JP2622210B2 - Target support member for manufacturing optical fiber preform - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a target support member for producing an optical fiber preform, and more particularly to a porous glass preform for producing an optical fiber preform and a method of heating the porous glass preform. The present invention relates to a target support member for producing an optical fiber preform used when producing a transparent optical fiber preform.

[0002]

2. Description of the Related Art Various methods are known for manufacturing a preform for an optical fiber.
The VAD and OVD methods have attracted attention because they can be easily operated at high speed and are economical. In this method, an oxyhydrogen flame burner is installed in a reaction vessel, oxygen, hydrogen, and a glass raw material are guided to the burner, and glass fine particles generated by flame hydrolysis of the glass raw material are rotated on a target. A porous glass preform is produced by adhering and depositing on a quartz target, and this porous glass preform is heated in a heating furnace such as an electric furnace to form a transparent optical fiber preform. As a target support member for supporting a quartz target during the production of the porous glass base material and a target support member for heating the porous glass base material, those made of quartz have conventionally been used. (Japanese Utility Model Publication No. Sho 61-7215,
No. 12336).

[Problems to be solved by the invention]

However, cost reduction and mass production are indispensable for widespread use of this optical fiber. For this reason, recently, there has been a strong demand for an optical fiber base material having a large size and high-speed production. However, this requires the target to have a large diameter and a long length in order to form a porous glass base material, and accordingly, a burner, a large gas flow, and a high heat are required. It is required to increase the weight of the porous glass base material and increase the temperature of the heating furnace even in the process of making the porous glass base material transparent.
There is a problem that the get supporting member cannot cope with the shortage of strength and heat resistance due to insufficient strength and heat resistance.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a target supporting member for manufacturing an optical fiber preform which can solve such disadvantages, and targets a glass fine particle in a reaction vessel. In a target supporting member used in a step of forming a porous glass preform to be attached and deposited on a get and / or a step of heating the porous glass preform to form a transparent optical fiber preform, The get support member is made of ceramics having a volatile metal impurity content of 0.5% by weight or less and a softening temperature or a decomposition temperature of 1,600 ° C. or more.

That is, the present inventors have conducted various studies to develop a target support member that can withstand high temperatures and high temperatures.
The use of ceramics with a softening temperature or decomposition temperature of 1600 ° C or higher as the target support member used in the production of optical fiber preforms can cope with the increase in the weight of the optical fiber preform and the high temperature inside the reaction vessel. In addition to finding out what can be done, if this ceramic has a volatile metal impurity of 0.5% by weight or less, this impurity is prevented from being mixed into the porous glass base material and the optical fiber base material. The present invention was completed by confirming that the optical loss of the manufactured optical fiber could be prevented from increasing. This will be described in more detail below.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a target member for producing an optical fiber preform, which comprises the production of a porous glass preform by a known external method, and the production of an optical fiber by heating the porous glass preform. In the production of the base metal for use, the target support member used here is provided with a volatile metal impurity amount of 0.5.
% By weight or less, with a softening or decomposition temperature of 1,600 ° C
The gist of the present invention is to be made of the above ceramics.

The target supporting member for producing an optical fiber preform according to the present invention is provided with an oxyhydrogen flame burner in a reaction vessel, and a glass raw material such as oxygen, hydrogen and silicon tetrachloride. A glass compound produced by flame hydrolysis of this glass raw material is deposited on a rotating target such as quartz to form a porous glass base material. This target is supported in a method in which a glass preform is heated in a heating furnace such as an electric furnace to form an optical fiber preform.

However, the target supporting member is conventionally made of the same quartz because the target is usually made of a quartz glass rod. Because of the demand for large size and high-speed production, the burner becomes large and the gas flow rate increases.
Since the heat was increased, the weight of the optical fiber preform was increased, and the high temperature in the heating furnace was unavoidable, the target support member also lacked the strength and heat resistance of quartz, When this is used, there is a disadvantage that axial misalignment or eccentricity occurs, the dimensional accuracy of the target porous glass preform or optical fiber preform decreases, and the quality of the optical fiber preform decreases.

However, according to the present invention, when the target support member for producing an optical fiber preform is made of ceramics having a softening temperature or decomposition temperature of 1,600 ° C. or more,
Even if a high rotational moment is applied to a high temperature with this, it has high strength and heat resistance, so that there is no axial deviation or eccentricity, and therefore the target porous glass base material or optical fiber This has the advantage that the dimensional accuracy of the base material does not decrease, and the amount of volatile metal impurities is 0.5% by weight or less. Since it does not mix with the glass preform or the optical fiber preform, it does not mix with the optical fiber,
Therefore, an advantage that the disadvantage that the optical fiber has a large optical loss can be avoided is provided.

The ceramic used in the present invention has a volatile metal impurity such as iron, copper, zinc or the like of 0.5% by weight or less and a softening temperature or a decomposition temperature of 1600 ° C. or more as described above. This includes aluminum nitride, silicon nitride, boron nitride, titanium nitride,
Examples include a sintered body such as titanium boride and a CVD molded body.

When a sintered body is used as the ceramic, it is preferable to select a rare earth oxide, alumina, or magnesia having high purity as the sintering binder in order to reduce the amount of volatile metal impurities. In addition, this ceramic is resistant to heat shock during optical fiber manufacturing,
In addition, aluminum nitride and silicon nitride are the preferred materials because even a very small amount of decomposed matter jumps out of the ceramic body and has little effect on the optical fiber. The atmospheric pressure sintered body of the present invention has high heat insulation and strength, is resistant to corrosive gases such as hydrochloric acid generated in the manufacturing process and chlorine gas used for dehydration, and is low in cost. It is an optimal get support member.

Although the present invention relates to a target support member as described above, fixing a target to the target support member usually involves driving a fixing pin into the target support member. Done in the way
Since this fixing pin also requires strength and heat resistance, it is preferable that this fixing pin be made of the same ceramic as that of the target support member.

[0013]

Next, examples of the present invention and comparative examples will be described. Examples and Comparative Examples Oxygen, hydrogen, and a mixed gas of silicon tetrachloride as a glass raw material and germanium tetrachloride as a dopant were introduced into an oxyhydrogen flame burner installed in a reaction vessel and generated there. The silica fine particles and the germania fine particles thus obtained were adhered and deposited on a quartz target to prepare a 5 kg porous glass base material.

Next, as shown in FIG.
A porous glass preform 1 made by depositing silica fine particles on a get 2 and silicon nitride produced by normal pressure sintering using yttria (3% by weight) and alumina (2% by weight) as a sintering binder. Is fixed to a target support member 4 having a diameter of 20 mmφ and a length of 1,000 mm manufactured using silicon (the amount of volatile metal impurities is 0.3% by weight) with a fixing pin having a diameter of 2 mm made of the same silicon nitride and rotating. It was attached to part 5.

Next, the support member 4 is rotated by using the rotating shaft 5.
The porous gas base material 1 is also rotated by rotating at 30 rpm, the inside of the inner cylinder 7 is heated to 1,500 ° C. by the heater 6, and the helium gas mixed with chlorine is discharged from the gas inlet 8 to make the porous gas base material 1 porous. A preform for optical fiber was prepared by converting the gas preform to transparent glass.

In this embodiment, this operation is
The target support material and the fixing pin were slightly discolored at the tip, but there was no eccentricity or deformation, and there was no abnormality in the obtained optical fiber preform. Although not recognized, the target support member and the fixing pin were made of quartz of the same dimensions for comparison. In this case, the eccentricity and deformation occurred at the twelfth time, and the obtained light was obtained. Since the fiber preform had uneven diameter, it could not be used thereafter.

[0017]

The present invention relates to a target supporting apparatus for manufacturing a preform for an optical fiber, which comprises a step of forming a porous glass preform, and a step of forming an optical fiber preform from a porous glass preform. The target supporting device in the process is characterized by comprising ceramics having a volatile metal impurity content of 0.5% by weight or less and a softening temperature or a decomposition temperature of 1,600 ° C. or more. According to this report, since the target support member is made of ceramics having high strength and withstanding a high temperature of 1,600 ° C, the weight of the optical fiber base material increases due to mass production of optical fibers, and The material does not become eccentric or deformed even at high temperatures, and it also contains a small amount of volatile metal impurities of 0.5% by weight or less, so that it does not mix with the optical fiber preform. Since there also is also such Ino be increased optical loss in the future optical fiber made, the effect is given that can be advantageously produced good optical fiber quality.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an apparatus for producing a preform for optical fiber by heating a porous glass preform according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Porous glass base material 2 ... Target 3 ... Fixing pin 4 ... Target support member 5 ... Rotating part 6 ... Heater 7 ... Cylindrical 8 ... Gas inlet

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Osamu Kuriyama 2-3-1-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Isobe Plant (56) References JP-A-60-145923 (JP, A) JP-A-2-204339 (JP, A) JP-A-62-144945 (JP, U)

Claims (6)

(57) [Claims] 1. A process for forming a porous glass preform for adhering and depositing glass fine particles on a target in a reaction vessel and / or heating the porous glass preform to form a transparent optical fiber preform. In the target support member used in the process, the target support member is made of ceramics having a volatile metal impurity content of 0.5% by weight or less and a softening temperature or a decomposition temperature of 1600 ° C. or more. A target support member for manufacturing an optical fiber preform, characterized in that: 2. The target support member for manufacturing an optical fiber preform according to claim 1, wherein the ceramic is a nitride of aluminum and / or silicon. 3. The target support member according to claim 1, wherein the ceramic is a normal pressure sintered body of silicon nitride. 4. The target for manufacturing an optical fiber preform according to claim 1, wherein the fixing of the target to the target support member is performed by driving a fixing pin into the target support member.
Get support members. 5. The target support member for producing an optical fiber preform according to claim 4, wherein the fixing pin is made of aluminum and / or silicon nitride. 6. The target support member for producing an optical fiber preform according to claim 5, wherein the fixing pin is made of a normal pressure sintered body of silicon nitride.