JPH08327849A - Method for reinforcing optical fiber - Google Patents

Abstract

PURPOSE: To obtain a resilience and tensile strength and to miniaturize the reinforcing structure by injecting a specific coating resin into the space between a thermal shrinkage type protective tube and a fusion spliced part and thermally shrinking this tube to cure the coating resin. CONSTITUTION: The thermal shrinkage type protective tube 3 is put on the fusion spliced part 2 between right and left optical fiber coating parts 1, and the coating resin 4 of a thermosetting type or UV curing type mixed with a tensile strength fiber, for example, carbon fiber and glass fiber, is previously injected into the space between this protective tube 3 and the fusion spliced part 2 (and optical fiber coating parts 1). This coating resin 4 may be a resin tube having a low m.p. The entire part of such reinforcing structure is heated, thereby, the protective tube 3 of the thermal shrinkage type is shrunk. Further, the coating resin 4 is simultaneously cured as well when the coating resin 4 is of a thermosetting type. The bubbles intruding into the injected coating resin 4 are, therefore, squeezed outside together with the excess resin. The reinforcing part 10 is formed within the protective tube 3 in such a manner.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reinforcing optical fibers, and more particularly to a method for reinforcing fusion spliced portions of optical fibers.

The fusion splicing of optical fibers is characterized by a small connection loss and high reliability as compared with the connection method using a lens or the like. It is widely used for connecting components, but it is necessary to reinforce such a fusion spliced portion of an optical fiber because it is structurally weak.

[0002]

2. Description of the Related Art FIGS. 8A and 8B show an example of a conventionally known reinforcing method for an optical fiber. FIG. 8A is a side sectional view and FIG. 8B is a sectional view. 6 is a sectional view taken along line BB in FIG.

In the figure, optical fibers coated by an optical fiber coating portion 1 are fused at a fusion splicing portion 2, and the fusion splicing portion 2 is covered with a low melting point resin 21 and has a low melting point. The resin 21 is adjacent to the hard metal core 22, and the low melting point resin 21 and the metal core 22 are covered with the protective tube 23, and the connection reinforcing portion 30 is formed as a whole.

In such a conventional example, the reinforcing portion becomes long on a straight line, and when it is used in a module or the like, the module / device must be enlarged to accommodate the reinforcing portion.

Further, since it is reinforced by the metal core, it is difficult to bend and the reinforcing portion cannot be stored at an arbitrary position.

Further, since the fixing position of the reinforcing portion at the time of storage is limited, reconnection may be necessary if the position of the fusion splicing portion is not aligned, which complicates the connection and storage work.

On the other hand, a reinforcing method (Japanese Patent Laid-Open No. 56-2240, etc.) in which a composite of a photocurable resin and a heat-resistant fiber is applied to the fusion-spliced portion and its periphery and cured, and a heat-melting adhesive is applied to the inner surface. A reinforcing method in which a connecting portion between a thin rod having high rigidity and a fiber core wire is inserted into a heat-shrinkable tube having a layer formed thereon to induce heating (Japanese Patent Laid-Open No. 57-191614, etc.) A method of filling an adhesive in a heat-shrinkable tube and heat-shrinking the tube to integrate the connection part (JP-A-58-122508, etc.), and covering the fusion-bonded part with a transparent resin tube. A reinforcing method (for example, Japanese Patent Laid-Open No. 2-61602) in which an ultraviolet curable resin is injected and cured in this tube has already been proposed.

[0008]

In the prior art as described above, there is an improvement in the reinforcing portion shown in FIG. 8 in terms of size and easiness of bending. There is a problem that the strength is weak to prevent damage to the fiber.

Therefore, it is an object of the present invention to realize a method of reinforcing an optical fiber which is flexible, has a small reinforcing portion and has sufficient strength.

[0010]

[Means and Actions for Solving the Problems]

[1] In the present invention, for heat-curing type coating, a fusion-splicing portion of optical fibers is covered with a heat-shrinkable protective tube, and a space between the tube and the fusion-splicing portion is mixed with a tensile strength fiber. It is characterized by injecting a resin, shrinking the tube by heating, and curing the coating resin.

That is, by heating, the transparent heat-shrinkable protective tube covering the fusion splicing portion of the optical fibers is first shrunk. Further, the heating cures the thermosetting coating resin injected into the space between the tube and the fusion splicing portion.

As a result, the size of the reinforced optical fiber portion shrinks, and the problem of storage is solved. Also, the difficulty of bending is eliminated.

Further, since the tensile strength fiber is mixed in the coating resin in this case, the strength of this fusion splicing portion is increased and the optical fiber can be prevented from being damaged when tension is applied.

[2] In the present invention, an ultraviolet curable resin can be used instead of the thermosetting coating resin as described in [1] above. In this case, the protective tube is heat-shrinked. After that, by curing the coating resin with ultraviolet rays, it becomes possible to provide a similar reinforcing structure for the fusion spliced portion of the optical fiber.

[3] In the above [1] and [2], the reinforcing portion is formed by using the protective tube and the coating resin, but a tube provided with a split groove is prepared, and the split groove of the tube is prepared. From the fusion splicing portion of the optical fibers and the thermosetting or UV-curable coating resin mixed with the tensile strength fiber as described above, and squeezed until the split groove comes into contact, the coating After the application resin is cured by heating or ultraviolet rays, the split groove may be widened to remove the optical fiber (and the coating resin).

As a result, since the reinforcing portion can be made thinner by the absence of the protective tube as described above, the size of the storage portion can be reduced and the optical fiber can be easily bent.

[4] As the tube in the above [3], a tube made of Teflon or a tube having an inner surface coated with Teflon can be used.

[5] A thermosetting type in which a pair of blocks are used instead of the tubes in the above [3] and [4], a groove is provided in one block, and the above tensile strength fiber is mixed in this groove. Alternatively, a fusion splicing portion between the ultraviolet curable coating resin and the optical fibers is sequentially inserted.

Then, the other block is placed on the one block, the coating resin is cured, and then both blocks are removed. Then, the optical fiber (and the coating resin shown in [3] and [4] above is removed. The same reinforcement part as in () is obtained.

[6] Also in the above [5], as the block, a block made of Teflon or a block having an inner surface coated with Teflon can be used.

[7] Further, in the present invention, in the above [1], the fusion splicing portion may be provided along the flexible tensile strength support, and the heat shrinkable protection tube may be covered.

Thus, the fusion splicing portion can be formed into an arbitrary shape according to the storage place, and the radius of curvature can be prevented from locally becoming smaller than necessary.

[8] By using a rod-shaped tensile strength fiber as the support in the above [7], the strength can be further increased.

[0024]

[9] Furthermore, in the above [7] or [8], a shape memory alloy may be used in place of the support so that the heat-shrinkable protective tube has a desired shape when heated for contraction.

[0025]

FIG. 1 shows an embodiment (1) of a method for reinforcing an optical fiber according to the present invention. First, in FIG. 1 (a), fusion between the left and right optical fiber coating portions 1 is performed. The connection part 2 is covered with a heat-shrinkable protection tube 3, and the space between the protection tube 3 and the fusion splicing part 2 (and the optical fiber coating part 1) is
For example, a thermosetting or ultraviolet curable coating resin 4 in which a liquid tensile strength fiber such as carbon fiber or glass fiber is mixed is injected. The coating resin 4 may be a resin tube having a low melting point.

Then, as shown in FIG. 6B, the heat-shrinkable protective tube 3 is shrunk by first heating the entire reinforcing structure.

Further, when the coating resin 4 is of a thermosetting type, the coating resin 4 is also cured at the same time. As a result, the bubbles mixed in the injected coating resin 4 are squeezed out together with the excess resin.

However, when the coating resin 4 is of an ultraviolet curable type, the protective tube 3 is made transparent and the coating resin 4 can be cured by irradiating ultraviolet rays from the outside of the protective tube 3. .

In this way, in FIG.
As shown in FIG. 3C showing a cross section taken along line A, a reinforcing portion 10 in which the optical fiber coating portion 1 and the coating resin 4 are wholly shrunk is generated inside the protective tube 3, and The inner diameter after contraction can be reduced to about 0.5 mm.

Further, in the present invention, in order to reduce the tension applied to the fusion splicing portion 2, the resin 4 for coating is mixed with glass fiber or carbon fiber known as a tensile strength fiber having small expansion and contraction. There is.

By using the coating resin 4 mixed with such a tensile strength fiber, the minimum breaking strength is 0.5 k.
It has become possible to improve from g to 2 kg.

FIG. 2 shows an embodiment (2) of the optical fiber reinforcing method according to the present invention. In this embodiment, first, a split groove 50 is provided as shown in FIG. A Teflon tube 5 is prepared, a liquid coating resin 4 in which the tensile strength fiber is mixed is also put in the Teflon tube 5, and after that, the fusion splicing portion 2 of the optical fiber.
Insert

From this state, the coating resin 4 inside is cured by heating or ultraviolet rays while being squeezed until the split grooves 50 come into contact with each other as shown in FIG.

By expanding and taking out the split groove 50 of the Teflon tube 5, the fusion-spliced portion 2 covered with the coating resin 4 having a narrow outer shape can be obtained as shown in FIG.

As a result, even an optical fiber having a small coating outer shape such as an ultraviolet core wire can be provided with the same flexibility as that of the optical fiber and the handleability can be improved.

The tube 5 made of Teflon is used for easy removal. Also,
Instead of the Teflon tube, the inner surface of the tube 5 may be coated with Teflon.

FIG. 3 shows an embodiment (3) of the optical fiber reinforcing method according to the present invention. In this embodiment,
As shown in FIGS. 3A and 3B, two transparent blocks 6 and 7 are prepared, a groove 8 is provided in at least one of the blocks 6, and the groove 8 is provided in the optical fiber coating portion 1 and the fusion fiber. The same connecting liquid 2 as the above is put in as well as the connecting part 2.

Then, in this state, the coating resin 4 is cured by heating or UV curing in the same manner as in the above-mentioned embodiment of FIG. 2, and the blocks 6 and 7 are removed, so that the light as shown in FIG. The coating resin 4 fixed around the fiber coating portion 1 is obtained.

In this case, the blocks 6 and 7 may be made of Teflon, or the inner surface of the groove 8 may be Teflon coated.

FIG. 4 shows an embodiment (4) of the optical fiber reinforcing method according to the present invention. In this embodiment, the optical fiber coating portion 1 (and the coating resin 4) is provided in the protective tube 3. A tensile strength support 9 such as a copper wire having flexibility
And the tube 3 is shrunk and the coating resin 4 is cured as described above.

By doing so, the fusion splicing portion can be formed into an arbitrary shape according to the storage place, and the bending radius can be prevented from locally decreasing.

In this case, a linear shape memory alloy may be used as the support 9 so that the heat-shrinkable protective tube 3 has a desired shape when heated for contraction.

FIG. 5 shows an example of an apparatus (1) used for carrying out the method for reinforcing an optical fiber according to the present invention. In this embodiment, a thermosetting type resin 4 is particularly used as the coating resin 4. It is applied when there is.

That is, the reinforcing portion 10 of the optical fiber coating portion 1 is placed on the upper portion of the holder 12 having the heater 11, and the lid 13 is placed on the reinforcing portion 10. It should be noted that the holder 12 is provided with holes 121 and 122 for sucking also from a vacuum pump (not shown).

Therefore, by using such a device, the temperature of the central part is made slightly higher than the both ends, and the tube 3 is gradually contracted from the central part so that the bubbles can smoothly come out. ing.

Further, holes 121 and 122 are provided in the holder 12 to absorb the excess coating resin 4 that leaks out when the tube 3 contracts.
1,122 are drawn out by the suction force from the vacuum pump.

In this way, FIG. 1 (c) and FIG.
(C), the reinforcing structure of the optical fiber as shown in FIG. 3 (c) is obtained.

Further, in the apparatus example (2) shown in FIG.
For example, a sponge 14 is used as an absorber around the heater 11 to absorb the coating resin 4 leaking from the reinforcing portion 10.

FIG. 7 shows a device example (3) in the case where a resin for ultraviolet curing is used as a coating resin. In this device, a transparent glass 15 is provided on the upper part of the reinforcing portion 10, and this transparent glass is used. The optical fiber bundle 16 is connected to the optical fiber bundle 16 and the other end of the optical fiber bundle 16 is connected to the ultraviolet irradiation device 17
Are connected. The ultraviolet irradiation device 17 and the heater 11 are controlled by the CPU 18.

In such a reinforcing device, first, CP
U18 urges the heater 11 to heat-shrink the protective tube 3 in the reinforcing portion 10 and sucks the liquid coating resin leaking from the reinforcing portion 10 through the holes 121 and 122 with an external vacuum pump or the like.

After that, the CPU 18 controls the ultraviolet irradiation device 17
By urging the transparent glass 15 from the ultraviolet irradiation device 17 through the optical fiber bundle 16,
Further, when ultraviolet rays are applied to the reinforcing portion 10 through the transparent glass 15, the coating resin 4 as the ultraviolet curing type coating resin is cured, and the coating resin 4 shown in FIGS.
Thus, the reinforcing structure of the optical fiber as shown in FIG. 3C can be obtained.

[0052]

As described above, according to the optical fiber reinforcing method of the present invention, the fusion splicing portion between the optical fibers is covered with the heat-shrinkable protective tube, and the space between the tube and the fusion splicing portion is covered. A thermosetting or ultraviolet curable coating resin mixed with a tensile strength fiber is injected into the tube to heat-shrink the tube and cure the coating resin. Thus, it becomes possible to easily realize a small-sized optical fiber reinforcing structure that can be accommodated at any position.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining an embodiment (1) of an optical fiber reinforcing method according to the present invention.

FIG. 2 is a sectional view for explaining an embodiment (2) of the optical fiber reinforcing method according to the present invention.

FIG. 3 is a cross-sectional view for explaining an embodiment (3) of the optical fiber reinforcing method according to the present invention.

FIG. 4 is a cross-sectional view for explaining an embodiment (4) of the optical fiber reinforcing method according to the present invention.

FIG. 5 is a cross-sectional view showing a device example (1) used in the optical fiber reinforcing method according to the present invention.

FIG. 6 is a cross-sectional view showing a device example (2) used in the optical fiber reinforcing method according to the present invention.

FIG. 7 is a diagram showing a partial cross-section of a device example (3) used in the optical fiber reinforcing method according to the present invention.

FIG. 8 is a cross-sectional view for explaining a conventional example.

[Explanation of reference numerals] 1 optical fiber coating portion 2 fusion splicing portion of optical fiber 3 protective tube 4 coating resin 5 tube 50 split groove 6 grooved block 7 block 8 groove 9 flexible support 10 reinforcing portion same in the figure The reference numerals indicate the same or corresponding parts.

Claims (9)

[Claims] 1. A heat-shrinkable protective tube is covered on a fusion splicing portion of optical fibers, and a thermosetting coating resin mixed with a tensile strength fiber is injected into a space between the tube and the fusion splicing portion. Then, the tube is shrunk by heating and the coating resin is cured, and the reinforcing method of the optical fiber. 2. An ultraviolet curable resin is used as the coating resin instead of the thermosetting resin, the transparent tube is heat-shrinked, and then the coating resin is cured by ultraviolet rays. The method for reinforcing an optical fiber according to claim 1. 3. A thermosetting or ultraviolet curable coating resin mixed with a fusion splicing portion of optical fibers and a tensile strength fiber is inserted from a split groove provided in a tube and squeezed until the split groove comes into contact. A method for reinforcing an optical fiber, characterized in that the coating resin is cured in a state, and then the split groove is expanded to remove the optical fiber. 4. The method of reinforcing an optical fiber according to claim 3, wherein the tube is made of Teflon (registered trademark), or the inner surface of the tube is coated with Teflon. 5. A pair of blocks is used instead of the tube, and one block is provided with a groove, and the coating resin and the fusion splicing part are sequentially inserted into the groove, and then the other block is inserted. The method for reinforcing an optical fiber according to claim 3 or 4, wherein both blocks are removed after covering and curing the coating resin. 6. The method of reinforcing an optical fiber according to claim 5, wherein the block is made of Teflon or the inner surface of the block is coated with Teflon. 7. The method of reinforcing an optical fiber according to claim 1, wherein the fusion-spliced portion is covered with the heat-shrinkable protective tube along with a flexible and tensile strength support. 8. The method of reinforcing an optical fiber according to claim 7, wherein the support is a rod-shaped tensile strength fiber bundle. 9. The method of reinforcing an optical fiber according to claim 7, wherein a shape memory alloy is used instead of the support.