JP2017068220A - Connection structure and connection method of metal tube covered optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connection structure and a connection method of a metal tube covered optical fiber cable that enable improvement of workability and reliability.SOLUTION: A connection structure of a metal tube covered optical fiber cable houses optical fibers 3 in a first metal tube 1 and a second metal tube 2, and connects the optical fibers 3 to each other which are exposed from an end part of the first metal tube 1 and the second metal tube 2. The connection structure thereof includes: a sleeve tube 4 that has an inner diameter larger than an outer diameter of the first metal tube 1 and the second metal tube 2 and is disposed over a connection part of the optical fibers 3; and a first coupling tube 5 and a second coupling tube 6 that are fitted on the respective first metal tube 1 and second metal tube 2, and coupled to each of the first metal tube 1 and the second metal tube 2, and the sleeve tube 4, respectively.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a connection structure and a connection method for a metal tube coated optical fiber cable, and more particularly to a metal tube coated optical fiber cable in which an optical fiber such as an optical fiber, an optical fiber cord, and an optical fiber cable is accommodated in a metal tube. The present invention relates to a connection structure and a connection method.

  In recent years, an optical composite power cable is often used as a power cable laid on the seabed. By using the optical composite power cable, the communication line can be secured simultaneously with the construction of the power transmission line, and the laying cost of the optical fiber cable can be reduced.

  In the optical composite power cable, for example, a three-phase power cable for three-phase AC power transmission is twisted, and an optical fiber cable is disposed in a space formed by the twisted power cable. In this way, by using the empty space between the power cables, the power cable and the optical fiber cable can be combined without increasing the outer diameter of the entire cable.

  The optical fiber cable used at this time has a small outer diameter and is excellent in hermetic performance and corrosion resistance, so that a metal tube containing an optical fiber inside a metal tube such as a hollow iron wire or stainless steel tube is used. It may be used in the structure of a coated optical fiber cable. The space between the inside of the metal tube and the optical fiber is filled with a resin jelly. This jelly has a role of preventing transmission loss due to compression or microbending in the internal optical fiber due to the metal tube being crushed and deformed by water pressure when laid on the seabed.

  A connection structure and a connection method for a metal tube-covered optical fiber cable have been proposed in, for example, Patent Document 1.

FIG. 6 is an explanatory diagram for explaining a conventional method of connecting a metal tube-coated optical fiber cable, and FIG. 7 is a side sectional view showing a connection structure of a conventional metal tube-coated optical fiber cable.
First, the metal tube 50 is stripped off, and the standby is performed with the sleeve tube 51 fitted on one metal tube 50 side (see FIG. 6A), and the end faces of the optical fiber 52 are connected to each other at the connecting portion. 52a is connected by fusion splicing or the like (see FIG. 6B).

  Next, the sleeve pipe 51 is pulled back so as to cover the connecting portion 52a, and is arranged between the respective end portions of the stepped metal pipe 50 (see FIG. 6C).

  Next, if both ends of the sleeve pipe 51 are fixed to the metal pipe by a welded portion 53 by a welding machine 53 such as a laser beam welder (see FIGS. 6C and 6D), it is shown in FIG. Such a metal tube-coated optical fiber cable connection structure can be obtained (hereinafter, this technique is referred to as Conventional Example 1).

  Moreover, although the length which can manufacture an optical fiber cable and an electric power cable each has a limit, as a submarine cable, a cable longer than this is needed at the time of laying work. For this reason, it becomes possible to lengthen the optical composite power cable by connecting manufactured power cables or optical fiber cables at a factory.

  Since the connection portion (joint portion) of such an optical fiber cable is arranged in the empty space between the power cables as described above, for example, as in Patent Document 2, the outer periphery of the holder fixed to the tension member in this empty space It is fixed by being fitted into a recess (hereinafter, this technique is referred to as Conventional Example 2).

  Patent Document 3 proposes a cable containing an optical fiber in which an optical fiber is inserted into a hollow iron wire provided along the power cable (hereinafter, this technique is referred to as Conventional Example 3).

JP-A-5-119224 Japanese Patent No. 3714928 JP-A-6-309943

  In Conventional Example 1, the number of optical fibers to be accommodated is one or up to two, and the metal tube of this cable part is peeled off from about 100 mm to about 1000 mm to bring out the core of the optical fiber. After performing the fusion splicing, the sleeve tube is covered with a hollow metal tube-like sleeve tube so as to protect the fused portion, and both ends of the sleeve tube are welded to the metal tube to make the inside of the sleeve tube watertight. It has a structure. In this case, the sleeve tube is placed in a state where it is temporarily kept waiting on either the right or left of the two cables to be connected before the optical fiber connection work. A method is adopted in which the cable portions on both sides and the metal tube are overlapped by sliding so as to protect the connection portion.

  Here, the metal tube that accommodates the optical fiber has an inner diameter of 0.7 mm / an outer diameter of 0.9 mm (plate thickness of 0.1 mm) using a stainless steel material, for example, in an optical fiber single-core structure. The diameter is 0.25 mm. On the other hand, the sleeve tube has a structure of an inner diameter of 1.0 mm / an outer diameter of 1.2 mm (plate thickness of 0.1 mm) so as to have a clearance of 0.1 mm between the inner diameter of the sleeve tube and the outer diameter of the metal tube.

  In addition, a fusion splicing method is used to connect optical fibers. For the purpose of mechanically reinforcing the fusion spliced portion, when a heat shrinkable tube having a reinforcing metal rod called a reinforcing sleeve is used, the portion Since the outer diameter of the metal tube becomes thicker than about 3.0 mm, and the outer diameter of the metal tube becomes larger than 0.9 mm, it becomes impossible to store the metal tube in the sleeve tube. For this reason, as a mechanical reinforcement method of the fusion spliced portion instead of the reinforcing sleeve, a method called recoat obtained by irradiating UV after applying a UV curable resin is used, so that the outer diameter after reinforcement is also the original. It becomes possible to be suppressed to 0.25 mm which is substantially equal to that of the optical fiber, and the fusion splicing portion can be accommodated in the sleeve tube. Thereafter, the end of the sleeve tube is welded to the metal tube so that the inside can be watertight.

  On the other hand, when the number of optical fibers is increased to 48, for example, when a stainless steel material is used for the metal tube, the inner diameter is 3.2 mm / the outer diameter is 3.6 mm (plate thickness is 0.2 mm). Is used. In order to connect optical fiber cables, it is necessary to fuse and connect 48 optical fibers one by one. In this optical fiber connection work, when performing the fusion work of 48 fibers, from the left and right metal tubes to be connected, the fiber core wire is bare and approximately 1000 mm to 2000 mm is taken out and straightened. Therefore, fusion splicing and recoat reinforcement work will be performed. For this reason, the length of the bare optical fiber including the connected portion after this operation is about 2000 mm. This bare optical fiber portion is structured to be protected by a metal sleeve tube of 2000 mm or more.

In this case, the following attention is required.
(1) It is necessary to manage such that the lengths after the optical fibers 48 are fused and connected are all equal.

  (2) The connection of the optical fiber takes about 2000 mm in length, and it is necessary to perform fusion and recoating work while the optical fiber is bare, but the optical fiber itself has a glass material structure of 0.25 mm diameter. In handling, careful handling is necessary to avoid trauma and decisiveness.

  Since it is necessary to perform the fusion splicing and recoating work for 48 cores while paying attention to the above (1) and (2), a lot of management and skilled workers are required, and workability is very high. There was a problem of being bad.

In addition, since the sleeve tube and the metal tube are welded to obtain an internal watertight structure,
(Inner diameter of sleeve tube) = (Outer diameter of metal tube of cable part) +0.1 mm
As a result, the inner diameter of the sleeve tube was limited. For this reason, for example, a sleeve tube structure for connecting a 48-core optical fiber cable having a metal tube structure (tube structure inner diameter 3.2 mm / outer diameter 3.6 mm) has an inner diameter of 3.7 mm / outer diameter of 4.1 mm (plate thickness 0). .2 mm). In this case, the inner diameter of the sleeve tube is 3.7 mm thicker than 1.0 mm at the time of one or two cores. However, a reinforcing sleeve (outer diameter is about 3 mm) is still used as a reinforcing structure of the optical fiber fusion splicing portion. 0.0 mm), the space occupancy in the sleeve tube is 50% or more, so that the other 47 optical fibers are packed in a narrow space, and the optical transmission characteristics deteriorate. was there.

Also, in this case, the sleeve tube is placed in a state where it is temporarily waiting at either the right or left of the two cables to be connected before the optical fiber connection work, and after the optical fiber connection work, The method of sliding the splicing connection part so as to protect it and superimposing it on the cable metal tubes on both sides is the same as that for connecting one or two cores. However, in the case of 48 cores, the length of the bare optical fiber part and the optical fiber connection part is 2000 mm or longer after the connection work, and a sleeve tube (with an inner diameter of 3.7 mm) is slid on this. To cover
(1) Keep the bundle of 48 optical fibers in a lump. (2) When sliding the sleeve tube, do not damage the optical fiber in the bare state and the optical fiber connection. There is a problem that management is necessary and there is a problem in workability in this respect as well.

  Further, as a countermeasure against water pressure, it is necessary to fill the inside of the sleeve tube for housing the optical fiber connection portion with jelly. In this case, after applying a sufficient amount of jelly so that the outer diameter of the coated jelly is equal to the outer diameter of the metal tube in a state where multi-core optical fibers including the connecting portion are bundled together, the sleeve A general method is to fill a jelly inside the tube by sliding the tube. In this case, even when the space between the inner diameter of the sleeve tube and the optical fiber and its connecting portion is filled with jelly, there is a problem that some air gaps remain and the water pressure resistance is lowered.

  When the sleeve tube is slid, a part of the jelly applied to the optical fiber is scraped off by the mouth of the sleeve tube, and a part of the jelly is attached to the inside of the mouth of the sleeve tube. In this case, during the subsequent welding operation between the end portion of the sleeve tube and the metal tube, there is a problem that the jelly present at the sleeve tube opening causes a welding failure between the metals.

  Conventional example 2 and conventional example 3 do not disclose any connection structure and connection method of the metal tube coated optical fiber cable related to the present invention, and there is no description suggesting it.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a connection structure and a connection method for a metal tube-coated optical fiber cable that can improve workability and reliability.

The first metal tube-covered optical fiber cable connection structure of the present invention connects the optical fibers exposed from the end of the metal tube of a metal tube-covered optical fiber cable in which the optical fiber is accommodated in the metal tube. In the connection structure of metal tube coated optical fiber cable,
A sleeve tube having an inner diameter larger than an outer diameter of the metal tube and disposed on a connection portion of the optical fiber;
A connecting pipe fitted to the metal pipe and connected to the metal pipe and the sleeve pipe;
It is characterized by having.

The connection structure of the 2nd metal pipe covering optical fiber cable of this invention connects the said optical fibers exposed from the edge part of the said metal pipe of the metal pipe covering optical fiber cable which accommodates an optical fiber in a metal pipe. In the connection structure of the metal tube coated optical fiber cable, the sleeve tube has an inner diameter larger than the outer diameter of the metal tube, and is disposed on the connection portion of the optical fiber;
It has a connecting pipe which is arranged so that the end of the metal pipe may be covered, and is connected with the metal pipe and the sleeve pipe, respectively.

  A protective tube for protecting the connection portion of the optical fiber may be attached to the inside of the sleeve tube.

  The protective tube may be formed with a notch for injecting jelly.

The method for connecting a metal tube-coated optical fiber cable according to the present invention includes a metal tube coating for connecting the optical fibers exposed from the end of the metal tube of a metal tube-coated optical fiber cable in which an optical fiber is accommodated in a metal tube. In the connection method of the optical fiber cable,
A step of waiting a sleeve tube having an inner diameter larger than the outer diameter of the metal tube on one metal tube side;
Fitting and connecting a connecting pipe to each of the one metal pipe and the other metal pipe, or connecting the connecting pipe so as to cover each end; and
Disposing the sleeve tube on the connecting portion of the optical fiber, and connecting the sleeve tube and the connecting tube;
It is characterized by having.

  According to the connection structure of the metal tube-coated optical fiber cable of the present invention, the sleeve tube having an inner diameter larger than the outer diameter of the metal tube is arranged at the connection portion of the optical fiber housed in the metal tube. The storage space of the part becomes wide. As a result, work using the fusion sleeve is possible, and workability can be improved.

  Further, since the storage space for the optical fiber connection portion is wide, the optical fiber is not jammed, the optical transmission characteristics can be prevented from being deteriorated, and the reliability can be improved.

  According to the method for connecting a metal tube-coated optical fiber cable of the present invention, since the storage space for the optical fiber connection portion is large, the risk of causing damage to the optical fiber can be reduced when the sleeve tube is disposed on the optical fiber connection portion. Therefore, workability and reliability can be improved.

It is side surface sectional drawing which shows the connection structure of the metal pipe coating | coated optical fiber cable which concerns on the example of 1st Embodiment of this invention which accommodated the several single fiber in the metal pipe. BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view for demonstrating the connection structure and connection method of the metal pipe covering optical fiber cable which concern on the 1st Example of this invention, (A) is a state before connecting a sleeve pipe and a connection pipe. (B) shows the state after connection. It is side surface sectional drawing which shows the connection structure of the metal tube covering optical fiber cable which concerns on the example of 1st Embodiment of this invention which accommodated the several multi-fiber in the metal tube. It is a perspective view for demonstrating the connection structure and connection method of the metal pipe covering optical fiber cable which concern on the 2nd Example of this invention, (A) is a state before connecting a sleeve pipe and a connection pipe. (B) shows the state after connection. (A) is a perspective view showing a protective tube, (B) is a perspective view for explaining a connection structure and a connection method of a metal tube-coated optical fiber cable according to a third embodiment of the present invention equipped with a protective tube. (C) is a perspective view which shows the state which is injecting jelly into the notch part of a protective tube. (A)-(D) are explanatory drawings for demonstrating the connection method of the conventional metal tube covering optical fiber cable. It is side surface sectional drawing which shows the connection structure of the conventional metal pipe covering optical fiber cable.

  Embodiments of the present invention will be described below. FIG. 1 is a side sectional view showing a connection structure of a metal tube-coated optical fiber cable according to a first embodiment of the present invention in which a plurality of single-core optical fibers are housed in a metal tube, and FIG. It is a perspective view for demonstrating the connection structure and connection method of the metal pipe covering optical fiber cable which concern on the example of embodiment, (A) shows the state before connecting a sleeve pipe and a connection pipe, (B) Indicates the state after connection.

  As shown in FIG. 1, FIG. 2 (A) and FIG. 2 (B), the connection structure of the metal tube-covered optical fiber cable according to the first embodiment of the invention is the first metal tube 1 and the second metal tube. The optical fiber 3 is accommodated in the optical fiber 3 and the optical fibers 3 exposed from the ends from which the first metal tube 1 and the second metal tube 2 are removed are connected to each other. The inner diameter of the second metal tube 2 is larger than the outer diameter, and the sleeve tube 4 disposed on the connection portion of the optical fiber 3 is fitted to the first metal tube 1 and the second metal tube 2, respectively. And a first connecting pipe 5 and a second connecting pipe 6 respectively connected to the first metal pipe 1 and the second metal pipe 2 and the sleeve pipe 4.

  Since the inner diameter of the sleeve tube 4 is larger than the outer diameters of the first metal tube 1 and the second metal tube 2, there is no gap between the sleeve tube 4 and the first metal tube 1 and the second metal tube 2. A large clearance occurs.

  In order to adjust the clearance, first, the sleeve tube 4 is put on standby on the first metal tube 1 side.

  Next, the first and second short connecting pipes 5 and 6 made of metal having a predetermined thickness are fitted onto the first metal pipe 1 and the second metal pipe 2, so that the first The connecting pipe 5 and the second connecting pipe 6 are connected to the first metal pipe 1 and the second metal pipe 2 by welding or the like, respectively (see FIG. 2A).

  Next, after the optical fiber 3 is connected, the sleeve tube 4 is slid and placed on the connection portion of the optical fiber 3, and the sleeve tube 4, the first connecting tube 5 and the second connecting tube 6 are welded or the like. Connect each one. Thereby, the connection structure of the metal tube-coated optical fiber cable according to the first embodiment of the present invention is obtained (see FIG. 2B).

  For example, with respect to the first metal tube 1 and the second metal tube 2 (inner diameter 3.2 mm / outer diameter 3.6 mm) that accommodate the 48-core optical fiber cable, the inner diameter is 3.7 mm / outer diameter is 5.0 mm, long. When the first connecting pipe 5 and the second connecting pipe 6 having a thickness of 50 mm are used, the sleeve pipe 4 can have a structure of inner diameter 5.1 mm / outer diameter 5.7 mm (plate thickness 0.3 mm). become.

  When the first connecting pipe 5 and the second connecting pipe 6 are used, the number of welding points is increased to six. However, since the sleeve pipe 4 having a large inner diameter can be used, the fused portion of the optical fiber 3 can be used. The storage space is widened, and it is possible to work using the fusion sleeve 3a (see FIG. 1) having an outer diameter of about 3.0 mm as a reinforcing method of the fiber fusion portion, which improves workability compared to recoating. It becomes possible.

  As shown in FIG. 1, the use of a sleeve tube 4 with a large inner diameter increases the storage space, and when a single optical fiber is connected, a fusion sleeve 3a having an outer diameter of about 3.0 mm is used. All work is possible and workability is improved.

  FIG. 3 is a side sectional view showing a connection structure of a metal tube-coated optical fiber cable according to the first embodiment of the present invention in which a plurality of multi-core optical fibers are housed in a metal tube.

  As shown in FIG. 3, the use of a sleeve tube 4 with a large inner diameter increases the storage space, and a fusion sleeve for 8 cores that reinforces a portion where optical fiber 8 cores are taped together and fused together. Since the outer diameter of 3b is about 3.5 mm, it is possible to apply a connection method by 8-core batch fusion. With 8-core batch fusion, 48-fiber optical fiber cables can be completed with 6 fusion operations as shown in Fig. 3, dramatically improving workability in optical fiber connection operations. Can be made.

  FIG. 4 is a perspective view for explaining a connection structure and a connection method of a metal tube-covered optical fiber cable according to a second embodiment of the present invention. FIG. 4A is a view before connecting a sleeve tube and a connection tube. (B) shows the state after connection.

  As shown in FIG. 4, the first connecting pipe 7 and the second connecting pipe 8 in the metal tube-coated optical fiber cable according to the second embodiment of the present invention are the same as the first embodiment. The length is longer than that of the connecting pipe 5 and the second connecting pipe 6, and the tip ends of the first metal pipe 1 and the second metal pipe 2 are arranged so as to cover the intermediate portions thereof. . As a result, a connection structure with improved watertightness can be provided.

  Connecting the first connecting pipe 7 and the second connecting pipe 8 to the first metal pipe 1 and the second metal pipe 2 by welding or the like, and placing the sleeve pipe 4 on the connecting portion of the optical fiber 3; The sleeve tube 4 is connected to the first connecting tube 7 and the second connecting tube 8 by welding or the like. Thereby, the connection structure of the metal tube-coated optical fiber cable according to the second embodiment of the present invention is obtained.

  FIG. 5A is a perspective view showing a protective tube, and FIG. 5B is a diagram for explaining a connection structure and a connection method of a metal-tube-coated optical fiber cable according to a third embodiment of the present invention equipped with a protective tube. A perspective view and (C) are perspective views showing the state where jelly is injecting into the notch of a protection tube.

  Since the accommodation space inside the sleeve tube 4 has become wider, a space of, for example, about 0.05 to 2 mm is provided between the outer periphery of the optical fiber connection sleeve and the optical fiber bundled together and the inside of the sleeve tube 4. Is possible. Using this space, the protective tube 9 shown in FIG. 5A is attached to the metal tube-covered optical fiber cable connection structure according to the third embodiment of the present invention.

  As shown in FIGS. 5A and 5B, a protective tube 9 that protects the connection portion of the optical fiber 3 is attached to the inside of the sleeve tube 4. The protective tube 9 is formed by processing a plastic tube or a plastic sheet, and a cut portion 9a is formed in the longitudinal direction.

  For example, the optical fiber 3 in a bare state is used by using a protective tube 9 having an inner diameter larger than that of the first metal tube 1 and the second metal tube 2 and slightly smaller than the inner diameter of the sleeve tube 4. Further, by protecting the connection portion of the optical fiber 3, it is possible to prevent the optical fiber 3 from being damaged when the sleeve tube 4 is slid from the side.

  The protective tube 9 may have a structure in which a plastic film is wrapped or a structure in which a plastic tape is wound.

  Since the notch 9a is formed in the protective tube 9 in the longitudinal direction, as shown in FIG. 5C, by injecting jelly using a syringe-like injection device 10, the inside of the protective tube 9 It becomes possible to fill the gap between the optical fiber 3 and the connection portion of the optical fiber 3 with no jelly. At this time, the sleeve tube 4 having an inner diameter slightly larger than the outer diameter of the protective tube 9 is slid to be covered, thereby completing the structure of the connecting portion so that there is no air gap inside the sleeve tube 4. Therefore, it is possible to provide a connection structure with improved water pressure resistance.

  By making a part or all of the protective tube 9 from a transparent material, it is possible to monitor the state in which the internal jelly is filled and the state of the optical fiber 3 even if the protective tube 9 is covered. Since it is possible to cover the sleeve tube 4 after confirming whether or not there is no microbend or the like, reliability can be further improved and a high-quality connection structure can be provided.

  According to the connection structure of the metal tube-coated optical fiber cable of the present invention, the sleeve tube 4 having an inner diameter larger than the outer diameter of the first metal tube 1 and the second metal tube 2 is connected to the first metal tube 1 and Since it arrange | positions in the connection part of the optical fiber 3 accommodated in the 2nd metal pipe 2, the storage space of an optical fiber connection part becomes large. Thereby, work using the fusion sleeves 3a and 3b becomes possible, and workability can be improved.

  In addition, since the storage space for the optical fiber connection portion is wide, the optical fiber 3 is not packed in a narrow space, so that the deterioration of the optical transmission characteristics can be prevented and the reliability can be improved.

  According to the method for connecting a metal tube-coated optical fiber cable of the present invention, since the storage space for the optical fiber connection portion is widened, the risk of causing damage to the optical fiber 3 when the sleeve tube 4 is disposed on the optical fiber connection portion. Therefore, workability and reliability can be improved.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical matters described in the claims.

  The connection structure and connection method for a metal tube-coated optical fiber cable according to the present invention is a method for connecting a metal tube-coated optical fiber cable in which an optical fiber such as an optical fiber, an optical fiber cord, or an optical fiber cable is accommodated in a metal tube. Used for.

1: First metal tube 2: Second metal tube 3: Optical fiber 3a: Fusing sleeve 3b: Fusing sleeve 4: Sleeve tube 5: First connecting tube 6: Second connecting tube 7: First Connecting pipe 8: second connecting pipe 9: protective pipe 9a: notch 10: injection device

Claims (5)

In the connection structure of the metal tube-coated optical fiber cable for connecting the optical fibers exposed from the end of the metal tube of the metal tube-coated optical fiber cable formed by housing the optical fiber in the metal tube,
A sleeve tube having an inner diameter larger than an outer diameter of the metal tube and disposed on a connection portion of the optical fiber;
A connecting pipe fitted to the metal pipe and connected to the metal pipe and the sleeve pipe;
A metal tube-coated optical fiber cable connection structure characterized by comprising: In the connection structure of the metal tube-coated optical fiber cable for connecting the optical fibers exposed from the end of the metal tube of the metal tube-coated optical fiber cable formed by housing the optical fiber in the metal tube,
A sleeve tube having an inner diameter larger than an outer diameter of the metal tube and disposed on a connection portion of the optical fiber;
A connection structure for a metal tube-coated optical fiber cable, comprising: a connection tube disposed so as to cover an end portion of the metal tube and connected to the metal tube and the sleeve tube.   The metal tube-covered optical fiber cable connection structure according to claim 1, wherein a protective tube that protects the connection portion of the optical fiber is attached to the inside of the sleeve tube.   The metal tube-covered optical fiber cable connection structure according to claim 3, wherein the protective tube is formed with a notch for injecting jelly. In the method of connecting a metal tube-covered optical fiber cable for connecting the optical fibers exposed from the end of the metal tube of a metal tube-covered optical fiber cable containing an optical fiber in a metal tube,
A step of waiting a sleeve tube having an inner diameter larger than the outer diameter of the metal tube on one metal tube side;
Fitting and connecting a connecting pipe to each of the one metal pipe and the other metal pipe, or connecting the connecting pipe so as to cover each end; and
Disposing the sleeve tube on the connecting portion of the optical fiber, and connecting the sleeve tube and the connecting tube;
A method for connecting a metal tube-coated optical fiber cable, comprising:

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