WO2006077782A1

WO2006077782A1 - Process for producing porous glass preform and deposition burner

Info

Publication number: WO2006077782A1
Application number: PCT/JP2006/300390
Authority: WO
Inventors: Makoto Yoshida; Tetsuya Otosaka
Original assignee: Shin-Etsu Chemical Co., Ltd.
Priority date: 2005-01-19
Filing date: 2006-01-13
Publication date: 2006-07-27
Also published as: JP2006199527A; TW200628424A; JP4900762B2

Abstract

[PROBLEMS] To obtain a stable flame stream without damaging of burner cover by heat and produce an optical fiber preform being reduced in irregularity of refractive index distribution and having properties stabilized in the longitudinal direction thereof. [MEANS FOR SOLVING PROBLEMS] There is provided a process for producing a porous glass preform, comprising hydrolyzing a glass raw material in oxyhydrogen flame to thereby form glass microparticles and depositing the formed glass microparticles, wherein use is made of deposition burner (4) fitted with a double burner cover having inside cover (31) and outside cover (32). Arrangement is made so that providing that D0 is the outside diameter of deposition burner (4), D1 the inside diameter of inside cover (31), L1 the axial distance between the forefront of deposition burner (4) and the forefront of inside cover (31), D2 the inside diameter of outside cover (32), and L2 the axial distance between the forefront of inside cover (31) and the forefront of outside cover (32), there are satisfied the relationships (1) (D1/D0)≤1.3, (2) 1.2≤(L1/D0)≤2.5, (3) 1.6≤(D2/D0)≤3.2 and (4) 1.2≤(L2/L1).

Description

Specification

Porous glass base material manufacturing method and deposition pan

Technical field

The present invention relates to a method for producing a porous glass preform and a deposition pan. More specifically, the present invention relates to a deposition pan for depositing glass particles and a method for producing a porous glass base material using the same.

[0002] For designated countries where incorporation by reference of documents is permitted, the contents described in the specification of the following patent application are incorporated into the present application by reference and made a part of the description of the present specification.

Japanese Patent Application No. 2005—No. 011740 Filing Date January 2005 19th

Background art

[0003] As a method for producing a porous glass base material used as a material for an optical fiber, there is known a method in which a glass raw material is flame-hydrolyzed in an oxyhydrogen flame sprayed from a pan and the generated glass fine particles are deposited. ing.

[0004] In general, a concentric multi-tube spanner is used as the deposition spanner, and raw material gas, combustion gas, auxiliary combustion gas, and the like are supplied through this. Further, as described in Patent Document 1, the burner cover is formed on the outer periphery of the burner so that the flame flow generated in front of the burner is not disturbed by the surrounding air flow or the direction of the flame flow does not change. Has also been implemented! RU

[0005] In order to stabilize the flame flow, the burner cover provided in the deposition burner preferably has a large burner tip force and a distance to the burner cover tip. On the other hand, if this distance is increased, the burner cover may be damaged by heat due to the PANA flame. In addition, glass fine particles (silica) produced by flame hydrolysis may adhere to and grow on the tip of the burner cover, and then reattach to the exfoliated silica particle cartridge deposit. When such silica particles adhere, there is a problem that bubbles are generated when the porous glass base material is sintered and made into transparent glass.

[0006] Patent Document 2 shows the force to the end of the burner cover necessary to prevent the burner cover from being thermally damaged by the burner flame. But even higher quality In order to manufacture this optical fiber preform, it is necessary to further reduce the irregularity of the refractive index distribution, and to further reduce the flickering of the flame that causes it.

Patent Document 1: Japanese Patent Application Laid-Open No. 57-7834

Patent Document 2: Japanese Patent Laid-Open No. 2000-72448

Disclosure of the invention

Problems to be solved by the invention

[0008] As described above, if the distance between the end of the burner and the end of the burner cover is increased for the purpose of stabilizing the flame flow, the cover itself may be thermally damaged. On the other hand, if the distance between the end of the burner and the end of the burner cover is reduced, the effect of stabilizing the flame flow cannot be obtained! /.

[0009] Accordingly, an object of the present invention is to provide a deposition burner in which a stable flame flow is obtained and the burner cover is not damaged by heat. It is another object of the present invention to provide a method for producing a porous glass preform that can produce an optical fiber preform with small irregularity of the refractive index distribution and stable characteristics in the longitudinal direction using the deposition panner.

Means for solving the problem

[0010] As a first embodiment of the present invention, a glass raw material is hydrolyzed in an oxyhydrogen flame to produce glass fine particles, and the produced glass fine particles are deposited to produce a porous glass base material. Thus, there is provided a method for producing a porous glass base material, characterized in that a double burner cover is installed on the deposition spanner. The method for producing a porous glass base material of the present invention includes an inner cover and a distance between the tip of the PANANER and the cover so that the cover is not damaged by heat while maintaining the effect of reducing the flame and stabilizing the flame flow. The double inner structure with the outer cover that stabilizes the flame flow by reducing the influence of the turbulence of the air flow in the chamber by increasing the distance between the tip of the pan and the cover tip while increasing the inner diameter to prevent thermal damage. By doing so, the flame flow can be stabilized without causing problems such as thermal damage of the cover. As a result, it is possible to stabilize the flame flow without damaging the cover with heat, and to produce a porous glass base material with small non-circularity and stable characteristics in the longitudinal direction. Further, the obtained porous glass preform is dehydrated and sintered to form a transparent glass, thereby obtaining an optical fiber preform with a small non-circularity of the core and a small refractive index distribution.

[0011] Further, in the above manufacturing method, the double burner cover has an outer diameter of the deposition burner D, The inner diameter of the inner burner cover is L, the axial distance between the tip of the burner and the inner cover is L, the inner diameter of the outer burner cover is D, and the inner cover tip and the outer cover tip

1 2

When the axial distance is L,

2

(1) (D ZD) ≤1.3

Ten

(2) 1. 2≤ (L / Ό) ≤2.5,

Ten

(3) 1. 6≤ (D / D) ≤3.2

2 0

(4) 1. 2≤ (L ZL),

twenty one

It is provided so that each of these formulas may be satisfied. As a result, both flame stability and burner cover damage prevention can be achieved at a high level.

[0012] In the above manufacturing method, the outer cover has a cylindrical shape. As a result, a symmetric flame can be generated and glass particles can be deposited uniformly.

[0013] In the above manufacturing method, the outer cover has a shape obtained by obliquely cutting a cylinder.

. As a result, the soot shape, tip position, etc. can be observed or measured while maintaining the performance of the PANA.

[0014] In the manufacturing method, gas is allowed to flow between the outer cover and the inner cover. This allows the burner cover to be cooled with gas, further reducing damage from heat.

[0015] Further, in the above manufacturing method, the gas flowing between the outer cover and the inner cover can be any one of an inert gas, air, and oxygen. As a result, the influence on the adhesion of glass particles can be reduced.

[0016] Further, as a second aspect of the present invention, there is provided a deposition pan that hydrolyzes a glass raw material in an oxyhydrogen flame and deposits the generated glass fine particles to produce a porous glass base material. A deposition burner is provided that has a heavy burner cover. By using this stacking panner, the effects described above can be obtained using conventional manufacturing equipment.

[0017] In the above-described deposition panner, the double burner cover reduces the outer diameter of the deposition span D.

0

, The inner diameter of the inner burner cover is D, the axial distance between the end of the burner and the inner cover is L, the inner diameter of the outer burner cover is D, and the inner and outer cover tips are

1 2

Let L be the axial distance of

2

(1) (D ZD) ≤1.3 (2) 1. 2≤ (L / Ό) ≤2.5,

Ten

(3) 1. 6≤ (D ZD) ≤3.

2 0

(4) 1. 2≤ (L ZL),

twenty one

Satisfy each expression. As a result, it is possible to achieve both high stability of flame stability and prevention of burner cover damage.

[0018] Further, in the deposition pan, the outer cover has a cylindrical shape. As a result, a symmetric flame can be generated and glass particles can be deposited uniformly.

[0019] In the above-mentioned deposition panner, the outer cover has a shape obtained by cutting a cylinder obliquely. As a result, the soot shape, tip position, etc. can be observed or measured while maintaining the performance of the PANA.

[0020] Further, in the above-described deposition panner, gas is allowed to flow between the outer cover and the inner cover.

Thereby, this can reduce the influence on the adhesion of the glass fine particles.

[0021] Further, in the above-described deposition panner, the gas force that flows between the outer cover and the inner cover is any of inert gas, air, and oxygen. As a result, the burner cover can be cooled and the raw material gas can be supplied simultaneously.

[0022] However, the above summary of the invention does not enumerate all the necessary features of the present invention.

V ,. Sub-combinations of these feature groups can also be an invention.

The invention's effect

[0023] According to the present invention, thermal damage to the burner cover can be prevented, and a stable flame flow can be obtained. Therefore, it is possible to manufacture a porous glass base material with small non-circularity and stable characteristics in the longitudinal direction. Furthermore, the obtained porous glass preform is dehydrated and sintered to form a transparent glass, thereby obtaining an optical fiber preform with a small non-circularity of the core and a small refractive index distribution.

Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view showing an example of a conventional optical fiber preform manufacturing apparatus.

FIG. 2 is a schematic sectional view showing an example of a production apparatus used in the present invention.

FIG. 3 is a schematic cross-sectional view showing an outer cover having a cylindrical shape.

FIG. 4 is a schematic cross-sectional view showing an outer cover having a shape obtained by obliquely cutting a cylinder at an end. The

Explanation of symbols

[0025] 1 quartz chamber, 2 quartz substrate, 3 burner cover, 31 inner cover, 32 outer force bar, 4 deposition panner, 5 soot deposit, 6 exhaust port

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the claimed invention. In addition, all the combinations of features described in the embodiments are not necessarily essential for the solution of the invention.

FIG. 1 schematically shows an example of an apparatus for producing a porous glass base material by the VAD method.

In the quartz chamber 1, a quartz substrate 2 as an upper force deposition target is suspended, and a deposition pan 4 having a burner cover 3 is disposed obliquely upward in a downward force. The deposition panner 4 includes the core raw material, tetra-salt silicon (SiCl), and the dopepan that adjusts the refractive index.

Four

A raw material line such as tetrasalt 匕 germanium (GeCl) as a catalyst, and hydrogen for oxyhydrogen flame

Four

A gas line such as gas or oxygen gas is connected, and the glass fine particles generated by the flame hydrolysis are deposited on the quartz substrate to form the soot deposit 5. Exhaust gas is discharged from the exhaust port 6 to the outside of the system.

[0028] The deposition burner 4 is provided with a burner cover 3 in order to stabilize the flame flow.

Further, in order to stabilize the flame flow, it is preferable to take a large distance to the tip of the burner cover.

[0029] However, if this distance is increased, the burner cover is damaged by heat due to the flame generated in front of the PANA flame, or glass fine particles (silica) generated by flame hydrolysis at the tip of the burner cover. There were problems such as adhesion and growth, and then reattaching to the exfoliated silica particle deposits, causing bubbles to occur during sintering and transparent vitrification.

[0030] For this reason, in order to prevent the influence of the turbulence of the air flow in the chamber by restricting the flame, at the same time, preventing the thermal damage of the cover, and further preventing the growth of silica adhering to the cover, each problem There is no choice but to balance under conditions that reduce the occurrence.

[0031] By controlling the air flow and the cover loss, the role is divided between a cover intended to squeeze the flame and a cover intended to suppress the influence of the turbulence of the air flow. It was found that both wound avoidance can be achieved.

FIG. 2 is a schematic cross-sectional view showing an example of an apparatus for producing a porous glass base material provided with a deposition pan according to the present invention. In the quartz chamber 1, there is disposed a deposition pan 4 having an inner force bar 31 and an outer cover 32 facing downward and obliquely upward.

[0033] The deposition pan 4 includes silicon tetrachloride (SiCl) as a core material and a dopant that controls the refractive index.

Four

Raw material lines such as tetra-salt 匕 germanium (GeCl) as a coolant, and H gas for oxyhydrogen flame

4 2

A gas line such as O gas is connected. From the deposition pan 4 toward the target

2

By spraying raw materials and fuel gas, glass particles generated by flame hydrolysis are accumulated in the axial direction, and the quartz substrate 2 is pulled up while rotating to core with a high refractive index and cladding with a low refractive index. The soot deposit body 5 containing is formed, dehydrated in an electric furnace, and sintered to form a transparent glass, whereby an optical fiber preform is obtained.

[0034] In the above-described deposition panner, the outer diameter of the deposition spanner 4 is D and the inner cover 31

0

The diameter is D, the axial distance between the end of the PANANER and the inner cover 31 is L, the inner diameter of the outer cover 32 is D, and the axial distance between the inner cover 31 and the outer cover 32 is L.

2 2

(1) (D ZD) ≤1.3

Ten

(2) 1. 2≤ (L / D) ≤2.5,

Ten

(3) 1. 6≤ (D / D) ≤3.2

2 0

(4) 1. 2≤ (L ZL),

twenty one

It is provided to satisfy each of the following formulas.

[0035] In the above equation (1), the ratio of the inner diameter D of the inner cover to the outer diameter D of the PANA is 1.3 or more.

0 1

By setting it below, the flame can be squeezed and the flame flow can be stabilized.

[0036] The above equation (2) is the distance in the axial direction between the tip of the PANA and the tip of the inner cover with respect to the PANANER outer diameter D.

0

The ratio of the separation L is set to 1.2 to 2.5. By keeping the ratio within this range, thermal damage to the inner cover can be prevented.

[0037] In the above equation (3), the ratio of the inner diameter D of the outer cover to the outer diameter D of the PANA is 1.6 to 3.2.

0 2

By keeping within this range, thermal damage to the outer cover can be prevented. [0038] The above equation (4) is obtained by setting the ratio of the axial distance L between the front end of the inner cover and the front end of the outer cover to the axial distance between the front end of the panner and the front end of the inner cover to 1.2 or more.

2

The influence of the turbulence of the airflow in the bar can be reduced, and the flame flow can be stabilized.

FIG. 3 is a diagram illustrating the shape of the outer cover 32. As shown in the figure, the outer cover

32 can be a cylinder coaxial with Parner 4. As a result, a symmetrical flame is formed, which facilitates uniform deposition of glass particles.

FIG. 4 is a diagram illustrating another shape of the outer cover 32. As shown in the figure, the tip of the outer force bar 32 is cut obliquely so as to be inclined with respect to the axis.

The deposition pan 4 can be placed in an inclined state. As a result, the height of the entire manufacturing apparatus can be suppressed, and the degree of freedom in layout increases.

[0041] By causing an inert gas or a gas such as air or oxygen to flow between the outer cover and the inner cover provided in a double manner, thermal damage to the burner cover can be further prevented.

[0042] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these and various modes are possible.

Example

[0043] (Examples 1 to 7, comparative example)

The porous glass base material 5 was manufactured using the apparatus shown in FIG. The outer diameter D of the deposition burner 4 used is 20 mm.

0

24 hours deposition was carried out (Examples 1-7). The results are shown in Table 1. The comparative example is an example using a conventional single cover panner without the outer cover 32.

[0044] [Table 1]

Di / Do L1 / D0 D2 / D0 L ₂ / Li Covering Flame stability Comparative example 1.05 1.5 — — No problem Flickering Example 1 1.05 1.5 2.0 2.3 No problem No problem Example 2 1.20 1.5 2.0 2.3 No problem No problem Example 3 1.35 1.5 2.0 2.3 No problem Flicker Example 4 1.05 1.0 2.0 3.5 No problem Flicker Example 5 1.05 1.2 2.0 2.9 No problem No problem Example 6 1.05 2.5 2.0 1.4 No problem No problem Example 7 1.05 2.7 2.0 1.3 Damaged No problem

[0045] From Table 1, it is recognized that flame stability is improved by using the outer cover 32 in addition to the inner cover 31. Note that if the inner diameter of the inner cover is too large (Example 3), or if the axial distance L between the tip of the PANANER and the inner cover tip is short, flame stability will deteriorate (Example 4). (Example 7).

[0046] From the results shown in Table 1 above, it can be seen that it is preferable to set the range satisfying the following formula in the relationship between the deposition burner 4, the inner cover 31, and the outer cover 32.

(1) (D ZD) ≤1.3

Ten ,

(2) 1. 2≤ (L / Ό) ≤2.5

Ten ,

[0047] (Examples 8 to 16, comparative example)

Next, the outer diameter D of the deposition panner was set to 20 mm, and the dimensions of the outer cover were changed.

0

A porous glass base material was manufactured under the same conditions as in Examples 1 to 7 above. The results are shown in Table 2. The comparative example is an example using a conventional single cover panner without an outer cover.

[0048] [Table 2] Di / Do L1 / D0 D2 / D0 L ₂ / Li Cover Flame stability Comparative example 1.05 1.5 — — No problem Flicker Example 8 1.05 1,5 2.0 1.2 No problem No problem Example 9 1.05 1.5 1.5 1.2 Damage Yes No problem Example 10 1.05 1.5 1.6 1.2 No problem. No No Example 11 1.05 1.5 3.1 1.2 No problem No problem Example 12 1.05 1.5 3.3 1.2 No problem Flicker Example 13 1.05 1.5 2.0 1.1 No problem Flicker Example 14 1.05 1.5 2.0 1.7 No problem No problem

[0049] From Table 2, if the inner diameter of the outer cover is small, the cover is damaged (Example 9). The inner diameter of the outer cover is too large (Example 12). When the directional distance L is short, the flame stability is deteriorated (Example 13). Example 14 is

2

The axial distance between the inner cover tip and the outer cover tip was increased to the extent that the soot deposit tip position was covered, but no problem occurred.

2

[0050] From the results shown in Table 1 above, it can be seen that it is preferable to set the range satisfying the following formula in the relationship between the deposition burner 4, the inner cover 31, and the outer cover 32.

(3) 1.6≤ (D / Ό) ≤3.2

2 0,

(4) 1. 2≤ (L ZL),

twenty one

Industrial applicability

[0051] According to the present invention, an optical fiber preform with stable characteristics in the longitudinal direction can be obtained.

Claims

Claims [1] In a method for producing a porous glass base material by producing glass fine particles by hydrolyzing a glass raw material in an oxyhydrogen flame, and depositing the produced glass fine particles, A method for producing a porous glass base material, comprising installing a burner cover. [2] The double burner cover has D as the outer diameter of the deposition burner, D as the inner diameter of the inner burner cover, D as the axial distance between the end of the burner and the inner cover, and the inner diameter of the outer burner cover. D, and if the axial distance between the inner cover tip and the outer cover tip is L, 2 2

(1) (D ZD) ≤1.3

Ten

(2) 1. 2≤ (L / Ό) ≤2.5,

Ten

(3) 1. 6≤ (D / D) ≤3.2

2 0

(4) 1. 2≤ (L ZL

twenty one),

The method for producing a porous glass base material according to claim 1, wherein the porous glass base material is provided so as to satisfy each of the following formulas.

[3] The method for producing a porous glass base material according to claim 1 or 2, wherein the outer cover has a cylindrical shape.

[4] The method for producing a porous glass base material according to any one of claims 1 to 3, wherein the outer cover has a shape obtained by obliquely cutting a cylinder.

[5] The method for producing a porous glass base material according to any one of claims 1 to 4, wherein gas is allowed to flow between the outer cover and the inner cover.

[6] The method for producing a porous glass base material according to any one of [1] to [5], wherein the gas force flows between the outer cover and the inner cover, which is one of inert gas, air, and oxygen.

[7] A deposition pan that hydrolyzes a glass raw material in an oxyhydrogen flame and deposits the generated glass fine particles to produce a porous glass base material, characterized in that it has a double burner cover. Pana for deposition.

[8] The double burner cover sets the outer diameter of the deposition burner to D and the inner burner cover.

0

When D is the diameter, L is the axial distance between the end of the burner and the inner cover, D is the inner diameter of the outer burner cover, and L is the axial distance between the inner and outer cover tips. (1) (D ZD) ≤1.3

Ten

(2) 1. 2≤ (L ZD) ≤2.5,

Ten

(3) 1. 6≤ (D / D) ≤3.2

2 0

(4) 1. 2≤ (L ZL),

twenty one

The deposition pan according to claim 7, which is provided so as to satisfy the following formulas.

9. The deposition pan according to claim 7 or 8, wherein the outer cover has a cylindrical shape.

[10] The deposition spanner according to any one of claims 7 to 9, wherein the outer cover has a shape obtained by obliquely cutting a cylinder.

[11] The deposition spanner according to any one of claims 7 to 10, wherein gas flows between the outer cover and the inner cover.

[12] The deposition pan according to any one of [7] to [11], wherein the gas force flowing between the outer cover and the inner cover is one of an inert gas, air, and oxygen.