JPS59190235A - Production of parent material for optical fiber - Google Patents

Abstract

PURPOSE:A mixture of 2 or more different kinds of combustible gases is used as a flame-burning gas for synthesizing fine glass particles to enable high-speed production of the titled parent material, avoiding reduction in the deposition efficiency of fine glass particles. CONSTITUTION:Fine glass particles are synthesized in the flame flow so that the particles are deposited in the axis direction to form a porous parent material 1, then the material is heated and sintered at high temperatures to give a clear parent material for optical glass fibers. At this time, a mixed gas of 2 or more different kinds of combustible gases such as hydrogen, methane or propane is used as a flame-burning gas for synthesis of fine glass particles from, e.g., SiCl4+GeCl4. For example, a mixed gas of methane and hydrogen, as its mixing ratio is controlled by means of flow meters 3, 4, respectively and fed together with oxygen gas and the starting gas for glass to the synthesis torch 2 to form a flame and fine glass particles.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an optical fiber matrix using a VAD method.

Conventionally, in the VA, D method, only hydrogen (H2) gas was used as the flame combustion gas for synthesizing particles in Karasu'5. This conventional V'AD method (here,
In order to increase the flame temperature, that is, the total heat energy generated (moss), it is necessary to increase the hydrogen gas flow rate, and there is a problem that increasing the hydrogen gas flow rate increases the flame flow velocity. This causes a problem of lowering the deposition efficiency of glass particles on the surface of the porous base material.As a result, there is a drawback that the continuous production of the porous base material is reduced.

This drawback becomes noticeable when increasing the glass raw material strength and increasing the manufacturing speed of the porous base material, and in order to prevent the reaction efficiency from decreasing, it is necessary to increase the flame temperature, that is, the thermal energy generated. In the case of 0, an increase in the hydrogen gas flow rate, i.e. an increase in the flame flow velocity, resulted in a decrease in the deposition efficiency of glass particles, making it difficult to form a porous matrix at high speed.

In order to solve these drawbacks, the present invention uses G, hydrogen (H2
), methane [OH, ), propane (C3H8), etc. σ[
The feature is that a mixture of two or more combustible gases is used as a flame combustion gas to produce a porous a matrix, and its purpose is to prepare glass. The objective is to prevent a decrease in R particle deposition efficiency and improve high-speed base material production in the VAD method.

FIG. 1 is a drying diagram of an embodiment of the present invention, in which 1 is a porous base material, 2 is a synthetic torch, and 3 and 4 are flowmeters for methane gas and hydrogen gas, respectively. In this example, a mixture of hydrogen gas and methane gas was used as the combustion gas. Here, the combined ratio of hydrogen gas and methane gas used in the roasting furnace was determined by hand, with a total of 39 flows. Heat generation ht per unit volume is 1:8.12 for hydrogen gas and methane gas.
Therefore, methane gas has a higher calorific value per volume. Table 1 & Table 1 show the necessary ratio of hydrogen gas flow rate and methane gas flow i1 to obtain the same calorific value as that obtained with flow IH, 5 of hydrogen gas 401/ml.

To the mouth I+■Smashing Lotto phrase■〇-prison C risun-cto. Q:V
I to Aku to Aku to N ~ N Prison Bell's
To the life of the person
Synthetic torch 2 used in the example (combustion gas blowing layer,
The average flow velocity of the mixed gas at the tip with an outer diameter of 3 Q mmφ and an inner diameter of 24 mmφ is shown in the right column of Table 1 (
I showed this.

In this Example G, hydrogen gas and methane gas are combined in order to obtain the same exothermic energy (G), and the flow velocity at the tip of the synthesis torch is set to 34 cm/See to 260
I was able to change it up to Cm/SeC.

Figure 2 shows the relationship between the simulated flame Reynolds number and the glass particles deposited on the porous matrix using another model experiment.
This shows the relationship between Here, the flame Reynolds number Y
is defined as the amount expressed by In the case of , it can be interpreted as a quantity proportional to the flow velocity.This model experiment was carried out due to the oxygen gas flow velocity G used for combustion.Furthermore, in Fig. 2, FR is indicated. It shows the glass raw material supply.

According to Figure 2, each synthesis torch has an optimal gas flow rate (i.e., optimal Reynolds number) at which the amount of glass particles deposited is the largest, and when the optimal gas flow rate is exceeded, the gas flow D (i.e., Reynolds number) increases. As the number) increases, the glass fine particle deposition h4 decreases. The relationship between the gas flow velocity and the amount of glass particles deposited has a similar tendency with combustion gases such as hydrogen gas [2], and it can be seen that at the same flame temperature G, the faster the flow velocity is, the lower the deposition efficiency is. Ta. In this example, when 5iOA4 glass raw material was supplied at a rate of 597 mln, only hydrogen gas 'i: 40 t/
The yield of glass particles was about 30% when the combustion was performed at a flow rate of min. Add this to 12 l/ml of hydrogen gas
When a mixed gas of n and methane gas was used at 9 A'/min, the yield of glass particles was improved to about 60%. Also flow rate] 3
If only 1/min of methane gas is used, the flame will not be stable and the yield will be about 40%. By warming two types of combustible gases, it is necessary to adjust the flow rate of flame debris and improve the deposition efficiency. was completed.

Table 2 shows the total heat production of other combustible gases.

Similarly, when propane gas is used as the mixed gas,
1517ml of hydrogen gas was used for optimal mixing.

Propane gas was obtained at 8.51/min. At this time, the blowing speed of the mixed gas at the tip of the burner is approximately 1.20
There was Crn/SeC. In addition, the yield of glass particles is 5
5%, and the yield of glass fine particles G was improved compared to that in the case of using only hydrogen gas. Kneading is the same as mixing water, 9Z gas, and methane gas. The difference in yield between methane gas and propane gas is due to the difference in R sludge flow 14j required for stable production.

Also, the diameter of the oxygen gas outlet in the burner was set to 4 m.
With a burner larger than m, -6j, propane gas as a combined gas? When #+1 was used, the yield of glass fine particles was 0% halo.

In this way, depending on the burner diameter, glass raw material supply, etc., other combustible gases are combined with hydrogen gas, and the amount of mixture? Optimal selection of G made it possible to improve the yield of glass fine particles.

As explained above, the method G of the present invention improves the deposition efficiency of glass particles in the production of optical fiber preforms, so that it is possible to increase the synthesis rate of porous preforms in the VAD method. This has the advantage of reducing optical fiber manufacturing costs.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, and Fig. 2 is a diagram showing the relationship between the flame Reynolds number and the amount of dried sardines and yuzu in glass particles.・・・Porous bamboo mortar, 2...Synthesis torch, 3...Methane gas flow h (total), 4...Hydrogen gas flowmeter. Patent applicant: Nippon Telegraph and Telephone Public Corporation Figure 1 1 3i C14,000 Ge Cj, 4 Figure 2 'Inolus'

Claims (1)

[Claims] 1.Crow fine particles were synthesized in the flame flow, and the particles were deposited in the axial direction to form a porous matrix7.
Manufacturing method of heating and sintering the porous 'If fi material to a high temperature to obtain a transparent optical fiber matrix (V A D ; 7)
& Flame addition 1 for synthesizing glass particles
Water (H2), methane (OH4,), "i" as gases
Production of optical fiber base material characterized by forming a porous matrix using a mixed gas of two or more of the following: Method.