JP7294687B2 - Submarine branching device, method for configuring submarine branching device, and submarine cable system - Google Patents

Description

The present disclosure relates to a submarine branching unit, a method of configuring a submarine branching unit, and a submarine cable system.

For example, as disclosed in Patent Document 1, a submarine branching device that branches one submarine cable into a plurality of submarine cables is known.

Japanese Patent No. 4089276

Inside the associated submarine branching unit, one tail cable connected to one submarine cable is connected to an airtight structural member that prevents ingress of seawater. A plurality of optical fibers included in the tail cable are branched into a plurality of groups inside the airtight structural member. A plurality of tail cables leading out the optical fibers branched into a plurality of groups from the airtight structural member are each connected to the submarine cable.

Thus, in the related submarine splitter, it is necessary to split the multiple optical fibers contained in the tail cable into multiple groups inside the hermetic structural member. Since the airtight structural member is container-shaped and occupies a predetermined space, there is a problem that the submarine branching device becomes large.

On the other hand, if the tail cable can be branched into a plurality of cables while maintaining airtightness, the submarine cable can be branched without an airtight structural member. That is, an airtight structural member becomes unnecessary, and the size of the submarine branching device can be reduced.
However, it has been difficult to branch a tail cable in which a plurality of optical fibers are covered with a metal tube into a plurality of fibers while maintaining airtightness.

In view of such problems, an object of the present disclosure is to provide a submarine branching device that can be miniaturized by branching a tail cable into a plurality of cables while maintaining airtightness.

A submarine branching device according to one aspect of the present disclosure includes:
a main tail cable having a plurality of optical fibers and a metal tube covering the plurality of optical fibers;
a first branch tail cable having a first group of the plurality of optical fibers and a metal tube covering the first group;
a second branch tail cable having a second group of the plurality of optical fibers and a metal tube covering the second group;
a branching member that connects the main tail cable and the first and second branch tail cables and has therein a through hole for branching the plurality of optical fibers into the first group and the second group; prepared,
One ends of metal tubes of the main tail cable and the first and second branch tail cables are brazed to the open ends of the through holes of the branch member.

A method for configuring a submarine branching device according to an aspect of the present disclosure includes:
a main tail cable having a metal tube covering the plurality of optical fibers and the first group via a branching member having a through hole therein for branching the plurality of optical fibers into the first group and the second group; connecting a first branch tail cable with a covering metal tube and a second branch tail cable with a metal tube covering the second group;
and brazing one end of each metal tube of the main tail cable and the first and second branch tail cables to each open end of the through hole of the branch member.

A submarine cable system according to one aspect of the present disclosure includes:
a main submarine cable;
first and second branch submarine cables;
a submarine branching device that branches the main submarine cable into the first and second branch submarine cables;
The submarine branching device,
a main tail cable having a plurality of optical fibers and a metal tube covering the plurality of optical fibers and connecting to the main submarine cable;
a first branch tail cable having a first group of the plurality of optical fibers and a metal tube covering the first group and connecting to the first branch submarine cable;
a second branch tail cable having a second group of the plurality of optical fibers and a metal tube covering the second group and connecting to the second branch submarine cable;
a through hole for connecting the main tail cable and the first and second branch tail cables and for branching the plurality of optical fibers included in the main tail cable into the first group and the second group; a branching member comprising;
One ends of metal tubes of the main tail cable and the first and second branch tail cables are brazed to the open ends of the through holes of the branch member.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a submarine branching device that can be miniaturized by branching a tail cable into a plurality of cables while maintaining airtightness.

1 is a schematic cross-sectional view showing the configuration of a submarine branching device according to a first embodiment; FIG. FIG. 5 is a schematic cross-sectional view showing the configuration of a submarine branching device and a submarine cable system according to a second embodiment; FIG. 2 is a schematic cross-sectional view showing the configuration of a related submarine branching device and submarine cable system; 4 is an external perspective view of the branching member 20. FIG. 4 is a cross-sectional perspective view of the branching member 20. FIG. It is a top view which shows the manufacturing method of a tail cable.

Specific embodiments are described in detail below with reference to the drawings. In each drawing, the same reference numerals are given to the same or corresponding elements, and redundant description will be omitted as necessary for clarity of description.

(First embodiment)
<Configuration of submarine branching device>
First, the configuration of the submarine branching device according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing the configuration of the submarine branching device according to the first embodiment.
As shown in FIG. 1, the submarine branching device according to the first embodiment includes a branching member 20, a main tail cable MTC, and branch tail cables BTC1 and BTC2.

One end of the main tail cable MTC connects to an undersea cable (not shown in FIG. 1). The other end of the main tail cable MTC is connected to the branch tail cables BTC1, BTC2 via the branch member 20. As shown in FIG. The main tail cable MTC includes all the optical fibers, namely the fiber groups FG1, FG2 and the metal tubes covering the fiber groups FG1, FG2.
In FIG. 1, the optical fiber groups FG1 and FG2 inside the cable are indicated by thick solid lines for easy understanding.

As shown in FIG. 1, one end of a branch tail cable (first branch tail cable) BTC1 is connected to the main tail cable MTC via a branch member 20. As shown in FIG. The other end of the branch tail cable BTC1 is connected to a branch submarine cable (not shown in FIG. 1). The branch tail cable BTC1 includes an optical fiber group (first group of optical fibers) FG1 and a metal tube covering the optical fiber group FG1.

As shown in FIG. 1 , one end of branch tail cable (second branch tail cable) BTC2 is connected to main tail cable MTC via branch member 20 . The other end of the branch tail cable BTC2 is connected to a branch submarine cable (not shown in FIG. 1). The branch tail cable BTC2 includes an optical fiber group (second group of optical fibers) FG2 and a metal tube covering the optical fiber group FG2.

As shown in FIG. 1, the branch member 20 connects the main tail cable MTC and the branch tail cables BTC1, BTC2. Further, the branching member 20 is internally provided with a through hole 21 for branching a plurality of optical fibers included in the main tail cable MTC into the optical fiber groups FG1 and FG2.

Here, one end of each metal tube of the main tail cable MTC and the branch tail cables BTC1 and BTC2 is brazed to each open end of the through hole 21 of the branch member 20 . Therefore, the insides of the branch member 20, the main tail cable MTC, and the branch tail cables BTC1 and BTC2 are kept airtight, and the intrusion of seawater into them is suppressed.
The branch member 20, the main tail cable MTC, and the branch tail cables BTC1 and BTC2 collectively form a tail cable.

As described above, in the submarine branching device according to the present embodiment, the main tail cable MTC branches into the branch tail cables BTC1 and BTC2 while airtightness is maintained by the brazed branch member 20 . That is, the tail cable branches while maintaining airtightness. Therefore, instead of the airtight structural member, the submarine cable can be branched through the branched tail cable while maintaining airtightness. As a result, a container-like airtight structural member that occupies a predetermined space becomes unnecessary, and the submarine bifurcation device can be miniaturized.
In the branching member 20 shown in FIG. 1, the plurality of optical fibers included in the main tail cable MTC are branched into two groups, but they may be branched into three or more groups.

(Second embodiment)
<Configuration of submarine branching device and submarine cable system>
Next, with reference to FIG. 2, configurations of the submarine branching device and the submarine cable system according to the second embodiment will be described. FIG. 2 is a schematic cross-sectional view showing the configuration of the submarine branching device and the submarine cable system according to the second embodiment.

As shown in FIG. 2, the submarine cable system according to the second embodiment comprises a main submarine cable MSC, branch submarine cables BSC1, BSC2, and a submarine branching device. In addition to the branch member 20, the main tail cable MTC, and the branch tail cables BTC1 and BTC2 shown in FIG. It has covers 30a and 30b.

The housing 10 is a cylindrical body that houses the branch member 20, the main tail cable MTC, and the branch tail cables BTC1, BTC2. The housing 10 has strength to withstand water pressure at a depth of 8000 m, for example, and is made of, for example, a beryllium copper alloy.
As shown in FIG. 2, one end of the main tail cable MTC is connected to the main submarine cable MSC via a joint box JB. The other end of the main tail cable MTC is connected to the branch tail cables BTC1, BTC2 via the branch member 20. As shown in FIG. Here, main tail cable MTC may be supported by support member 40 fixed to housing 10 .

As shown in FIG. 2, the main tail cable MTC contains all the optical fibers (ie, optical fiber groups FG1, FG2) inside a metal tube. As will be described later in detail, the metal pipe is, for example, a copper pipe, which protects the optical fibers (optical fiber groups FG1 and FG2) and functions as a feeder line. In the joint box JB, the feeders and optical fibers of the main submarine cable MSC and the main tail cable MTC are connected to each other.
In FIG. 2 as well, the optical fiber groups FG1 and FG2 inside the cable are indicated by thick solid lines for easy understanding.

As shown in FIG. 2, one end of branch tail cable BTC1 is coupled to main tail cable MTC via branch member 20 . The other end of branch tail cable BTC1 is connected to branch submarine cable BSC1 via joint box JB1. Here, the branch submarine cable BSC1 may be supported by a support member 41 fixed to the housing 10 .

Branch tail cable BTC1 accommodates optical fiber group FG1 in a metal tube. The metal tube is, for example, a copper tube, which protects the optical fiber group FG1 and also functions as a feeder line. In the joint box JB1, the feeder lines and the optical fibers of the branch submarine cable BSC1 and the branch tail cable BTC1 are connected to each other.

As shown in FIG. 2, one end of branch tail cable BTC2 is coupled to main tail cable MTC via branch member 20 . The other end of branch tail cable BTC2 is connected to branch submarine cable BSC2 via joint box JB2. Here, the branch submarine cable BSC2 may be supported by a support member 42 fixed to the housing 10 .

Branch tail cable BTC2 accommodates optical fiber group FG2 in a metal tube. The metal tube is, for example, a copper tube, which protects the optical fiber group FG2 and also functions as a feeder line. In the joint box JB2, the feeder lines and the optical fibers of the branch submarine cable BSC2 and the branch tail cable BTC2 are connected to each other.

As shown in FIG. 2, the branch member 20 connects the main tail cable MTC and the branch tail cables BTC1, BTC2. Further, the branching member 20 is internally provided with a through hole 21 for branching a plurality of optical fibers included in the main tail cable MTC into the optical fiber groups FG1 and FG2.

Here, one end of each metal tube of the main tail cable MTC and the branch tail cables BTC1 and BTC2 is brazed to each open end of the through hole 21 of the branch member 20 . Therefore, the insides of the branch member 20, the main tail cable MTC, and the branch tail cables BTC1 and BTC2 are kept airtight, and the intrusion of seawater into them is suppressed.
The branch member 20, the main tail cable MTC, and the branch tail cables BTC1 and BTC2 collectively form a tail cable.
Details of the branch member 20 will be described later.

The joint cover 30a is a hollow member connected to one end of the housing 10 and housing the joint box JB. One end of the joint cover 30a is fitted or screwed into the housing 10 and fixed. The other end of the joint cover 30a is opened to introduce the main submarine cable MSC, and the diameter is tapered toward the main submarine cable MSC side.

The joint cover 30b is a hollow member connected to the other end of the housing 10 and housing the joint boxes JB1 and JB2. One end of the joint cover 30b is fitted or screwed into the housing 10 and fixed. The other end of the joint cover 30b has two openings for introducing the branch submarine cables BSC1 and BSC2.
Note that seawater enters the inside of the housing 10 and the joint covers 30a and 30b.

<Configuration of related submarine branching equipment and submarine cable system>
Now, with reference to FIG. 3, the configuration of the associated submarine branching device and submarine cable system will be described. FIG. 3 is a schematic cross-sectional view showing the configuration of a related submarine branching device and submarine cable system.

As shown in FIG. 3, the associated submarine bifurcation device includes an airtight structural member 100 in place of the housing 10 shown in FIG. Also, the associated subsea bifurcation does not include a bifurcation member 20 .
As shown in FIG. 3 , the airtight structural member 100 has a configuration in which an internal unit 111 is housed in a cylindrical pressure-resistant housing 112 .

The pressure-resistant housing 112 is provided with a lead-in portion 130 that guides the optical fibers (optical fiber groups FG1 and FG2) included in the main tail cable MTC to the internal unit 111 .
Then, inside the internal unit 111, the optical fibers included in the main tail cable MTC are branched into the optical fiber groups FG1 and FG2.

Further, the pressure-resistant housing 112 is provided with a lead-out portion 131 for leading out the optical fiber group FG1 led out from the internal unit 111 to the branch tail cable BTC1. Furthermore, the pressure-resistant housing 112 is provided with a lead-out portion 132 for leading out the optical fiber group FG2 led out from the internal unit 111 to the branch tail cable BTC2. The pressure-resistant housing 112, the introduction section 130, and the discharge sections 131 and 132 have an airtight structure so that seawater does not enter the pressure-resistant housing 112 from the introduction section 130 and the discharge sections 131 and 132 and the like.

As shown in FIG. 3, in the related submarine branching device, inside the airtight structural member 100, it is necessary to branch the optical fibers included in the main tail cable MTC into the optical fiber groups FG1 and FG2. Here, since the airtight structure member 100 is in the shape of a container and occupies a predetermined space, the undersea bifurcation device is enlarged.

In contrast, in the submarine branching device according to the present embodiment, as shown in FIG. 2, the main tail cable MTC branches into branch tail cables BTC1 and BTC2 while airtightness is maintained by brazed branch members 20. ing. That is, the tail cable branches while maintaining airtightness. Therefore, instead of the airtight structural member 100 shown in FIG. 3, the main submarine cable MSC can be branched into the branch submarine cables BSC1 and BSC2 via the branched tail cables while maintaining airtightness. As a result, in the submarine branching device according to the present embodiment, the container-shaped airtight structural member 100 that occupies a predetermined space is not required, and the submarine branching device can be miniaturized.

<Details of branch member 20>
Next, details of the branch member 20 will be described with reference to FIGS. 4 and 5. FIG. 4 is an external perspective view of the branching member 20. FIG. FIG. 5 is a cross-sectional perspective view of the branch member 20. FIG.
As shown in FIG. 5, inside the branch member 20, a Y-shaped through hole 21 is formed in plan view. Counterbore holes 22 , 221 , and 222 having larger inner diameters than the through hole 21 are formed at three open ends of the Y-shaped through hole 21 .

As shown in FIG. 5, one end of a copper tube CP forming the main tail cable MTC is inserted into the counterbored hole 22 to a depth of, for example, several millimeters. Further, as shown in FIG. 4 , a tapered portion 22 a is formed at the open end of the counterbore 22 so as to increase in diameter outward from the inner peripheral surface of the counterbore 22 .

By providing the tapered portion 22a, insertion of the copper pipe CP into the counterbored hole 22 and brazing of the branch member 20 and the copper pipe CP are facilitated. Specifically, as shown in FIG. 5, a ring-shaped brazing portion is formed by filling a gap between the tapered portion 22a and the copper pipe CP with a brazing material.

As shown in FIG. 5, one ends of copper tubes CP1 and CP2 forming branch tail cables BTC1 and BTC2 are inserted into the counterbore holes 221 and 222 to a depth of, for example, several millimeters. Similarly to the counterbore 22, taper portions 221a and 222a are formed at the opening ends of the counterbore holes 221 and 222, respectively, so as to increase the diameter from the inner peripheral surface toward the outside.

By providing the tapered portions, the insertion of the copper pipes CP1 and CP2 into the counterbore holes 221 and 222 and the brazing of the branch member 20 and the copper pipes CP1 and CP2 are facilitated. Specifically, as shown in FIG. 5 , ring-shaped brazing portions are also formed in tapered portions 221 a and 222 a of counterbore holes 221 and 222 in the same manner as tapered portion 22 a of counterbore hole 22 .

5, the optical fiber group FG1 is inserted through the copper pipe CP1 of the branch tail cable BTC1 and the through hole 21 of the branch member 20 into the copper pipe CP of the main tail cable MTC. Similarly, the optical fiber group FG2 is inserted through the copper pipe CP2 of the branch tail cable BTC2 and the through hole 21 of the branch member 20 into the copper pipe CP of the main tail cable MTC.

Therefore, in the example shown in FIG. 5, in the through hole 21, the paths connecting the copper pipes CP1, CP2 and the copper pipe CP are formed smoothly so as to draw arcs in plan view. With such a configuration, bending of the optical fiber groups FG1 and FG2 can be suppressed.

Further, in the example shown in FIG. 5, the diameter of the through-hole 21 is formed larger than the inner diameters of the copper pipes CP1 and CP2, and the inner diameter of the copper pipe CP is formed larger than the diameter of the through-hole 21. . Therefore, when the optical fiber groups FG1 and FG2 are inserted, the step between the inner peripheral surfaces of the copper pipes CP1 and CP2 and the through hole 21 or the step between the through hole 21 and the inner peripheral surface of the copper pipe CP causes the optical fiber group It is possible to prevent the tips of FG1 and FG2 from being caught.

The branch member 20 has strength to withstand water pressure at a depth of 8000 m, and is made of, for example, a steel material, copper, a copper alloy (for example, a beryllium copper alloy), or the like. Further, in order to ensure airtightness, as described above, the branch member 20 is brazed to the ends of the copper pipe CP of the main tail cable MTC and the ends of the copper pipes CP1 and CP2 of the branch tail cables BTC1 and BTC2. ing. Furthermore, the branch member 20 protects the optical fiber groups FG1 and FG2 and also functions as a feeder line, like the copper pipes CP, CP1 and CP2.

Thus, the material for the branch member 20 is selected in consideration of the strength, the brazing property with the copper pipe, the electrical resistance, and the like. As for the electrical resistance of the entire feeder line, the electrical resistance of the copper tube is dominant, so the electrical resistance has a low priority when selecting the material for the branch member 20 .
Further, in manufacturing the branching member 20, since it is difficult to machine the Y-shaped branched through-hole 21, the branching member 20 is manufactured by, for example, lamination molding using metal powder (a so-called metal 3D printer).

As an example, the branch member 20 is manufactured by additive manufacturing using maraging steel powder. By using high-strength maraging steel, the branch member 20 can be made thinner (that is, smaller and lighter). Furthermore, the thinning of the branch member 20 suppresses heat dissipation during brazing, making it easier to melt the brazing filler metal and improving weldability. Here, compared to copper and copper alloys, iron and steel materials have higher strength and can be made thinner, and their thermal conductivity is lower, so heat removal during brazing can be suppressed. For example, the thickness of the portion where the counterbored hole 22 to be brazed with the copper pipe CP is formed can be set to 2 mm or less (for example, 1.2 mm).

As shown in FIGS. 4 and 5, the branch member 20 has a smooth outer shape corresponding to the Y-shaped through hole 21 . On the other hand, in the branch member 20, the portion between the pair of counterbore holes 221 and 222 into which the copper pipes CP1 and CP2 are inserted protrudes outward.

Here, as will be described later in detail, the branch member 20 is insulated and molded. If a concave portion is formed between the counterbore holes 221 and 222 during insulation molding, a void is likely to occur. In the branch member 20 shown in FIGS. 4 and 5, since the portion between the counterbore holes 221 and 222 protrudes outward, air gaps are suppressed during insulation molding, and the withstand voltage is improved.

Further, as shown in FIG. 4, the corners of the branch member 20 located at the boundary between the outer peripheral surface and the end surface are chamfered. If the branching member 20 has corners during insulation molding, voids are likely to occur at the corners. In the branching member 20 shown in FIGS. 4 and 5, since the corners are chamfered, voids during insulation molding are suppressed and the withstand voltage is improved. In addition, the electric field strength itself at the corners is suppressed, and the withstand voltage is improved.

<Method for manufacturing tail cable>
Next, a method of manufacturing the tail cable will be described with reference to FIG. FIG. 6 is a plan view showing a method of manufacturing the tail cable. FIG. 5 will also be referred to as appropriate.
As described above, the tail cable consists of branch member 20, main tail cable MTC, and branch tail cables BTC1, BTC2.

As shown in the upper part of FIG. 6, the main tail cable MTC includes a copper tube CP whose outer peripheral surface is coated with an insulation coating layer ICL. The branch tail cable BTC1 includes a copper tube CP1 whose outer peripheral surface is coated with an insulation coating layer ICL1. The branch tail cable BTC2 includes a copper tube CP2 whose outer peripheral surface is coated with an insulating coating layer ICL2. The insulating coating layers ICL, ICL1, and ICL2 are made of polyethylene, for example.

First, as shown in the upper part of FIG. 6, the insulation coating layer ICL at one end of the main tail cable MTC to be inserted into the branch member 20 is removed to expose the copper pipe CP. Also, the insulating coating layer ICL1 at one end of the branch tail cable BTC1 inserted into the branch member 20 is removed to expose the copper pipe CP1. Similarly, the insulating coating layer ICL2 at one end of the branch tail cable BTC2 inserted into the branch member 20 is removed to expose the copper pipe CP2. In the example shown in FIG. 6, after the copper tubes CP1 and CP2 are inserted into the branch member 20, the exposed copper tubes CP1 and CP2 are bent in advance so that the branch tail cables BTC1 and BTC2 are parallel. back.

Next, as shown in the middle part of FIG. 6, the copper pipes CP, CP1 and CP2 are inserted into the branch member 20 and assembled and brazed.
The details are as described with reference to FIG.

Next, as shown in the lower part of FIG. 6, the outer peripheral surface of the branch member 20 and the exposed outer peripheral surfaces of the copper pipes CP, CP1, and CP2 are insulated and covered with an insulating coating layer ICL3. During insulation molding, the insulating coating layer ICL3 is integrated with the insulating coating layers ICL, ICL1, and ICL2. Like the insulating coating layer ICL3, the insulating coating layers ICL, ICL1, and ICL2, it is made of polyethylene, for example.

5, the optical fiber group FG1 is inserted through the copper tube CP1 of the branch tail cable BTC1 and the through-hole 21 of the branch member 20 into the copper tube CP of the main tail cable MTC. Similarly, the optical fiber group FG2 is inserted through the copper pipe CP2 of the branch tail cable BTC2 and the through hole 21 of the branch member 20 into the copper pipe CP of the main tail cable MTC.

A tail cable is manufactured by the above. The tail cable has a withstand voltage of, for example, 15 kV or more due to the insulating coating layers ICL, ICL1 to ICL3. Further, corrosion of the copper pipes CP, CP1, CP2 and the branch member 20 made of metal can be suppressed by the insulating coating layers ICL, ICL1 to ICL3.

Note that the present disclosure is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present disclosure.

10 housing 20 branching member 21 through holes 22, 221, 222 counterbore holes 22a, 221a, 222a tapered portions 30a, 30b joint covers 40, 41, 42 supporting members BSC1, BSC2 branching submarine cables BTC1, BTC2 branching tail cables CP, CP1 , CP2 copper tube (metal tube)
FG1, FG2 Optical fiber group ICL, ICL1 to ICL3 Insulation layer JB, JB1, JB2 Joint box MSC Main submarine cable MTC Main tail cable

Claims (8)

a main tail cable having a plurality of optical fibers and a metal tube covering the plurality of optical fibers;
a first branch tail cable having a first group of the plurality of optical fibers and a metal tube covering the first group;
a second branch tail cable having a second group of the plurality of optical fibers and a metal tube covering the second group;
a branching member that connects the main tail cable and the first and second branch tail cables and has therein a through hole for branching the plurality of optical fibers into the first group and the second group; prepared,
A counterbored hole is provided at each open end of the through hole of the branch member,
one end of each metal tube of the main tail cable and the first and second branch tail cables is inserted into each of the counterbore holes and brazed ;
At the opening end of each countersunk hole of the through hole, a tapered portion whose diameter is expanded from the inner peripheral surface toward the outside is provided,
A brazed portion is formed on each of the tapered portions,
Submarine bifurcation device. outer peripheral surfaces of the metal tubes of the main tail cable and the first and second branch tail cables are both coated with an insulating coating layer;
The outer peripheral surface of the branch member is covered with an insulating coating layer,
the insulating coating layer of the branch member is integrated with the insulating coating layers of the main tail cable and the first and second branch tail cables;
The submarine branching device according to claim 1. In the branch member,
A portion between the pair of counterbore holes into which the metal tubes of the first and second branch tail cables are inserted protrudes outward.
The submarine branching device according to claim 1 or 2 . The diameter of the through-hole is larger than the inner diameter of the metal tubes of the first and second branch tail cables, and the inner diameter of the metal tube of the main tail cable is larger than the diameter of the through-hole.
A submarine branching device according to any one of claims 1 to 3 . A corner located at the boundary between the outer peripheral surface and the end surface of the branch member is chamfered.
A submarine branching device according to any one of claims 1 to 4 . wherein the branch member is made of maraging steel;
A submarine branching device according to any one of claims 1 to 5 . a main tail cable having a metal tube covering the plurality of optical fibers and the first group via a branching member having a through hole therein for branching the plurality of optical fibers into the first group and the second group; connecting a first branch tail cable with a covering metal tube and a second branch tail cable with a metal tube covering the second group;
brazing one end of each metal tube of the main tail cable and the first and second branch tail cables to each open end of the through hole of the branch member ;
A counterbored hole is provided at each open end of the through hole of the branch member,
one end of each metal tube of the main tail cable and the first and second branch tail cables is inserted into each of the counterbore holes and brazed;
At the opening end of each countersunk hole of the through hole, a tapered portion whose diameter is expanded from the inner peripheral surface toward the outside is provided,
a brazed portion is formed on each of the tapered portions;
A method of configuring a submarine branching device. a main submarine cable;
first and second branch submarine cables;
a submarine branching device that branches the main submarine cable into the first and second branch submarine cables;
The submarine branching device,
a main tail cable having a plurality of optical fibers and a metal tube covering the plurality of optical fibers and connecting to the main submarine cable;
a first branch tail cable having a first group of the plurality of optical fibers and a metal tube covering the first group and connecting to the first branch submarine cable;
a second branch tail cable having a second group of the plurality of optical fibers and a metal tube covering the second group and connecting to the second branch submarine cable;
a through hole for connecting the main tail cable and the first and second branch tail cables and for branching the plurality of optical fibers included in the main tail cable into the first group and the second group; a branching member comprising;
A counterbored hole is provided at each open end of the through hole of the branch member,
one end of each metal tube of the main tail cable and the first and second branch tail cables is inserted into each of the counterbore holes and brazed ;
At the opening end of each countersunk hole of the through hole, a tapered portion whose diameter is expanded from the inner peripheral surface toward the outside is provided,
A brazed portion is formed on each of the tapered portions,
submarine cable system.

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