JP2957170B1 - Optical fiber preform, optical fiber preform, and methods for producing them - Google Patents

Abstract

The present invention provides an optical fiber porous preform having an improved glass fine powder deposition weight per batch which greatly contributes to an improvement in production capacity and a reduction in manufacturing cost. SOLUTION: A porous optical fiber preform in which glass fine powder is deposited around a center member, wherein the deposit has a controlled pore diameter. And a method for producing a porous optical fiber preform by depositing a glass fine powder around the center member while rotating the central member, wherein the pore diameter of the deposit of the glass fine powder is controlled. The method of manufacturing the material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a porous optical fiber preform, an optical fiber preform, and a method for producing the same.
In particular, the present invention relates to an optical fiber porous preform having an improved weight of glass fine powder deposited on the periphery of a member, an optical fiber preform obtained therefrom, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, an optical fiber porous preform is manufactured by depositing a glass fine powder around a member of the optical fiber porous preform while rotating the member of the optical fiber porous preform, for example, by an external method. In order to deposit the glass fine powder around the above-mentioned member, for example, the member is placed in a device called a chamber which surrounds both ends in the axial direction of the member, and a fuel gas is supplied from a flame burner located at the front of the chamber. Or raw material gas to generate fine glass powder around the member in the flame,
A mechanism is provided for depositing this gas and exhausting unreacted gas, reaction product gas, undeposited glass fine powder, and the like from an exhaust port of the chamber opposite to the flame burner.

As described above, an optical fiber porous preform obtained by depositing a glass fine powder around a member can be excellent in purity and other various qualities. As described above, in recent years, the manufacturing technology of the optical fiber porous preform has made remarkable progress in quality.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a porous optical fiber preform having various excellent qualities as described above, which further improves the production capacity and lowers the production cost. It is an object of the present invention to obtain a base material having an improved weight of the above-mentioned glass fine powder.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, in order to increase the weight of glass fine powder deposited on a member, it goes without saying that the strength of the member is improved. It has been found that it is necessary to improve the strength of the glass fine powder deposit itself when depositing on the member. That is, in improving the glass fine powder deposition weight,
The strength of the member can be accommodated by making it thicker,
Regarding the glass fine powder deposit, if the deposit is simply increased, it will be broken by handling when the deposit is passed to the next step. That is, when passing the glass fine powder deposit to the next process, for example, it is placed on a cart via a cushion and moved,
Despite the use of the cushion, the lower part of the glass fine powder deposit is broken by its own weight. Therefore, it is required to improve the strength of the glass fine powder deposit itself.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the invention according to claim 1 is an optical fiber porous preform in which glass fine powder is deposited around a member. An optical fiber porous preform characterized in that its pore diameter is controlled. As described above, by controlling the pore diameter of the glass fine powder deposit, the strength of the glass fine powder deposit can be improved, and therefore, the weight of the glass fine powder deposited on the member can be improved.

According to the invention described in claim 2 of the present invention, the fine glass powder deposit has a median pore diameter of 0.1.
This is an optical fiber porous preform controlled to be 1 to 1 μm. As described above, the optical fiber porous preform in which the pore diameter is controlled in the above range is particularly long, large-diameter, that is, an optical fiber in which heavier glass fine powder is deposited and which is optically superior. It can be.

[0008] The invention described in claim 3 is an optical fiber preform obtained by fusing the above optical fiber porous preform. By vitrifying the porous optical fiber preform, a long and large-diameter optical fiber preform can be manufactured, and thus an optical fiber having excellent optical properties can be obtained.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a porous optical fiber preform by depositing a glass fine powder around a member while rotating the member. A method for producing a porous optical fiber preform characterized by controlling. As described above, by controlling the pore diameter of the glass fine powder deposit, the strength of the glass fine powder deposit can be improved, and as a result, a long, large-diameter, ie, heavier, glass fine powder can be obtained. A deposited optical fiber porous preform can be produced.

The invention described in claim 5 is a method for producing a porous optical fiber preform in which the median pore diameter of a deposit of fine glass powder is controlled to 0.1 to 1 μm. As described above, by controlling the median of the pore diameter of the deposit of the glass fine powder to 0.1 to 1 μm, particularly, a long and large-diameter optical fiber porous mother on which a heavier glass fine powder is deposited. A material can be manufactured, and an optical fiber superior in optical quality can be manufactured.

The invention described in claim 6 is characterized in that the pore diameter of the deposit of glass fine powder is controlled by controlling the flow rates of the raw material gas for glass fine powder and the fuel gas. Or a method for producing a porous optical fiber preform according to claim 5. As described above, the pore diameter of the deposit of the glass fine powder can be controlled, for example, by controlling the flow rates of the raw material gas for the glass fine powder and the combustion gas.

Further, the invention according to claim 7 is a method for manufacturing an optical fiber preform, wherein the optical fiber porous preform manufactured by any one of the above manufacturing methods is melt-vitrified and manufactured. As described above, by using the porous optical fiber preform of the present invention, a long, large-diameter optical fiber preform can be manufactured, and a large number of optical fibers superior in optical quality can be manufactured. be able to.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. FIG. 1 shows a soot 6 being deposited on a target 1. In the porous optical fiber preform of the present invention, as shown in FIG. 1, a glass fine powder 6 is deposited around a member (hereinafter sometimes referred to as a “target”) 1. The target 1 serves as an optical fiber core, and is specifically a quartz glass rod or the like. According to the present invention, it is possible to obtain an optical fiber porous preform on which a long, large-diameter, ie, heavier, glass fine powder 6 is deposited. Therefore, in order to support such a high-weight base material, the target 1 to be used is, for example, one having a length of 200 mm or more and a diameter of 30 mm or more, and ensuring its strength.

In the optical fiber porous preform of the present invention, the glass fine powder 6 is deposited on the periphery of the target 1 having the above-mentioned increased strength (hereinafter, this deposit is referred to as “sooting”).
There is a case. ). The porous optical fiber preform of the present invention does not cause cracking even when heavy soot is deposited. Specifically, in the porous optical fiber preform of the present invention, the soot can be handled without cracking even if the soot is deposited on a target, for example, 80 kg or more.

That is, the present invention is characterized in that the pore size of the soot 6 is controlled. In this way, by controlling the pore size of the soot, the strength of the soot is improved, and as a result, a large amount of soot can be deposited on the target without causing the soot to crack. Cracking can be prevented. Suit 6
Has a median of 0.1 to 1 μm, particularly 0.1 μm.
Those controlled to 2 to 0.6 μm are preferred. If the median is less than 0.1 μm, when the optical fiber porous preform is melted and vitrified in an atmosphere such as chlorine in the next step, the OH groups on the silica particle surface are not removed because chlorine is not sufficiently diffused. , OH groups may remain. Also, if the median exceeds 1 μm, the soot strength may be degraded and soot cracking may occur.

The optical fiber preform of the present invention is obtained by melt-vitrifying the above-mentioned optical fiber porous preform of the present invention.
By using the optical fiber porous preform of the present invention, a long and large-diameter optical fiber preform can be obtained. Further, the optical fiber obtained therefrom has no OH group and the like, and therefore has little optical absorption and scattering loss due to the OH group and has very small transmission loss.

In the method for producing a porous optical fiber preform according to the present invention, soot is deposited around the target while rotating the target. By rotating the target 1, the soot 6 can be uniformly deposited. The rotation speed is
It is appropriately selected, but may be, for example, 10 to 50 rpm. 1 and 2, a target 1 is a chamber 2
It is rotatably housed inside, and both ends thereof are held by a chuck 3 or the like. Then, a flame 5 from the burner 4 is blown around the target 1 while rotating the target 1 and reciprocating the flame burner 4 at a constant speed. As a result, the glass fine powder (soot) 6 is uniformly deposited around the target 1.

That is, from the flame burner 4, a soot raw material gas (eg, a silicon compound such as SiCl ₄ ), a fuel gas (eg, H ₂ , O _2, etc.) are supplied. Then, the raw material gas is hydrolyzed in the oxyhydrogen flame to generate glass fine powder, and the generated glass fine powder is sprayed around the target 1 and deposited. In addition, target 1
Can be applied both upright and sideways.

The chamber 2 usually has a chuck cover 2 that covers one end of the target 1 as is apparent from the schematic diagram of the entire structure of the optical fiber porous preform manufacturing apparatus shown in FIG.
a, and a chuck cover 2b for covering the other end of the target 1. The flame burner 4 reciprocates along the opening 2c of the chamber 2 in parallel with the axial direction of the member. On the other hand, on the rear side (right side in the figure) of the chamber 2,
For example, a plurality (one or more) of exhaust ports 2d for exhausting unreacted gas, reaction product gas, undeposited glass fine powder, and the like are provided.
It is provided. The exhaust port 2d is connected to the exhaust pipe 7, and the inside of the chamber 2 is given a predetermined suction force (exhaust suction pressure) by an exhaust means 8, for example, a suction pump incorporated in the exhaust pipe 7 or the like. It sucks and exhausts.

The method for producing a porous optical fiber preform according to the present invention is characterized in that the pore diameter of the glass fine powder deposit is controlled. As described above, for example, the median is 0.1 to 1 μm, particularly 0.2 to 0.6 μm as described above.
Is preferably controlled.

Specifically, the control of the pore diameter is performed by controlling the flow rates of the raw material gas for glass fine powder and the fuel gas from the flame burner 4. That is, the pore diameter can be controlled by controlling the flow rates of the hydrogen gas and the oxygen gas in the fuel gas corresponding to the combustion energy considered to be directly related to the pore diameter with respect to the raw material gas. For example, if the flow rate of the fuel gas is increased relative to the source gas and the flow rate of the hydrogen gas and the oxygen gas is increased, the pore diameter becomes smaller. Conversely, the smaller the flow rate of the fuel gas with respect to the source gas, the larger the pore diameter.

Specifically, for example, when the flow rate of the SiCl ₄ raw material gas is 10 to 30 L / min, the hydrogen gas in the fuel gas is 100 to 600 L / min and the oxygen gas is 100 to 300 L / min.
L / min or the like. In addition, the pore diameter can be further controlled by controlling the number of revolutions of the target and the like.

In the method of manufacturing an optical fiber preform of the present invention, the optical fiber porous preform of the present invention is manufactured by melting and vitrifying. Specifically, the optical fiber porous preform is placed in, for example, an electric furnace and the like.
To obtain the optical fiber preform of the present invention.

Thereafter, the optical fiber preform of the present invention produced as described above can be made into an optical fiber by a usual method, for example, melt drawing. The optical fiber manufactured in this manner has no OH group and the like, and thus has little optical absorption and scattering loss due to the OH group, and is optically very excellent with very small transmission loss.

[0025]

The present invention will be specifically described below with reference to examples. (Examples 1 to 3 and Comparative Examples 1 and 2) A porous optical fiber preform was manufactured using the manufacturing apparatus shown in FIGS. That is, a target 1 having a diameter of 40 mm
Was mounted, the number of revolutions was unified to 30 rpm, and soot 6 was deposited under the conditions shown in Table 1. At that time, gas introduction
The raw material SiCl ₄ and the fuels H ₂ and O ₂ are jetted from the flame burner 4, and after hydrolysis, soot 6 is deposited using SiO ₂ as a glass fine powder, and the soot weight is reduced to 70.
８０80 kg.

Table 1 shows the pore diameter median of each of the obtained optical fiber porous preforms, the presence or absence of soot cracks, and the residual amount of OH groups after chlorination. In addition, the measurement of the pore diameter was performed by cutting a soot into a block of 1 cm square and measuring this with a mercury intrusion porosimeter.

[0027]

[Table 1]

As is evident from Table 1, when the amount of the fuel gas is larger than the amount of the raw material gas, the median pore diameter becomes smaller, and as a result, the residual amount of OH groups increases. Conversely, it can be seen that if the fuel gas is less than the source gas, the median pore diameter increases, and as a result, the soot cracks.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

[0030]

According to the present invention, an optical fiber porous preform having a high soot strength can be manufactured. Therefore, an optical fiber porous preform on which a long and large-diameter, ie, heavy, soot is deposited can be obtained. As a result, in manufacturing the porous optical fiber preform, the production capacity can be improved, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a partially enlarged schematic view of an apparatus for manufacturing a porous optical fiber preform, showing a soot being deposited on a target.

FIG. 2 is a schematic diagram of the entire configuration of an optical fiber porous preform manufacturing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Target (member), 2 ... Chamber, 2a and 2b
... Cover part cover, 2c ... Opening, 2d ... Exhaust port, 3 ...
Chuck, 4 ... flame burner, 5 ... flame, 6 ... suit, 7 ...
Exhaust pipe, 8 ... Exhaust means.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hideo Hirasawa 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Research Laboratory (56) References JP-A-5-116980 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C03B 37/00-37/16 C03B 8/04

Claims (7)

(57) [Claims] 1. A porous optical fiber preform in which glass fine powder is deposited around a member, wherein the deposit has a controlled pore diameter. 2. The optical fiber preform according to claim 1, wherein the deposit has a median pore diameter controlled to 0.1 to 1 μm. 3. An optical fiber preform obtained by melt-vitrifying the porous optical fiber preform according to claim 1. 4. A method for producing a porous optical fiber preform by depositing glass fine powder around a member while rotating the member, wherein the diameter of the pores of the deposit of glass fine powder is controlled. A method for producing a porous base material. 5. The method for producing a porous optical fiber preform according to claim 4, wherein the median of the pore diameter of the deposit of the glass fine powder is controlled to 0.1 to 1 μm. 6. The method according to claim 4, wherein the flow rate of the raw material gas for the glass fine powder and the flow rate of the fuel gas are controlled to control the pore diameter of the deposit of the glass fine powder.
3. The method for producing a porous optical fiber preform according to item 1. 7. A method for producing an optical fiber preform, wherein the optical fiber porous preform produced by the production method according to claim 4 is melt-vitrified. Method.