JPH03260607A - fiber optic cable - Google Patents

Abstract

PURPOSE:To provide the optical cable having high strength and flexibility by using metallic tubes for straight parts, providing deflecting tubes near a connector and inserting optical fibers into these tubes. CONSTITUTION:The metallic tubes 35 are used for the extension parts where the strength of the cable is required and the deflecting tubes 2 are provided near the connector for connecting the cable. The optical fibers are inserted therein apart spacings provided between the same. The metallic tubes 33 are formed of copper, aluminum and other materials and seamless tubes, heat treated and welded tubes, etc., are used. Sheets of metals or synthetic resins which are formed into a bellows shape or synthetic resin tubes made of vinyl chloride, etc., or rubber tubes are used for the deflecting tubes 2. The sufficient strength and corrosion resistance are, therefore, obtd. and the flexibility is imparted near the connector.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention provides a cable portion of an optical fiber cable coated with a metal tube near a connector that has flexibility,
The present invention relates to an optical fiber cable that can be easily handled without damaging this portion of the optical fiber.

[Conventional technology] Optical communication cables that have become widely used in recent years are
To improve the strength of optical fiber cables, as well as to make them lighter and smaller in diameter, optical fiber cables are used, which are optical fibers (bare fibers, strands, core wires, coats, cables) wrapped in metal tubes. It is becoming more and more common. For example, optical fiber cables that are extended over the air, under the sea, underground, etc. need to be smaller in diameter and lighter in consideration of ease of construction.
In addition, in consideration of environmental resistance, it is necessary to improve mechanical strength and corrosion resistance. Mechanical strength that cannot be cut is required to protect against bites from rats and other animals, and improved weather resistance is required to prevent the coating from dissolving due to oil mist and deteriorating due to sunlight. There is. To solve these problems, cables containing optical fibers inside metal tubes have been used.

On the other hand, flexibility is required near the connector at the end of the cable. For this reason, if you try to reduce the cross-sectional area of the metal part of the metal tube or use a softer material in order to achieve the same flexibility as a general polymer coated optical fiber cable, the resulting mechanical efficiency will be reduced. For example, from the standpoint of flexibility, it is necessary for the metal tube (505304) to have an outer diameter of 0.8 mm or less and a wall thickness of 0.06 mm or less. Fatigue failure can easily occur due to bending caused by stress or repeated bending stress. That is, it has not been possible to provide an appropriate optical fiber cable that meets the needs of having sufficient mechanical strength in the intermediate portion other than the vicinity of the connector and flexibility in the vicinity of the connector.

When installing optical fiber cables in an optical fiber communication path of a certain length (for example, between connectors), consider the environment of the installation site and handling issues, and use optical fiber cables with different mechanical properties. Securing the communication path by preparing the cables in advance and connecting them (using fusion welding or connectors). In other words, the flexible optical fiber cable is prepared separately at the end of the optical fiber cable covered with a metal tube. By connecting these, it is also possible to obtain an optical fiber cable that meets the above needs.

However, this requires more optical fiber connections than necessary, increases transmission loss due to the connections, and requires careful connection of the optical fibers themselves, which is undesirable.

[Problem to be solved by the invention] While retaining the advantages of high strength, light weight, and small diameter of optical fiber cables coated with metal tubes, it is desired to have optical fiber cables that have flexibility near connectors. . This is precisely the problem that the present invention attempts to solve. The present inventors investigated numerous cable installation situations and obtained the following knowledge. In other words, in most cases, the locations where mechanical strength is required and the locations where flexibility is required in a single cable route are different, and in actual line extension work (overheads, pipes, etc.) It was found that a wire drawing tension of . For example, locations where mechanical strength is required include overhead installation locations. In order to install cables between overhead spans without slack, the necessary tension is calculated by taking into account the cable's own weight, span distance, wind and snow loads, and allowable slack, but generally it is several tens of kg.
A tension of f is required. On the other hand, the location where flexibility is required is the location near the connector. Connector installation for various optical-related devices is preset, and flexibility is required to set the optical cable side accordingly. Also, these places are
There are many opportunities to connect and disconnect connectors during various inspections and repairs.
Flexibility is required for this purpose. Furthermore, in the wire extension work, a wire tension is required to extend the optical cable along the installation path. The necessary wire tension varies depending on the method of laying, the condition of the laying route, the cable's own weight, the coefficient of friction between the cable and the laying route, the length of laying, etc., but it is generally a tens of kgf. Based on these findings,
Optical cables that can withstand the tension during cable extension, maintain high strength in locations that require mechanical strength after installation, and have sufficient flexibility in locations that require flexibility are the most effective optical cables for communications. I found this to be the most important and useful hint for practical purposes.

The present invention provides an optical fiber cable that has the advantages of high strength, light weight, and small diameter, which are the characteristics of optical fiber cables covered with metal tubes, and also has flexibility in the vicinity of the connector. With the goal.

[Means for Solving the Problems] The optical fiber cable of the present invention is connected to a metal tube having an extension length that requires at least strength, and to an end or both ends of the metal tube, and the cable is connected at least during cable connection work. The optical fiber is inserted into the metal tube and the flexible tube with a gap between them.

Further, the optical fiber cable of the present invention has one of the flexible tubes.
The pitch block has a large diameter portion having a first annular end protruding inwardly at one end, and a second annular end protruding outwardly at one end.
and a small diameter part connected to the large diameter part via an annular connecting part, and the second annular end is located within the large diameter part of an adjacent block and is substantially connected to the first annular end. It is formed of a single band-shaped plate such that adjacent blocks are movable in the tube axis direction and connected in a spiral manner.

The metal tube is made of steel, aluminum or other desired material, and may be a seamless tube or a heat-treated welded tube, such as a TIG welded tube, a high frequency welded tube, a forge welded tube, or the like, which may be expanded depending on the case. The outer diameter and wall thickness of the metal tube are determined by taking into account the breakage during tube drawing, the outer diameter, strength, and elongation of the final product, the optical fiber coat, or the thickness of the metal tube from the viewpoint of workability when inserting the optical fiber. The inner diameter is at least 0.1 greater than the outer diameter of the optical fiber.
It must be larger by mm. Furthermore, when a long optical fiber coat is required, a plurality of metal tubes are connected in the longitudinal direction to obtain the required length.

In addition, for metal pipes, except for seamless pipes, be sure to remove the welded parts.
It has different structures such as forge welds, which cause changes in mechanical properties depending on the circumferential area of the product. This change in mechanical properties due to the circumferential portion gives the small diameter metal tube a curl, which is undesirable in terms of construction. Therefore, it is desirable to perform annealing at least once under conditions such that different structures such as welded parts and forge welded parts become the same or have the same mechanical properties as the structures of other parts.

To connect the flexible tube to the metal tube, it may be fixed, removably fixed, or connected via a suitable connecting member. To secure a flexible tube to a metal tube,
Adhesion, brazing, caulking, etc. are used. To removably fix a flexible tube to a metal tube, methods such as spring coupling, gripping by elastic deformation, and tightening with nuts are used. The simplest method is to removably fix the metal pipe and flexible pipe via a connecting member. In this case, the flexible pipe can be connected at any point on the metal pipe, and it is easy to connect the flexible pipe at the construction site. It is advantageous over other connection methods in that it can be implemented in many ways.

A flexible tube is a metal or synthetic resin thin plate formed into a bellows shape or spirally wound, a synthetic resin tube such as vinyl chloride or polyethylene, or a rubber tube.

The flexible tube has a loop escape radius of 15 mm or more,
Further, it is desirable that the loop forming radius is 200 mm or less. The relief radius of the flexible tube means the minimum radius of curvature r at which the loop L is eliminated when the loop of the flexible tube 2 is narrowed by the method shown in FIG. That is, the flexible tube 2
are held horizontally at intervals that allow loop formation, for example, 75 cm, and are compressed in the axial direction of the flexible tube to form a loop L in the vertical plane. If you pull the flexible tube 2 in the axial direction, only the loop will be resolved, or the loop L will be removed at the moment the loop is resolved.
The flexible tubes 2, which had crossed each other at the upper end, are separated.

The radius of curvature of the loop L at this time is defined as the loop relief radius r. The loop relief radius r can be increased by increasing the wall thickness of the flexible tube 2, using a hard material, or increasing the diameter of the flexible tube. The loop escape radius r needs to be greater than or equal to the allowable radius of curvature of the optical fiber 11.

If the loop relief radius r is 15+nm or more, hunt linking becomes possible with a bending radius greater than or equal to the allowable bending radius of the included optical fiber 11.

The loop forming radius of the flexible tube 2 means the minimum radius of curvature R when forming a loop by the method shown in FIG. That is, the interval that allows the flexible tube 2 to form a loop, for example, 75c.
The flexible tube is gripped horizontally with an interval of ln and compressed in the axial direction of the flexible tube. The curved portion M that hangs downward due to compression rotates in a vertical plane. When rotated by 90 degrees, the radius of curvature in the vertical direction of the curve becomes the minimum, and when rotated by 180 degrees, they intersect at the upper end to form a loop L. The radius of curvature of the loop L when rotated by 90 degrees in this vertical plane is defined as the loop forming radius R. If the loop forming radius exceeds 200 mm, sufficient flexibility will not be obtained when routing the loop inside the box. It is possible to reduce the loop forming radius by reducing the wall thickness of the flexible tube 2, using a soft material, or reducing the diameter of the flexible tube. When the loop forming radius R is 200 mm or less, hunt link properties with sufficient flexibility can be obtained.

The length of the cable to be bent during cable connection work is approximately several tens to hundreds of times the outer diameter of the cable.

Note that the fact that the optical fiber is inserted with a gap between it and the inner wall of the flexible tube means that the optical fiber and the inner wall of the flexible tube are in contact with each other with a degree of freedom, and the optical fiber is inserted freely regardless of the expansion and contraction of the inner wall of the tube. This means that there is room for movement. Here, the optical fiber refers to a bare fiber, a bare fiber, a cored optical fiber, a single-core or multi-core core coated with plastic or metal.

[Function] The optical fiber cable of the present invention has sufficient mechanical strength, corrosion resistance, and weather resistance because it is coated with an optical fiber or a metal tube, and is free from excessive stress during installation (overhead, pipe running, etc.) work. It withstands wire extension loads and ensures protection of optical fibers after installation. Moreover, the cladding tube at the side end of the connector of the optical fiber cable is a flexible tube, and since the loop relief radius is greater than the allowable bending radius of the optical fiber and has flexibility, good handling properties can be obtained. In other words, the optical fiber of the cable near the connector end can be easily handled without damaging it.

Further, the flexible tube configured as described above has a property of trying to maintain straightness in the longitudinal direction. In the natural state where it extends straight, the first annular end and the second annular end of the flexible tube are in contact with each other, so if a compressive force is applied to the flexible tube, it will contract, but even if a tensile force is applied, it will not stretch. do not have. Further, when the optical fiber cable is subjected to bending deformation, the first annular end portion and the second annular end portion of the flexible tube strongly contact each other on the outside of the bend and separate from each other on the inside. Thus, the flexible tube can retract on the inside and maintain substantially the same length on the outside. As a result, no tension or compression force is applied to the optical fiber enclosed with a gap between it and the inner wall surface of the flexible tube.

[Example] Figures 1 and 2 show an example of the present invention.
The figure shows an overall view of the optical fiber cable 1, and FIG. 2 shows a sectional view of the main part. The optical fiber cable 1 has an optical fiber 11 inserted into a cladding tube consisting of a seamless metal tube 33 and a flexible tube 2 connected to the end of the metal tube 33 by a connecting member 34, so that the optical fiber is protected by the cladding tube. ing.

A connector 35 is attached to the end of the flexible tube 2. As shown in FIG. 2, the flexible tube 2 and the metal tube 33 are connected by fitting the flexible tube 2 and the metal tube 33 from both sides of a cylindrical connecting member 34 and fixing them removably with a set screw 36 and an insertion screw 37. ing.

The metal tube 33 is coated with PV (polyvinyl) 38, and the optical fiber 11 inside the flexible tube 2 is sealed with a silicone resin tube 30.

It is preferable to connect the flexible tube 2 to the metal tube 33 after the wire drawing operation. That is, after the wire drawing operation, the end side metal tube portion that requires flexibility is removed to expose the optical fiber, and then the optical fiber is inserted into the flexible tube that connects the flexible tube 2 and the metal tube 33 via the connecting member 34. 11 is included. Of course, it is also possible to connect the caulked metal tube 33 and the flexible tube 2. However, in this case, it is necessary to know the exact length and flexibility of the installation path and the exact location and length of the required sections.

Further, since the optical fiber itself is unconnected, it is possible to avoid the work of connecting the optical fiber itself and to prevent an increase in transmission loss due to the connection.

Furthermore, when connecting the metal tube 33 and the flexible tube 2 via a connecting member, the connection can be made at any location.
This is advantageous in construction and on-site connection work.

Specific examples of flexible tubes are shown in FIGS. 3(a), (b), (c), and (d). (a) and (b) are formed by winding a flat hoop in a spiral shape, and the flexible tube 2 in (a)
1 is a type in which hoops 31 are formed without overlapping and a gap is provided between adjacent hoops, and the flexible tube 22 in FIG.
1 is formed by overlapping them. (C) Flexible tube 23
The flexible tube 24 shown in (d) is formed into a spiral shape by forming hoops 39 having an S-shaped cross section so that only adjacent hoops engage with each other. shows. Next to the flexible tube of FIG. 3(d), the flexible tube of FIG. 3(d) will be explained in detail with reference to FIGS. 6 to 9.

To explain the optical fiber cable configured as above with reference to the drawings, as shown in FIG. It consists of The large diameter portion 4 has a first annular end portion 5 at one end that projects toward the inner diameter side. Similarly, the small diameter portion 7 has a second annular end 8 protruding outwardly at one end.
It is equipped with The large diameter portion 4 and the small diameter portion 7 are connected via an annular connecting portion 9. As shown in FIG. 6(b), adjacent blocks 3 are movable in the tube axis direction and are connected in a spiral manner. At this connecting portion, the second annular end 8 is located within the large diameter portion 4 of the adjacent block 3 and is substantially in contact with the first annular end 5 .

In order to enable the adjacent blocks 3 to be displaced in the tube axis direction, the first annular end 5 and the second annular end 8 are located outside the small diameter portion 7 and inside the large diameter portion 4 of the adjacent blocks, respectively, It has a gap between it and the annular connecting part 9.

Also, the inner diameter of the first annular end 5 is larger than the outer diameter of the small diameter part 7 so as to create a gap, and the outer diameter of the second annular end 8 is larger than the inner diameter of the large diameter part 4. is also small enough to create a gap of ℃2, and depending on the size of this gap,
It is also possible to adjust the amount of deflection of the flexible tube 2.

In order to form the flexible tube 2 into the above-mentioned shape, for example, as shown in FIG. 7, the strip plate 15 is bent into an S-shaped cross section and subjected to secondary processing. The second annular end portion 8 is located within the large diameter portion 4 of the adjacent block 3 and the first annular end portion 5
The above-mentioned secondary workpiece 16 is spirally wound so as to be in contact with the material.

The material of the strip plate 15 forming the flexible tube 2 is selected depending on the usage conditions of the optical fiber cable 1, and may be metal, plastic, paper, or the like. The flexible tube 2 may have an opening on its circumferential surface, that is, the inside of the flexible tube 2 does not need to be sealed.

In order to facilitate the molding process of the flexible tube 2 and to improve the contact between the first annular end 5 and the second annular end 8, the first annular end 5, the second annular end 8, and the connecting portion are 9 is preferably inclined along the pitch angle of the spiral.

The flexible tube 2 configured in this manner has a property of trying to maintain straightness in the longitudinal direction. In the straight and natural state, the first annular end 5 of the flexible tube 2 as shown in FIG.
Since the flexible tube 2 is in contact with the second annular end 8, it will contract when a compressive force is applied to the flexible tube 2, and will not expand even when a tensile force is applied. Furthermore, when bending deformation is applied to the flexible tube 2, the first annular end 5 and the second annular end 8 of the flexible tube 2 are in strong contact with each other on the outside of the bend, as shown in FIG. 9, and on the inside of the bend. leave each other. Thus, while the flexible tube 2 contracts on the inside, it maintains substantially the same length on the outside. As a result, no tension or compression force is applied to the optical fiber 11, which is enclosed with a gap between it and the inner wall surface of the flexible tube. Of course, depending on the accuracy of forming the strip plate, the two annular ends 5 and 8 may not be in complete contact with each other due to the stretching force acting in the longitudinal direction, or the inner side may shrink preferentially, so that the actual There is almost no outward extension.

Further, the flexible tube 2 having the above-mentioned shape is connected to the strip plate 1.
By winding 5 in a spiral shape, one strip plate 15 is formed.
It can be molded and processed.

[Specific Example] (Specific Example 1) The above-mentioned FIGS. 1 and 2 show an example of the optical fiber cable of the present invention. The optical fiber cable 1 of this specific example has an optical fiber core il+ inserted into a sheathed tube consisting of a metal tube 33 made of stainless steel and a flexible tube 2 made of stainless steel.

Metal tube: Semi-seamless tube made of stainless steel (505304) (tube made by brightly annealing a welded tube to make it homogeneous and then elongating it), outer diameter 1.0+nm, wall thickness 0.15mm, coating with 1mm thick PV Covered flexible tube: Made of stainless steel # (SLIS304), shape shown in Figure 3(d), inner diameter 3.0 mm, outer diameter 4.6 mm, thickness 0.8 m
m, Loop relief radius r: 34 mm Loop formation radius R: 131 mm Optical fiber, core 50 μm, craat 125 μm, resin coating outer diameter 250 μm quartz glass optical fiber flexible tube The optical fiber in the flexible tube is a silicone resin tube 3o with substantially no rigidity. It is sealed with.

Connecting member: Stainless steel (SUS304) connector with the shape shown in Figure 2 Brass FC type connector with Ni plating.

(Specific Example 2) FIG. 10 shows another example of the optical fiber cable of the present invention. The flexible tube 25 of the optical fiber cable in this specific example has a flexible tube main body 24 with a finished outer diameter of 5.0 nm.
It is the same as Example 1 except that E coating 25 is added.

Loop relief radius r: 47 mm Loop formation radius R: 163 mm [Effects of the Invention] The present invention has the advantages of high strength, light weight, and small diameter, which are the characteristics of optical fiber cables coated with metal tubes, and A flexible optical fiber cable can be provided near the connector. In other words, since the optical fiber cable of the present invention is coated with a metal tube, it has sufficient mechanical strength, corrosion resistance, and weather resistance, and does not cause excessive damage during installation (overhead, pipe running, etc.) work. It withstands wire extension loads and ensures protection of optical fibers after installation. In addition, the cladding tube at the connector side end of the optical fiber cable is a flexible tube, and the loop escape radius is greater than the allowable bending radius of the optical fiber, and flexible handling can be achieved. In other words, it is possible to easily handle the optical fiber of the cable near the connector side end without damaging it.

When the flexible tube of the optical fiber cable of the present invention is configured as shown in FIGS. 6 to 9, when bending deformation is applied, the inner side shrinks and the outer side has substantially the same length. Excessive tensile stress is not generated in the encapsulated optical fiber. In addition, since there is a gap between the optical fiber and the inner wall of the flexible tube, it is possible for the optical fiber to move independently of the inner wall of the flexible tube, and even if lateral pressure is applied to the flexible tube, there is no lateral pressure on the optical fiber. It doesn't cost much. Therefore, by appropriately designing the band plate material, wall thickness, flexible tube diameter, and the amount of overlap between the first and second annular ends, etc., it is possible to achieve a bending diameter that is equal to or greater than the allowable bending diameter of the optical fiber. It is possible to obtain a long-hitting hunt link property with the ability.

Further, in the present invention, one strip-shaped plate can be formed and processed in the same manner in the longitudinal direction. Therefore, it is possible to manufacture flexible tubes at low cost.

[Brief explanation of drawings]

Figure 1 is an overall side view showing an embodiment of the optical fiber cable of the present invention, Figure 2 is a sectional view of the main part of Figure 1, and Figure 3 (a).
, (b), (c), and (d) are side views showing specific examples of flexible tubes, FIG. 4 is an explanatory diagram of the loop relief radius of the flexible tube, and FIG. 5 is an explanation of the loop forming radius of the flexible tube. 6(a) is a cross-sectional view showing an example of a block constituting a part of the flexible tube, FIG. 6(b) is a cross-sectional view showing the connection of the blocks, and FIG. ), FIG. 8 is a partial cross-sectional view of the flexible tube shown in FIG. 6(a) in a straight state, and FIG.
This figure is a sectional view of the flexible tube shown in FIG. 6(a) in a bent state, and FIG. 10 is a partial sectional view showing another specific example of the optical fiber cable. 1...Optical fiber cable, 2.2+, 22.2:1
．． 24.25... Flexible tube, 3... Flexible tube block, 4... Large diameter portion, 5... First annular end, 7...
・Small diameter part, 8... Second annular end part, 9... Connection part, +
1-... Optical fiber, 33... Seamless metal tube,
34... Connecting member, 35... Connector.

Claims (1)

[Claims] 1. A metal tube having at least a length of wire that requires strength, and a flexible tube connected to one or both ends of the metal tube and having at least a length to bend the cable during cable connection work. and an optical fiber inserted into the metal tube and the flexible tube with a gap therebetween. 2. A 1-pitch flexible tube block has a large diameter portion having a first annular end protruding inwardly at one end, a second annular end protruding outwardly at one end, and an annular shape. a small diameter part connected to the large diameter part via a connecting part,
The second annular end portion is located within the large diameter portion of the adjacent block and substantially contacts the first annular end portion, and the adjacent blocks are displaceable in the tube axis direction and connected in a spiral shape to form one strip plate. The optical fiber cable according to claim 1, wherein the optical fiber cable is formed.