JPS59128227A - Manufacture of base material for optical fibre - Google Patents

Abstract

PURPOSE:To manufacture a glass base material having no variation in outside diameter by supplying a starting material for glass and a gas for flame into a reaction chamber by a synthetic torch, and adjusting an angle between a flame stream from the synthetic torch and a glass round bar in the manufacture of round bar-shaped porous glass for a base material for an optical fibre. CONSTITUTION:A synthetic torch 1 is inserted in a reaction vessel 2 and a mixture of a starting fine powder material for glass and a gas for flame is blown out to generate a flame, and glass fine particles are produced by a flame hydrolysis decomposition reaction to be deposited at the top end of a glass seed bar. Thus, a produced base material of porous glass 3 is pulled up by a driving apparatus 6, heated and defoamed in a heating apparatus 5 to obtain the transparent glass base material having no bubbles. In this case, a bar of glass base material 3 having a uniform diameter is formed at a high speed by adjusting an angle theta formed between a flame stream from the synthetic torch 1 and the bar 3 of the glass base material to 20 deg.-40 deg..

Description

[Detailed description of the invention] The present invention is directed to a method of manufacturing an optical fiber preform.

The method of producing a round rod-shaped porous glass base material, heating it, and degassing it to obtain a transparent glass base material is commonly known as the VAD method.

In this method, glass raw materials and flame gas are supplied into a reaction vessel using a synthesis torch, and glass particles are immediately synthesized through a flame hydrolysis reaction, which is then blown onto the tip of a seed rod that is pulled up while rotating. A round bar-shaped porous glass m+A is produced by depositing the glass, which is then heated to 1,600 to 1,700°C to degas it in an upper heating furnace to obtain a transparent base material.

Conventionally, various synthetic torches and flame flow directions in this method have been tried, and prototype examples have been reported with angles between 0 and 60 degrees with respect to the rotation axis of the porous base material.

However, if the angle of the flame flow +

In view of this situation, the present invention aims to provide a method for manufacturing an optical fiber base material with good reproducibility, little variation in outer diameter, and high growth rate by specifying the optimal range of flame flow angles. purpose.

That is, the gist of the present invention is to set the angle of the flame flow blown out from the synthetic torch to the rotation axis of the seed rod and the porous base material by 20
This is because the angle is in the range of 40° to 40°.

An embodiment of the present invention will be specifically described with reference to the drawings.

In the figure, 1 is a synthesis torch, 2 is a reaction vessel, and 3 is a porous glass base material.
The distance from the center of the growth end face is 50 to 100 m, and the flame stream blown out from the synthesis torch 1 is inclined at an angle of 20' to 40° with respect to the rotation axis of the seed rod and the porous glass base material 3.

Reference numeral 4 denotes an exhaust device, which exhausts gases and fine particles that did not form the porous glass base material 3.

5 is a heating device, and 6 is a driving device, which rotates and pulls up the deposited porous glass base material 3 and heats it to turn it into transparent glass.

According to the experiments conducted by the present inventors, at this time, the outer diameter variation and growth rate are as shown in Tables 1 and 2 depending on the angle formed between the flame flow and the rotation axis of the porous glass base material 3. Ta.

J3, the oxygen flow rate in this experiment was 6ffl/min.
.

Hydrogen flow t2H, t3J/min, glass raw material O,,3
11/Table 1 Table 2 From the above experiments, unlike the conventional superstition that 10 to 60° inclination is better than no inclination, 20 to 40'
It is clear that the angle of inclination is better than the angles before and after it.

As explained above, with the manufacturing method of the present invention, the outer diameter variation is small and the growth rate in the axial direction is high, so the optical fiber base material can be manufactured with high precision and high efficiency.

[Brief explanation of drawings]

The figure is an explanatory diagram showing one embodiment of the present invention. 1: Synthesis torch, 2: Reaction vessel, 3: Porous glass BJ
Moon, 4: Exhaust device, 5: Heating device, 6: Drive device.

Claims (1)

[Claims] Fine glass particles are synthesized from glass raw materials through a flame hydrolysis reaction using a synthesis torch, and the particles are sprayed and deposited on the tip of a seed rod that is pulled up while rotating to create a porous glass matrix in the shape of a round rod. In the manufacturing method of optical fiber base material, which is heated and degassed to make it transparent,
A flame stream blown out from a synthetic torch is tilted by 20' to 40 degrees with respect to the rotation axis of the seed rod and the porous glass base material to deposit glass fine particles, thereby obtaining a round bar-shaped porous glass base material. A method of manufacturing an optical fiber mother H, characterized by: