JPH09230159A - Tube structure for connecting optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to surely hold the connecting parts of first and second optical fibers even if the outside diameters of protective films vary from each other by forming the difference in the sizes between the outside diameters of the respective protective film parts of these optical fibers and the bore of the inner peripheral surface part of a tube to an equal difference. SOLUTION: The inside tube 3 is formed by a rigid synthetic resin which is shrunk by applying heat thereon from the outside. The small-diameter part 3c of the bore R3 slightly larger than the outside diameter R of the protective film 13 of the coated optical fiber 10 is formed in the inner peripheral surface part near the end 3a. A large-diameter part 3d is formed in the inner peripheral surface part near the other end 3b at the bore R7=R5+(R3-R1) obtd. by adding the size R3-R1 subtracting the outside diameter R1 of the protective film 13 from the bore R3 to the outside diameter of the protective film 23 of the coated optical fiber 20. As a result, the timing at which the inner peripheral surface part of the thermally shrunk inside tube 3 comes into tight contact with the protective films 13, 23 of the coated optical fibers 10, 20 is approximately aligned and the sure holding of both optical fibers 10, 20 is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a tube for protecting the connecting portions of optical fiber core wires whose protective coatings for protecting the core fibers have different diameters although the outer diameters of the core fibers are the same. Is.

[0002]

2. Description of the Related Art As shown in a sectional view of FIG. 4, in general, an optical fiber core wire 20 includes a bare optical fiber 21 made of glass or plastic, which is composed of a core and a clad around the core, and a protective coating 23 made of a soft synthetic resin. When connecting the optical fiber core wires 20 having such a configuration, the sleeves are attached to the connection parts in a state where the end portions of the optical fiber core wires 20 are in contact with each other. Install.

FIG. 5 is a cross-sectional view showing a schematic structure of a sleeve that has been generally used in the past.
The conventional sleeve indicated by 0 has a double tube 31
33, and a metal-made reinforcing mandrel 35 inserted between the tubes 31 and 33.

The inner tube 31 has a cylindrical shape having an inner diameter slightly larger than the outer diameters of the protective coatings 23 of the two optical fiber core wires 20 to be connected, and is made of a hard synthetic material which contracts when heat is applied from the outside. It is made of resin. The outer tube 33 has a cylindrical shape with an inner diameter larger than the outer diameter of the inner tube 31, and, like the inner tube 31, is made of a hard synthetic resin that contracts when heat is applied from the outside. A caulking portion 33a, which is caulked and reduced in diameter from the outside to the inside, is formed in a substantially central portion in the longitudinal direction of the outer tube 33. The mandrel 35 is formed with a diameter that is clamped between the inner peripheral surface of the outer tube 33 and the outer peripheral surface of the inner tube 31 at the crimped portion 33a.

When the two optical fiber core wires 20 are connected by the sleeve 30 constructed as described above, first,
One of the optical fiber core wires 20 is passed through the sleeve 30, and at the end portion of the optical fiber core wire 20, the protective coating 23 is formed so that the bare optical fiber 21 is exposed with a dimension shorter than half the dimension of the sleeve 30 in the longitudinal direction. And a protective coating 23 on the end of the other optical fiber core 20 so that the bare optical fiber 21 is exposed with the same size.
In the same manner, the connection pretreatment for removing is performed to bring the end surfaces 21a of the two bare optical fibers 21 into contact with each other. Next, both of the bare optical fibers 21 having the end faces 21a brought into contact with each other are heat-welded, the sleeve 30 is displaced, and as shown in FIG.
The connection portion of the heat-welded naked optical fiber 21 is covered. Then, the entire sleeve 30 is uniformly heated from the outside,
The outer tube 33 is contracted by heat, and the inner tube 31 is contracted by heat applied to the entire sleeve 30 and heat transferred from the outer tube 33 through the mandrel 35.

Then, as shown in FIG. 7, the heat-shrinkable inner tubes 31 are brought into close contact with the end portions of the respective optical fiber core wires 20 so that the inner tubes 31 of both the optical fiber core wires 20, 20. The heat-shrinkable outer tube 33 presses the mandrel 35 against the inner tube 31 while protecting the connection portion, and the outer tube 33 portion without the mandrel 35 adheres to the inner tube 31.

Therefore, the inner tube 3 after the heat shrinkage, in which the two optical fiber core wires 20 and 20 are closely adhered to their ends, respectively.
The optical fibers 1 and 2 are held so as not to be pulled out by 1 and heat-shrinked inside and outside the tubes 31 and 33.
The connection part of 0 and 20 is protected, and the inner tube 31
By the mandrel 35 pressed against the two optical fiber core wires 2
The 0, 20 connection is reinforced. In addition, the heat-shrinkable inner tube 31 forms the bare optical fiber 2 of each optical fiber core wire 20.
1 and the protective coating 23 are in close contact with each other, the strength of each optical fiber core 20 portion of the bare optical fiber 21 and the protective coating 23 is equal to the thickness of the inner tube 31 in close contact therewith and structurally integrated. Only, both optical fiber cores 2
The 0, 20 connection is further reinforced.

By the way, the connection of the optical fiber core wires 20 using the above-mentioned sleeve 30 has generally been conventionally performed between the optical fiber core wires 20 having the same outer diameter, but in recent years, the number of the arranged optical fiber core wires 20 becomes closer to the end. In view of the fact that the installation space becomes narrower despite the increase in the number of wires, the outer diameter of the core wire is the same as that on the main wire side, but an optical fiber whose outer diameter of the protective coating is smaller than that on the main wire side There have been cases where it is required to connect two optical fibers having different outer diameters of coatings.

FIG. 8 is an explanatory view showing a case where two optical fibers having different outer diameters of the above-mentioned protective coating are connected by the sleeve of FIG. The optical fiber core wire indicated by reference numeral 10 in FIG. 8 is the optical fiber core wire 2 shown in FIG.
As in the case of 0, a bare optical fiber 11 made of glass or plastic consisting of a core and a clad around the core is covered with a protective coating 13 made of a soft synthetic resin, and the bare optical fiber 11 is an optical fiber. The protective coating 13 is formed to have the same diameter as the bare optical fiber 21 of the fiber core wire 20.
Is thinner than the protective coating 23 of the optical fiber 20 and has an outer diameter smaller than that of the protective coating 23.

The optical fiber core wire 10 thus configured
By the sleeve 30 described above.
When connecting with 0, the optical fiber core wire 2 described above
Perform the same work as when connecting 0 and 20. That is, at the ends of the optical fiber cores 10 and 20, the protective coatings 13 and 23 are removed by a dimension shorter than half the dimension of the sleeve 30 in the longitudinal direction to expose the bare optical fibers 11 and 21, respectively. Both optical fiber core wires 10 and 20
End portions of the inner tubes 31 are inserted into the inner tubes 31 from both ends, and the end surfaces 11a and 2 of the bare optical fibers 11 and 21 are inserted.
The inner tubes 31 are brought into contact with each other. And
The entire sleeve 30 is uniformly heated from the outside to shrink the inner and outer tubes 31 and 33, respectively.

[0011]

However, if the two optical fiber core wires 10 and 20 are connected by using the inner tube 31 of the conventional sleeve 30, the following problems will occur. That is, while the inner tube 31 is formed with the same inner diameter over the entire length in the longitudinal direction of the sleeve 30, the optical fiber core wire 1 inside the inner tube 31 is formed.
In Nos. 0 and 20, the outer diameter of the protective coating 13 is smaller than the outer diameter of the protective coating 23. Therefore, the portion of the inner tube 31 in which the optical fiber core wire 10 is inserted is protected by the protective coating 13
If the inner tube 31 does not shrink sufficiently to the inner diameter corresponding to the outer diameter of the inner tube 31, the inner tube 31 comes in close contact with the protective coating 23 to pull out the optical fiber core wire 20 and force it to hold the optical fiber core 20 in an unbreakable manner. , The inner tube 31 adheres to the protective coating 13 to pull out the optical fiber core wire 10, and the force for holding the optical fiber core 10 in an unbreakable manner is poor,
The first inconvenience occurs that the inner tube 31 may not be able to reliably hold the optical fiber core wire 10.

If the heat-shrinkable inner tube 31 is not sufficiently adhered to the protective film 13 and held, the optical fiber core wire 10 wobbles inside the inner tube 31.
1 is contacted with the inner peripheral surface of the inner tube 31 and a relative bending force is applied from the inner peripheral surface of the inner tube 31 to the bare optical fiber 11, resulting in damage to the bare optical fiber 11 or thermal welding of the bare optical fibers 11 and 21. A second inconvenience occurs that the connection part may be damaged. Further, if the heat-shrinkable inner tube 31 does not sufficiently adhere to the protective coating 13, the strength of the optical fiber core wire 10 in the protective coating 13 portion is increased by the thickness of the inner tube 31, and the protective coating 13 portion is protected. A third problem occurs that the optical fiber core wire 10 cannot be reinforced.

Further, since the inner tube 31 is formed with the same inner diameter and outer diameter, that is, the same wall thickness over its entire length, the inner tube 31 shrinks due to heating from the outside of the sleeve 30. Moves from both end portions in the longitudinal direction, which are heated not only on the outer peripheral surface but also on the end surface, toward the intermediate portion. Therefore, due to the heat shrinkage of the inner tube 31 starting from both ends, the inner tube 31 starts to adhere to the protective coating 23 having a large outer diameter first, and the inner tube 31 adheres to the protective coating 13 having an outer diameter smaller than the protective coating 23. To start
It will be a little later than that. Therefore, when the inner tube 31 is in close contact with the end face 21a from the bare optical fiber 21 near the protective coating 23 of the optical fiber core wire 20, the inner tube 31 is a protective coating 1 for the optical fiber core wire 10.
The bare optical fiber 11 located closer to 3 moves ahead of the end face 11a in close contact with the bare optical fiber 11, and thereby the bare bare coating film 13 closer to the protective coating 13 than the place where the end faces 11a and 21a of the bare optical fibers 11 and 21 abut. As shown in the enlarged cross-sectional view of FIG. 10, an inner tube 31 facing the optical fiber 11 has a raised portion 31a which is substantially chevron-shaped in plan view and is not heat-contracted.

At the raised portion 31a of the inner tube 31, as shown by arrows A and B in FIG.
The reaction forces of the two thermal contraction forces that try to reduce the diameter of 1 collide with each other, but these two reaction forces A and B are approximately proportional to the dimension of the inner tube 31 with the raised portion 31a as a boundary. Therefore, the sizes are not equal, and the optical fiber core wire 20
The reaction force B on the side exceeds the reaction force A on the optical fiber core 10 side.
Therefore, even if the inner tube 31 is sufficiently heated, the raised portion 3 of the bare optical fiber 11 near the protective film 13 described above.
1a is not solved, and the bare optical fiber 1 of the optical fiber core wire 10
The inner tube 31 does not adhere sufficiently to 1 as in the case of connecting the two optical fiber core wires 20.

Therefore, the raised portion 31 of the inner tube 31
Air remains between the a and the bare optical fiber 11 of the optical fiber core wire 10 and is hermetically sealed.
The strength of the optical fiber core wires 10 and 20 of the part is set to the inner tube 3
These bare optical fibers 1 are increased by the thickness of 1
The fourth inconvenience occurs that the optical fiber core wires 10 and 20 in the portions 1 and 21 cannot be reinforced.

The raised portion 3 of the inner tube 31 described above
1a can be similarly applied when connecting two optical fiber core wires 20. However, the outer diameters of the protective coatings 23 of the respective optical fiber core wires 20 are equal, and the adhesion of the inner tubes 31 from the both ends of the inner tube 31 toward the central portion to the respective optical fiber core wires 20 progress at substantially the same time, Since the raised portion is formed at the substantially central portion of the inner tube 31, the reaction forces of the heat shrinkage forces of both sides become equal to each other, so that the reaction forces of both sides cancel each other out, and finally, the raised portion also. The heat shrinks and adheres to the bare optical fiber 21 of the optical fiber core wire 20. Therefore, when the optical fibers having the same outer diameter of the protective film are connected to each other, the above-mentioned fourth problem does not occur.

The present invention has been made in view of the above circumstances.
A first object of the present invention is to solve the above-mentioned first to third problems, and as long as optical fiber core wires having the same outer diameter of bare optical fibers are used, even if the outer diameters of the protective coatings are different from each other. , The connection parts of both optical fiber cores can be held securely, and further, the bare optical fiber part of the connection parts from which the protective film has been removed is reliably prevented from being damaged by external force, and is covered with the protective film. Another object of the present invention is to provide an optical fiber connecting tube structure capable of reliably improving the strength of the connecting portion of the optical fiber core wire.

A second object of the present invention is to solve the above-mentioned fourth problem in addition to the above-mentioned first to third problems, and to connect optical fiber core wires having the same outer diameter of a bare optical fiber. If so, even if the outer diameter of the protective coating is different from each other,
An object of the present invention is to provide a tube structure for connecting optical fibers, which can surely improve the strength of a bare optical fiber portion where the protective coating is removed from the connecting portions of both optical fiber cores.

[0019]

In order to achieve the first object, the present invention according to claim 1 provides a bare optical fiber of a first optical fiber core wire from which a protective coating on the end is removed, and The first and second optical fiber cores are used for connecting to a bare optical fiber of a second optical fiber core wire having a protective coating having a thickness different from that of the first optical fiber core wire removed at an end thereof. A structure of a tube having a heat-shrinkable tubular shape for covering and protecting a connecting portion of a wire, the outer diameter of a protective coating portion near an end of the first optical fiber core wire, and the first optical fiber. The dimensional difference from the inner diameter of the first inner peripheral surface portion of the tube facing the protective coating portion near the end of the optical fiber is the outer diameter of the protective coating portion near the end of the second optical fiber optical fiber, Of the second inner peripheral surface portion of the tube facing the protective coating portion near the end of the second optical fiber core Characterized by being formed equal to dimensional difference between the diameter.

The present invention according to claim 2 is characterized in that a third inner peripheral surface portion located on the inner peripheral surface of the tube between the first inner peripheral surface portion and the second inner peripheral surface portion, It is formed with a dimension that changes from the inner diameter of the first inner peripheral surface portion to the inner diameter of the second inner peripheral surface portion from the first inner peripheral surface portion side to the second inner peripheral surface portion side. I decided.

Further, in order to achieve the second object, the present invention according to claim 3 forms the tube with the same outer diameter over the entire length of the tube.

According to the first aspect of the present invention, the distance between the protective coating portion near the end of the first optical fiber core wire and the first inner peripheral surface portion of the tube is the second optical fiber core wire. Of the first inner peripheral surface portion of the tube which has been heat-shrinked, so that the first inner peripheral surface portion of the heat-shrinkable tube matches the distance between the protective coating portion near the end of the tube and the second inner peripheral surface portion of the tube. And the timing at which the second inner peripheral surface portion of the heat-shrinkable tube comes into close contact with the protective coating portion of the second optical fiber core. Therefore, the first and second inner peripheral surface portions of the tube are surely brought into close contact with the protective coating portions of the corresponding first and second optical fiber core wires,
It is possible to surely hold the first and second optical fiber core wires.

Further, according to the present invention as set forth in claim 1, the first and second inner peripheral surface portions of the tube respectively correspond to the corresponding first
And the second optical fiber core wires are surely brought into close contact with the protective coating portions of the respective optical fiber core wires, and the first and second optical fiber core wires are reliably held, respectively. Each optical fiber core wire does not wobble,
Therefore, the bare optical fiber portion from which the protective coating of the first and second optical fiber core wires is removed is the third inner peripheral surface portion due to the wobbling of the first and second optical fiber core wires in the tube. It is possible to reliably prevent the bare optical fiber portion of each of the first and second optical fiber core wires from being damaged by contact with the third inner peripheral surface portion and receiving a relative bending force from the third inner peripheral surface portion. Become.

Further, according to the invention of claim 1,
The first and second inner peripheral surface portions of the tube surely come into close contact with the protective coating portions of the corresponding first and second optical fiber core wires, respectively, so that the first and second optical fibers The protective coating portion of the core wire and the corresponding first and second inner peripheral surface portions are structurally integrated, respectively, and
The strength of the protective coating portion of each of the first and second optical fiber core wires is increased by the thickness of the first and second inner peripheral surface portions to protect the first and second optical fiber core wires. The coated portion can be reliably reinforced by the tube.

Moreover, by applying the present invention according to claim 3 to the present invention according to claim 1, there is a difference in thickness between the first and second inner peripheral surface portions of the tube. The difference in thickness causes a difference in heat shrinkage. Therefore, the first
If the outer diameter of the protective coating portion of the second optical fiber core wire is larger than the outer diameter of the protective coating portion of the optical fiber core wire, the first inner peripheral surface is larger than the thickness of the second inner peripheral surface portion. The thickness of the portion becomes larger, so that the heat shrinkage of the first inner peripheral surface portion proceeds earlier than the heat shrinkage of the second inner peripheral surface portion.
On the contrary, when the outer diameter of the protective coating portion of the first optical fiber core wire is larger than the outer diameter of the protective coating portion of the second optical fiber core wire, it is larger than the thickness of the first inner peripheral surface portion. The thickness of the second inner peripheral surface portion becomes larger, so that the heat contraction of the second inner peripheral surface portion progresses faster than the heat contraction of the first inner peripheral surface portion.

Therefore, before a part of the inner peripheral surface of the tube is brought into close contact with the bare optical fiber portion of each of the first and second optical fiber cores, both the first and second inner peripheral surface parts of the tube are Both of the first and second corresponding optical fiber core wires are closely adhered to each other, and the tube portion and the first and second optical fiber core portions are adhered to each other.
The possibility that air will remain between the respective optical fiber core wires of the optical fiber core wire and the bare optical fiber area to be sealed, and a part of the inner peripheral surface of the tube will be partially exposed to the naked light of the first and second optical fiber core wires. It is possible to easily adhere to the fiber portions, increase the strength of these bare optical fiber portions by the thickness of the portion of the tube, and reinforce the bare optical fiber portions with the tube.

According to the second aspect of the present invention, the first inner peripheral surface portion and the second inner peripheral surface portion are adjacent to each other and a large step is generated at the boundary between the two. The inner diameter difference is equal to the dimensional difference between the outer diameter of the protective coating portion of the first optical fiber core wire and the outer diameter of the protective coating portion of the second optical fiber core wire. Both the first and second inner peripheral surface portions can be easily formed on the inner peripheral surface of a single tube.

Moreover, by applying the present invention according to claim 3 to the present invention according to claim 2, there is a difference in thickness between the first to third inner peripheral surface portions of the tube. The difference in thickness causes a difference in heat shrinkage. Therefore, the first
If the outer diameter of the protective coating portion of the second optical fiber core wire is larger than the outer diameter of the protective coating portion of the optical fiber core wire, the third inner peripheral surface is larger than the thickness of the second inner peripheral surface portion. The thickness of the portion is larger, and the thickness of the first inner peripheral surface portion is larger than the thickness of the third inner peripheral surface portion, so that the thickness of the second inner peripheral surface portion is smaller than that of the second inner peripheral surface portion. The heat shrinkage of the third inner peripheral surface portion progresses faster, and the heat shrinkage of the first inner peripheral surface portion progresses faster than the heat shrinkage of the third inner peripheral surface portion.

On the contrary, when the outer diameter of the protective coating portion of the first optical fiber core wire is larger than the outer diameter of the protective coating portion of the second optical fiber core wire, the first inner peripheral surface portion The thickness of the third inner peripheral surface portion is larger than the thickness, and
The thickness of the second inner peripheral surface portion becomes larger than the thickness of the inner peripheral surface portion, so that the heat contraction of the third inner peripheral surface portion is faster than that of the first inner peripheral surface portion. The heat shrinkage of the second inner peripheral surface portion progresses faster than the heat shrinkage of the third inner peripheral surface portion.

For this reason, the heat shrinkage of the tube progresses from the first and second inner peripheral surface portions toward the third inner peripheral surface portion, respectively, and two heat contracting forces that merge at the third inner peripheral surface portion. It is possible to prevent the occurrence of a situation in which the portion that cannot be heat-shrinked by the reaction force remains, and the third inner peripheral surface portion cannot be sufficiently adhered to the bare optical fiber portions of the first and second optical fiber cores, and thus, Air remains between the third inner peripheral surface portion and the bare optical fiber portions of the first and second optical fiber cores so as not to be sealed, and the strength of these bare optical fiber portions is adjusted to the third inner peripheral surface. It is possible to increase the thickness of the portion and reinforce the bare optical fiber portion with a tube.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION An optical fiber connecting tube structure according to an embodiment of the present invention will be described below with reference to the drawings.

First, the tube structure according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory diagram showing a case where two optical fibers having different outer diameters of protective coatings are connected using an optical fiber connecting sleeve adopting a tube structure according to the first embodiment of the present invention.
The same members and parts as those shown in FIG. 8 will be described with the same reference numerals as those shown in FIG.

The sleeve of the first embodiment shown by reference numeral 1 in FIG. 1 is the two optical fiber core wires 1 shown in FIG.
0 and 20, which are used to connect the outer tube 33 and the mandrel 35 having the crimped portion 33a, which is similar to the conventional sleeve 30 shown in FIG. 5, and the inner tube 3 different from the conventional sleeve 30. Is equipped with.

The inner tube 3 (corresponding to a tube) is
A hard synthetic resin that shrinks when heat is applied from the outside is formed into a substantially cylindrical shape having the same outer diameter over the entire length of the sleeve 1 in the longitudinal direction, and the optical fiber extends from one end 3a of the inner tube 3 to the inside. The end portion of the core wire 10 (corresponding to the first optical fiber core wire) is inserted, and the end portion of the optical fiber core wire 20 (corresponding to the first optical fiber core wire) is inserted inside from the other end 3b. .

A small diameter portion 3c (first inner peripheral surface portion) having an inner diameter R3 slightly larger than the outer diameter R1 of the protective coating 13 of the optical fiber core wire 10 is provided on the inner peripheral surface portion near the one end 3a of the inner tube 3. Is formed), and the other end 3b of the inner tube 3 is formed.
On the inner peripheral surface portion closer to the outside, a dimension R3-R1 obtained by subtracting the outer diameter R1 of the protective coating 13 of the optical fiber core wire 10 from the inner diameter R3 of the small diameter portion 3c is provided outside the protective coating 23 of the optical fiber core wire 20. Dimension R5 + (R3-R added to diameter R5
1) That is, the inner diameter R that is larger than the inner diameter R3 of the small diameter portion 3c
The large diameter portion 3d (corresponding to the second inner peripheral surface portion) is formed by 7 = R5 + (R3-R1). In the present embodiment, the length of the small diameter portion 3c in the longitudinal direction (axial direction) of the inner tube 3 is the inner tube 3 in the longitudinal direction.
Of the large diameter portion 3d in the longitudinal direction is smaller than half the total length of the small diameter portion 3c.
Is formed with the same dimensions as the length of.

Further, in the inner peripheral surface portion of the inner peripheral surface of the inner tube 3 between the small diameter portion 3c and the large diameter portion 3d, the diameter decreases from the one end 3a side to the other end 3b side of the inner tube 3. A tapered relay portion 3e is formed that changes from the inner diameter R3 of the portion 3c to the inner diameter R7 of the large diameter portion 3d so that the inner diameter increases. Therefore, the thickness of the inner tube 3 is larger in the relay portion 3e than in the large diameter portion 3d, and further larger in the small diameter portion 3c than the relay portion 3e.

Incidentally, in this embodiment, the relay portion 3e corresponds to the third inner peripheral surface portion in the claims. Further, in the present embodiment, the small diameter portion 3c is formed in the outer tube 33 at the outer peripheral surface portion of the inner tube 3 near the one end 3a.
A guide protrusion 33b is provided so that it can be easily recognized which end of the guide is located.

Next, the operation (action) of the inner tube 3, particularly when the optical fiber core wires 10 and 20 are connected by the sleeve 1 of the first embodiment having the above-described structure, will be described.

First, at the ends of the optical fiber core wires 10 and 20, the relay portion 3 in the longitudinal direction of the sleeve 1 is provided.
The protective coatings 13 and 23 are removed by half the length of the dimension e to expose the bare optical fibers 11 and 21, respectively. Next, connect the optical fiber core wire 10 from the end 3a side to the inner tube 3
Or the optical fiber core wire 20 is inserted into the inner tube 3 from the other end 3b side, and the end surfaces 11a and 21a of the two bare optical fibers 11 and 21 are brought into contact with each other outside the inner tube 3.

Subsequently, the bare optical fibers 11 and 21 having the end faces 11a and 21a brought into contact with each other are heat-welded, the inner tube 3 is displaced, and the end of the optical fiber core wire 10 covered with the protective film 13 is displaced. The portion is positioned over the entire length in the longitudinal direction of the small diameter portion 3c, and the end portion of the optical fiber core wire 20 covered with the protective coating 23 is positioned over the entire length in the longitudinal direction of the large diameter portion 3d. The outer tube 33 is displaced so as to be located outside the inner tube 3, and the mandrel 35 is inserted between the outer tube 33 and the inner tube 3. This allows
Between the protective coating 13 of the optical fiber core wire 10 and the small diameter portion 3c of the inner tube 3, and between the protective coating 23 of the optical fiber core wire 20 and the large diameter portion 3d of the inner tube 3, the inner tube 3 Gaps H1 and H having the same radial dimension of
You can do 3 respectively.

In this state, the entire sleeve 1 is uniformly heated from the outside to shrink the outer tube 33, and the heat applied to the entire sleeve 1 and the heat transmitted from the outer tube 33 through the mandrel 35. The inner tube 3 is shrunk by heat. Then, the thickness of the inner tube 3 becomes larger than that of the large-diameter portion 3.
The relay unit 3e is larger than the relay unit 3d, and the relay unit 3e
Since the small-diameter portion 3c has a larger size than the e, the inner tube 3 undergoes heat contraction from the one end 3a side to the other end 3a.
The small diameter portion 3c, the relay portion 3e, and the large diameter portion 3d proceed in this order toward the side b.

Therefore, due to the heat shrinkage of the inner tube 3, the small-diameter portion 3c adheres to the protective coating 13 of the optical fiber core wire 10, and the relay portion 3e adheres to the bare optical fiber 11 of the optical fiber core wire 10. At the same time, the optical fiber core wire 20 is substantially in close contact with the bare optical fiber 21, and the large diameter portion 3d is in close contact with the protective coating 23 of the optical fiber core wire 20 to be deformed into the state shown in FIG. And this heat-shrinkable inner tube 3
Protects the connecting portion of both optical fiber core wires 10 and 20, and the heat-shrinkable outer tube 33 presses the mandrel 35 against the inner tube 3, and the outer tube 33 without the mandrel 35.
The part comes into close contact with the inner tube 3.

Therefore, the inner tube 3 after the heat shrinkage, in which the both optical fiber core wires 10 and 20 are closely adhered to their ends, respectively.
The optical fiber core wires 10 and 2 are held by the inner and outer tubes 3 and 33 that are heat-shrinkable while being retained by the optical fiber core wires 10 and 2.
0 is protected, and the mandrel 35 pressed against the inner tube 3 causes both optical fiber core wires 10 and 20.
The connection part of is reinforced. In addition, the heat-shrinkable inner tube 3 is the bare optical fiber 11 of each of the optical fiber core wires 10 and 20,
21 and the protective coatings 13 and 23 respectively, the strength of the optical fiber core wires 10 and 20 of the bare optical fibers 11 and 21 and the protective coatings 13 and 23 is closely adhered to them and structurally integrated. The thickness of the inner tube 3 is increased by the thickness of the inner tube 3 to further reinforce the connecting portion between the optical fiber core wires 10 and 20.

Thus, according to the inner tube 3 of the first embodiment, the bare optical fiber 1 is obtained by removing the protective coating 13 at the end.
One end 3 into which the optical fiber core wire 10 exposing 1 is inserted
The small diameter portion 3c formed on the inner peripheral surface portion on the a side and the protective coating 23 having an outer diameter larger than the protective coating 13 of the optical fiber core wire 10 are removed to expose the bare optical fiber 21 at the end. Large diameter portion 3d formed on the inner peripheral surface portion on the other end 3b side into which the fiber core wire 20 is inserted, and a relay portion formed on the inner peripheral surface portion between the small diameter portion 3c and the large diameter portion 3d. 3e, of which the dimensional difference between the inner diameter R3 of the small-diameter portion 3c and the outer diameter R1 of the protective coating 13 of the optical fiber core wire 10 is defined as the inner diameter R7 of the large-diameter portion 3d and the optical fiber core wire 20. The dimension was equal to the dimension difference from the outer diameter R5 of the protective coating 23.

Therefore, even the optical fiber core wire 10 having the protective coating 13 having the outer diameter R1 smaller than the outer diameter R5 of the protective coating 23 is surely held by the inner tube 3 like the optical fiber core wire 20. As a result, it is possible to reliably prevent the optical fiber core wire 10 from wobbling in the small diameter portion 3c of the inner tube 3 and causing the bare optical fiber 11 to come into contact with the small diameter portion 3c and receive a bending force to be damaged. be able to. And the protective coatings 13 and 23 and these protective coatings 13 and 23
The small-diameter portion 3c and the large-diameter portion 3d, which are in close contact with each other, are structurally integrated with the respective inner tube 3 portions, and the protective coating 1
The strength of each of the optical fiber core wires 10 and 20 in the portions 3 and 23 is increased by the thickness of the small-diameter portion 3c and the large-diameter portion 3d, and the optical fiber core wires 10 in the protective coatings 13 and 23 are
20 can be reliably reinforced by the inner tube 3.

Further, according to the sleeve 1 of the first embodiment, the inner diameter R3 of the small diameter portion 3c is increased between the small diameter portion 3c and the large diameter portion 3d from the one end 3a side to the other end 3b side of the inner tube 3. To the inner diameter R7 of the large-diameter portion 3d, a tapered relay portion 3e that changes so as to increase the inner diameter is interposed. Therefore, the relay portion 3e interposed between the small diameter portion 3c and the large diameter portion 3d allows the small diameter portion 3c and the large diameter portion 3d.
Are prevented from being adjacent to each other and a large step is generated at the boundary between them, and the protective coatings 13 and 23 of the optical fiber core wires 10 and 20 are provided.
The small diameter portion 3c and the large diameter portion 3d having an inner diameter difference equal to the dimensional difference R5-R1 between the outer diameters R1 and R5 are easily formed on the inner peripheral surface of the inner tube 3 manufactured using, for example, a mold. can do.

Moreover, according to the sleeve 1 of the first embodiment, the outer diameter of the inner tube 3 is the same over the entire length in the longitudinal direction of the sleeve 1, and the relay portion is larger than the large diameter portion 3d. 3e, and a smaller diameter portion 3 than the relay portion 3e
c has a large thickness, and due to the difference in this thickness,
Bare optical fiber 11, 21 of each optical fiber core wire 10, 20
The contact of the small diameter portion 3c to the protective coating 13 of the optical fiber core wire 10 precedes the contact of the relay portion 3e to the protective film 23 of the optical fiber core wire 20 and the close contact of the large diameter portion 3d to the protective coating 23 of the optical fiber core wire 20. I tried to be late. Therefore, each optical fiber core wire 10,
Air remains between the 20 bare optical fibers 11 and 21 and the relay section 3e to be sealed, whereby the optical fiber core wire 1
The bare optical fibers 11, 21 are prevented from being insufficiently adhered to the 0, 20 bare optical fibers 11, 21 by the relay portion 3e.
And the relay unit 3 that is in close contact with the naked optical fibers 11 and 21.
Structurally integrating the inner tube 3 part of e with the respective optical fiber core wires 10 and 20 of the bare optical fibers 11 and 21 parts.
Increase the strength of each by the thickness of the relay portion 3e,
Each optical fiber core wire 10 of the bare optical fibers 11 and 21,
20 can be reliably reinforced by the inner tube 3.

Next, the tube structure according to the second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view showing the structure of an inner tube according to a second embodiment of the present invention, which is used for an optical fiber connecting sleeve instead of the inner tube of the first embodiment, and is the same as that shown in FIG. 1 in FIG. The same reference numerals as those given in FIG. 1 are attached to the members and places of FIG.

In the inner tube of the second embodiment shown by reference numeral 3A in FIG. 3, the outer diameter is changed according to the change in the inner diameter of the small diameter portion 3c, the relay portion 3e, and the large diameter portion 3d, The small diameter portion 3c, the relay portion 3e, and the large diameter portion 3d.
The inner tube 3A is different from the inner tube 3 of the first embodiment in that the thickness of the inner tube 3A is the same, and the other points are the same as those of the inner tube 3 of the first embodiment. ing.

The inner tube 3A of the second embodiment having such a structure is used in place of the inner tube 3 of the first embodiment, and a sleeve is formed with the outer tube 33 and the mandrel 35, and the optical fiber core is formed by this sleeve. Lines 10 and 2
When 0 is connected, the inner tube 3A has the same thickness over the entire length in the longitudinal direction.
0, the small diameter portion 3c adheres to the protective film 13, the optical fiber core wires 10 and 20 adhere to the relay portion 3e to the bare optical fibers 11 and 21, and the optical fiber core wire 20 largely adheres to the protective film 23. The diameter portions 3d are brought into close contact with each other at substantially the same time. Therefore, also by the inner tube 3A of the second embodiment, air remains between the bare optical fibers 11 and 21 of the respective optical fiber core wires 10 and 20 and the relay section 3e, and the optical fiber core wires are thereby sealed. Adhesion of the relay section 3e to the bare optical fibers 11 and 21 of 10 and 20 does not become insufficient.

The same effect as the inner tube 3 of the first embodiment can be obtained also by the inner tube 3A of the second embodiment having such a configuration.

In the sleeve 1 of the first embodiment, the protrusion 33b provided on the outer peripheral surface of the outer tube 33 may be replaced with a mark by printing, a concave groove, or the like, or may be omitted. The present invention is not limited to the inner tubes 3 and 3A used as the sleeve 1 together with the outer tube 33 and the mandrel 35, but the outer diameters of the bare optical fibers are the same, and the outer diameters of the protective coatings covering the bare optical fibers are different. When connecting two optical fiber core wires with different optical fibers, it is widely applicable to general heat shrinkable tubes that cover and protect the end portions to which both optical fiber core wires are connected. Needless to say.

[0053]

As described above, according to the present invention described in claim 1, the bare optical fiber of the first fiber core wire from which the protective coating on the end is removed, and the first optical fiber core wire Is used to connect the bare optical fiber of the second optical fiber core wire from which the protective coating having a different thickness is removed at the end, and covers the connection portion of both the first and second optical fiber core wires. A tube structure having a heat-shrinkable tubular shape for protection, the outer diameter of a protective coating portion near the end of the first optical fiber core wire, and the end portion of the first optical fiber core wire The dimensional difference from the inner diameter of the first inner peripheral surface portion of the tube facing the protective coating portion, and the outer diameter of the protective coating portion near the end of the second optical fiber core, and the second optical fiber. Dimensional difference from the inner diameter of the second inner peripheral surface portion of the tube facing the protective coating portion near the end of the core wire It was configured to lay formation.

Therefore, the interval between the protective coating portion near the end of the first optical fiber core wire and the first inner peripheral surface portion of the tube is such that the protective coating portion near the end of the second optical fiber core wire. And the second inner peripheral surface portion of the tube are matched with each other, whereby the first inner peripheral surface portion of the heat-shrinked tube is brought into close contact with the protective coating portion of the first optical fiber core, and the heat contraction is performed. The timing at which the second inner peripheral surface portion of the formed tube comes into close contact with the protective coating portion of the second optical fiber core wire substantially coincides. Therefore, the first and second inner peripheral surface portions of the tube are surely brought into close contact with the corresponding protective coating portions of the first and second optical fiber cores, respectively, and the first and second
It is possible to surely hold both the optical fiber core wires.

According to the first aspect of the present invention, the first and second inner peripheral surface portions of the tube have the corresponding first
And the second optical fiber core wires are surely brought into close contact with the protective coating portions of the respective optical fiber core wires, and the first and second optical fiber core wires are reliably held, respectively. Each optical fiber core wire does not wobble,
Therefore, the bare optical fiber portion from which the protective coating of the first and second optical fiber core wires is removed is the third inner peripheral surface portion due to the wobbling of the first and second optical fiber core wires in the tube. It is possible to reliably prevent the bare optical fiber portion of each of the first and second optical fiber cores from being damaged by contact with the third inner peripheral surface portion and receiving a relative bending force from the third inner peripheral surface portion.

Further, according to the invention of claim 1,
The first and second inner peripheral surface portions of the tube surely come into close contact with the protective coating portions of the corresponding first and second optical fiber core wires, respectively, so that the first and second optical fibers The protective coating portion of the core wire and the corresponding first and second inner peripheral surface portions are structurally integrated, respectively, and
The strength of the protective coating portion of each of the first and second optical fiber core wires is increased by the thickness of the first and second inner peripheral surface portions to protect the first and second optical fiber core wires. The coated portion can be reliably reinforced by the tube.

According to the present invention as set forth in claim 2, a third inner peripheral surface located on the inner peripheral surface of the tube between the first inner peripheral surface portion and the second inner peripheral surface portion. A dimension in which the portion changes from the inner diameter of the first inner peripheral surface portion toward the inner diameter of the second inner peripheral surface portion as it goes from the first inner peripheral surface portion side to the second inner peripheral surface portion side. It is configured to be formed by.

Therefore, the first inner peripheral surface portion and the second inner peripheral surface portion are adjacent to each other, and a large step is generated at the boundary between the two.
A third inner peripheral surface portion interposed between these two portions prevents the outer diameter of the protective coating portion of the first optical fiber core and the second
The first and second inner peripheral surface portions having an inner diameter difference equal to the outer diameter of the protective coating portion of the optical fiber core wire can be easily formed on the inner peripheral surface of a single tube. it can.

Further, according to the present invention described in claim 3, the tube is formed to have the same outer diameter over the entire length of the tube. Therefore, when the present invention described in claim 3 is applied to the present invention described in claim 1, there is a difference in thickness between the first and second inner peripheral surface portions of the tube. The difference causes a difference in heat shrinkage. Therefore, when the outer diameter of the protective coating portion of the second optical fiber core wire is larger than the outer diameter of the protective coating portion of the first optical fiber core wire, the heat shrinkage of the first inner peripheral surface portion is larger than that of the first inner peripheral surface portion. Second
Thermal contraction of the inner peripheral surface progresses faster. On the contrary, the second
When the outer diameter of the protective coating portion of the first optical fiber core wire is larger than the outer diameter of the protective coating portion of the optical fiber core wire, the first inner circumference is larger than the heat shrinkage of the second inner peripheral surface portion. The heat shrinkage of the surface portion progresses faster.

Therefore, when the present invention described in claim 3 is applied to the present invention described in claim 1, the tube portion is in close contact with the bare optical fiber portion of each of the first and second optical fiber core wires. Previously, the first and second inner peripheral surface portions of the tube are both closely adhered to the corresponding protective coating portions of the first and second optical fiber cores, and the tube portion and the first and second The possibility of air remaining between the optical fiber cores and the bare optical fiber locations of the respective optical fiber cores is reduced, and the tube portion is closely attached to the bare optical fiber locations of the first and second optical fiber cores. The strength of these bare optical fiber portions can be increased by the thickness of the tube, and the bare optical fiber portions can be reinforced by the tube.

When the present invention described in claim 3 is applied to the present invention described in claim 2, there is a difference in thickness between the first to third inner peripheral surface portions of the tube. The difference in heat shrinkage causes a difference. Therefore, if the outer diameter of the protective coating portion of the second optical fiber core wire is larger than the outer diameter of the protective coating portion of the first optical fiber core wire,
The thickness of the third inner peripheral surface portion is larger than the thickness of the inner peripheral surface portion, and the thickness of the first inner peripheral surface portion is larger than the thickness of the third inner peripheral surface portion. As a result, the heat shrinkage of the third inner circumferential surface portion progresses faster than the heat shrinkage of the second inner circumferential surface portion, and the heat shrinkage of the first inner circumferential surface portion is faster than the heat shrinkage of the third inner circumferential surface portion. Contraction progresses faster.

On the contrary, when the outer diameter of the protective coating portion of the first optical fiber core wire is larger than the outer diameter of the protective coating portion of the second optical fiber core wire, the first inner peripheral surface portion The thickness of the third inner peripheral surface portion is larger than the thickness, and
The thickness of the second inner peripheral surface portion becomes larger than the thickness of the inner peripheral surface portion, so that the heat contraction of the third inner peripheral surface portion is faster than that of the first inner peripheral surface portion. The heat shrinkage of the second inner peripheral surface portion progresses faster than the heat shrinkage of the third inner peripheral surface portion.

Therefore, when the present invention described in claim 3 is applied to the present invention described in claim 2, the first and second inner peripheral surface portions are respectively directed toward the third inner peripheral surface portion. As the heat shrinkage of the tube progresses, a portion that cannot be heat-shrinked remains due to the reaction force of the two heat shrinking forces that merge at the third inner peripheral surface portion, and the third inner peripheral surface portion has the first and second optical fiber core wires. It is possible to prevent the situation in which it is not possible to sufficiently adhere to the bare optical fiber portion of the above, and by doing so, the third inner peripheral surface portion and the first
And the air is not sealed between the second optical fiber core wire and the bare optical fiber portion so that the strength of these bare optical fiber portions is increased by the thickness of the third inner peripheral surface portion, The bare optical fiber location can be reinforced with a tube.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a case where two optical fiber core wires having different outer diameters of protective coatings are connected using an optical fiber connecting sleeve adopting a tube structure according to a first embodiment of the present invention. .

FIG. 2 is an explanatory diagram showing a state where the sleeve of FIG. 1 is heated from the outside.

FIG. 3 is a sectional view showing a structure of an inner tube according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a configuration of a general optical fiber core wire.

FIG. 5 is a sectional view showing a schematic configuration of a conventionally known optical fiber connecting sleeve.

FIG. 6 is an explanatory diagram showing a case where two optical fiber core wires are connected using the sleeve of FIG.

FIG. 7 is an explanatory diagram showing a state where the sleeve shown in FIG. 6 is heated from the outside.

8 is an explanatory diagram showing a case where two optical fiber core wires having different outer diameters of protective coatings are connected using the sleeve of FIG.

9 is an explanatory diagram showing a state in which the sleeve shown in FIG. 8 is heated from the outside.

10 is an explanatory diagram showing an enlarged view of a heat-shrinkable state of the inner tube in the sleeve after heating shown in FIG. 9. FIG.

[Explanation of symbols]

 3,3A Inner tube (tube) 3c Small diameter portion (first inner peripheral surface portion) 3d Large diameter portion (second inner peripheral surface portion) 3e Relay portion (third inner peripheral surface portion) 3f Very small diameter portion (third inner portion) Peripheral surface part) 10 optical fiber core wire (first optical fiber core wire) 11,21 bare optical fiber 13,23 protective coating 20 optical fiber core wire (second optical fiber core wire) R1, R5 protective coating outer diameter R3 small diameter inner diameter (first inner peripheral surface partial inner diameter) R7 large diameter inner diameter (second inner peripheral surface partial inner diameter) R9 bare optical fiber outer diameter (second inner peripheral surface partial inner diameter) R11 extremely small diameter inner diameter (third (Inner diameter of inner peripheral surface)

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[Procedure amendment]

[Submission date] November 5, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bare optical fiber having the same outer diameter, but a protective coating for protecting the bare optical fiber covers a connecting portion between optical fiber core wires having different diameters. It relates to the structure of the tube to be protected.

Claims (3)

[Claims] 1. A bare optical fiber of the first optical fiber core wire from which the protective coating on the end is removed, and a second bare optical fiber having a thickness different from that of the first optical fiber core wire on the end. A tubular heat-shrinkable tube structure used for connecting an optical fiber core wire to a bare optical fiber and covering and protecting the connecting portions of the first and second optical fiber core wires. An outer diameter of a protective coating portion near the end of the first optical fiber core wire and a first inner peripheral surface portion of the tube facing the protective coating portion near the end of the first optical fiber core wire The dimensional difference between the inner diameter and the outer diameter of the protective coating portion near the end portion of the second optical fiber core wire and the first diameter of the tube facing the protective coating portion near the end portion of the second optical fiber core wire 2. An optical fiber connecting cheek, characterized in that the dimensional difference is equal to the inner diameter of the inner peripheral surface portion. Over blanking structure. 2. A third inner peripheral surface portion located between the first inner peripheral surface portion and the second inner peripheral surface portion on the inner peripheral surface of the tube is disposed from the first inner peripheral surface portion side. 2. The optical fiber connecting device according to claim 1, wherein the optical fiber connecting portion is formed with a dimension that changes from the inner diameter of the first inner peripheral surface portion toward the inner diameter of the second inner peripheral surface portion toward the second inner peripheral surface portion side. Tube structure. 3. The tube structure for connecting an optical fiber according to claim 1, wherein the tube has the same outer diameter over the entire length of the tube.