JP6284516B2 - Optical fiber preform manufacturing method and optical fiber preform manufacturing apparatus - Google Patents

Description

  The present invention relates to an optical fiber preform manufacturing method and a manufacturing apparatus therefor.

  As a method for producing a glass particulate deposit for an optical fiber, there is an OVD method (Outside Vapor Deposition method). In the OVD method, a glass material containing silicon is introduced into a burner together with a combustion gas such as a flammable gas and an auxiliary combustible gas, and the glass material is hydrolyzed or oxidized in a flame. In this method, an aggregate is generated, and this is deposited mainly on the outer periphery of a target material that is a core, thereby forming a glass particulate deposit.

  In the clad synthesizing process performed in this way, for example, if fine foreign matter adheres to the outer periphery of the target material, the strength of the product may be lowered after the optical fiber drawing process. Therefore, it is necessary to prevent adhesion of foreign matters in the manufacturing process.

  In order to suppress such foreign matter adhesion, there is a burner that suppresses the generation of metal oxide (for example, Patent Document 1).

  However, even if the generation of metal oxide from the burner during cladding synthesis is suppressed, soot and the like in the burner are scattered as foreign matter and taken into the preform when the burner is ignited, thereby reducing the strength of the optical fiber. There is a case.

  On the other hand, when the burner is ignited, there is a method of moving the burner again toward the target material after retracting the burner to a position away from the target material or after igniting the burner in the other direction. Conceivable. That is, when the burner is ignited, there is a method of providing a moving mechanism that moves the burner to a position different from that at the time of manufacturing the optical fiber preform (for example, Patent Document 2).

JP 2000-310404 A JP 2013-40064 A

  However, larger optical fiber preforms are required in recent optical fiber manufacturing. Therefore, it is necessary to produce a larger glass fine particle deposit by the OVD method or the like. Therefore, the glass particle deposition apparatus itself is increased in size and it is difficult to take up the retreat space for the burner. Further, since the temperature becomes extremely high, it is difficult to ensure the reproducibility of the burner position if a moving mechanism, a rotating mechanism, or the like that shifts the burner from the central axis is provided.

  The present invention has been made in view of such a problem, and provides a method for manufacturing an optical fiber preform that can suppress a decrease in optical fiber strength due to scattering of foreign matters during burner ignition. With the goal.

  In order to achieve the object described above, the first invention manufactures an optical fiber preform by depositing glass fine particles generated by supplying a glass raw material gas and a combustion gas to a burner on the outer periphery of the target material. In the method, when the burner is ignited, a shielding member is disposed between the burner and the target material, and after the burner is ignited, the shielding member is retracted, and the glass is applied to the target material. An optical fiber preform manufacturing method characterized by depositing fine particles.

  It is desirable that a plurality of the burners are arranged along the target material, and the movement of the shielding member and the ignition of the burner where the shielding member is located are sequentially performed on the plurality of burners.

  At this time, it is preferable that a plurality of the burners are arranged in the vertical direction and the burners are ignited sequentially from above.

  An igniter for igniting the burner may be integrally disposed on the shielding member.

  According to the first aspect, by arranging the shielding member between the burner and the target material when the burner is ignited, it is possible to prevent foreign matters scattered from the burner from adhering to the target material. Further, after the burner is ignited, the shielding member may be retracted, and the burner itself does not need to be moved / rotated. For this reason, the accuracy of the burner and the target material can be maintained.

  In addition, when a plurality of burners are arranged along the target material, the burners are ignited in order, and the shielding members are sequentially moved to the igniting burners, so that the foreign materials from each burner can be reliably removed by the small shielding members. Can be shielded.

  In particular, when a plurality of burners are arranged in the vertical direction, the upper burner is prevented from igniting unintentionally due to the flame of the lower burner by sequentially igniting the burner while moving the shielding member. Can do.

  Further, by arranging an igniter such as a lighter or an ignition integrally with the shielding member, the shielding member can be moved and the burner can be ignited at the same time.

  The second invention includes a reaction vessel in which a target material is disposed, a burner that ejects glass raw material gas and combustion gas to the target material, a shielding member that is movable between the target material and the burner, An operation unit that operates the shielding unit, and the operation unit is capable of moving the shielding member between the target material and the burner when the burner is ignited. When the glass fine particles are deposited on the optical fiber preform, the shielding member can be retracted from between the target material and the burner.

  According to the second aspect of the invention, it is possible to prevent foreign matter from adhering to the target material during burner ignition.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the preform | base_material for optical fibers etc. which can suppress the fall of optical fiber intensity | strength by scattering of the foreign material at the time of burner ignition can be provided.

Schematic which shows the glass fine particle deposition apparatus 1 for optical fibers. The AA sectional view taken on the line B in FIG. Schematic which shows the glass fine particle deposition apparatus 1 of the state which ignited the upper burner 11. FIG. Schematic which shows the glass fine particle deposition apparatus 1 of the state which moved the shielding member 13 below. Schematic which shows the glass fine particle deposition apparatus 1 of the state which ignited the 2nd burner 11. FIG. Schematic which shows the glass fine particle deposition apparatus 1 of the state which ignited the burner 11 to the lowest stage. The figure which shows the operation | movement which retracts the shielding member 13. FIG. The figure which shows the state which manufactured the porous glass base material 15. FIG. Schematic which shows the glass fine particle deposition apparatus 10 of the other state which ignited the upper burner 11. FIG. Schematic which shows the glass fine particle deposition apparatus 20. FIG. The figure which shows the frequency | count of a fracture | rupture of the optical fiber for every lot.

  Hereinafter, the glass fine particle deposition apparatus 1 concerning embodiment of this invention is demonstrated. FIG. 1 is a schematic configuration diagram of a glass fine particle deposition apparatus 1 which is an optical fiber preform manufacturing apparatus. The glass fine particle deposition apparatus 1 mainly includes a reaction vessel 3, a target material gripping portion 7, a burner 11, a shielding member 13, and the like.

  A pair of target material gripping portions 7 are provided inside the reaction vessel 3. The target material 5 is gripped by the target material gripping portion 7. The target material 5 is, for example, a rod having an optical fiber core and a part of a clad. Both end portions of the target material 5 are fixed to the target material gripping portion 7.

  Inside the reaction vessel 3, a plurality of burners 11 are arranged at predetermined intervals along the target material 5. In the illustrated example, a plurality of burners 11 are arranged in the vertical direction. In particular, when a large optical fiber preform is manufactured, a plurality of burners 11 are desirably arranged in the vertical direction. The number of burners 11 arranged is not limited to the illustrated example.

  The burner 11 has a multi-layer structure, a raw material gas flow path for ejecting glass raw material gas, an auxiliary combustion gas flow path for ejecting auxiliary combustible gas, a combustible gas flow path for ejecting combustible gas, and a seal gas flow for ejecting seal gas Roads are provided.

As the gas supplied to the burner 11, for example, the raw material gas flow path SiCl ₄ supporting gas flow passage O _2, H ₂ combustible gas channel _may be allowed to flow Ar to seal gas flow passage.

  The reaction vessel 3 is provided with an air supply port (not shown), and clean air or the like is introduced into the reaction vessel 3 from the air supply port, together with glass particles or the like scattered inside the reaction vessel without being deposited. The gas is discharged from the exhaust port 9.

  FIG. 2 is a cross-sectional view taken along line AA in the portion B of FIG. A shielding member 13 is disposed between the burner 11 and the target material 5. The shielding member 13 is normally disposed at a position retracted from between the burner 11 and the target material 5. When the burner 11 is ignited, the shielding member 13 is moved by an operation unit (not shown) such as a motor, and the shielding member 13 is disposed at a position between the burner 11 and the target material 5 (arrow in the figure). C).

  The shielding member 13 may be manually disposed between the burner 11 and the target material 5. In this case, the shielding member 13 may be provided with a handle (not shown).

  The shielding member 13 is made of, for example, ceramics or metal. If the shielding member 13 is not deformed by the heat generated when the burner 11 is ignited, and if it is easy to remove wrinkles attached to the surface of the shielding member 13, The material is not particularly limited.

  The shielding member 13 is desirably disposed at a position close to the target material 5 so as not to interfere with the target material 5. If the shielding member 13 is too close to the burner 11, foreign matter scattered from the burner 11 may wrap around the back side of the shielding member 13 and adhere to the target material 5.

  In the illustrated example, the shielding member 13 is a planar plate member, but the shape of the shielding member 13 is not limited thereto. For example, it may have a curved shape so as to cover the burner 11, or may have a curved shape that covers the target material 5.

FIG. 3 is a view showing a state in which the uppermost burner 11 is ignited. When the burner 11 is ignited, it is ignited by an igniter such as a lighter or an ignition with a small amount of H ₂ flowing through the combustible gas passage of the burner 11. At this time, since the foreign matter scattered from the burner 11 when the burner 11 is ignited is shielded by the shielding member 13, it can be prevented from adhering to the target material 5.

  Next, as shown in FIG. 4, the shielding member 13 is moved from the top to the position of the second burner 11 by an operation unit (not shown) (arrow D in the figure). After the shielding member 13 has moved to the position of the burner 11, the burner 11 is ignited (FIG. 5). Even if there are a plurality of burners 11, the facility can be simplified by flowing a small amount of combustible gas through all the burners 11 almost simultaneously. In addition, since a small amount of combustible gas flows through all the burners 11, it can be easily ignited by moving the lighter or ignition.

  In this way, by moving the shielding member 13 and igniting the burners 11 where the shielding member 13 is located in order to the plurality of burners 11, all the burners 11 are ignited as shown in FIG. be able to.

  When all the burners 11 have been ignited and glass particles are deposited on the target material, as shown in FIG. 7, a shielding member is interposed between the burner 11 and the target material 5 by an operation unit not shown. 13 is retracted (arrow E in the figure).

  After the shielding member 13 is completely retracted from between the target material 5 and the burner 11, a predetermined amount of glass raw material gas, auxiliary combustion gas, combustible gas, seal gas, etc. is flowed to manufacture a porous glass base material.

  As shown in FIG. 8, glass fine particles are synthesized by supplying a glass raw material gas into a flame composed of an auxiliary combustion gas and a combustible gas ejected from a burner 11, and the glass fine particles are mixed with the outer peripheral surface of the target material 5. Can be deposited.

That is, the method for manufacturing an optical fiber preform according to the present invention uses the shielding member 13 when the burner 11 is ignited, and then causes the glass material gas and the combustion gas to be ejected from the burner 11 to the target material 5. The porous glass base material 15 is manufactured by hydrolyzing the glass to produce glass fine particles, and depositing the produced glass fine particles on the target material 5.
A vitrified optical fiber preform is obtained by dehydrating and sintering the produced porous glass preform by a known method.

  In addition, the target material 5 and the burner 11 can reciprocate relatively with respect to the axial direction of the target material 5 (arrow F in the figure). Further, the target material 5 (porous glass base material 15) can be rotated about the axis direction of the target material 5 as an axis of rotation (arrow G in the figure). That is, the flame of the burner 11 can be uniformly applied to the longitudinal direction and the circumferential direction of the target material 5.

  In addition, you may provide the auxiliary burner which abbreviate | omitted illustration in the target material holding part 7 vicinity. By using the auxiliary burner, heat that is not sufficiently applied by the burner 11 in the vicinity of the end of the target material 5 and a low-density porous glass is formed can be baked.

  Further, the burner 11 is moved away from the target material 5 (porous glass base material 15) with the growth (increase in diameter) of the porous glass base material 15 that is a glass particulate deposit. By doing so, glass particles can be deposited while the distance between the burner 11 (flame) and the surface of the porous glass base material 15 is always constant.

  As mentioned above, according to this Embodiment, since the shielding member 13 is arrange | positioned between the burner 11 and the target material 5, and the burner 11 is ignited, a foreign material scatters from the burner 11 at the time of ignition of the burner 11, and a target Adhesion to the material 5 can be prevented.

  At this time, since it is not necessary to provide a moving mechanism for retracting the burner 11 from the target material 5, the structure is simple, and the reproducibility and durability of the position of the burner 11 deteriorates in a high temperature / corrosive gas environment. There is no.

  Further, by igniting the burner 11 in order while shielding the burner 11 and the target material 5 with the shielding member 13, all the burners 11 are ignited at once, and foreign matter does not scatter in a wide range. . Moreover, since the shielding member 13 may be a size corresponding to one burner 11 by moving the shielding member 13, it is small in size and excellent in handleability. In addition, as long as the shielding member 13 is a size that can shield all the burners 11, the shielding member 13 may be only inserted and extracted between the burner 11 and the target material 5.

  In addition, by sequentially igniting the burner 11 from above, it is possible to prevent the upper burner 11 from being unintentionally ignited by the flame of the lower burner 11 before the shielding member 13 is disposed.

  Next, a second embodiment will be described. FIG. 9 is a diagram showing a glass particle deposition apparatus 10 according to the second embodiment. In the following description, components having the same functions as those of the glass fine particle deposition apparatus 1 are denoted by the same reference numerals as those in FIG.

  In the second embodiment, the ignition part 17 is integrally disposed on the shielding member 13. The ignition unit 17 is a lighter or ignition that ignites the burner 11.

  When the shielding member 13 is arranged at the position of each burner 11 in a state where a small amount of combustible gas or the like is flowed from each burner 11, the burner 11 can be ignited by the ignition unit 17. For this reason, the movement of the shielding member 13 and the ignition of the burner 11 can be performed simultaneously. Therefore, the burner 11 can be ignited in order while moving the shielding member 13 from above to below.

  In the second embodiment, the same effect as in the first embodiment can be obtained. Moreover, since the ignition part 17 is provided in the shielding member 13, it is not necessary to perform separately the movement of the shielding member 13, and an ignition operation | work, and workability | operativity is favorable. Further, when the ignition part 17 is ignited, the shielding member 13 is surely positioned in front of the burner 11, so that the position of the shielding member 13 is not shifted during the ignition operation.

  Next, a third embodiment will be described. FIG. 10 is a diagram showing a glass particle deposition apparatus 20 according to the third embodiment. In the following description, components having the same functions as those of the glass fine particle deposition apparatus 1 are denoted by the same reference numerals as those in FIG.

  The third embodiment is different from the first embodiment in that the shielding member 13 is large enough to cover the entire plurality of burners 11.

  The front of all the burners 11 is covered with the shielding member 13, and the burners 11 are ignited in order from the top in a state where a small amount of combustible gas or the like is supplied from each burner 11. A lighter or an ignition is used to ignite the burner 11.

  In the third embodiment, the same effect as in the first embodiment can be obtained. Moreover, since the shielding member 13 covers the whole of the plurality of burners 11, it is not necessary to move the shielding member 13, and workability is good. Further, when the burner 11 is ignited, the shielding member 13 is surely positioned in front of the burner 11, so that the position of the shielding member 13 is not shifted during the ignition operation.

  A porous glass preform was prepared using the glass fine particle deposition apparatus of the present invention, and dehydrated and sintered by a well-known method to obtain an optical fiber preform. The obtained optical fiber preform was drawn by a known method to obtain an optical fiber, and the obtained optical fiber was evaluated. Specifically, a so-called screening test was performed in which a certain tension was applied to the obtained optical fiber, and the number of breaks for each lot was evaluated.

  FIG. 11 is a diagram showing the number of times the optical fiber is broken for each lot. Lot No. Reference numerals 1 to 16 denote optical fibers manufactured by a conventional method. That is, the porous glass base material is manufactured by a predetermined procedure after the burner 11 is ignited without using the shielding member 13.

  On the other hand, lot no. Nos. 17 to 25 are manufactured by using the shielding member 13 when the burner 11 is ignited. In all the lots, the manufacturing conditions other than the use / non-use of the shielding member 13 are the same.

  As is apparent from the figure, compared to the number of breaks per lot in a lot (G in the figure) where the shielding member 13 is not used when the burner 11 is ignited, the lot (in the figure) where the shielding member 13 is used when the burner 11 is ignited. The number of breaks per lot in H) is small. This is because the shielding member 13 shields the foreign matter scattered when the burner 11 is ignited and prevents it from being mixed into the porous glass base material.

  As mentioned above, although embodiment of this invention was described referring an accompanying drawing, the technical scope of this invention is not influenced by embodiment mentioned above. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

DESCRIPTION OF SYMBOLS 1, 10, 20 ......... Glass particle deposition apparatus 3 ......... Reaction container 5 ......... Target material 7 ......... Target material holding part 9 ......... Exhaust port 11 ...... Burner 13 ......... Shielding member 15 ……… Porous glass base material 17 ………… Ignition part

Claims (5)

A target material is provided in the reaction vessel,
A method for producing an optical fiber preform by depositing glass fine particles generated by supplying a glass raw material gas and a combustion gas to a burner on the outer periphery of the target material,
When the burner is ignited, a shielding member is disposed between the burner and the target material, and after the ignition of the burner, the shielding member is retracted to deposit the glass fine particles on the target material. An optical fiber preform manufacturing method characterized by the above.   A plurality of the burners are arranged along the target material, and the movement of the shielding member and the ignition of the burner where the shielding member is located are sequentially performed on the plurality of burners. The manufacturing method of the optical fiber preform of description.   The method of manufacturing an optical fiber preform according to claim 2, wherein a plurality of the burners are arranged in a vertical direction, and the burners are ignited sequentially from above.   The method for manufacturing an optical fiber preform according to any one of claims 1 to 3, wherein an igniter for igniting the burner is integrally disposed on the shielding member. A reaction vessel in which the target material is placed;
A burner for ejecting glass source gas and combustion gas to the target material;
A shield member movable between the target material and the burner;
An operating part for operating the shielding member;
Comprising
The operation unit is capable of moving the shielding member between the target material and the burner when the burner is ignited,
The apparatus for manufacturing an optical fiber preform, wherein when the glass particles are deposited on the target material by the burner, the shielding member can be retracted from between the target material and the burner.

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