JPS6292B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to an improvement in an apparatus for producing an optical fiber base material. The present invention relates to an optical fiber base material manufacturing apparatus that can efficiently introduce raw material gas.

(b) Background of the technology One method for manufacturing optical fiber preforms made of inorganic glass used as optical transmission lines is the internal chemical vapor deposition method (internal CVD method) using a moving heating source. It is widely used because it provides a low-loss base material for optical fibers.

(c) Prior Art and Problems Conventionally, as shown in FIG. 1, the above-mentioned manufacturing method and apparatus have a method in which, as shown in FIG. From one end of the reaction tube 1, a glass layer is formed of, for example, silicon tetrachloride (SiCl ₄ ), phosphorus oxychloride (POCl ₃ ) for controlling the refractive index, germanium tetrachloride (GeCl ₄ ), etc., vaporized at a predetermined temperature. A carrier gas carrying a raw material gas and oxygen gas are simultaneously introduced, and the outer wall of the reaction tube 1 is locally heated by a heating means that moves in the longitudinal direction of the tube, such as an oxyhydrogen burner 3, to complete the reaction. The raw material gas in the tube 1 undergoes a thermal oxidation reaction, and the generated glass products (soot) are sequentially deposited on the inner wall surface of the tube and melted to form a transparent glass layer 4 of a desired thickness. After that, while further rotating this reaction tube 1, the oxyhydrogen burner 3
The diameter of the tube 1 is densely reduced by heating to form a solid material, thereby forming an optical fiber base material.

By the way, in the configuration of the manufacturing apparatus as described above, since the raw material gas for forming the glass layer introduced into the reaction tube 1 serving as the starting material is vaporized at a temperature higher than room temperature, the gas introduction tube (not shown) is used. The gas introduction end 1a of the reaction tube 1 connected thereto is kept at a predetermined temperature by a heating cover as shown by a chain line 5. However, since the rotational support mechanism 2 cannot be heated, the raw material gas is cooled and liquefied in the reaction tube 1 section installed in the rotational support mechanism 2, which tends to cause problems such as adhesion to the inner wall of the tube. However, there was a drawback that the glass layer 4 having the desired refractive index and thickness could not be deposited on the predetermined inner wall surface of the reaction tube 1.

(d) Purpose of the Invention In order to eliminate the above-mentioned conventional inconveniences, the present invention provides that a reaction tube serving as a starting material is supported on a rotary support mechanism with one end of the gas introduction side closed, and that the reaction tube near the closed end is A novel optical fiber preform manufacturing apparatus is provided, which has a structure in which the raw material gas for forming a glass layer is introduced in a heated state, and the raw material gas for forming a glass layer is fed at a predetermined flow rate into the glass layer deposition region in the reaction tube. The purpose is to provide

(e) Structure of the Invention According to the present invention, the above object is to introduce a raw material gas for forming a glass layer from one end of a reaction tube serving as a starting material supported by a rotating mechanism, and to move the gas along the longitudinal direction of the reaction tube. In an apparatus configuration for vitrifying the reaction product deposited on the inner wall surface of the tube by locally heating the reaction tube with a heating means, the gas introduction end of the reaction tube is closed, and the gas inlet end of the reaction tube is closed, and the A gas introduction hole is provided in the side wall of the tube and is supported by the rotation mechanism, and the gas introduction portion having the gas introduction hole is provided with a gas introduction hole.
This is achieved by providing an optical fiber preform manufacturing apparatus characterized in that it is equipped with a rotational connection mechanism with heat insulating means for introducing raw material gas.

(f) Embodiments of the invention Examples of the invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional view of a main part conceptually showing an embodiment of the optical fiber preform manufacturing apparatus according to the present invention.

Note that parts equivalent to those in FIG. 1 are given the same reference numerals.

In the figure, reference numeral 21 denotes a hollow reaction tube made of quartz as a starting material, one end of which is closed, and a support rod 21a is attached. Further, a gas introduction hole 22 is bored in the side wall of the tube near the closed end.

The reaction tube 21 is connected to the support rod 21 at the one end.
A and the other end are attached to and supported by the rotation mechanism 2 of the device. 3 is a heating means that moves along the longitudinal direction of the reaction tube 21 and locally heats the tube wall;
For example, an oxyhydrogen burner.

Furthermore, in the present invention, an annular rotary connector 23 having a gas inlet 24 to which a raw material gas inlet pipe (not shown) is connected is airtightly and It is slidably attached to the outer circumference of the pipe. The outer periphery of the annular rotary connector 23 and the reaction tube 21 in its vicinity
The portion is covered with a heat insulating cover 25 using, for example, hot air or electric heating in the shape shown by the chain line, and is configured to maintain heat at a predetermined temperature up to about several hundred degrees.

Therefore, in the apparatus configured as described above, the vaporized raw material gas for glass layer formation is introduced into the reaction tube 21 through the annular rotary connector 23 from a heat-retaining type raw material gas introduction pipe (not shown). When the raw material gas liquefies and stagnates in a region other than the glass layer deposition region in the reaction tube 21, no sagging occurs, and the glass deposited layer 4 has a uniform glass composition and refractive index in the longitudinal direction of the reaction tube 21.
can be easily formed to a predetermined thickness.

(g) Effect of the invention As is clear from the above explanation, according to the configuration of the optical fiber preform manufacturing apparatus according to the present invention, the raw material gas for forming the glass layer is introduced into the reaction tube serving as the starting material within the rotating mechanism. Instead of being introduced through the tube, it is introduced through an annular rotary connector with a heat-insulating cover installed in the reaction tube section before the section supported by the rotation mechanism, so that the introduced raw material gas forms a glass layer. There is no fear of liquefaction and retention in parts other than the area, and it becomes possible to easily form a glass deposited layer having a uniform glass composition and refractive index to a predetermined thickness in a predetermined region within the reaction tube. Therefore, it is necessary to use a manufacturing equipment that forms an optical fiber base material using a glass layer forming raw material gas containing, for example, potassium trichloride (GaCl ₃ ) or aluminum trichloride (AlCl ₃ ), which needs to be vaporized at a relatively high temperature. It is extremely advantageous to apply.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part explaining a conventional optical fiber preform manufacturing apparatus, and FIG. 2 is a main part sectional view conceptually showing an embodiment of an optical fiber preform manufacturing apparatus according to the present invention. be. In the drawing, 2 is a rotation mechanism, 3 is an oxyhydrogen burner, 4 is a glass deposited layer, 21 is a reaction tube, 21a is a support rod, 22 is a gas introduction hole, 23 is an annular rotary connector, 24 is a gas introduction port, 25 indicates a heat insulation cover.

Claims (1)

[Claims] 1. A raw material gas for forming a glass layer is introduced from one end of a reaction tube, which is a starting material, supported by a rotating mechanism, and the reaction tube is locally heated by a heating means that moves along the longitudinal direction of the reaction tube, so that the inside of the tube is heated. In an apparatus configuration for vitrifying reaction products deposited on a wall surface, the gas introduction side end of the reaction tube is closed, and a gas introduction hole is bored in the tube side wall surface near the closed end. What is claimed is: 1. An optical fiber preform manufacturing apparatus, which is supported by a rotation mechanism and further includes a rotation connection mechanism with a heat insulating means for introducing a raw material gas, which is attached to a gas introduction section having a gas introduction hole.