JPH04345111A - Method and apparatus for producing metal pipe clad optical fiber cable - Google Patents

Abstract

PURPOSE:To prevent an optical fiber from moving and deviating a prescribed surplus length at the time of adjusting tension by temporarily cooling a metallic pipe just before a traction device after a high-temp. gel is injected into the metallic pipe. CONSTITUTION:The high-temp. gel from a gel injecting pipe 7 is injected into an introducing pipe 6 and while the gel is packed into the metallic pipe, the optical fiber is delivered by the viscosity of the gel. The optical fiber is introduced and the metallic pipe packed with the gel travels through a cooler 18. The gels solidifies to a high viscosity and eventually holds the optical fiber securely in this position when the pipe is cooled down to a prescribed temp. during this time. The metallic pipe is thereafter pulled in such a manner that the tension thereof attains a prescribed value while the metallic pipe is wound by a capstan 12 which is a tension varying device. The position of the optical fiber in the metallic pipe is securely held by the solidified gel at this time and is prevented from biasing inward of the winding radius at the time of winding by the capstan. The surplus length is thus prevented from changing from the prescribed value when the metallic pipe is afterward stretched straight.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for manufacturing metal tube coated optical fiber cables.

0002

2. Description of the Related Art From the viewpoint of transmission efficiency of optical fibers, it is necessary to provide a tensile strength member to an optical fiber or a bundle of optical fibers. Furthermore, it is known that the strength of optical fibers decreases due to the influence of humidity. For this reason, when laying optical fiber cables under high humidity or high pressure environments such as on the seabed, under water, underground, etc., metal tube-covered optical fiber cables, in which optical fibers or optical fiber bundles are loosely sheathed with thin metal tubes, are used. ing. The metal tube-covered optical fiber cable includes a single-core cable type in which one optical fiber is sheathed with a metal tube, and a multi-core cable type in which a plurality of optical fibers are sheathed in a metal tube. In some cases, these cables are further assembled into a single thick cable.

[0003]A device and method for continuously manufacturing this metal tube coated optical fiber cable are disclosed in, for example, Japanese Patent Laid-Open No.
It is disclosed in Japanese Patent No.-35514.

[0004] This known apparatus for manufacturing metal-clad optical fiber cables first forms a continuous longitudinally fed flat metal strip into a metal tube having a longitudinally extending gap at the top. An introduction tube is inserted into the metal tube through the gap in the metal tube, and the optical fiber is introduced into the metal tube using the introduction tube. After closing the gap in the metal tube into which the optical fiber has been introduced, the metal tube is sent to a laser welding device.

The laser welding device positions the longitudinally extending abutting portion of the fed metal tube using a guide roller, and irradiates the abutting portion with a laser beam that is focused at a position away from the surface of the abutting portion. Weld. By defocusing on the outside of the abutment in this way, welding of the abutment can be achieved without protecting the optical fiber with a heat shielding material.

[0006] After the outer diameter of the metal tube containing the optical fiber is reduced to a predetermined size, it is wound around a capstan and continuously drawn out.

When pulling this metal tube, in the above-mentioned known device, an inert gas is flowed into the introduction tube, and the metal tube is wound and engaged with the capstan while carrying the optical fiber by the viscous resistance of the gas. By blowing the optical fiber on the outside of the inner surface of the metal tube, that is, on the outer radius of the winding diameter at the capstan, the length of the optical fiber becomes longer than the metal tube when the metal tube is stretched straight. The optical fiber is slackened within the metal tube to provide a so-called extra length to prevent distortion of the optical fiber due to installation tension or the like. Furthermore, in order to prevent water from entering through the hole and deteriorating the optical fiber if the metal tube is damaged and has a hole, gel is injected into the metal tube while the gas is positioned. ing.

[0008]

However, in the process of later winding up a metal tube pulled by a capstan, the optical fiber inserted into the tube often breaks. This is caused by stress concentration acting on the optical fiber during the process in which the optical fiber, which has been stretched at the input side of the capstan, contracts at the capstan. This stress concentration occurs because the optical fiber hits impurities in the gel, spatter from welding, protrusions at the welded portion of the metal tube, and the like. Optical fibers are difficult to move due to the high viscosity of the gel sealed inside the metal tube, but because of the fact that they are wound around a capstan and the tension, they tend to move inward within the radius of the capstan's winding diameter. It is close to the inner surface of the metal tube and comes into contact with foreign objects easily.

[0009] Furthermore, the fact that the optical fiber is close to the inner surface of the metal tube at the capstan means that there is a difference between the winding length of the metal tube and that of the optical fiber. Later, when the tension applied to the metal tube or optical fiber is released, the optical fiber becomes shorter than a predetermined value, reducing the controllability of the remaining length.

[0010] In order to prevent this phenomenon, it would be better to use a gel with a higher viscosity, but in that case, the high viscosity of the gel would conversely increase the tension acting on the optical fiber, making it more likely to break. There is. In other words, at the point in the introduction tube where the optical fiber and gel are injected, the optical fiber experiences resistance from the gel. This resistance increases as the viscosity of the gel increases, and this resistance applies tension to the optical fiber, which is a contributing factor to its breakage.

The present invention solves these problems and uses a gel with a conventional viscosity, even if it is not very high in viscosity, so that the resistance does not increase when introducing the optical fiber, and moreover, the optical fiber is not made of metal in the capstan. It is an object of the present invention to provide a method and apparatus for manufacturing a metal tube-covered optical fiber cable that can extend to a predetermined position within a tube and maintain a predetermined extra length.

0012

[Means for Solving the Problems] According to the present invention, the above object relates to a method for forming a metal tube-covered optical fiber cable by inserting an optical fiber or an optical fiber bundle and a gel-like filling into a metal tube. This is achieved by: a step of pulling the metal tube while winding it; and a step of pulling the metal tube while winding it up; and increasing the viscosity of the gel-like filling in the metal tube by cooling before the step of pulling the metal tube.

[0013] Furthermore, regarding an apparatus for carrying out the above method, there is provided a cable in which an optical fiber or an optical fiber bundle and a gel filling are inserted into a pulled metal tube to form a metal tube-covered optical fiber cable. a forming means, a pulling means for winding up and pulling the metal tube charged with the gel-like filling, and a cooling means installed upstream of the pulling means to increase the viscosity of the gel-like filling in the metal tube. This is achieved by having

[0014]

In the present invention, the optical fiber is positioned at a predetermined position within the metal tube before entering the capstan, for example at the center of the metal tube, by utilizing the positional relationship between the introduction tube and the capstan. On the other hand, a gel having a normal viscosity is injected into the metal tube so as to fill the area around the optical fiber at the position.

Thereafter, the metal tube heads toward the capstan, but in the present invention, the metal tube, or the gel therein, is cooled by cooling means at a position immediately before the capstan. The gel then becomes more viscous and enters a solidified state, holding the optical fiber in place. Therefore, even when the metal tube is wound around the capstan, the optical fiber hardly moves.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. As shown in the figure, the metal tube coated optical fiber cable manufacturing apparatus of this embodiment includes a first assembly 3 that curves and shapes the cross section of a metal strip 1 into a U-shape, and a first assembly 3 that curves and shapes the cross section of a metal strip 1 and abuts both ends of the metal strip. a second assembly 4 forming a tube, and an assembly 2 provided between the first assembly 3 and the second assembly 4 to introduce an optical fiber into the formed metal tube, as described below. It has an introduction tube 6 as an optical fiber introduction means and an injection tube 7 as a gel injection means.

As shown in FIG. 2, the optical fiber introducing tube 6 is curved in an arc shape, enters from the upper gap of the metal strip 1 having a U-shaped cross section, and the tip thereof is inserted into the metal strip until the metal strip is completely covered. It has a circular cross section and extends to the part that becomes a metal tube. The introduction pipe 6 is connected to the U-shaped metal strip 1 due to its own elasticity or a spring (not shown).
The curved part contacts the bottom of the metal tube,
Also, because the tip is raised due to elasticity,
Even if the optical fiber contacts the curved inner surface at the curved portion of the introduction tube 6, it comes to a predetermined position in the radial direction of the metal tube at the exit portion of the introduction tube 6 and comes into contact with the metal tube up to the position of the capstan, which will be described later. It is designed not to. Note that the introduction tube does not have to be curved and may be straight. Furthermore, in the present invention, the optical fiber may be in contact with the inner surface of the metal tube at one or more locations until reaching the capstan.

The introduction tube 6 extends upwardly outside the U-shaped metal strip 1 and joins the gel injection tube 7 at a connection 62 . Thus, the high temperature gel is transferred from the injection pipe 7 to the introduction pipe 6.
The viscosity of the optical fiber sends it out from the introduction tube 6 into the metal tube.

[0020] A welding device 8, which is a laser welding means, is provided at the rear of the second assembly 4 for welding the abutted portions of the circular metal tubes in which both ends of the second assembly 4 are abutted. There is.

[0021] At the rear of the laser welding device 8, a measuring section 9 for checking the welding state and a diaphragm device 10 as a diaphragm means for adjusting the diameter and wall thickness of the metal tube to predetermined values are provided in series. Between this drawing device 10 and cable winding machine 11,
It has a traction device 15 consisting of a tension variable device 12 using a capstan and a tension adjustment device 14 for a metal tube-covered optical fiber cable 13.

This tension variable device 12 and tension adjustment device 1
4, a tension adjustment device 16 for the metal strip 1 and a tension adjustment device 17 for the optical fiber 5 provided at the front stage of the assembly 2.
This constitutes an extra length control device that adjusts the relative length of the optical fiber cable with respect to the metal tube, that is, the extra length.

In the present invention, a cable forming device is constituted by a series of devices from the above assembly to the laser welding device.

The apparatus of this embodiment further includes a cooling device 18 as a cooling means immediately before the tension adjusting device 12. As shown in FIG. 3, the cooling device 18 has guide tubes 18B and 18C passing through the front and rear wall plates of the box body 18A to guide the metal tubes in a sealed state.
A refrigerant whose temperature is controlled to a predetermined temperature is sealed within the 8A. For example, when a metal tube filled with optical fibers and gel is run at 30 cm/s, ethyl alcohol as a refrigerant is maintained at -70° C. by a control device (not shown).

In the apparatus of this embodiment, the metal tube-covered optical fiber cable is manufactured in the following manner. (2) The metal strip 1 is curved into a U-shape and a circular cross section by the assemblies 2, that is, the first assembly 3 and the second assembly 4. Then, the curved abutting portions are welded by the laser welding means 8 to form a complete tube and sent out. (2) On the other hand, between the first assembly 3 and the second assembly 4, the optical fiber 5 is introduced into the metal tube at a position ahead of the second assembly 4 via the introduction tube 6. At this time, due to the positional relationship between the introduction tube 6 whose outlet is located above the center line of the metal tube and the capstan 12 which is located below the center line, the optical fiber is located within the metal tube and It is brought to a predetermined position in the radial direction where it is not in contact with the other, and the extra length is set to a predetermined value. (2) Furthermore, high-temperature gel is injected from the gel injection tube 7 into the introduction tube 6, filling the inside of the metal tube and sending out the optical fiber 5 forward due to its viscosity. (2) After the welding state of the metal tube is inspected by the measuring section 9, it is squeezed to a predetermined thickness by the squeezing device 10. (2) Next, the metal tube into which the optical fiber is introduced and filled with gel passes through the cooling device 18, during which it is cooled to a predetermined temperature. When the gel cools, it solidifies and becomes highly viscous, holding the optical fiber firmly in place. (2) Thereafter, the metal tube is wound by the capstan 12, which is a tension variable device, and is pulled so that the tension becomes a predetermined value. At this time, the optical fiber inside the metal tube is firmly held in position by the solidified gel, so that it does not move inside the winding radius when it is wound around the capstan, and the metal tube is later stretched straight. The remaining length does not change from the predetermined value even when the length is changed. (2) Thus, the metal tube-coated optical fiber is wound up by the winding machine 11.

[0026]

Effects of the Invention As described above, the present invention temporarily cools a metal tube-covered optical fiber cable at a position immediately before a tension adjustment means such as a capstan to solidify the gel filled in the optical fiber cable. Since it was decided to firmly maintain a predetermined position, the optical fiber will not shift its position within the metal tube even if it is wound around the capstan and subjected to tension, so that when the metal tube is subsequently stretched in a straight line, the optical fiber will not shift its position within the metal tube. This has the effect that the extra length will never deviate from a predetermined value.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the introduction tube and gel injection tube portion of the device in FIG. 1;

FIG. 3 is a partially cutaway enlarged perspective view of the cooling device of the device in FIG. 1;

4 is an enlarged plan view of the traction device of the device of FIG. 1; FIG.

FIG. 5 is an enlarged front view of the traction device of the device in FIG. 1;

[Explanation of symbols]

1 Metal strip 2 Assembly 6 Introduction means (device) 7 Injection tube 8 Laser welding means (device) 15 Traction means (device) 18 Cooling means (device)

Claims (3)

[Claims] 1. A step of charging an optical fiber or an optical fiber bundle and a gel filling into a metal tube to form a metal tube-covered optical fiber cable; and a pulling and winding step of pulling the metal tube while winding it. , A method for manufacturing a metal tube-covered optical fiber cable, wherein the viscosity of the gel-like filling in the metal tube is increased by cooling before the above-mentioned pulling and winding step. 2. Cable forming means for charging an optical fiber or an optical fiber bundle and a gel-like filling into a metal tube to be pulled to form a metal tube-covered optical fiber cable; A metal tube-covered optical fiber cable comprising: a pulling means for pulling the metal tube while winding it; and a cooling means installed upstream of the pulling means to increase the viscosity of the gel-like filling in the metal tube. manufacturing equipment. 3. The cable forming means includes an assembly comprising a plurality of pairs of rollers that form a metal strip and abut both ends thereof to form a metal tube, and an assembly that irradiates the abutting portions of the metal tubes with a laser beam to join the metal tubes. The metal tube coated optical fiber cable according to claim 2, further comprising laser welding means for sealing the metal tube and introduction means for introducing the gel and the optical fiber or the optical fiber bundle into the formed metal tube through the introduction tube. manufacturing equipment.