Method for manufacturing an optical fiber protection metal tube

Abstract

To provide an optical fiber protective metal tube which does not directly damage an optical fiber housed therein even in the presence of metal burrs that may be caused by cutting an optical cable.SOLUTION: An optical fiber protective metal tube provided herein is for housing and protecting an optical fiber therein and comprises a metal tube and an inner sheath made of a synthetic resin adhered on an inner surface of the metal tube.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a metal tube for protecting an optical fiber. of the pipe

Background Art

[0002] An optical fiber cable generally has a structure in which an optical fiber is inserted into a metal tube. As in Patent Document 1, the outer surface of the metal tube of the optical fiber cable is often coated with a synthetic resin, but the inner surface remains metallic and the optical fiber is inserted therein.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When an optical fiber cable is cut, metal burrs are generated on the cut surface of the metal tube. If left unattended, these burrs can damage the internal optical fiber. Therefore, it is necessary to insert a protective tube made of synthetic resin between the tube and the fiber after cutting. Since this operation is sometimes complicated, an optical fiber cable that does not require such an operation has been desired.

[0005] Therefore, an embodiment of the present application aims to provide an optical fiber protection metal tube and a manufacturing method thereof such that even when burrs are generated when the optical fiber cable is cut, the burrs do not directly damage the internal optical fiber.

Means for Solving the Problems

[0006] An embodiment of the present application is an optical fiber protection metal tube that houses and protects an optical fiber therein, characterized by comprising a metal tube and an inner coating made of synthetic resin that adheres to the inner surface of the metal tube. ​

[0007] The optical fiber protection metal tube according to the embodiment of the present application is provided with an inner coating made of synthetic resin that adheres to the inner surface. Thereby, when it is cut with an optical fiber inserted inside, the burrs generated on the cut surface of the metal tube are covered by the inner coating, so that the burrs do not come into contact with the internal optical fiber.

[0008] In addition, for the optical fiber protection metal tube according to the embodiment of the present application, it is desirable that the outer surface of the metal tube is covered with an outer coating made of synthetic resin in order to prevent damage and corrosion of the metal tube.

[0009] The manufacturing method of the optical fiber protection metal tube according to the embodiment of the present application is characterized in that, with a synthetic resin tube inserted into the metal tube, the metal tube is stretched to reduce its diameter, and an inner coating made of synthetic resin is adhered to the inner surface of the metal tube.

[0010] The optical fiber protection metal tube manufactured by the manufacturing method according to the embodiment of the present application is provided with an inner coating made of synthetic resin that adheres to the inner surface. Thereby, when it is cut with an optical fiber inserted inside, the burrs generated on the cut surface of the metal tube are covered by the inner coating, so that the burrs do not come into contact with the internal optical fiber.

[0011] In addition, for the manufacturing method of the optical fiber protection metal tube according to the embodiment of the present application, it is desirable that the stretching of the metal tube is performed by drawing. Also, it is desirable that heating is simultaneously performed during this drawing process.

Advantages of the Invention

[0012] Since the embodiment of the present application is configured as described above, it is possible to manufacture and provide an optical fiber protection metal tube in which, when an optical fiber cable is cut, even if metal burrs are generated, they do not directly damage the internal optical fiber.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present application will be described with reference to the drawings. Note that the drawings described below are schematic diagrams, and the positional relationship and size ratio between the components are not necessarily the same as those of the actual objects.

[0015] FIG. 1 is a schematic diagram showing the structure of an optical fiber protection metal tube 10 according to an embodiment of the present application. The optical fiber protection metal tube 10 houses and protects an optical fiber (not shown). The metal tube 20 is a flexible steel tube made of, for example, stainless steel, formed to be long (for example, with a total length of 10 m or more), and its outer surface is covered with an outer coating 40 made of synthetic resin. The outer coating 40 is provided to prevent damage and corrosion of the metal tube 20. Further, an inner coating 30 made of synthetic resin is in close contact with the inner surface of the metal tube 20. The materials of the inner coating 30 and the outer coating 40 are not particularly limited as long as they are synthetic resins, but polyethylene resin, polypropylene resin, or polyvinyl chloride resin is preferred.

[0016] An example of a method for manufacturing the optical fiber protection metal tube 10 of the present embodiment will be described with reference to FIGS. 2 and 3. First, as shown in FIG. 2, a synthetic resin tube 35 having an outer diameter smaller than the inner diameter of the metal tube 20 is inserted into the metal tube 20 having a predetermined inner diameter.

[0017] In this state, when the metal tube 20 is stretched and reduced in diameter by a drawing process, for example, passing it through a die, the inserted synthetic resin tube 35 is also stretched and thus reduced in diameter at the same time. As a result, as shown in FIG. 3, the synthetic resin tube 35 adheres to the inner surface of the metal tube 20 and becomes the inner coating 30. If the outer surface of the metal tube 20 is covered with the outer coating 40 from this state, the optical fiber protection metal tube 10 shown in FIG. 1 is obtained. Here, due to the processing heat generated during the drawing process, the synthetic resin tube 35 softens, so when it is cooled later, the synthetic resin tube 35 adheres to the metal tube 20. In addition, in order to ensure that the synthetic resin tube 35 adheres firmly to the metal tube 20, electromagnetic induction heating or high-frequency induction heating may be applied simultaneously with the drawing process to promote heating of the synthetic resin near its melting point.

[0018] Another example of the manufacturing method of the optical fiber protection metal tube 10 of the present embodiment will be described with reference to FIGS. 4 and 5. First, as shown in FIG. 4, a synthetic resin tube 35 having an outer diameter smaller than the inner diameter of the metal tube 20 is inserted into the metal tube 20 having a predetermined inner diameter. A compressor (not shown) is connected to the synthetic resin tube 35.

[0019] In this state, while pressurizing the inside of the synthetic resin tube 35 with a compressor, if the metal tube 20 is heated to a temperature equal to or higher than the melting point of the synthetic resin constituting the synthetic resin tube 35, as shown in FIG. 5, the synthetic resin tube 35 expands and contacts the inner surface of the metal tube 20. When the metal tube 20 is cooled in this state, the synthetic resin tube 35 solidifies in the expanded state and becomes the inner coating 30 that adheres to the inner surface of the metal tube 20. If the outer surface of the metal tube 20 is covered with the outer coating 40 from this state, the optical fiber protection metal tube 10 shown in FIG. 1 is obtained.

[0020] An appropriate number of optical fibers, and if necessary, tensile strength fibers or intervening materials are inserted into the optical fiber protection metal tube 10 manufactured by each of the above methods to form an optical fiber cable.

[0021] The optical fiber cable using this optical fiber protection metal tube 10 is cut to an appropriate length according to the usage state and application. When cutting, burrs are generated on the cross-section of the metal tube 20, but these burrs do not directly contact the optical fiber due to the interposition of the inner sheath 30. Therefore, with the cutting of the optical fiber cable, there is no need to insert a protective tube or the like that separates the metal tube and the optical fiber at the cut end, and the optical fiber is not damaged by the burrs.

[0022] Note that the optical fiber protection metal tube of the embodiment of the present application is not limited to being manufactured by the method described above, and may be manufactured by other methods.

Explanation of Reference Numerals

[0023] 10 Optical fiber protection metal tube 20 Metal tube 30 Inner sheath 35 Synthetic resin tube 40 Outer sheath

Claims

1. A method for manufacturing an optical fiber protection metal tube, characterized in that, with a synthetic resin tube inserted into a flexible metal tube having a total length of 10 mm or more, the metal tube is extended and thinned without inserting an optical fiber, and an inner coating made of synthetic resin is adhered to the inner surface of the metal tube.

2. The method for manufacturing an optical fiber protection metal tube according to Claim 1, wherein the extension of the metal tube is performed by drawing.

3. The method for manufacturing an optical fiber protection metal tube according to Claim 2, characterized in that heating is also performed simultaneously during the drawing process.

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