JPS5924097B2 - Glass body manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of glass fiber preforms for optical transmission.

Light as a medium for optical communication. Transmission fibers are required to have low optical transmission loss and low transmission distortion. Optical transmission loss increases due to impurities such as metal fibers, minute defects, and the like. Furthermore, hydroxyl ions (-Si-OH) in the glass cause an increase in loss due to vibration, particularly in the wavelength region used for optical transmission, around 0.95 μm. Therefore, it is desired to eliminate these defects as much as possible.

Furthermore, the magnitude of transmission distortion is largely determined by the radial refractive index distribution of the fiber. Up to now, fibers having structures having various refractive index distributions, such as clad type, graded type, and O-guide type, have been proposed.

In glass manufacturing, these materials are required to have an arbitrary refractive index distribution in the radial direction. The present method relates to an improvement on the method proposed by Corning Corporation for making optical transmission glass fiber preforms that can meet these requirements.

In Fig. 1, (to) is an explanatory diagram of the conventional manufacturing method, (
c]) shows an explanatory diagram of the process of heat treating the soot-coated rod. In FIG. 1, dense soot 2 is deposited on a high-purity graphite or refractory ceramic core 1 by flame hydrolysis of slct 4 containing a dopant such as SiC 14 or GeCl 4 using a flame 3 . The flame is burner 4
made by.

Further, the core 1 is rotated and reciprocated 5. in this way,
The soot-covered rod is slowly inserted into the heating furnace T at an appropriate speed, heated in He gas, CT2 gas, and O2 gas, and the gas in the preform is gradually removed to obtain a transparent glass body 6.

Here, the He gas serves to expel the gas in the soot gaps, the Cl2 serves to replace hydrogen in the hydroxyl groups in the tin glass, and the O2 serves to prevent the reduction process of the doping element. Furthermore, according to the present invention, it is also possible to synthesize fluorine-containing silica glass having a refractive index lower than that of pure silica.

Next, the present invention will be explained with reference to FIG. First, a glass rod or pipe 1, a refractory material 1 made of metal or ceramic covered with a glass pipe 11, or a refractory material 1 is rotated at a constant angular velocity as shown by arrow 5 and moved back and forth at a constant speed. put. However, at this time, the forward and reverse speeds may be different.

On this starting member 1, a raw material gas 15 is fed into an oxyhydrogen burner 4 made of quartz glass at the same time as a combustion gas, and synthetic glass soot is made in the flame 3, which is then transferred to the starting member 1.
feed on top. When a halide of Si or other elements is used as a raw material, it is hydrolyzed by high-temperature steam caused by an oxyhydrogen flame to form soot, and when an organic compound or hydride of Si or other elements is used, it is oxidized by a flame. oxidizes and forms soot. Synthetic glass soot having a predetermined composition and amount can be produced depending on the composition and amount of the raw material gas, the flame temperature, and the distance and positional relationship between the layer of synthetic glass to be deposited and the burner. The glass powder (soot) produced in this way is deposited on the starting part, which is subsequently treated by the hot gas (17A or 17B) by the reciprocating movement 5 of the starting part 1.

When the back-and-forth speed is appropriate, only one high-temperature gas is sufficient. Generally, the hot gas (1rA or 17B) consists of a dry halide and optionally an inert gas containing an oxidizing gas. In particular, as shown in the figure, a high-frequency plasma torch (
16A or 16B) into which a mixed gas consisting of either Ct2, F2, a ct compound or an F compound and He gas containing 02 gas as necessary is preferably fed.

Here again, by changing the above composition, amount, and temperature in response to the reciprocating motion, and by changing the positional relationship such as angle, appropriate sintering can be achieved corresponding to the amount and composition of glass to be deposited. Must be set as a condition. After the soot synthesized by the flame 3 is deposited in this way, high-temperature gas (11A or 1rB) is used to eliminate hydroxyl groups and gaps in the soot to create transparent glass 2, which is then attached to the starting member 1. It can be layered on top. Regarding the refractive index of glass, silica glass containing B2O or F has a refractive index lower than that of pure silica glass, and other P, Ge
It is well known that the refractive index of silica glass containing oxides such as , Al, Ti, and Sb is higher than that of pure glass, and that the rate of change in the refractive index is proportional to the amount of doping. well known. Therefore, the refractive index distribution of the transparent glass body produced by the above-mentioned lamination can be controlled in any manner by controlling the type and amount of the dopant.

When a glass rod is used as a starting material, the synthetic glass laminated rod is melted and heated and stretched to form a fiber.

When a glass pipe is used as a starting member, the inner surface of the pipe laminated with synthetic glass is cleaned by hydrofluoric acid cleaning, flame polishing, or a combination thereof, and then melt-spun to produce a fiber.

Note that a step of collapsing the pores using surface tension may be added between the washing step and the spinning step by heating the material to a high temperature (or evacuating it at the same time). Even when a refractory made of glass is used as the starting material, fibers can be made according to the above method. An embodiment of the present invention will be described below with reference to FIG.

A quartz pipe 11 with a wall thickness of 0.3 TWnt was used as a starting member on a carbon rod (5wnφ) (1), and the rod was moved back and forth at a speed of 2.5 minutes each way at a rotation speed of 60 rpm and a distance of 500 mm. Ivy. In order to create the oxyhydrogen flame 3, combustion gases of H2: 4t/Min and O2: 3t/Wlin were fed into the quartz burner 4. First, raw material gas 1
5, 02:2.0t/Mln, GeCl4:20
0CC/city 1n, SC14: 200cc/Rnin 1
After that, the flow rate of 02 and SiCl4 remained the same, and the amount of GeCl4 was gradually reduced to 0cc/1n after 1 hour, and this state was continued for another 2 hours. In this way, GeO2-SiO2 glass powder (soot) is synthesized and deposited on the above (1), and at the same time, using 3 MHz high frequency plasma torches 16A and 16B, He: 10 t/Mlln, Ct2: 300 cc/Tomi 1
Plasma flames 1rA and 11B were created by replenishing a mixed gas at a ratio of 500 cc/1n, and sintering was performed while adjusting the temperature of the deposited soot to be 1300 to 1500°C. The row diameter 15rm 1 length 450vV that was created in this way! ．． When the carbon rod was pulled out from the transparent synthetic glass body 2, it came off easily.

After this, the part corresponding to the base quartz pipe 11 is removed with hydrofluoric acid and washed with water, and the male diameter 15 made of only the synthetic glass body 2 is removed.
A pipe with a diameter of wnφ, an inner diameter of 6wnφ, and a length of 400 m1 was created. This pipe was melt-spun in a high-frequency induction heating furnace at a temperature of nearly 2000°C to produce a fiber array with a diameter of 200 μm (A. 145 km in length).

When I put light into this fiber and measured it, it was 0.95.
Transmission loss in μm is 10dB/Km and 1.06μ
The transmission loss at m was 3 dB/Km.

From this, it can be seen that this glass has very few impurities, and the amount of hydroxyl groups is extremely small, not exceeding 8 ppm.
Furthermore, the refractive index distribution in one cross section of this fiber was trapezoidal as expected.

This also shows that it is easy to control the refractive index in the radial direction.

Next, an example of a method for producing an optical fiber base material containing fluorine will be shown.

The starting member used was the same as above (a carbon rod covered with a quartz pipe).

To create oxyhydrogen flame 3 H2:4b grapes 1n, 023t
/Min combustion gas was sent to the quartz burner 4.

200cc of 02:2.0b 1n, SiCtx:200cc/MinSiF4 as raw material gas
/Min was played.

From plasma torch 16A, 16B, He: 10b pain 1
nSF6: 300cc/Min, O2: 500cc/M
In was supplied to the plasma flames 17A and 1TB, and the temperature of the deposited soot was maintained at 1300 to 1500°C.

By maintaining the deposition for the necessary time in this manner, a glass material containing fluorine was obtained.

The carbon rods on the starting member could be easily removed in the same manner as above. Another starting material, a quartz pipe, was removed by dissolving it in hydrofluoric acid, resulting in a pipe made only of synthetic glass.

A separately prepared high-purity pure quartz glass rod with extremely low 0H group content is inserted into the synthetic pipe described above and collapsed to create the synthetic glass rod containing pure quartz glass containing fluorine. An optical fiber base material with cladding was obtained.

The refractive index of the cladding portion of the optical fiber base material, which is made of fluorine-containing synthetic glass, is higher than that of the pure quartz core.
It was about 1% lower. An optical fiber was obtained by melting this optical fiber base material in a heating bath and drawing it. The transmission loss of this optical fiber at a wavelength of 0.95 μm is approximately 1
0 dB/Km, and a low-loss optical fiber with little increase in transmission loss due to the OH group was obtained. The method of the invention has the following advantages.

(1) Unique advantages of flame hydrolysis method Good yield when glass is contained from one raw material gas.

2. In particular, the yield of Ge and soybean dopant is better than the method using thermal oxidation (Uchizuke method).

3. Fast manufacturing speed.

(2) Advantages specific to this method 1. Since soot is sintered immediately after it is deposited, a large synthetic glass body without air bubbles can be produced.

(Because soot can be deposited and sintered over and over again on the surface of the synthetic glass body) (3) High-quality, inexpensive glass can be produced.

1.If the purity of raw material gas combustion gas and high temperature gas is improved,
Glass with few impurities can be made.

2 In particular, hydroxyl groups can be removed by the following reaction.

This is because -SlOH+Ct2=-SL-0-CtThis reaction proceeds easily by increasing the sintering temperature. 3. It is easy to obtain a glass body with a predetermined refractive index distribution in the radial direction and a fiber spun from the glass body.

The yield of glass from the 4 raw materials is good, the combustion gas only provides the heat and water necessary for the reaction, so only a small amount is required, and He in the plasma is easily ionized, so less electricity is required (expensive He
(Gas is recovered) etc., it is possible to make inexpensive synthetic glass bodies.

゜(4) Other advantages In addition to making soot by partially containing fluorine or a fluorine compound as a raw material gas for flame hydrolysis or thermal oxidation, He, F2, and 02 gas are further added as high-temperature gases. By using it, fluorine-containing, silica-based glass can be made.

(Furthermore, it is not necessary to use fluorine compounds when making soot.)

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view showing a conventional soot application process, and FIG. 2 is a partial cross-sectional view showing forming a preform of an optical fiber according to the present invention.

Claims (1)

[Claims] 1. In a method of producing a glass fiber preform for optical transmission by reacting a raw material gas with an oxyhydrogen burner, rotating the generated glass powder, and sequentially depositing it on the surface of a reciprocating starting member, in the vicinity of the burner. vitrifying the glass powder into transparent glass by means of a high-temperature gas ejected from a high-frequency plasma torch disposed at a high-temperature plasma torch; A method for producing a glass fiber base material for optical transmission, characterized in that it contains a gas.