JPS60246232A - Manufacture of optical fiber preform - Google Patents

Abstract

PURPOSE:To keep the inner diameter of an exhaustion tube at nearly definite level, and to obtain an optical fiber preform having uniform characteristics along the longitudinal direction, by oscillating the discharge tube wall after forming a specific porous preform, thereby removing the excess fine glass particles attached to the discharge tube. CONSTITUTION:The core nozzle 1A of the burner 1 is supplied with a glass- forming gas such as SiCl4, GeCl4, etc., and the annular nozzle 1B is supplied with combustible gas, etc. such as O2, H2, etc. The glass-forming gas is hydrolyzed in the oxyhydrogen flame 2 to fine glass particles 3 (soot) depositing on the starting substrate ascending under rotation, to form a porous preform 4. The deposition of the soot on the growth surface 4A is continued, and the excess soot 3A (about 30% of the whole soot) failed to deposit is discharged from the reaction system through the discharge tube 5, and sent to the scrubber, etc. The excess soot 3A accumulated gradually on the inner surface of the discharge tube 5 is removed by applying small vibration 7 to the wall of the discharge tube 5 continuously or intermittently by driving the vibrator 6 attached closely to the outer wall.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a method for manufacturing an optical fiber core material by a vapor phase axial method.

[Description of prior art]

A vapor phase axial method is known as a method for manufacturing optical fiber base materials.

This gas phase axis method (", 5ICJ4, GeC1,1"
I11 containing oxygen and hydrogen
Gas is supplied to a combustion burner and these glass forming raw materials are hydrolyzed in a flame to produce glass fine particles (hereinafter referred to as type K [soot 1]).
After obtaining a porous base material in the shape of a circle II by depositing and growing the soot in the axial direction from the tip of a rod-shaped starting base material, this porous FiI base material is heated and sintered at a high temperature to form a transparent material. Glass [J throat.

1. An optical transmission fiber can be obtained by IL-stretching the transparent glass rod to a small diameter on a heating table. The vapor axis fJ method described in 1 can be used in many other ways, such as the inside method of depositing soot inside a glass vibrator or the external method of depositing soot on the outer periphery of the glass vibrator. It has the great advantage that there are fewer restrictions on length compared to the high-quality Itr4 forming method, and the production of ultra-long fibers f1 has also been investigated.

[Problem that the invention seeks to solve]

In the gas-phase axial method, not all of the soot generated by flame hydrolysis is deposited on the porous base material;
Approximately 30% of the exhaust gas is led to an exhaust gas treatment device such as a scrubber through an exhaust pipe connected to the reaction chamber. For this reason, excess soot mixed in the exhaust gas adheres to the inside of the exhaust pipe, and the effective inner diameter of the exhaust pipe changes over time, causing fluctuations in the exhaust volume and pressure in the reaction section, which in turn causes the soot flow from the burner to change. The direction of VC will also fluctuate slightly.

If the flow direction of the soot flow toward the porous base material is unstable in this way, the properties of the generated porous base material will be non-uniform in the length direction. As a countermeasure to the L problem, a method of keeping the exhaust volume constant, and a method of keeping the pressure of the reaction part constant by measuring the pressure of the reaction part and controlling the exhaust volume have been proposed. However, the thickness of the soot adhering to the exhaust pipe is not necessarily uniform, so the center of the exhaust gas flow changes over time, and even if the internal pressure of the reaction section is kept constant, the effective inner diameter of the exhaust pipe changes. 1. There is a problem in that the flow velocity of exhaust gas fluctuates greatly.

Such turbulence in the exhaust system (n of the base metal growth surface, A rV
What about the soot flow and base material growth? It is difficult to create a porous base material that has stable properties in the length direction by disturbing the j relationship over time.

In particular, in the high-speed synthesis of the Noiba base material, which has been a focus of recent development, the amount of raw materials supplied increases and the amount of soot discharged outside the reaction system is also large. The problems mentioned are becoming more and more important.

[Purpose of the invention]

The purpose of the present invention is to stabilize the soot flow from the combustion burner in the vapor phase shafting method by eliminating as much as possible the change in the effective inner diameter of the discharge pipe over time due to the adhesion of excess soot discharged from the reaction yarn. An object of the present invention is to provide a method for manufacturing an optical fiber preform having stable properties in the transverse direction.

[Summary of the invention]

The method of the present invention which achieves the first objective is to deposit glass fine particles obtained by reacting volatile glass-forming raw materials in a flame on a base material to form a porous base material, and then to form a porous base material. In a method for producing an optical fiber base material in which a material is heated and sintered to make it transparent, glass particles adhering to a discharge pipe that guides excess glass particles out of the reaction system are removed continuously or intermittently during the deposition process. The purpose is to remove it.

[Function and effect of the invention]

According to the above-mentioned method, the excess soot adhering to the inner surface of the discharge pipe is constantly removed during the molding process of the base material through the pores 5, so that the effective inner diameter of the discharge pipe is kept constant. Alternatively, by combining it with displacement control, it is possible to suppress the turbulence of the soot flow from the combustion burner to a smaller range than before, and it is possible to manufacture a porous base material with uniform properties in the length direction. .

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments shown in the drawings.

In the figure, / is a burner, and the center of this burner/through part/AKS]Ce4. 1f-y gas forming raw material gas such as GeCe4 is supplied, and combustible gases such as oxygen and hydrogen and inert gases such as argon gas are supplied as necessary. be done. Top 2
The glass forming raw material is the oxyhydrogen flame λ generated in the burner/
The soot 3 is converted into JK by a hydrolysis reaction, and this soot 3 is deposited on the starting base material (not shown) which rises while rotating, producing a porous base material q, and thereafter the growth of the base material. It is deposited sequentially on surface 4'AK. The excess soot (1) JA deposited on the porous base material L is led out of the reaction system through a discharge pipe S and sent to exhaust gas treatment equipment such as a scrubber. In the prior art, as shown in FIG. 3, excess soot JA following the discharge pipe S adheres and accumulates on the inner surface of the discharge pipe S over time, causing the above-mentioned problem.

Therefore, in the present embodiment, the impeller A is attached in close contact with the outer wall of the discharge pipe, and this vibration f-B is driven to generate the discharge pipe wall Ky and small vibrations 7 either continuously or intermittently (one time λ). As a result, even if excess soot 13A adheres to the inlet end or the inner wall surface of the discharge pipe, the KIkR immediately falls off and does not accumulate in a thick layer as in the conventional case.

Therefore, the effective inner diameter of the discharge pipe j is always kept constant,
The flow rate of the passing airflow remains constant.

As a result, the effective soot flow for depositing the porous base material 4IVC has a stable flow rate throughout the entire period of base material formation, and the properties in the longitudinal direction of the base material can be made highly uniform.

In the embodiments described below, the attached soot is removed by applying vibration to the wall of the discharge pipe, but the method of the present invention is not intended to limit the specific method of soot removal.

For example, as shown in FIG. 2, a scraping member groove is inserted from the outlet 1 side of the discharge pipe S, and with the scraping member groove in contact with the inner wall of the discharge pipe, the drive device 11 is operated as appropriate to discharge the discharge area S.
The attached soot may be scraped off by moving the tube in the longitudinal direction and circumferential direction.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, FIG. 2 is a longitudinal sectional view showing another embodiment of the invention, and FIG. 3 is a sectional view of essential parts showing a conventional state. (7) /0. . Burner 2. +・Flame 3...0 soot 3A...excess soot 1q...porous base material qA...growth surface S...discharge pipe B...vibrator zone...scraping member (g) Figure 1 Small

Claims (1)

[Claims] (1) Glass particles obtained by reacting volatile glass-forming raw materials in a flame are deposited on a base material to form a porous base material, and then this porous base material is heated and sintered to create a transparent glass. 7. A method for producing an Ivar base material, characterized in that glass particles adhering to a discharge pipe that guides excess glass particles out of the reaction system are removed continuously or intermittently during the deposition process. Method for manufacturing fiber matrix. (2. The method for manufacturing an optical fiber base material according to claim 7, wherein the removal of glass particles also adhering to the discharge tube is carried out by applying vibration to the discharge tube wall.