JP2004037758A - Recoating device for optical fiber, recoating method for optical fiber using same and optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recoating method for an optical fiber for preventing air bubbles from remaining and increasing mechanical strength and to provide a recoating device capable of highly reliably recoating the optical fiber without leaving air bubbles in the coating. <P>SOLUTION: The recoating device is provided with an upper die and a lower die composed by forming a molding groove having an inner diameter almost the same as the outer diameter of an optical fiber fusion splicing part and forming an injection groove for injecting resin in the internal space of the molding groove so as to form a recoating layer at the bare fiber part of the optical fiber fusion splicing part. An air bubble discharge space formed upwards from the molding groove is provided. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a recoating apparatus, a method for recoating an optical fiber using the same, and an optical fiber.
[0002]
[Prior art]
When the optical fibers are fusion-spliced, it is necessary to recoat and reinforce the optical fiber connection.
As one of methods for performing re-coating in this way, a method for re-coating an optical fiber connection portion using a mold has been proposed (Japanese Patent Laid-Open No. 7-31316).
[0003]
In this method, the resin is poured into the cavity formed between the lower mold and the upper mold while the optical fiber connection part is placed on the cavity, thereby recoating the optical fiber connection part.
A gas vent groove is provided on both sides of the cavity, that is, in parallel with the recoat groove so as to be connected to the recoat groove. The viscosity of the resin supplied to the recoat groove is connected to the gas vent groove and the recoat groove. By adjusting the pressure, the residual air is discharged together with the resin.
[0004]
[Problems to be solved by the invention]
However, in this method, there is a problem that air bubbles easily accumulate in the upper portion of the recoat groove, and the air bubbles are not easily pushed out.
For this reason, even with the above method, bubbles may remain in the resin layer re-coated on the optical fiber connection portion, and the following adverse effects may occur if the bubbles remain.
[0005]
First, when bubbles are large, the glass is exposed and the glass is easily broken.
Secondly, when exposed to a low-temperature environment, non-uniform distortion occurs in the bubble portion, so that transmission loss due to microbending tends to increase.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for recoating an optical fiber that prevents large bubbles from remaining and has high mechanical strength and small optical transmission loss.
It is another object of the present invention to provide a recoating apparatus capable of performing highly reliable recoating of an optical fiber without leaving large bubbles.
[0007]
[Means for Solving the Problems]
Therefore, the present invention provides an upper fiber mold and a lower mold formed with a molding groove having an inner diameter substantially equal to the outer diameter of the optical fiber on which the coating layer is formed, and comprises a bare fiber portion of the optical fiber fusion spliced portion. In order to form a recoating layer, a resin is injected into the internal space of the molding groove via an injection groove, and the resin is cured, so that a bubble discharge space formed upward from the molding groove is removed. It is characterized by comprising.
[0008]
Preferably, the bubble discharge space is a space formed from an inner wall of the molding groove along a longitudinal direction of the molding groove.
[0009]
Preferably, the bubble discharge space is a space formed to open upward along the longitudinal direction of the molding groove.
[0010]
Preferably, the bubble discharge space is formed so as to penetrate an end face of the molding groove so as to open at both ends of the molding groove along a longitudinal direction of the molding groove. The bubble discharge space may be formed partially or may be formed over the entire length of the molding groove. In short, it is desirable to open at the portion (edge) at the time of the recoating portion, that is, at both ends of the forming groove.
[0011]
Preferably, the bubble discharge space is formed above the molding groove of the upper die.
[0012]
Preferably, there is a plurality of the bubble discharge spaces.
[0013]
Preferably, the bubble discharge space communicates with the molding groove above the molding groove.
[0014]
The method for recoating an optical fiber according to the present invention comprises the steps of: mounting a fusion spliced portion of an optical fiber in a molding groove of the recoating apparatus having the above-described bubble discharge space; and supplying resin into the molding groove. Curing the resin; and removing the fusion spliced portion of the optical fiber recoated with the resin from the recoating device.
[0015]
Desirably, the method further includes a deburring step of removing resin flash generated by the bubble discharge space.
[0016]
Preferably, in the optical fiber of the present invention, the optical fiber connection portion is recoated, and the diameter of bubbles contained in the recoated portion is substantially 10 μm or less.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0018]
(First Embodiment)
As shown in FIGS. 1 to 5, the apparatus according to the present embodiment has an outer diameter of the optical fiber fusion spliced portion so as to form a recoating layer on the bare fiber portion 1 of the optical fiber fusion spliced portion. Re-coating with upper and lower molds 101B and 101A formed with a molding groove 102 (102A, 102B) having substantially the same inner diameter and an injection groove for injecting resin into the internal space of the molding groove. The apparatus is characterized by including a bubble discharge space 100 formed above the molding groove 102.
[0019]
In the recoating method using this apparatus, a mold including the upper mold 101B and the lower mold 101A is mounted on the bare fiber portion 1 of the optical fiber fusion splicing section, and the mold is filled with an ultraviolet curable resin. When irradiating ultraviolet rays to cure the ultraviolet curable resin and recoat the bare fiber portion, bubbles are efficiently discharged by the bubble discharge space formed above the molding groove 102, and the cavities due to stagnation of the bubbles are formed. A recoating layer 113 is formed to suppress the occurrence.
[0020]
Here, FIG. 1 is an exploded perspective view of a mold of the recoating apparatus. 2 is a sectional view of the mold, FIG. 3 is a sectional view taken along line AA of FIG. 2, FIG. 4 is an overall front view of the recoating apparatus, and FIGS. 5 (a) and 5 (b) are process sectional views of the recoating method. is there.
In this apparatus, burrs may occur slightly due to the presence of the bubble discharge space 100. If burrs occur even slightly, the molds 101A and 101B are removed and the burrs are removed to form a good re-coating layer 113 (see FIG. 5 (b)) having neither cavities nor burrs. It becomes possible.
[0021]
Here, the molds 101A and 101B are made of quartz glass, and can be visually checked for a resin filling state, and are formed so that the resin is cured to transmit ultraviolet rays. Further, light-shielding layers 105a and 105b are provided on the contact surface between the upper surface of the lower mold 101A and the lower surface of the upper mold 102B so as to prevent the resin leaking from the clearance from hardening and to suppress the generation of burrs. You may comprise. Here, 107a and 107b are clamps for fixing the optical fiber for recoating, and 106a and 106b are metal fittings for fixing the upper mold.
[0022]
That is, first, as shown in FIGS. 2 and 3, a bare fiber portion 1 having an outer diameter of about 125 microns, which is fusion-spliced, is formed at the center of a cavity 102 formed between a lower mold 101A and an upper mold 101B. Arrange so that they come together.
[0023]
Then, as shown in FIG. 4, a urethane acrylate resin 950Y200 manufactured by JSR Corporation is filled into the molding groove 102 forming a cylindrical cavity having an inner diameter of about 250 μm through the injection groove 104, and the ultraviolet lamp 108 is used. Irradiate from outside of the mold for about 45 seconds. The irradiation time can be adjusted according to the magnitude of the UV lamp power.
In this way, a recoating layer 113 made of urethane acrylate is formed as shown in a sectional view of FIG.
[0024]
Then, the upper mold and the lower mold are removed.
At this time, the resin may seep into the bubble discharge space and harden to form burrs B. In this case, by removing the burrs B by a mechanical method or a chemical method, the burrs-free recoating layer 113 can be obtained as shown in FIG. 5B.
[0025]
In this way, it is possible to obtain a recoated optical fiber. This recoating length L was about 38 mm.
[0026]
The optical fiber thus formed has a very good recoating area without the presence of large bubbles. Here, a large bubble refers to a bubble having a diameter exceeding 10 μm. Alternatively, when bubbles having a diameter of 10 μm or less are densely formed and bubbles having a diameter substantially exceeding 10 μm are formed, it may be considered that large bubbles are formed. When large bubbles having a diameter exceeding 10 μm substantially occur in the re-coated portion, the re-coated portion is easily broken or transmitted due to uneven shrinkage stress generated when the re-coated portion shrinks in a low-temperature environment. Loss may increase. The optical fiber of the present invention does not have these problems.
[0027]
In the above embodiment, the bubble discharge space is a space formed so as to penetrate the upper mold upward from the inner wall of the molding groove along the longitudinal direction of the pre-molding groove. Residual air can be discharged very efficiently.
Further, since the bubble discharge space is formed over substantially the entire length of the recoating layer formation region, the bubbles in the recoating layer formation region are efficiently discharged.
[0028]
In addition, since the bubble discharge space is a space formed to open upward, the residual air is efficiently guided upward, and the generation of large bubbles due to the residual air can be suppressed.
[0029]
In addition, since the bubble discharge space is formed substantially at the upper end of the molding groove, the bubbles in the molding groove can be efficiently discharged, and the generation of large bubbles due to residual air can be suppressed. And a highly reliable recoating layer can be formed.
[0030]
(Second embodiment)
Next, a second embodiment of the present invention will be described. In the first embodiment, the bubble discharge space 100 is formed continuously over the entire length of the molding groove, but in this example, as shown in FIGS. A plurality of bubble discharge holes 200 are formed at intervals. FIG. 6B is a sectional view taken along line BB of FIG. 6A.
The other parts are formed in the same manner as in the first embodiment, and the description is omitted, but the same parts are denoted by the same reference numerals.
[0031]
The hole diameter of the gas discharge hole 200 is desirably about 100 to 300 μm, and is determined according to the viscosity of the resin liquid used so that the resin flows so that the gas is pushed out to the gas discharge hole 200.
As described above, the bubble discharge space is not formed as a space formed by penetrating the molding groove in the longitudinal direction as in the first embodiment, but is formed as a plurality of holes, so that the resin seeps. Can be suppressed.
Even if burrs are formed, they may be removed by a physical method or a chemical method.
[0032]
Since the bubble discharge hole is formed upward in the upper part of the upper mold groove, it is possible to discharge bubbles efficiently.
That is, since the bubble discharge space communicates with the molding groove above the molding groove, the air in the molding groove can be more efficiently discharged.
[0033]
(Third embodiment)
Next, a third embodiment of the present invention will be described. In the first embodiment, the bubble discharge space 100 is formed above the molding groove. However, in this example, as shown in FIGS. A long groove-shaped bubble discharge space 300 is formed in the vicinity of the interface between the upper mold and the lower mold, and formed obliquely upward. FIG. 7B is a cross-sectional view taken along the line cc of FIG. 7A.
[0034]
Here, the molds 101A and 101B are also made of quartz glass, so that the filling state of the resin can be visually checked, and the resin is cured so as to transmit ultraviolet rays. However, the light-shielding layers 105a and 105b are provided on the contact surface between the upper surface of the lower die 101A and the lower surface of the upper die 102B, and the bubble discharge space 300 is formed in a region where the light-shielding layers 105a and 105b exist. ing. Therefore, even if the resin exudes into the bubble discharge space 300, the exuded resin is not irradiated with the ultraviolet light, so that the resin is prevented from being cured and the generation of burrs can be suppressed. Further, even if burrs appear, they may be removed by a physical method or a chemical method.
[0035]
(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. In the first embodiment, the bubble discharge space 100 is formed so as to open upward from the upper end of the molding groove of the upper die 101B, but in this example, it is formed so as to open laterally. Features. That is, as shown in FIG. 8, a bubble discharge formed of a long groove having a small opening width at the upper end of the molding groove so as to open over the entire longitudinal direction of the molding groove, and formed at the side surfaces 801A and 801B of the upper mold. A space 800 is provided.
Portions other than the bubble discharge space 800 are formed in the same manner as in the first embodiment, and description thereof is omitted, but the same portions are denoted by the same reference numerals.
[0036]
This bubble discharge space is formed along the longitudinal direction of the molding groove, and is formed so as to open to the side surface of the upper mold. The bubbles moved to the upper part of the resin are discharged from the openings opened to the side surfaces 801A and 801B of the upper die through the bubble discharge ports, and it is possible to suppress the generation of bubbles due to residual air on the end surfaces. In the example of FIG. 8, a bubble discharge space is formed from the boundary between the coating portion and the bare fiber portion where the bubbles are likely to remain, and the side surface of the upper mold. The coating discharge space may be formed over the entire length of the molding groove in the longitudinal direction.
[0037]
(Fifth embodiment)
In the first embodiment, the resin is completely cured by one irradiation of ultraviolet rays. However, the curing step is divided into two steps, the resin is removed from the mold in a semi-cured state, and seeps into the bubble discharge space. After removing the burrs, curing may be performed again.
[0038]
That is, using the same apparatus as used in the first embodiment, first, in the first ultraviolet irradiation step, the irradiation energy of the ultraviolet lamp 108 is reduced, and the molds 101A and 101B are in a semi-cured state. After removing the burrs and wiping off the burrs with alcohol etc., by irradiating ultraviolet rays sufficient for curing the ultraviolet curable resin again and curing it, even large cavities with a diameter exceeding 10 μm can be obtained with higher reliability. It is possible to form a good recoating layer 113 free of flash.
[0039]
And since it is completely cured by additional irradiation, it is extremely reliable in terms of strength.
[0040]
The process up to the resin injection step is the same as that of the first embodiment, but first, the ultraviolet lamp 108 is irradiated from outside the mold for 10 seconds. The irradiation time can be adjusted according to the magnitude of the UV lamp power.
At this time, a resin layer 113S made of urethane acrylate in a semi-cured state is formed. At this time, as shown in FIG. 5A, burrs B may be formed from the resin that has oozed into the bubble discharge space 100.
Thereafter, the upper mold and the lower mold are removed.
Then, the burrs B are wiped off using a non-woven fabric impregnated with alcohol to obtain burrs-free semi-cured resin 113S.
[0041]
Finally, ultraviolet rays are irradiated for 30 seconds to completely cure the semi-cured resin 113S, thereby forming the re-coating layer 113 as shown in FIG. 5B. The irradiation time can be adjusted according to the magnitude of the UV lamp power.
In this way, it is possible to obtain a recoated optical fiber. This recoating length L was about 38 mm.
[0042]
The optical fiber thus formed has a very good recoating area without large cavities and burrs.
[0043]
According to this method, since the burrs are wiped off in a semi-cured state, they can be easily wiped off with alcohol, and the burrs can be removed very well.
[0044]
And since it is completely cured by additional irradiation, it is extremely reliable in terms of strength.
[0045]
In the fifth embodiment, the ultraviolet irradiation for obtaining the semi-cured state is performed by adjusting the irradiation time, but the irradiation energy may be reduced.
[0046]
The irradiation energy in the temporary curing step is preferably set so that the degree of curing of the ultraviolet curable resin is about 50% to 80%, more preferably about 60% to 70% of the completely polymerized state.
If it exceeds 80%, it becomes difficult to remove the burrs, and the peripheral portion may peel off together with the burrs.
[0047]
On the other hand, if it is less than 50%, it is likely to be deformed, the mold part is peeled off when wiping with alcohol, the appearance after curing is reduced, and the strength is sometimes insufficient.
[0048]
Although the urethane acrylate resin is used in the first to fifth embodiments, it is needless to say that another ultraviolet curable resin may be used.
[0049]
(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described.
In the fifth embodiment, the mold is removed from the mold in a semi-cured state, the burrs are removed, and then, the mold is completely cured by additional irradiation while the mold is removed. Alternatively, a mold having no resin may be mounted and cured by irradiating ultraviolet rays in the mold.
In this additional irradiation step, the same mold as the mold used in the first UV irradiation step may be used.
[0050]
In other words, in this method, the steps up to FIGS. 1 to 3 are the same as those of the fifth embodiment, and instead of the step of FIG. Then, ultraviolet irradiation is performed from outside the mold.
[0051]
According to this method, it is possible to obtain a recoating whose outer diameter is adjusted with higher precision.
[0052]
(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described.
In the first to sixth embodiments, an example using an ultraviolet curable resin has been described. However, the present invention is not limited to this, and can be applied to a case where a thermosetting resin such as a phenol resin is used. is there.
In this case, if the curing step is to be divided into a plurality of times, the heat energy may be adjusted, the burrs may be removed from the mold, and the curing may be completed by the additional heating step.
[0053]
According to this method, highly reliable recoating can be performed with good productivity.
[0054]
As the thermosetting resin, a phenol resin, a urea resin, a melamine resin, a polyester resin, or the like can be used.
[0055]
Further, in the above-described embodiment, the bubble discharge space is formed in the upper mold. However, in the case where the resin injection groove is formed in the lower mold, the lower mold may be used. The opening to the molding groove of the bubble discharge space is provided above the resin injection groove, and the bubbles are discharged almost efficiently by the bubble discharge space formed upward from this opening.
[0056]
【The invention's effect】
As described above, according to the apparatus of the present invention, it is possible to perform recoating with no large cavities and good strength.
According to the method of the present invention, recoating with no large voids and good strength can be obtained with extremely high productivity. Further, it is possible to obtain an optical fiber which does not contain large bubbles in the recoating portion, is less likely to break, and has less transmission loss.
[Brief description of the drawings]
FIG. 1 is an exploded view of a mold of an optical fiber recoating apparatus according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a mold of the recoating apparatus according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a cross-sectional view taken along line AA of FIG. 2;
FIG. 4 is a diagram showing a recoating apparatus according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a recoating step of the optical fiber according to the first embodiment of the present invention.
FIG. 6 is a diagram showing an optical fiber recoating apparatus according to a second embodiment of the present invention.
FIG. 7 is a diagram showing an optical fiber recoating apparatus according to a third embodiment of the present invention.
FIG. 8 is a diagram showing an optical fiber recoating apparatus according to a fourth embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 bare fiber portion 1S fiber fusion portion 100 bubble discharge groove 101A lower die 101B upper die 102A molding groove 102B molding groove B flash 111 coating resin 113S semi-cured resin 113 recoating layer 101A, 101B mold 102 cavity 108 ultraviolet lamp

Claims (9)

An upper mold and a lower mold having a molding groove having an inner diameter substantially equal to the outer diameter of the optical fiber on which the coating layer is formed are provided. In order to form, in a re-coating apparatus in which a resin is injected into the internal space of the molding groove via an injection groove and is cured.
An optical fiber recoating device comprising a bubble discharge space formed above the molding groove. 2. The air bubble discharge space is a space formed from an inner wall of the molding groove along a longitudinal direction of the molding groove.
An optical fiber recoating apparatus according to claim 1. The optical fiber recoating apparatus according to claim 1, wherein the bubble discharge space is a space formed to open above the molding groove. The optical fiber re-coating apparatus according to claim 2, wherein the bubble discharge space is formed to penetrate the end face of the molding groove so as to open at both ends of the molding groove. The optical fiber re-coating device according to any one of claims 1 to 4, wherein the bubble discharge space is formed above the molding groove of the upper die. The optical fiber re-coating device according to any one of claims 1 to 5, wherein a plurality of the bubble discharge spaces are provided. Mounting a fusion spliced portion of the optical fiber in the molding groove of the recoating device according to claim 1,
Supplying a resin into the molding groove,
Curing the resin,
Removing the fusion spliced portion of the optical fiber recoated with the resin from the recoating device. 8. The optical fiber re-coating method according to claim 7, further comprising a deburring step of removing a resin flash caused by the bubble discharge space. An optical fiber in which the optical fiber connection part is a recoated optical fiber, wherein bubbles in the recoated part have a diameter of substantially 10 μm or less.

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