JP2616282B2 - Optical fiber introduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical fiber cable coated with a metal tube.
The present invention relates to an optical fiber introduction device that injects gel while introducing a gel.

[0002]

2. Description of the Related Art A so-called metal tube-coated optical fiber cable is
An optical fiber or an optical fiber bundle (hereinafter, referred to as an optical fiber) has a structure in which it is loosely covered with a metal tube. With this structure, the metal tube functions as a strength member, and the transmission efficiency of the optical fiber is prevented from lowering by laying the optical fiber loosely to some extent. When laying a metal tube-coated optical fiber cable on the sea floor or in the ground, the space between the metal tube and the optical fiber is filled with a gel, which is a viscous substance having waterproof and water-blocking properties. To prevent water degradation.

[0003] As a method of manufacturing such an optical fiber cable coated with a metal tube, for example, as disclosed in Japanese Patent Application Laid-Open No. 57-100402, an optical fiber and a gel are simultaneously introduced into a metal tube by a single tube. As described in Japanese Patent Application Laid-Open No. 58-95304, a double-tube introduction tube composed of an outer tube and an inner tube is used. A method of introducing a gel between an inner tube and an outer tube into a metal tube has been adopted.

Further, in order to install the optical fiber loosely in the metal tube, it is necessary to perform a so-called extra length control in which the length of the optical fiber is adjusted to be longer than the length of the metal tube at a certain rate. As described above, in order to provide an extra length to the optical fiber, various controls are added to the transport of the optical fiber. For example, Japanese Patent Application Laid-Open No. 57-100402 discloses a method in which a gel is blown from an upstream side of a metal tube continuously formed from a metal strip, and the excess length is given by effectively utilizing the viscosity of the gel. Is disclosed. However, in this method, since the gel is blown out from the metal pipe, when the formed metal pipe is hermetically sealed by welding, there is a concern that the welding may be adversely affected. On the other hand, Japanese Patent Application Laid-Open No. 61-17447, which is a technique related to Japanese Patent Application Laid-Open No. 58-95304, discloses a method of adjusting the tension of a metal tube or an optical fiber to provide an extra length. According to the method of adjusting the tension as described above, since there is no fear of the above-mentioned adverse effects at the time of welding, the butted portion of the metal pipe can be welded by soldering, TIG welding, or laser welding. Further, the extra length can be controlled more finely than the extra length control based on the gel viscosity.

[0005]

However, in order to meet the demands for high quality, it is necessary to further determine and control the extra length ratio by the tension control. For this purpose, the tension of the optical fiber may be adjusted in advance by a mechanical means such as dancer roll, but unexpected tension is applied to the optical fiber in the introduction pipe. For example, when introducing an optical fiber and gel while using a single-tube introduction tube to prevent the gel from blowing out from the metal tube, the interaction between the optical fiber and the gel in the introduction tube causes the optical fiber Causes a large back tension, and the extra length varies non-uniformly from the target value. This is due in part to the uneven viscosity of the gel. This decrease is more pronounced when the diameter of the metal tube is reduced and the diameter of the inlet tube is reduced accordingly, or when a highly viscous gel is used.

When a double-tube introduction tube is used, there is no interaction between the optical fiber and the gel in the introduction tube as described above. Thus, the optical fiber can be introduced into the metallic space. However, when the metal pipe has a small diameter, the introduction pipe having the double pipe structure must be thinned accordingly. In this case, there is a limit to reducing the diameter of the inner tube for guiding the optical fiber or reducing the thickness of the tube. Also,
There is a limit to increasing the diameter of the outer tube. Particularly, when a metal tube is to be welded, there is a problem of erosion immediately below the welded portion, so that the outer tube has to be reduced in diameter. For this reason, the gap between the inner tube and the outer tube through which the gel passes is very narrow. in this case,
To send a predetermined amount of gel into a metal tube in a predetermined time,
Requires very high injection pressure. There is a risk that the outer tube will be deformed by this pressure. This reduction is more pronounced when using high viscosity gels. For this reason, the introduction pipe of the double pipe structure can be applied only to a metal pipe having a large diameter.

Further, when welding the butted portions of metal tubes, it is necessary to minimize the adverse effect of welding heat on the optical fiber. For this reason, the heat is shielded by the introduction pipe at the welding position. However, since the introduction pipe is only inserted into the metal pipe and is not particularly positioned, the vibration of the metal pipe during traveling sometimes causes the introduction pipe and the metal to move. The distance between the pipe and the welding surface becomes very small. For this reason, when operating for a long time, welding spatter deposited on the introduction pipe may come into contact with the inner wall of the metal pipe, which may cause poor welding, and it is not possible to continuously manufacture a long metal pipe-coated optical fiber. Was. In addition, there is a risk that the heat of the TIG welding or the laser welding may cause burnout on the upper surface of the introduction pipe to make a hole and burn the gel passing through the inside.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages, and it is intended to use a high-viscosity gel or a small-diameter metal tube in manufacturing a metal tube-coated optical fiber cable filled with gel. However, it is still another object of the present invention to provide an optical fiber introduction device that can control the extra length finely and precisely by tension control, and can prevent the adverse effect of welding and operate stably for a long time. Another object of the present invention is to provide an optical fiber introduction device that suppresses overflow of a gel-like substance.

[0009]

An optical fiber introducing device according to the present invention is an optical fiber guiding device which is inserted into a metal tube formed by molding a metal strip to guide an optical fiber or an optical fiber bundle and a gel-like substance into the metal tube. In an optical fiber introduction device having a fiber introduction tube, a tapered taper portion is provided near the metal tube insertion position of the optical fiber introduction tube.

The metal tube is formed by forming a metal strip and the butt portion is sealed by laser welding, and the optical fiber introduction tube is located at or near the laser beam irradiation position with the irradiation surface of the metal tube. It is preferable to elastically press against the opposite inner wall.

Further, the optical fiber introducing tube is connected to a first passage tube for passing an optical fiber or a bundle of optical fibers and a second passage tube for passing a gel-like substance. It is preferable that the diameter be smaller than the maximum diameter of the tapered portion of the introduction tube.

[0012]

In the present invention, the optical fiber introducing tube is made thicker up to the metal tube insertion portion, a tapered taper portion is provided in the metal tube insertion portion, and the tip from the metal tube insertion portion is made thinner.
The pressure loss of the gel flowing through the optical fiber introduction tube is reduced. Therefore, the gel injection pressure can be kept low.

The metal tube insertion portion of the introduction tube is inserted into the metal tube so as to elastically press against the inner wall of the metal tube opposite to the irradiation surface of the metal tube at the laser light irradiation position, and is welded. In the section, the inlet pipe is fixed to the inner wall of the metal pipe opposite to the welding surface to increase the distance between the welding surface and the inlet pipe.

In the optical fiber introducing tube, the first passage tube through which the optical fiber or the optical fiber bundle passes is made smaller than the maximum diameter of the tapered portion of the optical fiber introducing tube, so that the gel from the entrance of the optical fiber cable can be formed. Is prevented from flowing backward.

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention. As shown in the figure, an optical fiber introducing device 1 is attached to a manifold 5 connecting a seal pipe 3 for guiding an optical fiber cable 2 and a gel supply pipe 4, and to the other end of the manifold 5. And an optical fiber introducing tube 6. See
The pipe 3 has an inner diameter slightly larger than the outer diameter of the optical fiber cable 2, for example, about 0.1 mm to 0.3 mm. The optical fiber introducing tube 6 is made of a metal having a high reflectivity of a laser, for example, copper or a copper alloy in the case of carbon dioxide laser welding, and is bent in an elastic state so that the end covers the optical fiber cable 2. It is inserted into the metal tube 7. The mounting portion 6a of the introduction tube 6 with the manifold 5 has a relatively large inner diameter, and is formed of, for example, a tube having an outer diameter of 2.5 mm and a thickness of 0.1 mm.
A tapered taper portion 6b is provided at the tip of the attachment portion 6a, and the tip guide portion 6c of the taper portion 6b has, for example, an outer diameter.
It is formed of a thin tube with a thickness of 1.0 mm and a thickness of 0.1 mm. The inner diameter of the seal tube 3 is formed to be considerably smaller than the inner diameter of the mounting portion 6a. As a result, reverse outflow of the gel from the inlet of the optical fiber cable 2 caused by the high injection pressure of the gel can be suppressed.

As shown in FIG. 2, the optical fiber introducing apparatus 1 is a molding means for forming a metal strip 8 and forming a metal tube 7 by abutting both ends thereof, as shown in FIG. 9 is provided between the first assembly 9a and the second assembly 9b or before the first assembly 9a. A laser welding means 10 for welding the butted portion of the metal pipe 2 and a drawing means 11 for reducing the diameter of the welded metal pipe 7a to a metal pipe 7b having a predetermined outer diameter are provided downstream of the forming means 9.
Are connected. In order to reduce the tension of the metal tube 7b and the optical fiber cable 2 built in the metal tube 7b between the squeezing means 11 and the cable winder 12, the metal tube 7b coated with the optical fiber cable 2 is reduced several times. It has a wound capstan 13 and a dancer roll stand 15 for adjusting the tension of the metal tube-coated optical fiber cable 14.
The tension adjusting means 16 for the metal strip 8 and the tension adjusting means 1 for the optical fiber cable 2 provided in front of the capstan 13, dancer roll stand 15 and molding means 9.
7 constitutes extra length control means for adjusting the relative length of the optical fiber cable 2 to the metal tube 7b, that is, the extra length. The tip of the optical fiber introducing tube 6 of the optical fiber introducing device 1 passes through the laser welding means 10 and is inserted up to just before the narrowing means 11. And laser welding means 10
At the laser light irradiation position, the introduction tube 6 is pressed against and fixed to the inner wall of the metal tube 7 on the side opposite to the laser light irradiation position. When the introduction pipe 6 is pressed and pressed, the entirety of the introduction pipe 6 is pressed down and fixed, so that the distal end of the introduction pipe 6 is attached to the metal pipe 7 by utilizing the elastic force of the curved portion bent at a constant curvature. Can be pressed.

In the manufacturing apparatus configured as described above, the metal strip 8 sent through the tension adjusting means 16 is formed by the forming means 9 and formed into the metal tube 7 having a butt portion at the upper part. The optical fiber cable 2 is continuously fed to the metal tube 7 via the optical fiber introducing device 1, and is inserted while moving along the inner wall of the taper portion 6 b of the introducing tube 6. At the same time, an inert gas, for example, argon gas can be supplied from a gel supply pipe 4 connected to a manifold 5 of the optical fiber introduction apparatus 1, and is sent to a metal pipe 7 through an optical fiber introduction pipe 6. The butting portion on the upper part of the metal tube 7 is welded by the laser welding means 10 to form a sealed metal tube 7a containing the optical fiber cable 2. The diameter of the sealed metal tube 7 a is reduced to a predetermined diameter by the throttle means 11 and sent to the capstan 13. The tension between the metal tube 7b and the optical fiber cable 2 on the entry side of the capstan 13 is made different, and the tension between the metal tube 7b and the optical fiber cable 2 is reduced by the capstan 13 so that the capstan 13
The extra length is controlled by providing a difference in the amount of extension between the metal tube 7b and the optical fiber cable 2 on the exit side. The metal-tube-coated optical fiber cable 14 whose surplus length is controlled is wound around a winder 12 through a dancer roll stand 15.

When the gel is injected into the metal tube 7a thus formed, the gel is supplied from the gel supply tube 4 instead of the inert gas. Gel supply pipe 4
Is supplied to the metal pipe 7a through the manifold 5 and the introduction pipe 6. The injection speed of this gel is controlled so that it is almost the same as the pulling speed of the optical fiber cable 2 at the outlet of the introduction tube 6, and the diameter of the metal tube 7 a is reduced to a predetermined diameter by the downstream throttle means 11. , Is adjusted to a predetermined filling rate. When the gel flows through the optical fiber introducing tube 6, the viscosity of the gel causes the friction with the tube wall of the optical fiber introducing tube 6 and the friction inside the gel to hinder the flow, resulting in a pressure loss ΔP. This pressure loss ΔP can be expressed by the following equation.

[0019]

(Equation 1)

Here, d is the inner diameter of the optical fiber introducing tube 6,
L is the pipe length, v is the average flow velocity in the pipe, γ is the specific weight of the gel, λ
Indicates a friction coefficient, and g indicates a gravitational acceleration. As is apparent from the above equation, the pressure loss ΔP is equal to the inner diameter d of the optical fiber introduction tube 6.
And is proportional to the tube length L. Therefore, by increasing the inner diameter of the mounting portion 6a of the optical fiber introducing tube 6,
The pressure loss ΔPa in the mounting portion 6a is reduced. Further, a tapered taper portion 6b having a gentle taper is provided in the metal tube insertion portion of the mounting portion 6a, and is connected to the tip guide portion 6c having a small diameter, so that the loss coefficient due to a change in the cross-sectional area of the pipeline is reduced to zero. And the pressure loss ΔPb of the taper portion 6b can be reduced. By providing the mounting portion 6a and the taper portion 6b having a large inner diameter as described above, the length of the distal end guide portion 6 with respect to the entire length of the optical fiber introducing tube 6 can be reduced, and the pressure loss ΔPc due to the distal end guide portion 6 can be reduced. Can be reduced, and the pressure loss ΔP of the entire optical fiber introducing tube 6 can be reduced. Therefore, the injection pressure of the gel supplied from the gel supply pipe 4 can be reduced. For example, when the entire optical fiber introduction tube 6 is formed of a tube having an outer diameter of 1.0 mm, a thickness of 0.1 mm, and a length of 1 m, like the tip guide portion 6, the gel injection pressure needs to be about 100 kgf / mm ^2. However, the outer diameter of the mounting pipe 6a is 2.5mm and the thickness is 0.1m.
m, the length is 70 cm, and the length of the taper portion 6b and the tip guide portion 6c is 30 cm, the injection pressure of the gel is 40 to 50 kgf / mm.
Even if reduced to about ² , the gel can be sufficiently supplied into the metal tube 7a. Therefore, the back tension due to the injection pressure of the gel applied to the optical fiber cable 2 can be reduced, and the tension of the optical fiber cable 2 can be introduced into the metal tube while being accurately adjusted by the tension adjusting means 17. The extra length control can be performed with high accuracy and stability.

The tapered portion 6b of the introduction tube 6 is positioned before the metal strip 8 is formed into a substantially tubular shape, and is not inserted into the metal tube 7, thereby reducing the diameter of the mounting portion 6a. The diameter can be larger than the diameter of the metal tube 7. Even when the diameter of the metal tube 7 is small or when a highly viscous gel is used, the back tension due to the injection pressure of the gel applied to the optical fiber cable 2 is reduced. be able to.

In this way, while continuously feeding the optical fiber 2 and the gel into the metal tube 7, when welding the butted surface of the metal tube 7 running at a constant speed, the optical fiber 2
And the introduction pipe 6 for guiding the gel is pressed against the inner wall of the metal pipe 7 on the side opposite to the welding surface. 6 can be located on the side opposite to the welding surface, and the distance between the inlet pipe 6 and the welding surface can be always kept constant. For this reason, the power density of the laser light that enters the inlet tube 6 through the butted portion of the metal tube 7 can be reduced, and the radiant heat received from the welded portion can be reduced. The amount of heat absorbed can be reduced. Further, since the introduction pipe 6 is formed of copper or a copper alloy having good heat conductivity, the absorbed heat is quickly diffused to prevent the introduction pipe 6 from becoming high temperature. Therefore, the introduction pipe 6
Thus, the thermal effect of welding on the optical fiber 2 and the gel guided by the introduction pipe 6 can be reduced.

Further, since the introduction pipe 6 is pressed against the inner wall opposite to the welding surface, its position does not move and the distance from the welding surface can always be kept at a maximum, so that the operation is performed for a long time. Even if welding spatter is deposited on the upper surface of the introduction pipe 6, it can be prevented from contacting the metal pipe 7.

[0024]

As described above, according to the present invention, the optical fiber introduction tube is made thicker up to the metal tube insertion portion, a tapered taper portion is provided at the metal tube insertion portion, and the tip from the metal tube insertion portion is made thinner. By reducing the pressure loss of the gel flowing through the optical fiber introducing pipe, the injection pressure of the gel can be kept low, so that the back tension applied to the optical fiber cable by the injection pressure of the gel should be reduced. Thus, the tension of the optical fiber cable can be adjusted with high accuracy. Therefore, the extra length control can be performed with high accuracy and stability.

Further, the introduction tube is inserted and fixed in the metal tube so as to be elastically pressed against the inner wall opposite to the irradiation surface of the metal tube at the irradiation position of the laser light, so that the introduction tube is continuously connected. Even if vibration occurs in the metal tube sent while being molded,
The distance between the inlet pipe and the welding surface can always be kept to a maximum, the power density of the laser light applied to the inlet pipe is reduced, and the energy of the laser light absorbed by the inlet pipe is increased. The heat influence on the inlet pipe and the internal optical fiber can be reduced to a minimum, and even if welding spatter accumulates on the upper surface of the inlet pipe, it can be prevented from coming into contact with the metal pipe. Can be done.

The optical fiber introducing tube is formed such that the first passage tube through which the optical fiber or the optical fiber bundle passes is smaller than the maximum diameter of the tapered portion of the optical fiber introducing tube, so that the gel from the entrance of the optical fiber cable can be formed. Can be prevented from flowing backward.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of an apparatus for manufacturing a metal tube-coated optical fiber cable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber introduction apparatus 2 Optical fiber cable 3 Seal pipe 4 Gel supply pipe 5 Manifold 6 Optical fiber introduction pipe 6a Attachment part 6b Taper part 6c Tip guide part

Claims (3)

(57) [Claims] 1. An optical fiber introducing apparatus having an optical fiber introducing tube inserted into a metal tube formed by molding a metal strip and guiding an optical fiber or an optical fiber bundle and a gel-like substance into the metal tube. An optical fiber introduction device, wherein a tapered taper portion is provided in the vicinity of a metal tube insertion position of the introduction tube. 2. The metal tube is formed by forming a metal strip and sealing a butt portion by laser welding, and the optical fiber introducing tube is in contact with an irradiation surface of the metal tube at or near a laser beam irradiation position. The optical fiber introduction device according to claim 1, wherein the optical fiber introduction device is elastically pressed against the inner wall on the opposite side. 3. The optical fiber introducing tube is connected to a first passage tube for passing an optical fiber or a bundle of optical fibers, and a second passage tube for passing a gel-like substance. 3. The optical fiber introduction device according to claim 1, wherein the optical fiber introduction device is formed to be smaller than a maximum diameter of a tapered portion of the introduction tube.