JPH11202148A - Optical fiber connection part and connecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical fiber connection part which does not use any straight steel wire and can be bent small. SOLUTION: The optical fiber connection part consists of a core part formed by removing the coatings of terminal parts of two coated optical fibers 1 and connecting the end surfaces of the exposed glass fibers 1a by fusion splicing in an abutting state, more than one layer, i.e., plastic protection layers 2 and 3 provided covering the exposed parts of the glass fibers 1a of the core part, and a protection member 4 which is provided on the plastic protection layer 4. This protection member 4 has gaps extending in cross-section circumferential directions along the length and suppresses a decrease in radius of curvature below a certain value. The protection member 4 is formed of a coiled member, etc., obtained by winding a metal wire to suppress the decrease in the bend radius of the optical fiber connection part below the certain value and enable smaller bending than usual.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting a connection portion of an optical fiber core.

[0002]

2. Description of the Related Art In order to protect a fusion spliced portion of an optical fiber, a heat-shrinkable tube in which a steel wire and a tube of a hot-melt adhesive are embedded is used. FIG. 5 is a front view showing a state where the optical fiber core wires are fusion-spliced, and FIG. 6 is a longitudinal sectional view and a side view of a protection member for a connection portion.

First, when connecting the optical fibers, as shown in FIG. 5, the coating of the ends of the two optical fibers 1 connected to each other is removed to remove the glass fiber 1a.
To expose. The tip of the glass fiber is cut into a mirror surface using a cutter (not shown), and the ends of the glass fiber 1a are melted and connected by an arc 12a generated between the electrodes 12 while the end faces of the two glass fibers are opposed to each other. .

Since the glass fiber at the fusion spliced portion thus formed is easily damaged as it is, it is protected by a protection member having a built-in steel wire as shown in FIG. In FIG. 6, 9 is an adhesive tube made of a hot melt adhesive, 10 is a steel wire, and 11 is a heat shrink tube made of a plastic such as polyethylene. The glass fiber fusion-spliced portion is placed inside the hole 9a of the adhesive tube 9 and heated from around the heat-shrinkable tube 11, thereby melting the adhesive tube 9 and heating the heat-shrinkable tube 11. The steel wire 10 is contracted and fixed so as to cover a part of the coating of the glass fiber and the optical fiber core together with the steel wire 10. In addition, the steel wire 10 supports the connecting portion of the glass fiber 1a so as not to be bent, and the heat-shrinkable tube 11
Is inserted so that the heat shrinkage force in the longitudinal direction does not adversely affect the glass fiber.

[0005]

In the optical fiber connection section formed as described above, the length of about 4
Since the entire connecting portion is kept straight by the steel wire of 0 to 60 mm, the storage space of the connecting portion cannot be made too small. An object of the present invention is to provide an optical fiber connection portion that is easily bent without using a straight steel wire as a protective member for reinforcing the optical fiber connection portion.

[0006]

SUMMARY OF THE INVENTION An optical fiber connecting portion of the present invention is obtained by removing the coating of the terminal portions of two optical fiber core wires to be connected to each other and fusing the exposed end surfaces of the glass fibers to each other. It comprises a connected core portion, at least one plastic protective layer provided so as to cover an exposed portion of the glass fiber of the core portion, and a protective member provided on the plastic protective layer. The protection member suppresses the bending radius from being equal to or less than a predetermined value.

[0007] By using a tubular member such as a metal or a hard plastic having a plurality of gaps extending in the circumferential direction in the transverse cross section in the longitudinal direction as the protective member, it is possible to suppress the bending radius from being less than a certain value. . Further, as a specific example of the protection member, a coiled member wound with a metal wire or a slit tube made of metal or hard plastic provided with slits extending in the cross-sectional circumferential direction at regular intervals in the longitudinal direction is configured. By doing so, it is possible to suppress the bending radius of the optical fiber connecting portion from becoming less than a certain value.

Further, the plastic protective layer may be composed of two layers, the inner side may be an adhesive plastic layer such as a hot melt adhesive, and the outer side may be a heat shrinkable tube. It is also possible to use two plastic protective layers, the inside of which is made of an ultraviolet-curable adhesive resin, and the outside of which is a plastic layer which can transmit ultraviolet light.

Further, at both ends of the protective member, if the end of the protective member and a part of the coating of the optical fiber core are covered with a rubber or plastic core bending preventing tube, the protective member and the optical fiber core are covered. Since the occurrence of sharp bending at the boundary with the wire can be prevented, the reliability as a connection portion is further improved.

[0010] Further, a protective member in which a core wire bending preventing tube is fixed in advance at one end of the protective member is prepared, and the protective member is covered with the plastic protective tube and a partial coating of the optical fiber core, and further protected. If the other end of the member and a part of the coating of the optical fiber core are covered with a core bending prevention tube of the same type as the core bending tube, the work involved in reinforcing the connection portion can be performed. It can be simplified.

Also, a method of using a plastic tube having a hole on its surface and transmitting ultraviolet light, injecting an ultraviolet curable adhesive resin through the hole, and irradiating ultraviolet light from outside the plastic tube to cure the resin. Accordingly, it is useful to provide a plastic protective layer because the plastic protective layer can be formed relatively easily and the reliability is high.

[0012]

FIG. 1 is a longitudinal sectional view showing an embodiment of an optical fiber connecting portion according to the present invention. In producing the optical fiber connection part of the present invention, first, a core fiber connection part is produced by the same method as the conventional technique shown in FIG. That is, the coating of the ends of the two optical fiber core wires 1 connected to each other is removed to expose the glass fiber 1a, and the end of the glass fiber is mirror-cut with a cutter, and the end surfaces of the two glass fibers 1a are cut. While facing each other,
Between the glass fiber 1 and the
The tip of a is melted and connected.

Subsequently, as shown in FIG. 1, the exposed portion of the glass fiber 1a is covered with at least one or more plastic protective layers. In FIG. 1, the plastic protective layer is indicated by an inner layer 2 and an outer layer 3. The plastic protective layer may be constituted by forming the inner layer 2 as a layer of a hot-melt adhesive, the outer layer 3 as a heat-shrinkable tube, or the inner layer 2 as an ultraviolet-curable adhesive resin, and the outer layer 3 as a plastic capable of transmitting ultraviolet light. Desirably a tube layer.

In the former case, an adhesive tube made of a hot-melt adhesive is covered and heated to be melted and solidified, and then a heat-shrinkable tube is covered and heated to thermally shrink. By dividing the heating into two stages, it is possible to prevent the contraction force of the heat-shrinkable tube from being directly transmitted to the glass fiber.

In the latter case, as shown in FIG. 4, an outer ultraviolet-permeable plastic tube layer 3a is provided with a hole 13 in a partial cross section of the plastic tube layer 3a. The resin 2a is injected, and ultraviolet rays are irradiated from the outside of the plastic tube layer 3a capable of transmitting ultraviolet rays, thereby curing the ultraviolet curable adhesive resin 2a in the inner layer.

Then, as shown in FIG. 1, a protective member 4 wound around a steel wire and formed into a coil is fixed on the plastic protective layers 2 and 3 as a protective member having a plurality of gaps in the longitudinal direction. I do.

Further, the wire diameter, the coil length, and the number of windings are adjusted so that the coil-shaped protection member does not bend below a certain bending radius. For example, using a steel wire having a wire diameter of 0.5 mm, the coil length is 30 mm, the coil inner diameter is 2 mm, and the number of turns is 58.
When the coil is made straight, the gap between the windings of the coil is 1 mm in total when the coil is straight, and when the coil is bent at a bending radius of 30 mm, the gap between the windings of the coil is just inside the bend. Since it becomes zero, the coil has a bending radius of 30 m
m or less, it cannot be bent smoothly and the bending radius is 30m
m. Further, the steel wire is not limited to a wire having a round cross section, and may be a wire having a square cross section.

If both ends of the protective member 4 and a part of the coating of the optical fiber core 1 are fixed with a rubber or plastic core bending preventing tube 5, the protective member 4 and the optical fiber core 1 can be fixed. The optical fiber core wire at the boundary can be prevented from being sharply bent. Also,
The optical fiber bending tube has a cylindrical portion having an inner diameter corresponding to the outer diameter of the coated optical fiber on the optical fiber core side, and a cylindrical member having an inner diameter corresponding to the outer diameter of the protective member on the protective member side. The intermediate portion is formed in a tapered shape, and also has a function of fixing the protection member on the connection portion.

It should be noted that the plastic protective layer 3 is
If the protective member 4 is fixed on the plastic protective layer 3 with an adhesive or the like, the protective member 4 and the optical fiber core 1 can be connected to each other without the core wire bending preventing tube. It is possible to suppress extreme bending at the boundary.

FIGS. 2A and 2B are perspective views showing another embodiment of the protective member used for the optical fiber connecting portion of the present invention. The protection member shown in FIG. 2A is a metal or hard plastic slit tube 7 in which slits 7a extending in the circumferential direction of the cross section are provided at regular intervals in the longitudinal direction. The slit 7a has a length of about 1/4 circumference and a width of 0.1.
mm, and about 10 places are provided at intervals of about 1 to 3 mm. In order to make the slit tube 7 easily bendable in any direction, the position of the slit 7a in the cross section circumferential direction is 1/4.
It is desirable to provide it by making it around the circumference. In addition, it is also possible to arrange three or more slits in the circumferential direction by reducing the length of the slits, and to arrange them at regular intervals in the longitudinal direction.

In the tube 7 with a slit constructed as described above, when it is bent in the longitudinal direction, the interval between the slits inside the bend becomes narrow, and there is a constant bending radius at which the interval becomes zero. Therefore, if such a tube with a slit 7 is used as a protective member for the optical fiber connecting portion, the bending of the optical fiber connecting portion is suppressed so as not to be less than a certain bending radius. Can be prevented from being adversely affected by bending.

FIG. 2B shows a hard plastic 8a.
And a soft plastic member 8b. In the case of this protective member, bending causes the soft plastic 8b to expand outside the bend, contracts the soft plastic 8b inside the bend, and expands the hard plastic portion 8a without shrinking, so that the bending radius is constant. It can be suppressed that it becomes less than the value.

FIG. 3 shows an example of a member in which a core wire bending preventing tube is fixed to one side of a protective member in advance. In FIG. 3, reference numeral 4 denotes a protective member formed by winding a steel wire into a coil shape.
Are fixed in advance by an adhesive 5a or the like, and one member 6
It has become. The use of such a member 6 simplifies the work of attaching the protective member and the core wire bending preventing tube on the plastic protective layer 3. The fixing of the core wire bending preventing tube 5b to the other end of the protective member 4 is performed after the member 6 is mounted on the plastic protective layer 3.

[0024]

The optical fiber connecting portion of the present invention is provided so as to cover the core portion where the end faces of the glass fiber are butted and fusion-spliced, and the exposed portion of the glass fiber of the core portion. A plastic protective layer of at least one layer, and a protective member provided on the plastic protective layer, the bending radius of which is suppressed to be less than a certain value. Since something that can withstand a small bending radius compared to the optical fiber connection part can be made,
The accommodation location of the optical fiber connection can be reduced.

Further, the protective member may be a coiled member wound with a metal wire, or may be a tube with a slit made of metal or hard plastic provided with slits extending in the circumferential direction at regular intervals in the longitudinal direction. If
Bending of the protection member is suppressed where the line between the coils inside the bending or the slit gap becomes zero by bending,
Since the bending is also suppressed as the optical fiber connection part,
It is possible to prevent the bending radius of the optical fiber connecting portion from becoming smaller than a certain value.

It is to be noted that the plastic protective layer is made of two layers, the inside is made of an adhesive plastic layer such as a hot-melt adhesive, the outside is made of a heat-shrinkable tube, or the inside is made of an ultraviolet-curable adhesive resin, and the outside is made of ultraviolet ray. By using a plastic layer, the optical fiber connection portion can be hermetically protected and can also serve as a cushion for a protection member provided outside the optical fiber connection portion.

Further, if a part of the coating of the optical fiber is covered with the tube for preventing bending of the optical fiber from both ends of the protective member, abrupt bending at the boundary between the protective member and the optical fiber is prevented. Can be prevented.

A method of using a plastic tube having a hole on its surface and transmitting ultraviolet light, injecting an ultraviolet curable adhesive resin through the hole, and irradiating ultraviolet light from outside the plastic tube to cure the resin. Thereby, the method of providing the plastic protective layer and the handling of the adhesive resin are easy, and a highly reliable connection portion can be obtained without adversely affecting the glass fiber during curing.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an optical fiber connection section of the present invention.

FIGS. 2A and 2B are perspective views each showing another embodiment of a protective member used for an optical fiber connecting portion of the present invention.

FIG. 3 is a longitudinal sectional view showing an example in which a core wire bending preventing tube is fixed to a protective member used in the optical fiber connecting portion of the present invention in advance.

FIG. 4 is a longitudinal sectional view illustrating another embodiment of the plastic protective layer used in the optical fiber connecting portion of the present invention.

FIG. 5 is a front view showing a state where optical fibers are connected.

FIG. 6 is a longitudinal sectional view and a side view of a member for protecting a connecting portion in the prior art.

[Explanation of symbols]

 1: Optical fiber core wire 1a: Glass fiber 2, 3: Plastic protective layer 2a: UV-curable adhesive resin 3a: UV-permeable plastic tube layer 4: Protective member 5: Core wire bending prevention tube 6: For protective member A member to which a core wire bending prevention tube is fixed 7: Slit tube 7a: Slit 13: Hole

Claims (8)

[Claims] 1. A core portion formed by performing fusion splicing by abutting end faces of glass fibers exposed by removing coatings of terminal portions of two optical fiber core wires connected to each other, and
It comprises at least one plastic protective layer provided so as to cover the exposed portion of the glass fiber in the core portion, and a protective member provided on the plastic protective layer, wherein the protective member has a bending radius of a predetermined value or less. An optical fiber connection part characterized in that the optical fiber connection part is suppressed. 2. The optical fiber connection according to claim 1, wherein the protection member is formed of a coil-shaped member wound with a metal wire. 3. The optical fiber according to claim 1, wherein the protective member is formed of a metal or hard plastic slit tube provided with slits extending in a circumferential direction at regular intervals in a longitudinal direction. Connection. 4. The optical fiber connection according to claim 1, wherein the plastic protective layer is two layers, the inner layer is an adhesive plastic, and the outer layer is a heat-shrinkable tube. 5. The optical fiber according to claim 1, wherein the plastic protective layer is two layers, the inner layer is a UV-curable adhesive resin layer, and the outer layer is a UV-permeable plastic tube layer. Connection. 6. At both ends of the protective member, the end of the protective member and a part of the coating of the optical fiber core are covered with a rubber core or plastic bend preventing tube. The optical fiber connection according to claim 1. 7. The glass fiber is exposed by removing the coating of the terminal portions of two optical fiber core wires connected to each other,
A fusion splicing is performed by abutting the two end faces of the glass fiber, and one or more plastic protective layers are applied so as to cover the exposed glass fiber and a part of the coating of the optical fiber core. Using a protective member for suppressing a bending radius fixed to one end of a core wire bending prevention tube made of rubber or plastic having a cylindrical portion having an inner diameter corresponding to the outer diameter of the coating to prevent the bending radius from becoming a certain value or less. A core of the same type as the core bending prevention tube is placed on the protective tube and a part of the optical fiber core, and further on the other end of the protective member and the part of the optical fiber core. An optical fiber connection method comprising covering with a wire bending prevention tube. 8. The glass fiber is exposed by removing the coating on the terminal portions of two optical fiber core wires connected to each other,
A fusion splicing is performed by abutting two end faces of the glass fiber, and an ultraviolet-permeable plastic tube layer having a hole in a part of the surface thereof so as to cover a part of the coating of the exposed glass fiber and the optical fiber core is provided. UV-curable adhesive resin is injected from the hole, and the UV-curable adhesive resin is cured by irradiating ultraviolet rays from outside of the ultraviolet-permeable plastic tube layer. An optical fiber connection method, comprising: providing a layer of a protective member that suppresses the occurrence of the optical fiber.