JPS6232139B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for manufacturing a preform for communication optical fiber.

Figure 1 is a cross-sectional view of a conventional device of this type.
A burner 10 that burns flammable gases such as methane and propane together with oxygen contains SiCl ₄ , GeCl ₄ , BCl ₃ ,
Si, Ge, B, such as PCl ₃ , AlCl ₃ , GaCl ₃ etc.
Compound glass raw materials such as P, Al, and Ga are injected to synthesize glass fine particles in a flame, which are then blown onto one end of the starting rod 11 made of refractory material such as quartz glass, which moves upward while rotating, and is deposited. This causes the porous glass rod 12 to grow into a rod shape.
The glass synthesis reaction and deposition portions are performed in a reaction vessel 13 in order to prevent the porous glass from being contaminated by outside air. Gases such as water vapor, chlorine, and hydrogen chloride generated by the synthesis reaction are exhausted from the exhaust port 14.

The porous glass thus produced is heated and melted in a heating furnace 15 installed coaxially with the starting material.
Degassed and made into a transparent optical fiber base material or glass rod. These steps are performed continuously.

In this conventional device, exhaust from the reaction vessel was by natural exhaust or simply forced exhaust;
When the pressure inside the reaction vessel fluctuates, the flame that synthesizes the glass particles becomes unstable, and the deposition rate of the glass particles that adhere to the tip of the porous glass rod changes.
There were problems in that the outer diameter of the porous glass rod produced varied and the density of the porous body varied.

Causes of pressure fluctuations within the reaction vessel include changes in external atmospheric pressure, fluctuations in the amount of gas supplied to the burner, and adhesion of glass particles to the tip of the burner.

In order to solve the above-mentioned problem, the present invention provides an exhaust port 1
By keeping the flow rate of the gas discharged from 4 constant and growing porous glass under stable conditions, it is attempted to produce porous glass or transparent glass rods having uniform dimensions. The present invention will be explained in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, in which 20 is a burner, 21 is a starting rod, 22 is a porous glass rod, 23
24 is an exhaust port, and 25 is a heating furnace. In FIG. 2, as described above, a porous glass rod is grown, a valve 26 connected to an exhaust port 24 is placed, and the opening/closing degree of the valve 26 is measured by a gas flow measuring device 27 placed in the same piping system. , the gas flow rate is measured, and this signal is amplified by an amplifier 28 to drive a motor 29 that opens and closes the valve. The motor 29 moves the valve 26 in the direction in which it closes when the exhaust gas flow rate increases, and in the direction in which the valve 26 opens when the flow rate decreases.
is set to move. In such a circuit, the amplifier 28 maintains the exhaust gas flow rate at an initially set constant gas flow rate. Glass synthesis reaction vessel 2
3, the outer diameter of the porous glass can be kept constant by keeping the internal pressure of the reaction vessel 23 constant instead of controlling the exhaust gas flow rate to a constant value as described above. can.

Reference numeral 30 denotes a pressure sensor attached to the reaction vessel, which picks up the pressure inside the reaction vessel as an electrical signal and inputs it into the same amplifier 28 as in the previous embodiment, so that if the pressure is higher than the set pressure, the valve 26 is opened. The motor 29 is driven, and if the temperature is low, the motor 29 is driven to close the valve 26.

As explained above, the optical fiber base material manufacturing apparatus of the present invention exhausts water vapor, chlorine, hydrogen chloride, etc. generated by the glass synthesis reaction by controlling the valve connected to the exhaust port. Since the amount is kept constant and the gas flow inside the reaction vessel 23 is stabilized, the growth of the porous glass rod 22 is performed in a constant state.
The outer diameter, density, etc. of the porous glass rod 22 can be made uniform.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional optical fiber base material manufacturing apparatus, and FIG. 2 is a diagram showing an embodiment of the present invention. 20...Burner, 21...Starting rod, 22...Porous glass rod, 23...Reaction container, 24...Exhaust port, 25
...Heating furnace, 26...Valve, 27...Gas flow measuring device, 2
8...Amplifier, 29...Motor, 30...Pressure detector.

Claims (1)

[Claims] 1. A reaction vessel, a starting rod rotatably held in the reaction vessel so that it can be pulled up, a burner for synthesizing glass particles for depositing glass particles on the tip of the starting rod, and a compound glass raw material and a combustible material being fed to the burner. In an apparatus for manufacturing an optical fiber base material, the apparatus includes a supply system for supplying reactive gas and oxygen gas, and an exhaust system that is provided in the reaction vessel and exhausts gas generated in the reaction vessel, wherein the exhaust system is provided in the exhaust system. A base material for optical fiber, characterized in that it is equipped with a valve that controls the exhaust amount in conjunction with an exhaust gas flow meter installed in the chamber or a pressure detector installed in the reaction vessel, and keeps the pressure in the reaction vessel constant. Manufacturing equipment.