive r is vaporized by the raw material supply device and sent to the burner nozzle as raw gas, and the nuclear raw material gas is heated by a heating device provided separately from the raw material supply device. It is characterized by the fact that it is heated with a heated gas. There are two ways to heat the raw material gas with heated gas: one is to add heating gas that does not react with the raw gas directly into the raw gas piping and send it to the burner, and the other method is to heat the raw material in the burner. There is a method of feeding heating gas into a nozzle adjacent to a gas nozzle and indirectly heating the raw material gas through the nozzle wall.

<Example> First method for manufacturing a glass base material for optical fiber according to the present invention
An example of this is shown in FIG. FIG. 2 is a configuration diagram of an apparatus for manufacturing a glass base material by the VAD method. In Figure 2,
la is a carrier gas supply source, lb is a heating gas supply source,
2 is a carrier gas flow rate adjustment device, 3 is a glass raw material or glass additive supply device, 4 is a raw material gas concentration adjustment device,
51 and 5g are pipes, 6 is a burner, 7 is a produced glass base material, 8tij pipes 5i' and 5x joints, and 1G is a heating device for heating gas.

An inert gas is supplied as a carrier gas from a carrier gas supply source la, and the flow rate is adjusted to a desired value by a carrier gas flow rate regulator 2, and a glass raw material supply consisting of a container in which glass raw material, for example, liquid silicon tetrachloride-8iC14 is stored. Supplied to device 3. In the glass raw material supply device 3, the raw material gas at saturated vapor pressure is sent to the raw material concentration adjusting device 4 using a carrier gas, and the raw material gas having a desired concentration is sent to the burner 6 via a pipe 51. The raw material gas causes a reaction in the burner 6 and is deposited on the target as glass particles, forming a glass base material 7. In FIG. 2, a desired flow of a heating gas such as an inert gas or a gas that does not react even when mixed with the raw material gas is supplied from the heating gas supply device 1b, and the raw material gas is heated by the heating device IO. The heated gas is heated to a high temperature equal to or higher than the saturation temperature, and the heated gas passes through the pipe 5 and joins the source gas fed through the pipe 51 at the branch joint 8z just before the burner 6. The raw material gas tends to liquefy as the temperature drops, such as in the center of the burner and at the joints 8.
Since the second grade is also directly heated by the heating gas, it is sent to the burner 6 in a dry state.

According to the method for manufacturing a glass base material according to the present invention shown in FIG. 2, by mixing heating gas with the raw material gas and directly heating the raw material gas, the raw material gas can be heated even at the piping joint and the center of the burner nozzle. raw materials, without liquefaction or assimilation.

Since the gas is supplied to the burner while keeping the desired concentration adjusted by the raw material concentration adjusting device 4, there is no fluctuation in the concentration of glass raw materials and glass additives during the continuous production of glass base material using the burner. Glass preforms for optical fibers can be produced with a constant supply of raw materials.

In the example shown in FIG. 2, the branch joint 8 of the pipe 51! In the above example, the joint immediately after the raw material concentration adjustment device 4 is used as a branch joint, and the heated gas is connected to the pipe 51.
The raw material gas supplied to the piping 51 and the burner 6 may be heated. In this case, it is possible to prevent the raw material gas from liquefying or solidifying inside the pipe 51, the joint 81, and the burner pipe.

FIG. 3 shows the burner section in FIG. 2 in detail. In Fig. 3, raw material gas, heating gas, and combustion gas are supplied to the nozzle 61 of the multi-tube burner, and other gases, namely combustion gas (H) and auxiliary combustion gas (0,), are supplied to the nozzles 6f to 6n.
, seal gas (Ar, He, etc.), and other source gases are supplied. The raw material supply system shown in FIG. 2 corresponds to the part related to the raw material gas and heating gas supplied to the nozzle 61 in FIG. 3.

A second embodiment of the present invention will be explained using a glass base material manufacturing apparatus shown in FIG. In FIG. 4, la is a carrier gas supply source, lbu heated old gas supply source, 2 is a carrier gas flow rate adjustment device, 3 is a glass raw material or glass additive supply device, 4 is a raw material gas concentration adjustment device, 51° 5!
is piping, 6Vi burner, 7 is produced glass base material, F3tJ
d joint, 9 is a heating device for piping, and 10 is a heating gas heating device. In FIG. 4, an inert carrier gas is supplied from a carrier gas supply source 1a, and the carrier gas flow rate is adjusted to a desired flow rate by a carrier gas flow rate adjustment device 2. In FIG. The carrier gas is further used as a glass raw material such as liquid silicon tetrachloride Si.
The vaporized glass raw material is supplied to a glass raw material supplying device 3 consisting of a container containing C14, and is sent to a raw material concentration adjustment device 4 as a raw material gas at a saturated vapor pressure, and then transferred to a piping as a raw material gas at a desired concentration. 51'f, and is fed to the nozzle 61 of the burner 6 as shown in FIG. The raw material gas causes a reaction in the burner 6 and is deposited on the target as glass fine particles to form a glass base material 7. In Figure 4, furthermore,
A heating gas such as an inert gas is supplied from the gas supply source 1b and heated to a high temperature higher than the saturation concentration of the raw material gas by the heating device 10, and the heated gas is transferred to the joint 8! , is supplied to the nozzle 62 of the burner 6 through the pipe 5zi as shown in FIG.
Ru. Since there is a nozzle partition between the nozzles 61 and 62, the source gas supplied to the nozzle 61 via the pipe 5I is indirectly heated through the nozzle partition. Therefore, the raw material gas supplied to the central nozzle does not liquefy or solidify due to insufficient temperature within the nozzle, as in the conventional case. In the embodiment shown in FIG. 4, the piping 51i1 is heated by the piping heating device 9 as in the prior art to prevent the source gas from liquefying or solidifying at the piping and joints. FIG. 5 shows the structure of the burner 6 shown in FIG. 4 in more detail. The raw material gas supplied to the nozzle 61 of the burner 6 in the raw material supply system shown in FIG. 4 corresponds to the raw material gas supplied to the nozzle 61 of the multi-tube burner 6 in FIG.

Also, burner nozzle 6 in Figure 4! The heated gas supplied to corresponds to the heated gas supplied to the nozzle 61 of the multi-tube burner 6 in FIG. In addition, in FIG. 5, for the other nozzles 63 to 6n of the multi-tube burner 6, other gases include combustion gas (Hz)' - auxiliary combustion gas (
0□)l Seal gas (Ar, He...), other raw material gases, etc. are supplied.

Although the above two embodiments of the present invention have been described with reference to FIGS. 2 and 4, it is of course possible to use these two methods in combination. For example, it is possible to mix and heat a specific raw material gas with heated gas and supply it to one nozzle of a burner, and also to prevent the raw material gas from liquefying or solidifying by feeding the heated gas to an adjacent nozzle of the burner. . Furthermore, when a plurality of raw materials are used in one multi-tube burner, it is also possible to use two types of heating methods according to the present invention, for example, for raw materials A and B, respectively. The multi-tube burner section in this case is shown in FIG. What is shown in FIG. 6 is that the raw material gas and the heating gas are mixed and supplied to the nozzle 61 of the multi-tube burner 6 by the method of the first embodiment according to the present invention, and the mixture is supplied by the method of the second embodiment of the present invention. , raw material gas Bl nozzle 6! The heating gas tv4 contact nozzle 63 is supplied to and heated.
The raw material gas B is indirectly heated by being supplied to the gas. In Fig. 6, nozzle 64・* @6n K represents other gases,
Combustion gas (H), auxiliary combustion gas (01), seal gas (Ar
, Heaas), other raw material gases, etc. are supplied.

Moreover, the method using the VC of the present invention can of course be used in combination with a conventional heating method, that is, a method of heating the piping or burner itself with an external heating device.

A specific example of the method for producing a glass preform for optical fiber according to the present invention will be shown below.

(1) 5iC1< (silicon tetrachloride), htc in the raw material gas
t.

Aluminum chloride)'f, the vaporized material is supplied to a quartz glass seven-tube burner using stainless steel piping,
Argon gas is used as the heating gas.
It was heated to 10°C and fed to the burner after being mixed with iI [in contact gas (at 40°C p).The gas arrangement and flow rate conditions in the burner tube at this time are all shown in Table 1.The results are shown in Table 1. An extremely high quality porous glass base material with a diameter of 7 (Lm and a length of 350M) was obtained without liquefaction or solidification of the raw material and without causing instability.Furthermore, this glass base material was heated and made transparent. B has a homogeneous structure in the longitudinal direction, and by spinning this, an optical fiber with an extremely low loss of i 4 (1.6μ sacrificial) and a long distance line was obtained.

(2) Raw material gas Ic5iCz4 (silicon tetrachloride),
GeCta (germanium tetrachloride), TiCl4
(titanium tetrachloride) is vaporized and supplied to the nozzles of multiple quartz glass burners with outer diameter φ = 50 using pipes 51 made of fluororesin and stainless steel, and mixed with argon to the nozzles of adjacent burners. Gas was heated to 150° C. and supplied, and the raw material gas was heated to produce a glass base material. The gas arrangement and flow rate conditions at this time are shown in Table 2. As a result, the raw material gas did not liquefy or solidify in the burner section, causing no instability, and an extremely good porous glass base material r with a diameter of 75 sa+ and a length of 350 m was obtained.

The glass body made by heating this base material to make it transparent has a homogeneous sound structure in the longitudinal direction, and the difference in refractive index of the glass body with respect to silica is approximately 3.
He was in charge. When this glass body is spun, the loss is 2
0”).

A long-distance optical fiber with an extremely low loss of (1.6 μm) was obtained.

Table 1 *Input amount g/min Others are 47 minutes Table 2 *Input amount 27 minutes Others are 47 minutes Effect of invention 1> According to the method for manufacturing a glass base material for optical fiber according to the present invention, the raw material Because the raw material gas produced by the supply device is heated directly or indirectly using separately heated gas, the raw material glass does not liquefy or solidify in the piping or burner, so even if the raw material glass is operated continuously for a long time, no profit can be obtained. The quality of the glass base material thus obtained was extremely stable in the longitudinal direction.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a burner and raw material supply device for producing a glass preform by the conventional VAD method, and Fig. 2 illustrates a first embodiment of the method for producing a glass bead preform for optical fiber according to the present invention. FIG. 3 is a detailed view of the burner section in FIG. 2, FIG. 4 is a configuration diagram of an apparatus explaining another embodiment of the present invention, and FIG. 5 is a diagram of the burner shown in FIG. 4. FIG. 6 is a diagram showing the structure of the burner section when two embodiments of the method of the present invention are used together. In the figure, l is a gas supply source, la is a carrier gas supply source, lb is a heating gas supply source, 2 is a carrier gas flow adjustment device, 3 is a raw material supply device, 4 is a raw material gas concentration control device, 51 and 5z are pipes, 6 is a burner, 7 is a glass base material, 81 is a joint, 82 is a branch joint, a heating device for 9 pipes, and a gas heating device for heating 10 pipes. Patent Applicant: Sumitomo Electric Industries, Ltd. Nippon Telegraph and Telephone Public Corporation Representative Patent Attorney: Shibu Mitsuishi (and 1 other person) 1st Cause Figure 2 4 3 2 Figure 5 Figure 6

Claims (4)

[Claims] (1) Gas phase reaction for optical fiber? In the method for producing a glass base material, the raw material for the glass base material or the glass additive, whose boiling point is higher than room temperature, is heated and vaporized by a raw material supply device and fed to the burner nozzle as a raw material gas, and the raw material gas is supplied to the burner nozzle as a raw material gas. 1. A method for supplying a glass preform for an optical fiber, characterized by heating with gas heated by a heating device provided separately from the method. (2) The gas heated by the heating device rC provided separately from the raw material supply device is a gas that does not change in quality within the range of use even when mixed with the raw material gas, and the heated gas is used as the raw material gas. 2. The method for producing a glass preform for optical fiber according to claim 1, wherein the raw material gas is heated. − (3) The method for manufacturing a glass preform for optical fiber according to claim 2, wherein the heating gas is an inert gas. (4) A gas burner nozzle heated by a heating device provided separately from the raw material supply device is used to flow the raw material gas through a nozzle that is in contact with the nozzle vca through which the raw material gas flows, so that the raw material gas is heated by the nozzle wall. 2. A method for producing a glass preform for optical fiber according to claim 1, wherein the glass preform for optical fiber is heated.