JPS583979B2 - Method for manufacturing glass for optical transmission lines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing glass for optical transmission lines, particularly phosphate glass.

Glass for optical transmission lines, which is a material for optical transmission lines, must be obtained in a highly pure form by containing as few impurities as possible other than the specified elements in order to reduce the transmission loss of the optical transmission lines. It is.

Here, phosphate glass, which is one of the materials for optical transmission lines, is
Its melting point is relatively low at about 1400° C., and it can be melted in a quartz crucible with low impurity content, making it suitable as a material for glass fibers.

In addition, phosphate glass is made from its raw materials phosphorus oxychloride (POCl3), gallium trichloride (GaCl3), silicon tetrachloride (SICl4), and germanium tetrachloride (GeCl3).
4) Crow-forming chlorides such as boron trichloride (BC73) are popularly used in the semiconductor industry and are readily available in highly purified form.

In addition, the above POCl3, GaCl3, SiCl4, GeC
Phosphorous pentoxide obtained by flame hydrolysis of 14BCl3 (
P205), gallium oxide (Ga203), silicon oxide (
Glass-forming oxides such as germanium oxide (Geo2), boron oxide (B203), etc. are also obtained in highly pure form.

However, these oxides contain water, and when made into molten glass, they decompose to generate hydroxyl groups, and these hydroxyl groups have a diameter of 0.98 μm. It absorbs light of wavelengths such as 1.26 μm and 1.43 μm, so it is impossible to obtain an optical fiber having desired transmission characteristics.

Therefore, conventionally, for example, as a method for producing core glass of phosphate-based glass fiber, among the above oxides, P205, G
a2o3) After weighing Si02 and Ge02 to obtain a predetermined refractive index value, they are filled into a melting crucible, heated and melted, and chlorine (Cl2) gas is introduced into the molten glass,
Hydroxyl (OH) groups contained in the glass are removed.

When melting the glass-forming oxide in this way, Cl2 gas is introduced to remove water in the glass-forming oxide and reduce the content of OH groups in the glass fiber to be formed. A method of reducing optical transmission loss in a fiber has been proposed by one of the present inventors in Japanese Patent Application No. 54-023742.

However, the above-mentioned Cl2 gas uses Cl2 gas filled in commercially available cylinders, and the Cl2 gas is highly corrosive and corrodes metal parts such as pressure reducing valves for controlling the gas flow rate. Metal impurities may be mixed into the molten glass, and the impurities may be mixed into the molten glass.

That is, when molten glass was stirred using Cl2 gas as described above, a glass fiber for optical transmission was manufactured from the glass, and its transmission characteristics were investigated, the absorption loss due to OH groups at a wavelength of 0.98 μm was found to be 1 dB/Km or less,
An optical fiber with a low OH group content was obtained.

However, impurity absorption, which is assumed to be due to metal impurities mixed in from Cl2 gas, is 2 to 5 dB at a wavelength of 0.84 μm.
/Km, which was a fairly high value.

The present invention eliminates the above-mentioned problems and uses high-purity C.
The purpose is to obtain 12 gas and use it to obtain a glass for optical transmission lines with a low content of OH groups, and to add a trace amount of glass-forming oxide to the molten glass.

In other words, when glass-forming oxide, which is a material for optical transmission lines, is heated and melted in a crucible to vitrify it, a mixed gas of chloride vapor and oxygen that can be converted into glass-forming oxide is introduced into the crucible. A heating means is provided in the path.

Then, a reaction product collection container is branched downstream of the heating region by the heating means, and the heating means is heated to produce high-purity Cl obtained by thermally decomposing the mixed scum.
The present invention aims to provide a novel method for producing glass for optical transmission lines, which is characterized by melting and stirring glass using two gases.

Embodiments of the present invention will be described in detail below with reference to the drawings.

The figure is a schematic diagram of an apparatus for implementing the first and second embodiments of the present invention, where 1 is a supply pipe for oxygen (02) gas, and 2 is a POCl3 gas-forming chloride heated to 30°C. 3 is an introduction pipe that supplies a mixed gas of 02 gas and gaseous POCl3, and 4 is an evaporator that can accommodate the above 02 and POC
This is a thermal decomposition furnace for thermally decomposing the mixed gas with l3.

In the vicinity of the thermal decomposition furnace and in the downstream direction of the flow of the mixed gas, a storage container 6 is installed which branches off from the introduction pipe for the mixed gas and accommodates a reaction product 5 produced by thermal decomposition of the mixed gas. There is.

The tip A of the mixed gas introduction tube is inserted into molten glass 7 in which a glass-forming oxide is heated and melted.

The molten glass is placed in a quartz crucible 9 having a quartz lid 8, and is heated and melted in a heating furnace 10.

A first example will be described using the above-mentioned apparatus.

First, when forming the core glass of the phosphate glass fiber, 51.5 g of P205 was used. 30.0g of Ga203,
14.99 g of GeO2 and 3.6 g of 8102 were weighed and filled into the quartz crucible 9. After closing the quartz lid 8, the crucible was placed in the heating path 10.

Then, the temperature of the heating furnace is set to 1400° C., and the glass-forming oxide filled in the crucible is heated and melted to obtain molten glass.

At the same time, the temperature of the mixed gas thermal decomposition furnace 4 is raised to 800°C.

After that, the glass melts and the temperature of the mixed gas decomposition furnace reaches 800℃.
When reaching 02 gas from 02 supply point 1, 250m
POCl3 heated to 30° C. is introduced into the evaporator 2, which is filled with a flow rate of 1/min.

By introducing 02 gas into the liquid POCl3 heated to 30°C and stirring it, gaseous POCl3 is generated, and the mixed gas of this gaseous POCl3 and 02 is mixed from the gas introduction pipe 3. The gas is guided into the thermal decomposition furnace 4 .

In this thermal decomposition furnace, the mixed gas undergoes a thermal decomposition reaction as shown in equation (1) to generate gaseous P205 and Cl2.

2POCl3+3/202→P205+3Cl2...
(1) When this gaseous P205 flows out of the thermal decomposition furnace to the downstream side of the gas flow, it immediately solidifies into solid fine powder P205.5, which is stored in the storage container 6.

Highly purified Cl2 gas and 02 gas generated by the thermal decomposition are introduced into the molten glass 7 from the tip A through the mixed gas introduction pipe 3, and the molten glass is stirred by the Cl2 and 02 bubbles. It reacts with the OH groups in the molten glass as shown in equation (2) to form hydrogen chloride (
HCl) and oxygen (0.

) and occur.

20H+Cl2→2HCl+02・・・・・・・・・・
(2) The HCl and 02 gases thus generated are led out from the gap C between the quartz lid 8 and the gas introduction tube.

In this way, by stirring the molten glass for 2 hours using high-purity Cl2 gas with low moisture and metal impurity content, which is saved by thermally decomposing high-purity POCl3, it is possible to create a molten glass without contaminating trace amounts of moisture. The OH groups in the glass are removed.

At the same time, a glass with less absorption loss due to metal impurities can be obtained.

In addition to this embodiment, a second embodiment will be described which is effective in easily controlling the glass assembly type by adding a small amount of P205, which is produced from K obtained by thermally decomposing POCl3, into the molten glass.

When forming the core glass of the phosphate glass fiber using the second example, 50.5 g of P205, 50.5 g of Ga20
3 to 3o. og, 14.9g of Ge02, 3g of S102
．． After filling a 6 g quartz crucible 9, it is placed in a heating furnace 10, and the temperature of the heating furnace 9 is raised to 1400° C. to heat and melt the glass-forming oxide in the crucible.

When the glass is melted, the pyrolysis furnace for the mixed gas is put into a non-heated state, and the mixed gas 25 of 02 gas and POCl3 is heated.
Introduce 0ml into the mixed gas introduction tube.

The above mixed gas causes a reaction similar to that shown in equation (1) in the heating area B in the crucible, generating gaseous P205, P205 is dissolved in the molten glass, and Cl2 becomes bubbles. The molten glass is stirred and reacts with the OH groups in the glass to generate HCl gas and 02 gas in the same manner as shown in equation (2), thereby removing the OH groups.

If the mixed gas is introduced into the melting crucible for 20 minutes under the conditions described above, 1.5 g of P205 will be produced.

By introducing the mixed gas into the melting crucible for 20 minutes under the conditions described above, 1.5 g of P205 will be added to the glass component, so P205 will be 51.5% by weight and Ga203 will be 30.0% by weight. The glass composition has a weight ratio of GeO2 of 14.9 weight φ and S102 of 3.6 weight ratio.

Therefore, the method of the present invention is effective when adding a small amount of glass-forming oxide to glass to obtain glass with desired characteristics as described above.

Next, after the mixed gas heating furnace is kept in a non-heating state for a predetermined time of 20 minutes, the supply of the mixed gas is temporarily stopped.

Then, the temperature of the mixed gas heating furnace is increased, and when the temperature of the heating furnace reaches 800° C., the mixed gas is again supplied at the same flow rate as described above for 1 hour and 40 minutes.

In this way, only the Cl2 gas generated by thermal decomposition is introduced into the molten glass and stirs the glass.

Then, a trace amount of OH groups present in the molten glass is removed by a reaction similar to that shown in formula (2).

As described above, according to the method of the present invention, Cl2 gas can be easily obtained in a state that does not contain water and metal impurities, and if glass is stirred using this gas, it will be in a state that does not contain water and metal impurities than in the conventional method. The OH groups in the glass can be removed.

Also, POCl3 used when forming high purity Cl2
A desired amount of P205 produced by the thermal decomposition of P205 can be added to the common molten glass, and the components of glass formation can also be easily controlled.

If a glass fiber for optical transmission is manufactured using glass from which OH groups have been removed by the method of the present invention as described above, the optical transmission loss will be 1 dB even at a wavelength of 0.98 μm, where the peak of light absorption by OH groups appears. /Km or less, and also produces the effect of obtaining a glass fiber that absorbs less impurities caused by metal impurities.

In the above examples, POCl3 is used as the glass-forming chloride.
was used, but other glass-forming chlorides such as GaCl
Similar effects can be obtained by using 3, GeCl4, StCl4, etc.

[Brief explanation of drawings]

The drawing is a schematic illustration of an apparatus for carrying out the method of the invention. 1...02 Gas supply pipe, 2...POC
13 evaporator, 3... 02 and POCl3 mixed gas introduction pipe, 4... thermal decomposition furnace, 5...
・Reaction product, 6... Storage container, 7...
- Molten glass, 8...Quartz lid, 9...Quartz crucible, 10...Heating furnace, A...Tip of gas introduction tube, B... ...Heating area, C...
··gap.

Claims (1)

[Scope of Claims] 1. In a manufacturing method in which a glass-forming oxide, which is a material for an optical transmission line, is heat-melted and vitrified in a crucible, the glass-forming oxide is heated and melted while being stirred with a water removal gas. A heating means is provided in a path for introducing a mixed gas of chloride vapor and oxygen that can be converted into an oxide into the crucible, and a reaction product collection container is attached downstream of the heating area by the heating means. , when the heating means is heated,
A method for manufacturing optical transmission line glass, characterized in that molten glass is stirred using chlorine obtained by thermal decomposition of the mixed gas as the moisture removing gas. 2. Manufacturing the glass for optical transmission line according to claim 1, which includes a step of introducing the mixed gas into a crucible in a non-heated state for a predetermined period before the heating means is brought into a heated state. Method.