JP3691795B2 - Optical fiber manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing an optical fiber having a plurality of holes extending in the axial direction.
[0002]
[Prior art]
In recent years, the demand for optical fibers has increased mainly in optical communication applications and optical energy transmission applications. Among them, quartz glass fiber is widely used because of its low loss, and the demand for the glass fiber is greatly increased.
[0003]
Since this quartz glass optical fiber is made of quartz glass, which is a brittle material, the surface is coated with a resin such as urethane acrylate resin to protect the surface from scratching. The resin coating is performed by passing a die containing resin while heating and drawing an optical fiber from a base material and winding it around a bobbin, and then curing the resin with heat or ultraviolet rays. At this time, if the resin is not coated with a uniform thickness in the circumferential direction of the optical fiber, the optical fiber may bend due to shrinkage when the resin is cured, or the thin portion of the coating may be damaged and the optical fiber may be damaged. This causes a problem such as failure, resulting in poor quality. Accordingly, the coating thickness in the circumferential direction of the optical fiber is measured, and the position of the die is adjusted according to the thickness information to adjust the coating so as to obtain a uniform coating thickness.
[0004]
As shown in FIG. 2, the coating thickness measurement is performed by irradiating a visible light laser from two lateral directions of the optical fiber 2 immediately after coating and projecting the diffraction image 21 on the screen 13. The two visible light lasers are orthogonal to each other. As shown in FIGS. 6 and 7, in the diffraction image 21 of a normal solid optical fiber 2 having no pores, a laser spot is observed as a bright spot 41 at the center, and bright lines 43 extend from both sides thereof. Accordingly, dark spots 42 are observed in the middle of the bright lines 43, respectively. If the two distances between the bright spot 41 and the dark spot 42 are equal, the thickness of the coating 25 on both sides of the quartz glass portion 26 of the optical fiber 2 is equal in the radial direction of the optical fiber 2 perpendicular to the laser beam. Yes (see FIG. 6). Accordingly, the thickness of the coating 25 is adjusted uniformly by adjusting the position of the die so that the two distances between the bright spot 41 and the dark spot 42 are equal.
[0005]
[Problems to be solved by the invention]
However, as shown in FIG. 8, in the optical fiber 2 having a plurality of pores 27 in the fiber axial direction, such as a photonic crystal fiber, a large number of dark spots 42 appear in the diffraction image 21, and the thickness of the coating 25 is confirmed. I can't. For this reason, when manufacturing the optical fiber 27 having a plurality of pores, the above-described quality defect has occurred because the manufacture must be performed without adjusting the thickness of the coating 25.
[0006]
The present invention has been made in view of such circumstances. The object of the present invention is to reduce the coating thickness during the production of an optical fiber having a plurality of pores extending in the fiber axial direction by heating and stretching. An object of the present invention is to provide an optical fiber manufacturing method that can easily and easily form a coating having a uniform thickness in the circumferential direction without adjustment.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is a rod-shaped quartz glass comprising a first base material having a plurality of axially extending holes and a solid rod-shaped quartz glass, wherein the first matrix A base material forming step in which a fiber base material is formed by joining a base material and a second base material having substantially the same diameter so that the central axes coincide with each other; and the fiber base material formed in the base material forming step is used as the second base material. While the second base material is heat-stretched in the heat-stretching step, the heat-stretching step of heat-stretching from the end on the side, the coating step of coating the resin on the surface of the optical fiber heat-stretched in the heat-stretching step And a coating adjustment step of adjusting the coating thickness in the coating step so as to be substantially uniform in the circumferential direction of the optical fiber.
[0008]
The term “quartz glass” as used herein refers to pure quartz glass and those obtained by adding various additives such as B, Ge, and F to pure quartz glass. Further, the term “solid” means that there is no hollow portion and all quartz glass is clogged.
[0009]
According to the manufacturing method of claim 1, the fiber preform has two portions in which the first preform and the second preform have substantially the same diameter in the axial direction and the central axes coincide with each other. Since the optical fiber is started by heating and stretching from the portion, and the resin coating thickness is adjusted to be substantially uniform in the fiber circumferential direction while the second preform portion is heated and stretched, the same conditions are applied. As long as the film is heated and stretched, the optical fiber continues to be manufactured with the resin coating thickness being substantially uniform. Accordingly, even when an optical fiber having a plurality of pores is manufactured by heating and stretching the portion of the first base material, the coating is performed with a substantially uniform thickness in the circumferential direction of the fiber. There is no problem if you can't. That is, in the step of heating and stretching the portion of the first base material, the optical fiber is manufactured without adjusting the coating thickness while fixing the coating adjusting mechanism for adjusting the coating thickness. Furthermore, when manufacturing an optical fiber with a complicated configuration having a large number of holes, for example, a first base material having a through hole is easily manufactured by packing a large number of quartz capillaries in the hollow portion of a large-diameter quartz pipe. The base material forming step can be easily performed by joining this to the second base material.
[0010]
Next, the invention of claim 2 is the method of manufacturing an optical fiber according to claim 1, wherein the coating adjustment step is a step performed by a coating adjustment mechanism that moves the position of the coating device for coating. did.
[0011]
According to the manufacturing method of claim 2, the coating adjustment can be easily performed, and the generation of defective products with uneven coating thickness can be reduced.
[0012]
Next, a third aspect of the present invention provides a base for forming a fiber preform by forming a plurality of holes that are open only at one end and extend in the axial direction of a solid quartz glass rod in an unpenetrated state. A material forming step, a heat stretching step in which the fiber preform formed in the base material forming step is heated and stretched from an end portion where the hole is not opened, and a resin is coated on the surface of the optical fiber that has been heat stretched in the heat stretching step. A coating step for adjusting the coating thickness so that the coating thickness in the coating step is substantially uniform in the circumferential direction of the optical fiber before the holed portion of the fiber preform is heated and stretched in the heating and stretching step. An optical fiber manufacturing method comprising: an adjusting step.
[0013]
If it is the manufacturing method of Claim 3, a base material can be easily manufactured by making a some hole in a normal solid fiber base material, and a base material formation process can be performed easily. The other points are the same as in the first aspect.
[0014]
Next, the invention of claim 4 is the method of manufacturing an optical fiber according to claim 3, wherein the coating adjustment step is a step performed by a coating adjustment mechanism that moves a position of a coating device that performs coating. .
[0015]
If it is the manufacturing method of Claim 4, covering adjustment can be performed easily and generation | occurrence | production of the inferior goods with coating thickness unevenness can be decreased.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
(First embodiment)
The schematic diagram of the optical fiber manufacturing apparatus of 1st embodiment is shown in FIG. The fiber preform 1 is heated by an electric furnace 14 and drawn by a take-up capstan 16 to produce an optical fiber 2 and wound on a take-up bobbin 17. Between the electric furnace 14 and the take-up capstan 16, a die 11 (coating device) filled with a coating resin is installed, and the optical fiber 2 passes through the die 11 and the surface is coated with the resin. This resin is cured by the curing device 15. The resin coating thickness is measured before the optical fiber 2 enters the curing device 15. The coating thickness is measured by applying laser light from the side to the optical fiber 2 and projecting the diffraction image on the screen 13. Reference numeral 12 denotes a laser output device.
[0018]
As shown in FIG. 3, the fiber preform 1 includes a first preform 31 having a plurality of axially extending holes 3 and a solid second preform 32 having substantially the same diameter as the first preform 31. Are joined with their central axes coinciding with each other. This joining is performed in the base material forming step shown in FIG. That is, the end surfaces of the first base material 31 and the second base material 32 are heated and butt-joined. Heating may be performed by a flame, may be performed by a heater, laser heating, or the like, or may be combined. In addition, the first base material 31 may be produced by, for example, filling a large number of quartz capillaries 54 in a hollow portion 53 inside a large-diameter quartz pipe 52 as shown in FIG. A quartz rod 51 serving as a core is disposed at the center instead of the capillary 54.
[0019]
The fiber preform 1 is heated and stretched in a heating and stretching process to obtain an optical fiber 2 (see FIG. 4). The heating is performed in the electric furnace 14 and the stretching is performed in the take-up capstan 16. At this time, heating and stretching are started from the end on the solid second base material 32 side. By first manufacturing the solid optical fiber 2, the coating can be adjusted in the coating adjusting step so that the thickness of the coating 25 becomes substantially uniform. This is because, as described above, in the optical fiber 2 having pores, the thickness of the coating 25 cannot be confirmed, and the thickness cannot be adjusted.
[0020]
This resin coating is performed in the coating process using the die 11. In the coating adjustment step, the thickness of the coating 25 of the optical fiber 2 coated with resin is measured when it is removed from the die 11, and the position of the die 11 is adjusted based on this information as shown in FIG. 9 (coating adjustment mechanism). Adjust with. The method for measuring the thickness of the coating 25 is as described above. The adjusting device 28 includes a substrate 23, a table 24 installed on the substrate 23, and an XY stage 22 that moves the substrate 23 in a plane perpendicular to the optical fiber 2. The dice 11 are installed on a table 24. By operating the XY stage 22 and finely adjusting the position of the die 11 based on information on the unevenness of the thickness of the coating 25, the thickness of the coating 25 is made substantially uniform in the circumferential direction of the optical fiber 2. The die 11 has an inverted conical shape filled with resin, and has a hole at the tip, and the optical fiber 2 is passed therethrough. The thickness of the coating 25 is adjusted by adjusting the relative position between the hole and the optical fiber 2. The adjustment of the thickness of the covering 25 is finished before the portion of the first base material 31 is heated and stretched. When the portion of the first base material 31 is heated and stretched, the thickness of the coating 25 cannot be adjusted as described above. However, as long as it is heated and stretched under the same conditions as the portion of the second base material 32, the coating conditions are also Since the thickness does not change, the thickness of the coating 25 remains substantially uniform, and the portion of the first preform 31 is also heated and stretched and coated to form the optical fiber 2. That is, when the part of the first base material 31 is heated and stretched, the adjusting device 28 is fixed and does not move.
[0021]
As described so far, in the present embodiment, the first preform 31 having a plurality of holes extending in the axial direction and the solid second preform 32 are joined to form the second optical fiber preform 1. Heat drawing is started from the end on the base material 32 side to form the optical fiber 2, and the surface thereof is coated with resin so that the thickness of the coating 25 becomes substantially uniform while the second base material 32 portion is heat drawn. Therefore, the optical fiber 2 having a plurality of axially extending holes manufactured by heating and stretching the first base material 31 is also provided with a coating 25 having a substantially uniform thickness in the circumferential direction of the fiber 2. It becomes. Therefore, it is possible to easily manufacture the optical fiber 2 having a plurality of holes extending in the axial direction and having a uniform coating 25 thickness. Moreover, since the fiber preform 1 is formed by joining the first preform 31 and the second preform 32, even the optical fiber 2 having a plurality of holes extending in the axial direction with a complicated configuration can be easily manufactured. it can. Further, when the second base material 32 is heated and stretched, any defective portion that occurs at the beginning of stretching becomes the solid optical fiber 2, and the optical fiber 2 having a plurality of holes extending in the axial direction is the first base material 31. Can be manufactured without wasting, and the yield is improved.
[0022]
(Second embodiment)
In the second embodiment, a fiber preform 1 having a plurality of holes 5 extending in the axial direction from one end of a solid quartz glass rod to the middle is used (see FIG. 10). That is, a portion 33 having a plurality of holes hits a portion of the first base material 31 of the first embodiment, and a portion 34 having no holes hits the second base material 32 of the first embodiment.
[0023]
The fiber preform 1 may be formed by forming a hole 5 in a solid quartz glass rod with a drill or the like. This is a base material forming step. The subsequent steps are the same as in the first embodiment.
[0024]
In the second embodiment, since the fiber preform 1 can be formed by making a hole 5 in a solid quartz glass rod, the preform forming process can be easily performed in a short time. In particular, this embodiment can be preferably applied when the number of holes 5 is small, such as 2 to 40. The effects other than the base material forming step are the same as in the first embodiment.
[0025]
(Other embodiments)
The two embodiments described so far are examples, and the present invention is not limited to these examples. For example, Ge or the like may be added only to the core portion of the fiber preform 1, or any additive may be added to any location of the fiber preform 1 to provide functions such as dispersion compensation and polarization maintenance. You may manufacture the optical fiber 2 which has. The material to be coated may be any material such as urethane acrylate resin. Further, the arrangement of the holes 3 or the holes 5 in the fiber preform 1 is also arbitrary. For example, the center portion that is the core is surrounded by the six holes 3 or 5 in a hexagonal shape, and further concentrically outside thereof. Alternatively, the hole 3 or the hole 5 may be arranged in a hexagonal shape so as to surround the core portion several times. Moreover, the shape of the hole 3 or the hole 5 may be any shape such as a circular cross section, an elliptical shape, or a polygonal cross section, and these may be mixed. Further, the size of the holes 3 or 5 may all be the same, or there may be a plurality of hole diameters or hole diameters. The number of holes 3 or 5 may be two or more, but preferably six or more so as to surround the core portion in a single layer or more. Further, it is more preferable that 60 or more so as to function as a photonic crystal fiber.
[0026]
Also, the length of the second preform 32 or the portion 34 where the hole is not opened is 3 to 8 cm when the diameter of the fiber preform 1 is 20 mm or more and less than 60 mm, and the diameter of the fiber preform 1 is When the diameter is 60 mm or more and less than 120 mm, and when the diameter of the fiber preform 1 is 120 mm or more, it is 10 to 50 cm. If the first preform 31 or the perforated portion 33 is heated and stretched, the coating 25 is applied. It is preferable because the thickness is sufficiently long as necessary to be able to adjust the thickness substantially uniformly.
[0027]
The manufacturing process may include other processes such as preheating and cleaning. In the first embodiment, the first base material 31 may be formed by drilling a quartz rod. In the second embodiment, the plurality of non-through holes 5 of the fiber base material 1 are made of quartz glass. You may form by making a large diameter hole in a stick | rod and stuffing a capillary there. The die 11 is not limited to the inverted conical shape and may have any shape. Further, a pressure die may be used as the die 11. Further, the coating may be produced by a method other than the die 11, such as spraying. The measurement of the coating thickness is not limited to that by observation of a diffraction image with a laser beam, and any method such as an electrical measurement method may be used. The heating in the heating and stretching step may be performed by a laser other than the electric furnace, for example.
[0028]
【The invention's effect】
The present invention is implemented in the form as described above, and has the following effects.
[0029]
The fiber preform is composed of two parts, a solid part with no holes in the axial direction and a part with multiple holes extending in the axial direction, and the surface is coated by heating and stretching from the solid parts. Since the solid part is adjusted during stretching so that the coating thickness becomes substantially uniform in the fiber circumferential direction, the uniform thickness can be obtained without adjusting the coating thickness during heat stretching of the part where the hole exists. A high-quality optical fiber having a plurality of pores extending in the axial direction can be obtained by a simple and inexpensive method.
[Brief description of the drawings]
FIG. 1 is a schematic view of an optical fiber manufacturing apparatus.
FIG. 2 is a diagram showing measurement of coating thickness by a laser.
FIG. 3 is a view showing a fiber preform according to the first embodiment.
FIG. 4 is a drawing in which the fiber preform according to the first embodiment is heated and stretched.
FIG. 5 is a view showing joining of fiber preforms according to the first embodiment.
FIG. 6 is a diagram showing a solid optical fiber having a uniform coating thickness and a diffraction image thereof.
FIG. 7 is a diagram showing a solid optical fiber having a non-uniform coating thickness and its diffraction image.
FIG. 8 is a diagram showing a photonic crystal fiber having a uniform coating thickness and a diffraction image thereof.
FIG. 9 is a view showing a die adjusting device.
FIG. 10 is a view showing a fiber preform according to a second embodiment.
FIG. 11 is an end view of the first base material according to the first embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fiber preform 2 Optical fiber 3 Hole 5 Hole 25 Coating 28 Covering adjustment device 31 First preform 32 Second preform 33 Portionless portion of optical fiber preform 34 Portion of optical fiber preform

Claims (4)

A first base material having a plurality of holes extending in the axial direction, which is a rod-shaped quartz glass, and a solid rod-shaped quartz glass, the first base material and a second base material having substantially the same diameter as each other, with the central axes thereof A base material forming step of forming a fiber base material by joining them together; and
A heating and stretching step of heating and stretching the fiber preform formed in the preform formation step from the end on the second preform side; and
A coating step of coating a resin on the surface of the optical fiber heated and stretched in the heating and stretching step;
A coating adjusting step of adjusting the coating thickness in the coating step so as to be substantially uniform in the circumferential direction of the optical fiber while the second base material is heated and stretched in the heating and stretching step. Fiber manufacturing method. In claim 1,
The method of manufacturing an optical fiber, wherein the coating adjustment step is a step performed by a coating adjustment mechanism that moves a position of a coating device that performs coating. A preform forming step for forming a fiber preform by forming a plurality of holes that are open at only one end and extending in the axial direction of the rod in a solid quartz glass rod in an unpenetrated state;
A heating and stretching step in which the fiber preform formed in the preform forming step is heated and stretched from the end where the hole is not opened; and
A coating step of coating a resin on the surface of the optical fiber heated and stretched in the heating and stretching step;
A coating adjustment step of adjusting the coating thickness so that the coating thickness in the coating step is substantially uniform in the circumferential direction of the optical fiber before the holed portion of the fiber preform is heated and stretched in the heating and stretching step; An optical fiber manufacturing method comprising: In claim 3,
The method of manufacturing an optical fiber, wherein the coating adjustment step is a step performed by a coating adjustment mechanism that moves a position of a coating device that performs coating.

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