JPH04335306A - Optical fiber guiding-in device - Google Patents

Abstract

PURPOSE:To perform stable operation for a long time by controlling excessive length more finely under tension control and eliminating the adverse influence of welding. CONSTITUTION:A guide-in pipe 1 consists of an external pipe 6 which has a tip tapered part 6a and an internal pipe 7 which is provided concentrically in the external pipe 6 and inserted almost to the tapered part. The large- diameter part of the external pipe 6 is arranged outside the metallic pipe and the gap between the external pipe and internal pipe where jell is passed is made large to lower the pressing-in pressure for the jell. The small-diameter part of the guide-in pipe 1 is pressed elastically against the internal wall of the metallic pipe on the opposite side from its irradiated surface at a laser light irradiation position to prevent melting loss right below a weld zone.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] This invention provides an optical fiber cable that is placed inside a metal tube when manufacturing a metal tube coated optical fiber cable.
The present invention relates to an optical fiber introduction device that injects and fills gel while introducing blue.

0002

[Prior Art] The so-called metal tube coated optical fiber cable is
A structure is adopted in which an optical fiber or optical fiber bundle (hereinafter referred to as optical fiber) is loosely wrapped in a metal tube. This structure allows the metal tube to function as a tensile strength member, and by laying the optical fiber somewhat loosely, a decrease in the transmission efficiency of the optical fiber is prevented. Then, the metal tube coated optical fiber cable
When installing cables on the seabed or underground, the space between the metal pipe and the optical fiber is filled with gel, a viscous substance that has waterproof and water-stop properties, to prevent the optical fiber from deteriorating due to water. .

[0003] As a method of manufacturing such a metal tube-coated optical fiber cable, for example, as disclosed in Japanese Patent Application Laid-Open No. 57-100402, an optical fiber and gel are simultaneously introduced into a metal tube using a single introduction tube. As disclosed in Japanese Patent Application Laid-open No. 58-95304, an introduction tube with a double tube structure consisting of an outer tube and an inner tube of the same length is used, and an optical fiber is inserted into the inner tube. A method is adopted in which a gel is passed between the inner tube and the outer tube and introduced into the metal tube while being introduced.

[0004] Furthermore, in order to loosely install the optical fiber in the metal tube, it is necessary to perform so-called surplus length control, which adjusts the length of the optical fiber so that it becomes longer at a certain rate than the length of the metal tube. In order to provide the optical fiber with extra length in this way, various controls are applied to the transport of the optical fiber. For example, Japanese Patent Application Laid-Open No. 57-100402 discloses a method of jetting gel from the upstream side of a metal tube continuously formed from a metal strip and effectively utilizing the viscosity of the gel to provide extra length. is disclosed. however,
In this method, gel is blown out from the metal tube, so when sealing the formed metal tube by welding, there is a concern that it will have an adverse effect on the welding. On the other hand, JP-A-58-95
JP-A-61-174, which is a technology related to Publication No. 304
No. 47 discloses a method of adjusting the tension of a metal tube or optical fiber to provide extra length. According to this method of adjusting the tension, there is no concern about the adverse effects during welding as described above, and the butt portions of the metal tubes can be welded by soldering, TIG welding, or laser welding. Further, the extra length can be controlled more precisely than the extra length control based on the viscosity of gel.

[0005]

[Problems to be Solved by the Invention] However, in order to meet the demands for high quality, it is necessary to control the surplus length ratio by tension control more precisely. For this purpose, the tension of the optical fiber may be adjusted in advance using a mechanical means such as a dancer roll, but this results in unexpected tension being applied to the optical fiber within the introduction tube. For example, when introducing an optical fiber and gel using a single tube structure introduction tube while preventing the gel from blowing out from the metal tube, the interaction between the optical fiber and gel inside the introduction tube may cause the optical fiber to A large back tension acts on the material, and the remaining length ratio fluctuates unevenly from the target value. This is due to the non-uniformity of the gel's viscosity. This decrease becomes more noticeable when the diameter of the metal tube becomes smaller and the diameter of the introduction tube becomes smaller accordingly, or when a highly viscous gel is used.

[0006] Furthermore, when an introduction tube with a double tube structure is used, there is no interaction between the optical fiber and the gel as described above within the introduction tube, so the tension previously applied mechanically is maintained. The optical fiber can be introduced into the metal. However, if the metal tube has a small diameter, the introduction tube with a double tube structure must also be made thinner accordingly. In this case, there are limits to reducing the diameter and thickness of the inner tube that guides the optical fiber. Also,
There is also a limit to increasing the diameter of the outer tube, and especially when welding metal tubes, there is a problem of melting damage directly under the weld, so the diameter of the outer tube must be made smaller. Therefore, the gap between the inner tube and the outer tube through which the gel passes becomes very narrow. in this case,
In order 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 deform due to this pressure. This reduction is more pronounced when using high viscosity gels. For this reason, the double-tube structure introduction tube could only be applied to metal tubes with large diameters.

Furthermore, when welding the butt portions of metal tubes, it is necessary to prevent the adverse effects of welding heat on the optical fiber as much as possible. For this purpose, heat is shielded by an inlet pipe at the welding position, but since the inlet pipe is only inserted into the metal pipe and is not particularly positioned, vibrations of the metal pipe while running may cause the inlet pipe to overlap the metal pipe. The distance between the pipe and the welded surface becomes very small. For this reason, if the operation is continued for a long time, the welding spatter deposited on the inlet tube may come into contact with the inner wall of the metal tube, causing welding defects, making it impossible to continuously manufacture long metal tube-coated optical fibers. Ta. Furthermore, there was a risk that the heat of TIG welding or laser welding would burn out the top surface of the introduction tube, creating a hole and burning the gel passing inside.

[0008] The present invention has been made to solve these disadvantages, and when manufacturing a gel-filled metal tube coated optical fiber cable, it is difficult to use high viscosity gel or a small diameter metal tube. The object of the present invention is to provide an optical fiber introduction device that can precisely control the extra length by tension control, prevent the adverse effects of welding, and operate stably for a long time.

[0009]

[Means for Solving the Problems] An optical fiber introducing device according to the present invention molds a continuously fed metal strip, and laser welds the abutted portions to form an optical fiber or an optical fiber into a metal tube. An optical fiber introduction device having an introduction tube for guiding a bundle and gel, wherein the introduction tube has a tapered part, and an outer tube whose tip end is inserted to a position past the laser welding part; It is characterized by comprising an inner tube which is provided concentrically within the outer tube and whose distal end is inserted up to or near the tapered portion. It is preferable that the introduction tube is elastically pressed against the inner wall of the metal tube on the side opposite to the irradiation surface at the laser beam irradiation position.

0010

[Operation] In the present invention, the introduction tube is composed of an outer tube having a tapered portion and an inner tube provided concentrically within the outer tube and having its distal end inserted into the vicinity of the tapered portion. Since the large diameter portion of the outer tube is placed outside the metal tube and the small diameter portion of the outer tube is placed inside the metal tube, there is no restriction on the outer diameter of the large diameter portion of the outer tube, and the outer tube through which the gel passes can be used. The gap between the tube and the inner tube can be increased, and the press-fitting pressure for feeding the required amount of gel into the metal tube can be lowered.

Furthermore, by making the small diameter portion of the outer tube from the tapered portion as thin as a single tube, it can be inserted reliably into a narrow metal tube. At the laser beam irradiation position, this small diameter part is elastically pressed against the inner wall of the metal tube on the opposite side of the irradiation surface, and by inserting the tip of the small diameter part to a position past the laser weld, the weld Prevents melting damage directly below.

Furthermore, the optical fiber and gel do not come into contact with each other outside the metal tube, and the contact area between the optical fiber and gel is limited to the small diameter portion of the single-tube structure, so the viscous resistance of the gel is applied to the optical fiber. The applied tension can be reduced.

[0013] Also, the metal tube insertion portion of this introduction tube is inserted into the metal tube so that it is elastically pressed against the inner wall of the metal tube on the opposite side of the irradiation surface at the laser beam irradiation position, and welding is performed. At this point, the inlet pipe is fixed to the inner wall of the metal tube on the opposite side from the welding surface to increase the distance between the welding surface and the inlet pipe.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing an embodiment of the present invention. As shown in the figure, an introduction tube 1 for introducing an optical fiber 2 and a gel 3 into a metal tube 4 is made of a metal with good thermal conductivity, such as copper or a copper alloy, and is bent into an approximately L-shape with a certain curvature. part is inserted into a metal tube 4 that covers the optical fiber 2. This introduction tube 1 is composed of an outer tube 6 and an inner tube 7. The outer tube 6 has a tapered part 6a at the insertion part of the metal tube 4, and a large diameter part 6b outside the tapered part 6a. The portion inserted into the metal tube 4 beyond the tapered portion 6a is a small diameter portion 6c that is made thinner according to the inner diameter of the metal tube 4. The small diameter portion 6c is elastically pressed against the inner wall of the metal tube 4 on the side opposite to the irradiation surface at the irradiation position of the laser beam from the laser welding device 5, and its tip is positioned at the rear stage of the welding part. are doing. When pressing the introduction tube 1, by pressing the entire introduction tube 1 downward and fixing it, the tip of the introduction tube 1 is attached to the metal tube 4 using the elastic force of the curved part bent at a constant curvature. Can be pressure-welded. Further, a gel supply port 8 is provided in the middle portion of the large diameter portion 6b. The inner tube 7 is concentrically fixed within the large diameter portion 6b of the outer tube 6 by a seal portion 9, and its tip portion is located near the tapered portion 6a.

In the introduction tube 1 constructed as described above, the gel 3 is supplied at a constant pressure from the gel supply port 8 of the outer tube 6 while guiding the optical fiber 2 through the inner tube 7. The supplied gel 3 reaches the large diameter portion 6b of the inner tube 7 and outer tube 6 up to the tapered portion 6a.
The optical fiber 2 is sent through the gap between the two without contacting the optical fiber 2. The injection speed of the gel 3 is controlled to be approximately the same as the pulling speed of the optical fiber 2 while bringing the optical fiber 2 and the gel 3 into contact with each other at a relatively short distance small diameter portion 6c downstream of the tapered portion 6a. Then, the metal strip 4a is formed by a plurality of stages of forming means 10a to 10n and fed into the metal tube 4 running under constant tension. After the abutting portions of the metal tubes 4 are welded by a laser welding device 5, the diameter of the metal tubes 4 is reduced, the filling rate of the gel 3 is adjusted to an appropriate value, and the tubes are wound up.

When the optical fiber 2 passes through the inner tube 7 and the small diameter portion 6c of the outer tube 6, the tension T exerted on the optical fiber 2 by the gel 3 is given by the following equation.

[0017]

[Math. 1] T=K1・ΔP+K2・L・μ・V

0018
] However, K1 and K2 are constants determined by the length and cross-sectional area of the introduction tube, ΔP is the pressure loss of the gel, L is the contact length between the optical fiber and the gel, μ is the viscosity coefficient of the gel, and V is the feed of the optical fiber. It's speed.

Here, when the gel 3 passes through the gap between the inner tube 7 and the large diameter portion 6b of the outer tube 6, it is sent without contacting the optical fiber 2, so the gel 3 absorbs light at this portion. The tension T acting on the fiber 2 becomes zero. Further, since the large diameter portion 6b of the outer tube 6 is disposed outside the metal tube 4, its diameter can be increased. Therefore, by increasing the cross-sectional area of the gap between the inner tube 7 and the large diameter portion 6b, it is possible to reduce the viscous resistance of the gel 3 when passing through this gap. On the other hand, since the small diameter portion 6c in the metal tube 4 has a small cross-sectional area but a relatively short length, the viscous resistance of the gel 3 can be reduced compared to the case where the entire introduction tube 1 is composed of a single tube. Therefore, the press-fitting pressure of the gel 3 supplied from the gel supply port 8 can be made low. Therefore, the small diameter portion 6c
The pressure loss ΔP when passing through the optical fiber 2 becomes smaller.
Since the contact length L between the gel 3 and the gel 3 is also short, the tension T exerted by the gel 3 on the optical fiber 2 when the optical fiber 2 passes through the small diameter portion 6c becomes small. Therefore, the tension of the optical fiber 2, which is mechanically set before entering the introduction tube 1 in order to control the excess length, can be adjusted without causing a large change in the tension of the optical fiber 2.
can be introduced into the metal tube 4.

FIG. 2 compares the results of actually manufacturing a metal-coated optical fiber cable using this introduction tube 1 and measuring the extra length with the case where only a single introduction tube was used. Shown below. The outer tube 6 used here has a total length of 102 cm, the length of the large diameter part 6b is 35 cm, and the length of the small diameter part 6c is 6 cm.
It is 7cm. Further, the outer diameter of the large diameter portion 6b is 1.45 mm.
, the inner diameter is 1.3 mm, and the outer diameter of the small diameter portion 6c is 0.9 mm,
The inner diameter is 0.75 mm, and the outer diameter of the inner tube 7 is 0.55 m.
m, and the inner diameter is 0.4 mm. Also, the single-tube introduction tube has a total length of 102 cm, an outer diameter of 0.9 mm, and an inner diameter of 0.9 mm.
A piece having the same diameter as the small diameter portion 6c, 75 mm, was used. And each introduction tube has an optical fiber 2 with a diameter of 0.26 mm.
Gel 3 was supplied at an injection pressure of 20 kgf/cm 2 while passing through the fiber, and was produced at an optical fiber feed rate of 30 cm/s.

In FIG. 2, the horizontal axis shows the tension (gf) acting on the optical fiber 2, and the vertical axis shows the extra length (%) of the optical fiber. -Le 1
The sum of the tension T0 applied by mechanical means such as 1 and the tension T1 exerted by the gel 3 in the introduction tube 1 is shown. In addition, the tensions Ta and Tb indicate the tensions acting on the optical fiber 2 in this embodiment, Tc is the tension when using only a single introduction tube, and the tensions Ta and Tc are applied by the dancer roll 11. When the tension T0 is 20 gf, the tension Tb is 75 gf.

As shown in the figure, the tension T1 exerted by the gel 3 is approximately 22 gf in this example;
Compared to 580 gf when using only a single inlet tube, it was possible to significantly reduce the amount of gf. Therefore, when a tension T0 of 22 gf is set on the dancer roll 11, the tension Ta acting on the optical fiber 2 is approximately 42 gf, and the remaining length of the optical fiber at this time is approximately 0.26 gf, as shown by the white circle.
%Became. Furthermore, when the tension T0 of the dancer roll 11 is increased to 75 gf, the tension T0 acting on the optical fiber 2 is
b was about 97 gf, and the remaining length of the optical fiber at this time was about 0.09%, as shown by the black circle. On the other hand, when using only a single introduction tube, the tension T1 acting on the gel 3 becomes as large as 580gf, so the dancer row
When a tension T0 of 22 gf is set with the dancer roll, the extra length of the optical fiber is approximately 0.02% as shown by the triangle mark, and the tension T0 set with the dancer roll has the most effect on the extra length control. It's gone.

Thus, according to this embodiment, gel 3
Since the tension T1 acting on the dancer roll 11 can be made very small, the extra length of the optical fiber can be adjusted arbitrarily from about 0.01% to 0.3% by variably controlling the tension T0 applied by the dancer roll 11. can be controlled.

[0024] According to this embodiment, the tape of the outer tube 6
There is a possibility that the gel 3 will flow back into the inner tube 7 at the bar portion 6a and the optical fiber 2 and gel 3 will come into contact within the inner tube 7, but the gel 3 will cause a large bending loss at the optical fiber exit of the inner tube 7. Therefore, the gel 3 cannot enter the inner tube 7 unless there is pressure to overcome this bending loss. On the other hand, the pressure of the jelly 3 supplied to the outer tube 6 can be kept low considering the pressure loss due to the gap between the large diameter section 6b and the inner tube 7 and the pressure loss at the small diameter section 6c. can be made small, and the inner diameter of the inner tube 7 is small, so the gel 3
can be prevented from entering. In addition, since the optical fiber 2 is constantly sent out, even if the press-fitting pressure of the gel 3 temporarily increases and reaches a pressure level that allows the gel 3 to enter the inner tube 7, the gel that has entered the inner tube 7 It is sent out together with the optical fiber 2. Therefore, it is possible to prevent the gel 3 from flowing back inside the inner tube 7.

In this way, while continuously feeding the optical fiber 2 and gel into the metal tube 4, when welding the abutting surfaces of the metal tube 4 running at a constant speed, the optical fiber 2
The small diameter portion 6c of the gel introduction tube 1 can be made thinner according to the inner diameter of the metal tube 4, and the irradiation surface of the metal tube 4 is different from the laser beam irradiation position from the laser welding device 5. Since it is fixed in elastic pressure contact with the inner wall on the opposite side, even if vibration etc. occur in the metal tube 4, which is continuously being molded and fed,
The introduction pipe 1 can always be located on the opposite side to the welding surface, and the distance between the introduction pipe 1 and the welding surface can always be kept constant. Therefore, the power density of the laser light that enters the introduction tube 1 through the butt part of the metal tube 4 can be reduced, and the radiant heat received from the welded part can be reduced, so that the introduction tube 1 The amount of heat absorbed can be reduced. Furthermore, since the introduction tube 1 is made of copper or copper alloy with good thermal conductivity, the absorbed heat is quickly diffused and the introduction tube 1 is prevented from becoming high temperature. Therefore, the thermal influence of welding on the introduction tube 1, the optical fiber 2 guided by the introduction tube 1, and the gel can be reduced.

In addition, since the introduction pipe 1 is pressed against the inner wall on the opposite side of the welding surface, its position does not move and the distance from the welding surface can always be maintained at the maximum, so it can be operated for a long time. Even if welding spatter accumulates on the upper surface of the introduction tube 1, it can be prevented from coming into contact with the metal tube 4, and the small diameter portion 6c can be prevented from coming into contact with the metal tube 4.
The optical fiber 2 can be reliably separated from the weld bead, preventing the introduction tube 1 from being melted and damaged due to the heat of the weld.
and can prevent the gel from being damaged.

In the above embodiment, a curved introduction pipe 6 was used. However, a straight tapered introduction pipe is used, and a holding jig is used to hold the metal on the side opposite to the welding surface. Even if it is brought into pressure contact with the inner wall of the pipe, the same effect as in the above embodiment can be achieved. Further, in the above embodiment, the tapered portion 6a of the introduction tube 6 is provided near the insertion portion into the metal tube 4, but the tapered portion 6a is provided in the vicinity of the insertion portion into the metal tube 4.
The position of the pad portion 6a may be changed.

[0028]

Effects of the Invention As described above, in the present invention, the introduction tube is provided concentrically within the outer tube and the outer tube having a tapered portion at the metal tube insertion portion, and the tip portion is connected to the tapered portion. The large diameter portion of the outer tube is placed outside the metal tube, and the small diameter portion of the outer tube is located inside the metal tube. There is no restriction on the outer diameter, the gap between the outer tube and the inner tube through which the gel passes can be increased, and the press-fitting pressure for feeding the required amount of gel into the metal tube can be lowered.

Furthermore, by making the small diameter portion of the outer tube from the tapered portion as thin as a single tube, it can be inserted reliably into a narrow metal tube. At the laser beam irradiation position, this small diameter portion is elastically pressed against the inner wall of the metal tube on the opposite side of the irradiation surface, and by inserting its tip to the rear of the laser weld, the light beam directly below the weld is Not only can damage to the fiber and gel be prevented, but also melting and damage to the insertion tube can be prevented.

Furthermore, the optical fiber and gel do not come into contact with each other outside the metal tube, and the contact area between the optical fiber and gel is limited to the small diameter portion of the single-tube structure, so the viscous resistance of the gel affects the optical fiber. The tension that acts on the optical fiber can be reduced, the tension that acts on the optical fiber can be arbitrarily set, and the extra length of the optical fiber can be precisely controlled over a wide range.

[0031] Furthermore, by inserting and fixing the introduction tube into the metal tube so that it is in elastic pressure contact with the inner wall of the metal tube on the opposite side of the irradiation surface at the laser beam irradiation position, continuous Even if vibrations occur in the metal tube being sent while being formed,
The distance between the introduction pipe and the welding surface can always be maintained at the maximum, reducing the power density of the laser beam irradiated to the introduction pipe and increasing the energy of the laser light absorbed by the introduction pipe. In addition to reducing the thermal effect on the inlet tube and the optical fiber inside, it also prevents welding spatter from coming into contact with the metal tube even if it accumulates on the upper surface of the inlet tube, making long-term operation stable. It can be done by

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the invention.

FIG. 2 is a characteristic diagram of tension and surplus length acting on the optical fiber of the above embodiment.

[Explanation of symbols]

1 Introduction pipe 2 Optical fiber 3. Gel 4 Metal pipe 5 Laser welding equipment 6 Outer tube 6a Taper part 6b Large diameter part 6c Small diameter part 7 Inner pipe 8 Gel supply port

Claims (2)

[Claims] Claim 1: An optical fiber introduction device having an introduction tube for guiding an optical fiber or an optical fiber bundle and gel into a metal tube formed by forming a continuously fed metal strip and laser welding the abutting portions. wherein the introduction tube has a tapered portion, and the tip portion is provided concentrically within the outer tube and the outer tube is inserted to a position past the laser welding portion,
An optical fiber introduction device comprising an inner tube whose distal end portion is inserted up to or near the tapered portion. 2. The optical fiber introduction device according to claim 1, wherein the introduction tube is elastically pressed against an inner wall of the metal tube on the side opposite to the irradiation surface at the laser beam irradiation position.