JP5843084B2 - Glass base material manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a glass preform for an optical fiber.

  An optical fiber is manufactured by heating and softening one end of a glass base material having a substantially cylindrical shape and drawing. Moreover, the glass base material for optical fibers is manufactured by manufacturing methods, such as OVD method and MCVD method. Patent Document 1 discloses a glass base material manufacturing method by the OVD method.

  The glass base material manufacturing method disclosed in Patent Document 1 is intended to manufacture a glass base material for an optical fiber having a low moisture content, and the starting bar is inserted into a seed bar pipe. A glass fine particle deposit is produced by depositing glass fine particles on the outer periphery of the rod, and a starting rod is pulled out from the glass fine particle deposit to obtain a glass fine particle deposit having a central hole extending in the axial direction. Then, the glass fine particle deposit is heated to dry and solidify, and the central hole is closed to produce a transparent glass base material.

Japanese translation of PCT publication No. 2002-543026

  In the glass base material manufacturing method disclosed in Patent Document 1, the starting rod and the glass along the axial direction of the starting rod during the deposition process in which glass particulates are deposited on the outer periphery of the starting rod to produce a glass particulate deposit. A fine particle synthesizing burner is relatively reciprocated to deposit glass fine particles on the outer periphery of the starting rod from the tip of the starting rod to a part of the seed rod pipe to produce a glass fine particle deposit. When producing a glass fine particle deposit by such a deposition process, the glass fine particle deposit may be broken and the yield of manufacturing the glass base material may deteriorate.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a method capable of producing a glass base material with a high yield.

  The glass base material manufacturing method according to the present invention includes (1) a fixing step of producing a starting rod by inserting and fixing the starting rod into the seed rod pipe so that the tip of the starting rod protrudes from one end of the seed rod pipe; (2) After the fixing step, the starting rod and the glass fine particle synthesizing burner are relatively reciprocated along the axial direction of the starting rod to start from the tip of the starting rod to a part of the seed rod pipe. A deposition step for producing glass particulate deposits by depositing glass particulates on the outer periphery of the rod; (3) a withdrawal step for extracting the starting rod from the seed rod pipe and the glass particulate deposits after the deposition step; and (4) a withdrawal step. A transparent step of heating the glass particulate deposit to produce a transparent glass tube, and (5) reducing the pressure inside the transparent glass tube and heating the transparent glass tube after the transparent step. And a solidification process to create materials That.

  And the glass base material manufacturing method which concerns on this invention is a deposition process. WHEREIN: The distance from the end of the seed rod pipe along the axial direction of the starting rod to the direction of the tip of the starting rod is a predetermined position of 30 mm or more as a boundary. The relative movement speed of the starting rod and the glass particle synthesizing burner when the glass particles are deposited in the first range from the predetermined position to the tip of the starting rod is determined from the predetermined position to a part of the seed rod pipe. The relative movement speed of the starting rod and the glass particle synthesizing burner when the glass particles are deposited in the two ranges is set to be low, and the second reciprocal movement between the starting rod and the glass particle synthesizing burner is performed for each traverse. The relative moving speed in the range is different, and the relative moving speed in the second range is the slowest at one end of the seed rod pipe and gradually increases or decreases before and after one end of the seed rod pipe. To.

  In the glass base material manufacturing method according to the present invention, it is preferable that the minimum speed of the relative movement speed in the second range in the deposition step is 1 to 100 mm / min. In the deposition step, in the range from the first traverse to the tenth or less traverse of the relative reciprocating motion of the starting rod and the glass particle synthesizing burner, the second range from the relative moving speed in the first range. It is preferable that the relative movement speed at is low. In the deposition process, it is preferable to vary the second range for each traverse when the starting rod and the glass particle synthesizing burner are relatively reciprocated.

  The glass base material manufacturing method according to the present invention can manufacture a glass base material with a high yield.

It is a flowchart of the glass base material manufacturing method which concerns on this embodiment. It is a figure explaining fixing process S1 of the glass base material manufacturing method which concerns on this embodiment. It is a figure explaining deposition process S2 of the glass base material manufacturing method concerning this embodiment. It is a figure explaining drawing-out process S3 of the glass base material manufacturing method concerning this embodiment. It is a figure explaining transparentization process S4 of the glass base material manufacturing method concerning this embodiment. It is a figure explaining solidification process S5 of the glass base material manufacturing method which concerns on this embodiment. It is a figure explaining the deposition process S2 of the glass base material manufacturing method concerning this embodiment still in detail. It is the table | surface which put together various conditions and the favorable manufacturing rate D of Examples 1-6.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is a flowchart of the glass base material manufacturing method according to the present embodiment. As shown in this figure, the glass base material manufacturing method according to the present embodiment passes through a fixing step S1, a deposition step S2, a drawing step S3, a clarification step S4 and a solidification step S5 in order, To manufacture.
In addition, the glass base material manufactured by this glass base material manufacturing method is an optical fiber base material for manufacturing an optical fiber by drawing, for example, or becomes a core part among the optical fiber base materials. It should be a core base material.

  FIG. 2 is a view for explaining the fixing step S1 of the glass base material manufacturing method according to the present embodiment. FIG. 3 is a view for explaining the deposition step S2 of the glass base material manufacturing method according to the present embodiment. FIG. 4 is a view for explaining the drawing step S3 of the glass base material manufacturing method according to the present embodiment. FIG. 5 is a diagram for explaining the transparency step S4 of the glass base material manufacturing method according to the present embodiment. Moreover, FIG. 6 is a figure explaining solidification process S5 of the glass base material manufacturing method which concerns on this embodiment.

  In the fixing step S1 (FIG. 2), the starting rod 11 is inserted into the seed rod pipe 12 and fixed so that the tip end portion 11a of the starting rod 11 protrudes from the one end 12a of the seed rod pipe 12, whereby the starting rod 10 Is produced (see FIGS. 1A and 1B). The starting rod 11 is made of a material such as alumina, glass, refractory ceramics, or carbon. The seed rod pipe 12 is made of quartz glass. In the starting rod 10, a carbon film 11 b is preferably formed on the outer periphery of the portion of the starting rod 11 protruding from the one end 12 a of the seed rod pipe 12 by a flame from the burner 20 using a city gas burner or an acetylene burner. (Drawing (c). Even during carbon film formation in (c), starting rod 10 rotates about the central axis of starting rod 11, and burner 20 follows the axial direction of starting rod 11. The reciprocating motion is repeated relative to the starting rod 10.

  In the deposition step S2 (FIG. 3) after the fixing step S1, the starting rod 10 in which the starting rod 11 is inserted and fixed in the seed rod pipe 12 is rotated about the central axis of the starting rod 11. Further, the glass fine particle synthesis burner 21 that is arranged on the side of the starting rod 10 and forms an oxyhydrogen flame repeats reciprocating movement relative to the starting rod 10 along the axial direction of the starting rod 11. Then, by the OVD method, glass fine particles are deposited on the outer periphery of the starting rod 10 from the tip portion 11a of the starting rod 11 to a part of the seed rod pipe 12, whereby the glass fine particle deposit 13 is produced.

  In the deposition step S2, the feed material flow rate in the glass fine particle synthesis burner 21 is varied for each traverse. Thereby, the glass fine particles deposited on the outer periphery of the starting rod 11 have a predetermined composition distribution in the radial direction (that is, a refractive index distribution in the radial direction in the subsequent glass preform or optical fiber).

  In the extraction step S3 (FIG. 4) after the deposition step S2, the starting rod 11 is extracted from the seed rod pipe 12 and the glass particulate deposit 13. At this time, the seed rod pipe 12 and the glass fine particle deposit 13 remain fixed to each other. In addition, in order to form a carbon film on the outer periphery of the portion of the starting rod 11 protruding from the one end 12a of the seed rod pipe 12 in the fixing step S1, when the starting rod 11 is pulled out in this drawing step S3, the glass particulate deposit 13 The inner wall surface of the center hole is prevented from being scratched.

In the clearing step S4 (FIG. 5) after the drawing step S3, the glass fine particle deposit 13 is placed inside the heating furnace 22 into which He gas and Cl ₂ gas are introduced, together with the integrated seed rod pipe 12. It is put in and heated by the heater 23. Thereby, the transparent glass tube material 14 is produced.

In the solidification step S5 (FIG. 6) after the transparentization step S4, the transparent glass tube 14 is placed in a heating furnace and rotated, and SF ₆ is introduced into the center hole and heated by the heater 24. The inner wall surface of the center hole is vapor-phase etched (FIG. 1A). Next, the transparent glass tube material 14 is decompressed and heated by the heater 24 to be solidified (FIG. 5B), thereby producing a solid glass base material.

  The transparent glass preform manufactured in this way is further formed into a clad layer on the outside and subjected to a transparent treatment, and then preformed, and then the tip is heated and softened to draw an optical fiber. Is manufactured.

  FIG. 7 is a diagram for explaining the deposition step S2 of the glass base material manufacturing method according to the present embodiment in more detail. FIG. 2A shows a cross section including the axis of the starting bar 11. Moreover, the same figure (b) makes the position of the direction along the axial direction of the starting rod 11 a horizontal axis, and makes the relative movement speed of the starting rod 10 and the glass particle synthesis burner 21 in each position a vertical axis, It is a figure which shows the distribution of the said moving speed.

  In the deposition step S2 of the glass base material manufacturing method according to the present embodiment, from the one end 12a of the seed rod pipe 12 (position P2 in the same figure (b)) to the tip 11a (in the same figure (b)) of the starting bar 11. The relative movement speeds of the starting rod 10 and the glass fine particle synthesizing burner 21 are different at a predetermined position P1 whose distance in the direction of the position P0) is 30 mm or more.

  That is, in the deposition step S2, it extends from the position P1 to a part of the seed rod pipe 12 from the moving speed when the glass particles are deposited in the first range from the position P1 to the tip 11a (position P0) of the starting rod 11. The moving speed at the time of depositing the glass fine particles in the second range up to the position P3 is low. For example, the moving speed in the first range (P0 to P1) is 500 to 1500 mm / min, and the minimum moving speed in the second range (P1 to P3) is 1 to 100 mm / min.

  Assuming that the moving speed in the second range (P1 to P3) is the same as the moving speed in the first range (P0 to P1), the glass particulate deposit 13 has one end 12a (position P2) of the seed rod pipe 12. As a starting point, soot cracks may occur, and therefore the yield of glass base material production is poor. This soot crack is considered to be due to the presence of a step at one end 12a (position P2) of the seed rod pipe 12.

  On the other hand, in the present embodiment, the movement speed in the second range (P1 to P3) is lower than the movement speed in the first range (P0 to P1), so that the one end 12a of the seed rod pipe 12 is obtained. Since the glass fine particles are deposited so as to fill the step at (position P2), the occurrence of soot cracks starting from the one end 12a (position P2) of the seed rod pipe 12 is suppressed, whereby the glass base material can be produced with a high yield. Can be manufactured.

  In general, in the relative reciprocation of the starting rod and the glass particle synthesis burner in the deposition process, the number of traverses is about 1000 times. The traverse in which the moving speed in the second range (P1 to P3) is lower than the moving speed in the first range (P0 to P1) in the deposition step S2 may not be all traverses. If the number of traverses to be slowed down in the second range is too high, the glass particulates become hard (high density) at low speeds, resulting in a difference in the density of glass particulates near the boundary between the high speed traverse points and the low speed traverse points. Since the problem of soot cracking occurs, it is not preferable.

  Therefore, in order to suppress such an increase in the density distribution, in the deposition step S2, in the range from the first traverse to the 10th traverse or less, the first moving speed is higher than the relative moving speed in the first range. It is preferable that the relative movement speed in the two ranges is low. Further, in the deposition step S2, it is also preferable to make the second range different for each traverse, and making the relative movement speed in the second range different for each traverse is also preferable for reducing the density distribution. .

  In the deposition step S2, the relative movement speed in the second range is the slowest at the one end 12a (position P2) of the seed rod pipe 12, as shown in FIG. It is preferable to gradually increase or decrease before and after the one end 12a of the.

  Next, examples of the glass base material manufacturing method according to the present embodiment will be described. In the present embodiment, a glass base material for manufacturing a core of a graded index type optical fiber by drawing is manufactured.

  In the deposition step S2, an OVD apparatus is used to deposit glass particles. The starting rod 11 is made of alumina having an outer diameter of 9 to 10 mm and a length of 1200 mm. The seed rod pipe 12 is made of quartz glass having a length of 600 mm, an outer diameter of 20 to 40 mm, and an inner diameter of 9.8 to 21 mm.

The glass raw material gases introduced into the glass fine particle synthesis burner 21 forming an oxyhydrogen flame in the deposition step S2 are SiCl ₄ (input amount 1 to 3 SLM / piece) and GeCl ₄ (input amount 0.0 to 0.3 SLM). It is.

  A step of about 0.5 mm occurs at one end 12a (position P2) of the seed rod pipe 12. The range of 80 mm to 145 mm in length including the position P2 is set as the second range, and the moving speed in the second range (P1 to P3) is set lower than the moving speed in the first range (P0 to P1). The moving speed in the first range (P0 to P1) is 500 to 1500 mm / min.

After such a deposition step S2, a solidification step S5 is performed through a drawing step S3 and a transparency step S4. In the solidification step S5, the transparent glass tube 14 is installed in a heating furnace, rotated at 30 rpm, and moved in the longitudinal direction of the transparent glass tube 14 at a speed of 20 mm / min. To be heated. At this time, 50 to 100 sccm of SF ₆ gas is flowed into the center hole of the transparent glass tube material 14, and the inner wall surface of the center hole of the transparent glass tube material 14 is vapor-phase etched. Next, the transparent glass tube material 14 is decompressed to 10 kPa in the center hole, and is solidified at the same temperature as during etching to produce a glass base material.

  The glass base material manufactured in this way is stretched to a desired diameter, and jacket glass is synthesized on the outer periphery thereof by the OVD method to manufacture a glass base material for an optical fiber. This glass preform for optical fiber is drawn to produce a graded index type multimode fiber.

  In Examples 1 to 6, the number N of traverses that are lower in the second range than the first range, the moving speed X (mm / min) at the position P2 that is the lowest speed in the second range, and the second range The length W (mm) and the respective conditions are different, and a good production rate D (%), which is a probability that no soot cracks are generated in the glass fine particle deposit, is comparatively evaluated. In any of Examples 1 to 6, the distance between the position P1 and the position P2 is 30 mm or more. FIG. 8 is a chart summarizing the conditions and good production rate D 1 of each of Examples 1-6. In any of Examples 1 to 6, the good production rate D of the glass fine particle deposit is 90% or more.

  As can be seen by comparing the various conditions and good production rate D of each of Examples 1 to 6 shown in FIG. 8, the good production rate is obtained when the number N of traverses to be slowed down in the second range is larger than the first range. D becomes smaller. This is because if the number N is large, the glass fine particles become hard (the density is high) at low speed locations. For this reason, it is preferable to set the number of times N to 10 or less, it is also preferable to vary the second range for each traverse, and the relative movement speed in the second range is varied for each traverse. Is also suitable.

  In the comparative example, the moving speed in the second range (P1 to P3) is set to 500 mm / min, which is the same as the moving speed in the first range (P0 to P1). In this comparative example, the good production rate D of the glass fine particle deposit is 80%, and a good glass base material cannot be produced stably.

  DESCRIPTION OF SYMBOLS 10 ... Departure rod, 11 ... Departure rod, 12 ... Seed rod pipe, 13 ... Glass particulate deposit, 14 ... Transparent glass tube, 20 ... Burner, 21 ... Glass particulate synthesis burner, 22 ... Heating furnace, 23, 24 ... heater.

Claims (5)

A fixing step of making the starting rod by inserting and fixing the starting rod into the seed rod pipe such that the tip of the starting rod protrudes from one end of the seed rod pipe;
After the fixing step, the starting rod and the glass fine particle synthesizing burner are reciprocated relatively along the axial direction of the starting rod, and extend from the tip of the starting rod to a part of the seed rod pipe. A deposition step of depositing glass particulates on the outer periphery of the starting rod to produce a glass particulate deposit;
A drawing step of drawing the starting rod from the seed rod pipe and the glass particulate deposit after the deposition step;
A transparentization step of heating the glass particulate deposit after the drawing step to produce a transparent glass tube,
A solidification step of creating a solid glass base material by depressurizing the inside of the transparent glass tube material and heating the transparent glass tube material after the transparentization step;
With
In the deposition step, the departure from the predetermined position at a predetermined position where a distance from the one end of the seed bar pipe along the axial direction of the starting bar to the tip of the starting bar is 30 mm or more. Based on the relative moving speed of the starting rod and the glass particle synthesis burner when the glass particles are deposited in the first range over the tip of the rod, the first rod extends from the predetermined position to a part of the seed rod pipe. The relative movement speed of the starting rod and the glass particle synthesizing burner when depositing the glass particles in two ranges is set to be low, and each traverse is performed during the reciprocating motion of the starting rod and the glass particle synthesizing burner. The glass base material manufacturing method is characterized in that the relative movement speed in the second range is varied. A fixing step of making the starting rod by inserting and fixing the starting rod into the seed rod pipe such that the tip of the starting rod protrudes from one end of the seed rod pipe;
After the fixing step, the starting rod and the glass fine particle synthesizing burner are reciprocated relatively along the axial direction of the starting rod, and extend from the tip of the starting rod to a part of the seed rod pipe. A deposition step of depositing glass particulates on the outer periphery of the starting rod to produce a glass particulate deposit;
A drawing step of drawing the starting rod from the seed rod pipe and the glass particulate deposit after the deposition step;
A transparentization step of heating the glass particulate deposit after the drawing step to produce a transparent glass tube,
A solidification step of creating a solid glass base material by depressurizing the inside of the transparent glass tube material and heating the transparent glass tube material after the transparentization step;
With
In the deposition step, the departure from the predetermined position at a predetermined position where a distance from the one end of the seed bar pipe along the axial direction of the starting bar to the tip of the starting bar is 30 mm or more. Based on the relative moving speed of the starting rod and the glass particle synthesis burner when the glass particles are deposited in the first range over the tip of the rod, the first rod extends from the predetermined position to a part of the seed rod pipe. The relative movement speed of the starting rod and the glass particle synthesis burner when depositing the glass fine particles in two ranges is low, and the relative movement speed in the second range is the one end of the seed rod pipe. The glass base material manufacturing method is characterized in that it is the slowest and gradually increases or decreases before and after the one end of the seed rod pipe.   3. The glass base material manufacturing method according to claim 1, wherein a minimum speed of the relative movement speed in the second range is 1 to 100 mm / min in the deposition step.   In the deposition step, the relative moving speed in the first range in a range from the first traverse to the 10th traverse or less of the relative reciprocating motion of the starting rod and the glass particle synthesizing burner. The glass base material manufacturing method according to any one of claims 1 to 3, wherein the relative movement speed in the second range is set to a low speed.   The said 2nd range is varied for every traverse in the case of the relative reciprocation of the said starting rod and the glass particle synthesis burner in the said deposition process, The any one of Claims 1-4 characterized by the above-mentioned. Glass base material manufacturing method.

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