JP2957172B1 - Optical fiber preform, optical fiber preform, and methods for producing them - Google Patents

Abstract

The present invention provides a porous optical fiber preform having an improved adhesion rate of glass fine powder on a central member which greatly contributes to an improvement in production capacity and a reduction in manufacturing cost, and an optical fiber preform obtained therefrom. I do. SOLUTION: The surface area of the glass fine powder is 1 in an optical fiber porous preform in which the glass fine powder is deposited around a center member.
The total amount of adsorbed H ₂ O and OH group per m ² is 3.
An optical fiber porous preform weighing 5 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ g, and a method for producing a porous optical fiber preform by depositing fine glass powder around the central member while rotating the central member The adsorption H ₂ per 1 m ² of surface area of glass fine powder
The total amount of the O amount and the OH group amount is 3.5 × 10 ^{−5 to} 7.5 ×
A method for producing a porous optical fiber preform controlled to 10 ^-5 g.

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 a porous optical fiber preform having an improved glass fine powder adhesion rate on a member, an optical fiber preform obtained therefrom, and a method for producing 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 a 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 (rear portion of the chamber) of the chamber opposite to the flame burner.

The porous optical fiber preform obtained by depositing the glass fine powder around the member as described above has excellent various quality characteristics. 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 is a member which further improves the conventional optical fiber porous preform having various excellent qualities as described above, and which greatly contributes to improvement of production capacity and reduction of production cost. An object of the present invention is to provide an optical fiber porous preform having an improved adhesion rate of glass fine powder thereon, and an optical fiber preform obtained therefrom.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, have found that the adhesion rate of the above glass fine powder and the physical properties of the glass fine powder deposit, particularly the glass fine powder measured by the BET method. It has been found that there is a correlation between the total amount of the amount of adsorbed H ₂ O per m ² and the amount of the OH group per m ² calculated from the specific surface area of the above, and the present invention has been completed.

That is, according to the first aspect of the present invention, in a porous optical fiber preform in which glass fine powder is deposited around a member, adsorption H per 1 m ² of surface area of the glass fine powder.
The total amount of the ₂ O amount and the OH group amount is 3.5 × 10 ^{−5 to} 7.5.
An optical fiber porous preform weighing ^10-5 g. Thus, the adsorbed H ₂ O per 1 m ² of the surface area of the glass fine powder
By the total amount of the amount and the OH group amount is in the above range,
An optical fiber porous preform having a high adhesion rate of the glass fine powder on the central preform is obtained.

[0007] The invention according to claim 2 is an optical fiber preform obtained by fusing the above optical fiber porous preform. By using the optical fiber porous preform having an improved glass fine powder adhesion rate, a large-sized optical fiber preform having excellent optical characteristics can be manufactured at low cost.

According to a third aspect of the present invention, there is provided a method for producing a porous optical fiber preform by depositing a glass fine powder around the member while rotating the member, wherein the glass fine powder has a surface area of 1 m ² per 1 m ² . This is a method for producing an optical fiber porous preform in which the total amount of the adsorbed H ₂ O and the OH group is controlled to 3.5 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ g. Thus, the amount of adsorbed H ₂ O per 1 m ² of surface area of glass fine powder and OH
By controlling the total amount with the base amount in the above range, the adhesion rate of the glass fine powder can be improved, and thus the production cost of the optical fiber porous preform can be greatly reduced.

Further, according to the present invention, by controlling the flow rate of a gas supplied for depositing the glass fine powder, the adsorption H per 1 m ² of the surface area of the glass fine powder is controlled.
The total amount of the ₂ O amount and the OH group amount is 3.5 × 10 ^{−5 to} 7.5.
This is a method for producing an optical fiber porous preform controlled to × 10 ⁻⁵ g. As described above, in order to control the total amount of the adsorbed H ₂ O and the amount of the OH group per 1 m ² of the surface area of the glass fine powder within the above range, specifically, a gas supplied for depositing the glass fine powder is used. By controlling the flow rate.

A fifth aspect of the present invention is a method for manufacturing an optical fiber preform, wherein the porous optical fiber preform manufactured by the method of the present invention is melt-vitrified and manufactured. According to the production method of the present invention, an optical fiber porous preform can be produced at low cost. Therefore, by using such an optical fiber porous preform, an optical fiber preform can also be manufactured at low cost. Moreover, the obtained optical fiber preform has excellent optical characteristics.

[0011]

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. 2 shows that a glass fine powder is deposited on a member (hereinafter, sometimes referred to as “target”) 1 of an optical fiber porous preform (hereinafter, this deposit may be referred to as “soot”). ) Indicates the state. In the porous optical fiber preform of the present invention, a glass fine powder 6 is deposited around the target 1 as shown in FIG. Target 1 above
Is a core for an optical fiber, specifically a quartz glass rod or the like.

The porous optical fiber preform of the present invention is characterized in that the glass fine powder 6 is deposited on the periphery of the target 1 at a high adhesion rate. Such a high adhesion rate is caused by the fact that the total amount of the adsorbed H ₂ O and OH group per 1 m ² of the surface area of the glass fine powder is 3.5 × 10 ^−5.
This can be achieved by the above. FIG. 1 shows the relationship between the total amount of the adsorbed H ₂ O and the OH group and the glass fine powder adhesion rate. As is apparent from FIG. 1, when the total amount is less than 3.5 × 10 ⁻⁵ g, the adhesion ratio of the glass fine powder is 0.1%.
Less than 4 is not preferred. On the other hand, the total amount is 7.5
If the amount exceeds × 10 ⁻⁵ g, the adhesion rate becomes sufficient. However, when sintering the optical fiber porous preform into an optical fiber preform, the H ₂ O and OH groups adsorbed cannot be sufficiently removed in the dehydration step with chlorine, and OH groups remain in the sintered body. May be caused. As a result, OH groups and the like remain in the optical fiber manufactured therefrom, and optical absorption and scattering loss occur to promote transmission loss. Therefore, the total amount is 3.5 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ g, preferably 4 × 10 ⁻⁵ g.
× 10 ^{-5 to} 7 × 10 ^-5 g.

[0013] The term "adhesion ratio" refers to the ratio of the amount of adhered glass fine powder to the amount of glass fine powder sprayed onto a target or soot. The total amount of the amount of adsorbed H ₂ O and the amount of OH group per 1 m ² of surface area of the glass fine powder can be determined, for example, as follows. That is, the surface area of the glass fine powder per unit weight, that is, the specific surface area is determined by the BET method or the like. On the other hand, the total amount of the amount of adsorbed H ₂ O and the amount of OH groups present on the surface of the glass fine powder per unit weight is determined by an appropriate analysis means, for example, a Grignard method. May be used to measure only the amount of adsorbed H ₂ O.
Of the above total amount, the remaining amount of the OH group is also determined. ). From the specific surface area and the total amount, the total amount of H ₂ O and OH groups per 1 m ^{2 of} the surface area can be determined.

As described above, the surface area of the glass fine powder is 1 m
The total amount of adsorbed H ₂ O per ² and OH group content, positive correlation between the glass fine powder deposition rate is observed. The mechanism of adhesion of the glass fine powder having such a correlation to the soot is not clear, but the glass fine powder produced by hydrolysis in an oxyhydrogen flame has an O-bond having Si-OH bonds.
The H group is dehydrated and condensed with an OH group having a Si-OH bond on the soot to form a Si-O-Si bond, whereby the glass fine powder and the soot are combined, and as a result, the glass fine powder adheres. Conceivable. At this time, the adsorbed H ₂ O also reacts with various glass fine powders according to the following formula, and becomes a factor for generating OH groups in the glass fine powder as a bond, so that the adsorbed H ₂ O also increases the adhesion rate. Becomes

[0015]

Embedded image

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 having an excellent adhesion rate of glass fine powder, a large-sized optical fiber preform having excellent optical characteristics can be manufactured at low cost. Further, the optical fiber obtained therefrom has very little transmission loss because no OH group or the like remains, and therefore, there is almost no optical absorption or scattering 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. FIG. 2 shows the state of soot deposition on the target. In FIG. 2, a target 1 is rotatably housed in a chamber 2 and both ends thereof are held by a chuck 3 or the like. Then, the flame burner 4 is reciprocated at a constant speed while rotating the target 1, and the flame 5 from the burner 4 is blown around the target 1. As a result, fine glass powder (soot) is placed around the target 1
6 are deposited uniformly.

A gas for depositing glass fine powder is supplied from the flame burner 4. Specifically, a soot raw material gas (for example, a silicon compound such as SiCl ₄ or the like) and a fuel gas (for example, H ₂ or O ₂ gas) 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 to be deposited. Note that the arrangement of the target 1 can be applied by a mechanism that stands up and down or a mechanism that places it sideways.

FIG. 3 is a schematic diagram of the entire configuration of the optical fiber porous preform manufacturing apparatus. As is clear from FIGS. 2 and 3, the chamber 2 usually has a chuck cover 2a covering one end of the target 1 and a chuck cover 2b covering the other end of the target 1. Is reciprocated along the axial direction of the member. On the other hand, the rear side of the chamber 2 (right side in the figure)
Is provided with, 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. 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.

In the method for producing a porous optical fiber preform of the present invention, the total amount of the adsorbed H ₂ O and the OH group per 1 m ² of the surface area of the glass fine powder is adjusted to 3.5 × 10 ^{-5 to} 7 × 10 ^-5. .
The control is performed at 5 × 10 ⁻⁵ g, preferably 4 × 10 ^{−5 to} 7 × 10 ⁻⁵ g. As described above, by controlling the total amount in this way, the adhesion rate of the glass fine powder on the periphery of the target can be improved, and therefore, the optical fiber porous preform can be manufactured at low cost. it can. Moreover, the resulting optical fiber preform is OH
It is also excellent in optical properties, with almost no radicals remaining.

The total amount of the adsorbed H ₂ O and the OH group can be controlled, for example, by controlling the flow rate of a gas supplied for depositing the glass fine powder. Specifically, a soot raw material gas (for example, Si
It is preferable to control the flow rate of the fuel gas (for example, H ₂ , O ₂ gas, etc.) with respect to the flow rate of a silicon compound such as Cl ₄ . That is, when the flow rate of the fuel gas is reduced with respect to the raw material gas, the combustion energy is reduced and the specific surface area is increased. As a result, the amount of adsorbed H ₂ O per unit area is increased.
The total amount of the amount and the OH group amount becomes smaller. As a result, the adhesion rate decreases. Conversely, if the flow rate of the fuel gas is sufficient with respect to the raw material gas, the combustion energy increases and the specific surface area decreases, and as a result, the amount of adsorbed H ₂ O per unit area increases.
The total amount of the amount and the OH group amount becomes large. As a result, the adhesion rate is improved. However, if the flow rate of the fuel gas is excessively large, OH groups and the like remain during the sintering of the porous optical fiber preform, which causes a problem that the sintered body becomes cloudy.

Specifically, for example, when the flow rate of the SiCl ₄ source gas is 5 to 30 L / min, the flow rate of the hydrogen gas in the fuel gas is 150 to 600 L / min and the flow rate of the oxygen gas is 50 to 300 L / min. And so on. In addition, by controlling the number of rotations of the target and the like, the adhesion rate of the glass fine powder may be further controlled.

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 way has no OH group and the like, and therefore has almost no optical absorption or scattering loss, so that the transmission loss is very small and the optical fiber is very excellent.

[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, the target 1 of a quartz glass rod having a diameter of 40 mm was mounted in the chamber 2, and the soot 6 was deposited under the conditions shown in Table 1 at a constant rotation speed of 30 rpm. At this time, gas was introduced by injecting SiCl _{4 as} a raw material and H ₂ and O ₂ as fuels from a flame burner 4, hydrolyzing in an oxyhydrogen flame, and depositing soot 6 with SiO ₂ as glass fine powder. I let it.

A part of the soot 6 of each obtained optical fiber porous preform was rubbed by hand and pulverized to obtain a sample. For this sample, the total amount of the adsorbed H ₂ O amount and the OH group amount was measured by the Grignard method. At the same time, the specific surface area of this sample was measured by the BET method.
From the total amount and the specific surface area, the glass fine powder surface area 1 m
It was determined total amount of adsorbed H ₂ O per ² and OH group content. Further, the sample was sintered at 1500 ° C. for 5 hours in a chlorine atmosphere to obtain a soot sintered body. The appearance of the obtained sintered body was visually observed. The adhesion rate was determined as the molar amount of SiO ₂ adhered to the molar amount of supplied SiCl ₄ . Table 1 shows the adhesion rate, the BET specific surface area, the concentration per unit area of the total amount of the adsorbed H ₂ O amount and the OH group amount, the weight per area, and the appearance results of the sintered body.

[0027]

[Table 1]

As is clear from Table 1, as the flow rate of the fuel gas (H ₂ + O ₂ ) with respect to the SiCl ₄ source gas is increased, the adhesion rate of the glass fine powder increases. But,
If the fuel gas is too much relative to the SiCl ₄ raw material gas, it becomes cloudy after sintering (Comparative Example 1).

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, it is possible to manufacture an optical fiber porous preform on which glass fine powder is deposited at a high adhesion rate. Therefore, raw materials for glass fine powder and the like can be effectively used, and the production cost can be greatly reduced. Further, the optical fiber preform obtained by sintering this is adsorbed H ₂
Almost no O amount or OH group remains. Therefore, the optical fiber manufactured therefrom has very little optical absorption and scattering loss due to the OH group and the like, so that the transmission loss is very small and the optical fiber is very excellent.

[Brief description of the drawings]

FIG. 1 shows the relationship between the total amount of adsorbed H ₂ O and the amount of OH groups per 1 m ² of surface area of glass fine powder and the adhesion rate of glass fine powder.

FIG. 2 is a partially enlarged schematic view of an optical fiber porous preform manufacturing apparatus showing a state of soot deposition on a target.

FIG. 3 is a schematic diagram of the entire configuration of an optical fiber porous preform manufacturing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Target, 2 ... Chamber, 2a and 2b ... Chuck cover, 2c ... Opening, 2d ... Exhaust port, 3 ... Chuck, 4 ... Flame burner, 5 ... Flame, 6 ... Soot, 7 ... Exhaust pipe line, 8 ... Exhaust means.

────────────────────────────────────────────────── ─── of the front page continued (72) inventor Hideo Hirasawa Gunma Prefecture Annaka Isobe 2-chome 13th No. 1 Shin-Etsu chemical Co., Ltd. precision functional materials within the Institute (58) investigated the field (Int.Cl. ^6, (DB name) C03B 37/00-37/16 C03B 8/04

Claims (5)

(57) [Claims] 1. An optical fiber porous preform in which glass fine powder is deposited around a member, wherein a surface area of the glass fine powder is 1
The total amount of adsorbed H ₂ O and OH group per m ² is 3.
An optical fiber porous preform weighing 5 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ g. 2. An optical fiber preform obtained by melting and glassifying the porous optical fiber preform according to claim 1. 3. A method for producing a porous optical fiber preform by depositing glass fine powder around the member while rotating the member, wherein the amount of adsorbed H ₂ O per 1 m ² of surface area of the glass fine powder and OH group 3.5 × 10 ^{-5 to} 7.
A method for producing an optical fiber porous preform, wherein the production is controlled to 5 × 10 ⁻⁵ g. 4. The total amount of the amount of adsorbed H ₂ O and the amount of OH groups per 1 m ² of surface area of the glass fine powder is controlled by controlling the flow rate of a gas supplied for depositing the glass fine powder. 4. The method for producing a porous optical fiber preform according to claim 3, wherein the control is performed at 0.5 × 10 ^{−5 to} 7.5 × 10 ⁻⁵ g. 5. A method for producing an optical fiber preform, which comprises producing the optical fiber porous preform produced by the production method according to claim 3 by melt vitrification.