LANDING CABLE AND PARTIAL LANDING CABLE

Abstract

In order to suppress landing construction, these landing cables, which are installed offshore from a cable landing position, are each provided with: an initially used optical fiber that is used from the initial start of communication by the landing cable; and a preliminary optical fiber which is a preliminary optical fiber in addition to the initially used power feed line used from the initial start, wherein the preliminary optical fiber is connected from a cable landing position side terminal point to boundary points between the cable landing position side terminal point and a cable interval that does not include the preliminary optical fiber, and the terminal point of the preliminary optical fiber, which is the terminal point of the preliminary optical fiber in the boundary points, is held in a state of being usable in the future.

Claims

1. A landing cable that is installed offshore from a cable landing position, the landing cable comprising a preliminary optical fiber being a preliminary optical fiber in addition to an initially used optical fiber being an optical fiber used since start of communication by the landing cable and an initially used power feed line being a power feed line initially used from the start, wherein the preliminary optical fiber connects an endpoint on a side of the cable landing position and a boundary point with a district of a cable not including the preliminary optical fiber, and a preliminary optical fiber endpoint being an endpoint of the preliminary optical fiber is maintained in a future usable state at the boundary point.

2. The landing cable according to claim 1, wherein the boundary point is located on a landward side of a cable coupling unit on a landward side of a first repeater or a piece of submarine equipment when being traced from the landing position.

3. The landing cable according to claim 1, wherein the boundary point is located outside territorial sea.

4. The landing cable according to claim 1, wherein the boundary point is located in at least one of an area exceeding a zone in which a cable burial method is necessary, an area exceeding a zone in which a horizontal directional drilling method is necessary, and an area exceeding a zone in which authorization acquisition of installation operation is necessary.

5. The landing cable according to claim 1, further comprising a preliminary power feed line at an endpoint on a side of the landing position, wherein: the preliminary optical fiber and the preliminary power feed line are connected to the boundary point; at the boundary point, the preliminary optical fiber endpoint and a preliminary power feed line endpoint being an endpoint of the preliminary power feed line are maintained in a future usable state, bundled into one, and provided with a cable branching unit at an end on an offshore side; the landing cable is branched into an initially used submarine cable including the initially used optical fiber and the initially used power feed line, and a plurality of preliminary submarine cables having the preliminary optical fiber and the preliminary power feed line; the preliminary optical fiber endpoint and the preliminary power feed line endpoint are maintained in a future usable state at a submarine endpoint within the preliminary submarine cable; and the boundary point and the preliminary submarine cable are located in an area being landward side than a cable coupling unit on a landward side of a first repeater or the first submarine equipment when being traced from the landing position, outside territorial sea, in an area exceeding a zone in which a cable burial method is necessary, in an area exceeding a zone in which a horizontal directional drilling method is necessary, and in an area exceeding a zone in which authorization acquisition of installation operation is necessary.

6. The landing cable according to claim 5, wherein a streaming cable is connected to a submarine endpoint of the preliminary submarine cable, and the boundary point, the preliminary submarine cable, and the streaming cable are arranged in an area being landward side than the cable coupling unit, outside the territorial sea, in an area exceeding a zone in which the cable burial method is necessary, in an area exceeding a zone in which the horizontal directional drilling method is necessary, and in an area exceeding a zone in which the authorization acquisition is necessary.

7. The landing cable according to claim 5 that is a complex submarine cable made by compounding a plurality of armorless submarine cables, wherein the armorless submarine cable includes an optical fiber and a power feed line, and the cable branching unit separates a cable that is made by compounding a plurality of the armorless submarine cables into units of the armorless submarine cable and the landing cable is connected by using an existing submarine cable connection part and connection technique.

8. The landing cable according to claim 1, wherein the preliminary optical fiber is connected as a loopback connection to another of the preliminary optical fiber at the boundary point.

9. The landing cable according to claim 1, wherein some of optical fibers that are connected to the boundary point are used for an optical fiber sensing purpose.

10. A partial landing cable that is all portions of the submarine cable according to claim 1 in an area of a country in which the landing position is set, wherein the boundary point is arranged outside the area or supposed to be arranged outside the area.

11. A landing cable comprising an optical fiber group including a plurality of optical fibers, and a power feed line group including a plurality of power feed lines, the landing cable being installed from a landing position, wherein: an endpoint that is not arranged at the landing position is arranged at a first repeater being a first repeater traced from the landing position or between the landing position and the first repeater; the optical fiber group includes a first optical fiber group and a second optical fiber group; the optical fiber of the first optical fiber group is the optical fiber connecting to a beyond-first-repeater submarine cable being a submarine cable after the first repeater; the optical fiber of the second optical fiber group is the optical fiber that is preliminary and not connected to the beyond-first-repeater submarine cable; and an endpoint of the optical fiber of the second optical fiber group is maintained in a usable state.

12. The landing cable according to claim 11, wherein the endpoint is arranged in an area outside territorial sea.

13. The landing cable according to claim 11, wherein the endpoint is located in at least one of an area exceeding a zone in which a cable burial method is necessary, an area exceeding a zone in which a zone in which a horizontal directional drilling method is necessary is necessary, and an area exceeding a zone in which authorization acquisition of installation operation is necessary.

14. The landing cable according to claim 11, wherein optical fibers included in the second optical fiber group are connected as a loopback connection.

15. The landing cable according to claim 11, wherein the optical fiber of the second optical fiber group is maintained in a usable state by retaining a seaward side optical fiber endpoint of an optical fiber including the optical fiber of the second optical fiber group in an optical fiber slack storage unit.

16. The landing cable according to claim 15, wherein the optical fiber of the second optical fiber group is supposed to be used when a number of beyond-first-repeater submarine cable optical fibers included in the beyond-first-repeater submarine cable increases.

17. The landing cable according to claim 16, wherein the endpoint on a seaward side of the optical fiber of the first optical fiber group is connected to the beyond-first-repeater submarine cable by a connection device, and the optical fiber slack storage unit is included in the connection device.

18. The landing cable according to claim 17, wherein the optical fiber slack storage unit is molded with resin.

19. The landing cable according to claim 18, wherein the resin is polyethylene.

20. The landing cable according to claim 17, wherein the connection device is included in the first repeater.

21.-28. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0063] FIG. 1 is a schematic diagram illustrating a configuration example of a submarine cable system according to the first example embodiment.

[0064] FIG. 2 is a schematic diagram illustrating a configuration example of a cable coupling unit on the landward side of a first repeater according to the first example embodiment.

[0065] FIG. 3 is a schematic diagram illustrating a configuration example of a submarine cable system according to the second example embodiment.

[0066] FIG. 4 is a schematic diagram illustrating a first configuration example of a landing cable according to the second example embodiment.

[0067] FIG. 5 is a schematic diagram illustrating a second configuration example of a landing cable according to the second example embodiment.

[0068] FIG. 6 is a schematic sectional diagram illustrating a third configuration example of a landing cable according to the second example embodiment.

[0069] FIG. 7 is a schematic diagram illustrating a first configuration example of a branching unit according to the second example embodiment.

[0070] FIG. 8 is a schematic diagram illustrating a second configuration example of a branching unit according to the second example embodiment.

[0071] FIG. 9 is a schematic diagram illustrating a third configuration example of a branching unit according to the second example embodiment.

[0072] FIG. 10 is a schematic connection diagram illustrating a configuration example of a submarine cable system according to the example embodiment with optical fiber sensing application.

[0073] FIG. 11 is a diagram illustrating a form of a submarine network using a cable branching unit.

[0074] FIG. 12 is a diagram illustrating a form of a submarine network called Festoon.

[0075] FIG. 13 is a diagram illustrating a usage example of the submarine branching unit.

[0076] FIG. 14 is a diagram illustrating a method of preliminarily installing a streaming cable to be connected to the submarine branching unit and the landing cable.

[0077] FIG. 15 is a diagram illustrating an example of an ordinary technique for making redundant a landing cable.

[0078] FIG. 16 is a diagram illustrating an ordinary technique of landing a plurality of submarine cables.

[0079] FIG. 17 is a schematic diagram illustrating a minimum configuration of a landing cable according to the example embodiment.

EXAMPLE EMBODIMENT

[0080] The following example embodiments describe an example of a landing cable used for a submarine optical transmission system (submarine cable system) realizing a communication line to a foreign country across the sea.

First Example Embodiment

[0081] In the submarine cable system according to the present example embodiment, a preliminary optical fiber for extension (preliminary optical fiber) is provided within a landing cable. The preliminary optical fiber is provided assuming more optical fibers are used in the future in the submarine cable beyond (offshore side) a cable boundary point. By providing the preliminary optical fiber, when the number of the optical fibers to use increases in the future, the installed landing cable can be continually used. Therefore, the submarine cable system of the present example embodiment has the effect of suppressing the occurrence of cable landing construction.

[Configuration and Operation]

[0082] FIG. 1 is a schematic diagram illustrating a configuration of a submarine cable system 100 that is an example of the submarine cable system according to the present example embodiment. The submarine cable system 100 connects a cable landing station 16 to an opposing cable landing station that is not illustrated via the seabed. The landing cable 121 is a part of the submarine cable system 100 and is a submarine cable that lands to the cable landing station 16 via the land cable 18.

[0083] The configuration around the landing position 97 is described in detail. At the landing position 97, a beach manhole 17 that forms a demarcation point is installed. The landing cable 121 and the land cable 18 are connected at the beach manhole 17. The landing cable 121 may be directly pulled to the cable landing station 16, not via the land cable 18. However, since the landing cable is made firmly and lacking flexibility, it is difficult to maneuver. Therefore, generally, the land cable 18 that is flexible connects the land district.

[0084] The first repeater 11 is the first repeater when tracing the landing cable 121 from the landing position 97 to the offshore. There is a case that submarine equipment such as the BU explained in the Background Art section appears earlier than the repeater, however, the submarine equipment is included in the first repeater described here.

[0085] The landing cable 121 includes an optical fiber including 48 optical fibers that are not illustrated and a power feed line. The power feed line is for supplying power to the repeater within the submarine cable system 100 including the first repeater 11. The 16 optical fibers of the aforementioned 48 are used for communication with another country since the start of the communication by the submarine cable system 100. The remaining 32 optical fibers are not used at the beginning and are the preliminary optical fibers for extension when the number of optical fibers to use increases in the future.

[0086] At an endpoint of the landing cable 121 on the landward side, at least 16 optical fibers that are initially used are led to the cable landing station 16 via the land cable 18 along with the power feed line. These are connected to communication equipment that is not illustrated and installed in the cable landing station 16. All or some of the endpoints of the 32 preliminary optical fibers for extension are stored in the beach manhole 17 at the landing position or introduced to the cable landing station 16 via the land cable 18 and are stored in the cable landing station 16.

[0087] The 32 preliminary optical fibers for extension are connected to the boundary point 119 in the sea through the landing cable 121. In the present example embodiment, as described later, the boundary point 119 is set within the cable coupling on the side of the landing position of the first repeater 11. In other words, the preliminary optical fiber is not led to the inside of the main body of the first repeater where the optical amplification is performed, and not connected to the submarine cable beyond.

[0088] The boundary point 119 is set outside the territorial sea limit (12 nautical miles (22.2 km) from the coast). The distance from the shoreline to the first repeater 11 is generally 30 to 50 km, so the repeater can be expected to be beyond the territorial sea limit. Therefore, the boundary point 119 is desirable to be set around the first repeater 11.

[0089] The boundary point 119 is set in one of the area exceeding a zone in which a cable burial method is necessary, an area exceeding a zone in which HDD method is necessary, and an area exceeding a zone in which an authorization acquisition of installation operation is necessary.

[0090] FIG. 2 is a schematic diagram illustrating a configuration example of the first repeater 11 illustrated in FIG. 1. Hereinafter, a configuration of a general repeater is described. Then, an implementation configuration of one that configures the boundary point 119 in the present example embodiment is described.

[0091] The first repeater 11 includes a cable coupling unit 24 on the landward side, a repeater housing 37, and a cable coupling unit on the offshore side that is not illustrated. The cable coupling unit 24 includes a boot 38, a storage unit 35, and a bellows unit 36. The offshore side cable coupling unit includes similar components.

[0092] The boot 38 is a cone-shaped member that protects the proximity of the cable connection. The bellows unit 36 is bellows-shaped and allows the relative angle between a main body of the cable coupling unit and the repeater housing 37 to be changed.

[0093] The storage unit 35 includes a mold unit 34. The mold unit 34 is a PE mold, for example. Molding with PE secures electrical insulation.

[0094] The mold unit 34 includes a tensile wire retaining unit 33 and an optical fiber slack storage unit 31 inside. The landing cable 121 is fixed inside the mold unit 34 by the tensile wire retaining unit 33. The optical fiber within the landing cable 121 and the tail cable 23 extending from inside the repeater housing 37 are fused together and housed in the mold unit 34. The above configuration is also described in the Background Art section.

[0095] The implementation configuration of the boundary point 119 illustrated in FIG. 1 according to the present example embodiment is described. The implementation configuration is, briefly, to store the endpoint of the preliminary optical fiber that is connected from the landing position 97 inside the mold unit in a rolled state, for example.

[0096] The landing cable 121 is the same as the one illustrated in FIG. 1 and includes 48 optical fibers and a power feed line. Although not illustrated in the diagram, the 48 optical fibers are exposed to the right side for a predetermined length from an endpoint fixed to the tensile wire retaining unit 33 of the landing cable 121.

[0097] The 16 optical fibers that are initially used since the start of the communication of the 48 optical fibers are connected to the tail cable 23 and further connected to the optical fibers of the submarine cable leading further offshore via the optical amplifier that is not illustrated inside the repeater housing 37. On the other hand, the 32 preliminary optical fibers of the 48 optical fibers are stored in the optical fiber slack storage unit 31 by rolling, for example. These 32 preliminary optical fibers may be configured with loopback connections between 16 pairs of optical fibers. As a result, the number of executing a test of monitoring conduction of these 32 preliminary optical fibers from shore can be half of the number required when no loopback connection is made. Therefore, the conduction monitoring of the 32 preliminary optical fibers from shore becomes easy.

[0098] In the above description, the number of all the optical fibers included by the landing cable was 48, the number of optical fibers used from the start of the communication (initially used optical fibers) was 16, and the number of preliminary optical fibers was 32. However, the number of all the optical fibers, the number of initially used optical fibers, and the number of preliminary optical fibers included in the landing cable according to the present example embodiment are not limited to these numbers.

Effect

[0099] The landing cable of the present example embodiment includes a preliminary optical fiber. The preliminary optical fiber is preliminarily included in the landing cable to be installed in consideration of a case in which the number of the optical fibers used increases because of the future update of the submarine cable beyond the boundary point. When the number of optical fibers used increases, by using the preliminary optical fibers, the occurrence of cable landing cable construction can be suppressed.

[0100] Here, a supplementary explanation is provided on when the expansion to increase the number of optical fibers used (used optical fiber number) is performed in a submarine cable. There are two main reasons why the number of used optical fibers at the time of installing the cable is less than the maximum number of optical fibers that can be housed in the cable. One case is that there is a limit in the power supplied to the amplifying repeater. Since there is an upper limit in the power supplied to the submarine cable from the cable landing station, the power that can be consumed by one amplifying repeater has a limit. An amplifying repeater for each optical fiber is accommodated in the main body of the amplifying repeater, and when the number of optical fibers increases, the number of amplifiers increases, the power requirement increases. Therefore, when the power limit per one repeater is tight, there will be an upper limit to the number of optical fibers that can be amplified. The other case is that, at the time of installation, the maximum number of optical fibers that can be housed is not required when predicting future increases in communication demand. In this case, a smaller number of optical fibers than the maximum number of optical fibers that can be housed is selected in order to invest the minimum required.

[0101] In the former case, suppose that a future technical improvement improves energy conversion efficiency of an optical amplifier in a repeater and reduces the power required for optical amplification per one optical fiber. In this case, in the landing cable of the present example embodiment, using the already installed preliminary optical fiber, the number of optical fibers to be used can be increased without updating the landing cable.

[0102] In the latter case, suppose that the communication demand increases more rapidly than predicted. In this case, the number of optical fibers will be insufficient, and the submarine communication system including the landing cable will be upgraded. However, even in such a case, the landing cable according to the present example embodiment can be reused as a communication line for a new communication route where the communication counterpart is changed from the original communication counterpart.

[0103] Even with the landing cable according to the present example embodiment, when increasing the number of optical fibers used in the submarine cable, installation construction for updating the submarine cable and the repeater beyond the boundary point needs to be performed again. However, when the landing cable according to the present example embodiment is used, a preliminary optical fiber is preliminarily included in the landing cable. Therefore, the landing cable according to the present example embodiment can be used as a part of the new optical submarine cable system without installing a new landing cable.

[0104] A boundary point that is an offshore side endpoint of the preliminary optical fiber is set outside the territorial sea limit, in other words, the high seas. As described partially in the Background Art section, each country has implemented licensing laws for civil engineering and construction. The licensing system applies to a territorial sea under the sovereignty of the country. Therefore, construction work inside the territorial sea must be carried out by a contractor with a civil engineering and construction license from the country. The construction work inside the territorial sea is an economic activity within the country, so it must comply with the taxation system of the country. As a result, construction work inside the territorial sea takes effort and cost, and it is preferable to be avoided if possible. On the contrary, the law of the country is generally not in effect outside of the territorial sea. Therefore, the benefit of reducing labor and cost may be obtained by preliminarily installing a preliminary optical fiber to the outside of the territorial sea.

[0105] The boundary point is set in an area exceeding a zone in which cable burial method and horizontal directional drilling method are necessary. Since the cable burial method buries a submarine cable, it costs more than a method where the submarine cable is simply laid on the seabed. The horizontal directional drilling method is even more costly because a dedicated excavator and route designing based on a preliminary boring survey are necessary, as described in the Background Art section. When the boundary point is set in an area exceeding a zone in which cable burial method and horizontal directional drilling method are necessary, a method of simply laying on the seabed can be applied, so the benefit of reducing cost may be obtained.

[0106] The boundary point is also set in an area outside a zone in which authorization acquisition of the installation operation is necessary. As a result, even in a case in which the law of the country is applicable outside the territorial sea, the authorization acquisition becomes unnecessary, and the benefit of reducing labor and cost may be obtained.

[0107] The example where the boundary point is arranged within the cable coupling unit on the landward side of the first repeater has been described, however, the position of the boundary point is not limited to be within the cable coupling unit. For example, a boundary point may be set inside the submarine cable connection unit arranged between the shoreline and the first repeater. However, it is desirable that the preliminary optical fiber is connected as close to the first repeater as possible since it is only up to the relevant connection unit that can be reused when increasing the number of optical fibers used.

[0108] The boundary point may be set offshore than the first repeater. In this case, the first repeater also needs to include an optical amplifier for the preliminary optical fiber. As a result, the price of the first repeater increases because of becoming a special product with different specification from many other repeaters. In a submarine cable system, in order to speed up failure recovery, a preliminary product (preliminary equipment) for repairing a repeater and a submarine cable that takes a long time to manufacture are stored in a warehouse on land and are shipped for repair work. The preliminary equipment needs to be prepared for each type of repeaters, so when the number of types increases, the cost of manufacturing and storing the preliminary equipment also increases.

Second Example Embodiment

[0109] The landing cable according to the first example embodiment includes only preliminary optical fibers for the future extension but does not include a preliminary power feed line (preliminary power feed line). Therefore, with the landing cable according to the first example embodiment, a new submarine cable cannot be added to the landing cable.

[0110] On the contrary, the landing cable according to the second example embodiment has a single landing cable, so the landing construction work can be performed only once. Nevertheless, the landing cable according to the present example embodiment includes a configuration in which a preliminary branch submarine cable for connecting a new submarine cable is preliminarily installed on the seabed. Here, the branch submarine cable refers to a branched submarine cable. Therefore, the landing cable according to the present example embodiment may have the effect of suppressing the occurrence of cable landing construction when adding a new submarine cable in the future.

[Configuration and Operation]

[0111] FIG. 3 is a schematic diagram illustrating a configuration of a submarine cable system 200 that is an example of the submarine cable system according to the present example embodiment. The landing cable 221 of the submarine cable system 200 includes a preliminary optical fiber and a preliminary power feed line that are not used initially. The preliminary optical fiber is branched at a branching unit 41, and endpoints of the branched optical fiber and the preliminary power feed line configure a boundary point 219.

[0112] The landing cable 221 includes an optical fiber including optical fibers whose number is equivalent to the total of the number of optical fibers included in the four branch submarine cables 21a to 21d, and power feed lines whose number is equivalent to the number of power feed lines included in each branch submarine cable. The landing cable 221 is a single landing cable. The number of optical fibers distributed to each branch submarine cable is not fixed, however, an example in which the number is 16 is described here.

[0113] At an endpoint of the landing cable 221 on the landward side, at least 16 optical fibers that are used since the start of the communication by the landing cable 221 are led to the cable landing station 16, via a land cable for example, along with the power feed line used since the start of the communication. These are connected to communication equipment that is not illustrated and installed in the cable landing station 16. At the endpoint, all or some of the landward side endpoints of the preliminary optical fibers and power feed lines for an extension for connecting a new submarine cable on the offshore side are stored in the beach manhole at the landing position or introduced to the cable landing station 16 and are stored.

[0114] The branching unit 41 branches the optical fiber group and the power feed line included by the landing cable 221 into each branch submarine cable.

[0115] The boundary point 219, which is a boundary between a cable district including a preliminary optical fiber and a preliminary power feed line and a district not including them, is configured with a branching unit 41 and branch submarine cables 21a to 21d in the present example embodiment. However, a boundary point in the narrow sense is configured by the branching unit 41.

[0116] Only the branch submarine cable 21c among the branch submarine cables is used since the start of communication by the submarine cable system 200. The first repeater 11 is a general product similar to many other repeaters within the submarine cable system 200, and the number of optical fibers before and after the repeater is similar to other repeaters.

[0117] The branch submarine cables 21a, 21b, and 21d are preliminary for extension and are not used initially. The offshore side endpoints of the branch submarine cables 21a, 21b, and 21d are sealed watertight and streaming-off is performed. The streaming-off is a method in which a streaming cable is mechanically attached to an endpoint of a submarine cable which is the construction resuming point and installed on the seabed in order to be easily recovered when resuming, as described in the Background Art section. An optical fiber or a power feed line is not connected.

[0118] Although not illustrated, the branch submarine cable 21c is connected to another country via a plurality of repeaters beyond. Communication between the home country and another country is performed using the optical fiber included in the branch submarine cable 21c.

[0119] The branching unit 41 and the branch submarine cables 21a to 21d configuring the boundary point 219 are naturally set between the shoreline and the first repeater 11.

[0120] The branching unit 41 and the branch submarine cables 21a to 21d configuring the boundary point 219 are also set outside the territorial sea limit, in other words, the high seas. As described partially in the Background Art section, each country has implemented licensing laws for civil engineering and construction. The licensing system applies to a territorial sea under the sovereignty of the country. Therefore, construction work inside the territorial sea must be carried out by a contractor with a civil engineering and construction license from the country. The construction work inside the territorial sea is an economic activity within the country, so it must comply with the taxation system of the country. As a result, construction work inside the territorial sea takes effort and cost, and it is preferable to be avoided if possible. On the contrary, the law of the country is generally not in effect outside of the territorial sea. Therefore, the benefit of reducing labor and cost may be obtained by setting the boundary point 219 outside of the territorial sea.

[0121] The branching unit 41 and branch submarine cables 21a to 21d that configure the boundary point 219 are set in an area exceeding a zone in which cable burial method and horizontal directional drilling method are necessary. Since the cable burial method buries a submarine cable, it costs more than a method where the submarine cable is simply laid on the seabed. The horizontal directional drilling method is even more costly because a dedicated excavator and route designing based on a preliminary boring survey are necessary, as described in the Background Art section. When the boundary point 219 is set in an area exceeding a zone in which cable burial method and horizontal directional drilling method are necessary, a method of simply laying on the seabed can be applied, so the benefit of reducing cost may be obtained.

[0122] The branching unit 41 and branch submarine cables 21a to 21d that configure the boundary point 219 are also installed in an area exceeding a zone in which authorization acquisition of the installation operation is necessary. As a result, even in a case in which the law of the country is applicable outside the territorial sea, the authorization acquisition becomes unnecessary, and the benefit of reducing labor and cost may be obtained.

[0123] A configuration example of the landing cable 221 illustrated in FIG. 3 is described.

[0124] FIG. 4 is a schematic diagram illustrating the landing cable 21 that is the first configuration example of a landing cable 221 of FIG. 3. The landing cable 21 illustrated in FIG. 4 is a bundle of a plurality of smallest basic units of submarine cables, called Light Weight (LW) core cables, with an outer armorng. Hereinafter, an LW core cable may be abbreviated as an LW core. FIG. 4 (a) is a sectional diagram of the landing cable 21. FIG. 4 (b) is a sectional diagram of an LW core cable 51n that is a configuration example of the LW core cables 51a to 51d illustrated in FIG. 4 (a).

[0125] An outer armoring wire 52 of the landing cable 21 illustrated in FIG. 4 is for protecting the cable from fishing activity in shallow water, ship anchoring, and contact with cable burial machinery during a landing operation.

[0126] The landing cable 21 has a configuration in which four LW core cables 51a to 51d are loosely wound around an interposition 53 in the center and filled with inclusion such as resin.

[0127] The LW core cable 51n illustrated in FIG. 4 (b) is a basic unit of a general submarine cable. As illustrated in FIG. 4 (b), the LW core cable 51n includes an optical fiber housing pipe 56, a plurality of tensile wires 562 disposed to surround them, and a power feed line 54 further covering the outside, and the outside is covered with an insulating cover material 57. The tensile wire 562 is a steel wire that retains and resists when tension is applied to the cable. The optical fiber housing pipe 56 is a rigid steel pipe that withstands water pressure on the optical fiber and houses the optical fiber.

[0128] The number of LW core cables induced in the landing cable 21 is free. FIG. 5 is a schematic diagram illustrating a cross-section of the landing cable 21 including six LW core cables 51a to 51f that is the second configuration example of a landing cable 221 of FIG. 3. Each LW core cable has a similar configuration to the LW core cable 51n illustrated in FIG. 4 (b).

[0129] FIG. 6 is a cross-sectional schematic diagram illustrating the landing cable 21 that is the third configuration example of the landing cable 221 illustrated in FIG. 3. The landing cable 21 illustrated in FIG. 6 is configured as a single cable, unlike the first and second configuration examples that are the collection of basic unit configuration (LW core) of submarine cables. FIG. 6 (a) is a sectional diagram of the landing cable 21 and FIG. 6 (b) is a sectional diagram illustrating a power feed line 62 that is a configuration example of each power feed line illustrated in FIG. 6 (a).

[0130] The landing cable 21 illustrated in FIG. 6 has a tensile wire 61 in the center that is surrounded by insulated and covered power feed lines 62a to 62e in concentric circles. The landing cable 21 is further arranged with optical fiber housing pipes 63a to 63e in a valley where the power feed lines meet each other, and the structure up to this point is resin-molded. The landing cable 21 is further wound with outer armoring wire 52 for protection on the outside.

[0131] The tensile wire 58 is for achieving the tension performance of the cable and is a central interposition at the time of manufacturing the cable. As illustrated in FIG. 6 (b), the power feed line 62 is power supply conductor 621 wrapped with power feed line sheath 622 that is an insulating material such as resin. The optical fiber housing pipe 63 does not need to be rigid as the one used for the LW core cable. The configuration illustrated in FIG. 6 includes optical fiber housing pipes for the number of branches. However, the optical fibers may be grouped and placed in a single pipe. In this case, in the branching unit described later, the distribution of the optical fibers needs to be carried out without a mistake. The outer armoring wire 52 is similar to the ones illustrated in FIG. 4 and FIG. 5.

[0132] Since the above-described first and second configuration examples are a collection of LW core cables, when the landing cable 21 is disassembled to LW cores, the advantage is that the connection technique with general connection parts can be used, however, the disadvantage is that the cable becomes thicker. On the contrary, the third configuration can be optimally designed as a dedicated landing cable specialized for shallow sea, which can relax the specification values of tensile strength and water pressure, thus simplifying the structure, and is expected to have an advantage such as thinner diameter and lighter weight, but has a disadvantage of requiring a dedicated connection part.

[0133] A configuration example of the branching unit 41 illustrated in FIG. 3 is described. The branching unit 41 illustrated in FIG. 3 is described with an example with 4 branches, however, in the description below, an example of 3 branches is described to avoid complexity of the diagram.

[0134] FIG. 7 is a schematic diagram illustrating a first configuration example of the branching unit 41. The branching unit 41 illustrated in FIG. 7 is used when the landing cable 21 is a collection of LW cables, as in the configurations illustrated in FIG. 4 and FIG. 5.

[0135] The branching unit 41 illustrated in FIG. 7 includes boots 45a and 46a to 46c and a housing 47. The housing 47 includes an outer wire retaining unit 42 and mold units 44a to 44c. The mold units 44a to 44c include tensile wire retaining units 43a to 43c.

[0136] The outer armoring wire of the landing cable 21 (equivalent to the outer armoring wire 52 of FIG. 4) is fixed to the housing 47 by the outer wire retaining unit 42. The LW core cables 51a to 51c of the landing cable 21 are led to the inside of the mold units 44a to 44c in the housing 47. The LW core cables 51a to 51c comply with the UJ. The UJ is described in the Background Art section.

[0137] The branch submarine cables 21a to 21c also comply with the UJ. The branch submarine cables 21a to 21c are fixed to the mold units 44a to 44c by the tensile wire retaining units 43a to 43c. Although not illustrated in the diagram, since the mold units 44a to 44c are fixed to the housing 47, the branch submarine cables 21a to 21c are fixed to the housing 47. As a result, the branch submarine cables 21a to 21c are fixed to the outer armoring wire included in the landing cable 21 via the housing 47.

[0138] The optical fiber and the power feed line of the optical fiber that is not illustrated included in the LW core cable led by each mold unit are connected to the optical fiber and the power feed line of the optical fiber included by the branch submarine cable fixed to the mold member. The connection is performed by a method disclosed in the UJ specification. The UJ is described in the Background Art section.

[0139] The inside of the mold units 44a to 44c is molded with PE, for example. It is generally known that molding with polyethylene can secure the connection between optical fibers and between power feed lines, electrical insulation, water pressure resistance, and tensile strength equivalent to the cable.

[0140] FIG. 8 is a schematic diagram illustrating the second configuration example of a branching unit 41. The branching unit 41 illustrated in FIG. 8 is used when the landing cable 21 is designed exclusively as illustrated in FIG. 6 and does not include an LW core cable. The branching unit 41 illustrated in FIG. 8 differs from the one illustrated in FIG. 7 in that the optical wiring from the landing cable 21 led into each mold unit is not the LW core cables 51a to 51c of the landing cable 21, but the tail cables 48a to 48c. The tail cable is described in the Background Art section.

[0141] The tail cables 48a to 48c are also fixed to the mold units 44a to 44c by the chips 39a to 39c. The chip is described in the Background Art section.

[0142] The branching unit 41 illustrated in FIG. 8 also differs from the one illustrated in FIG. 7 in that the optical fibers and the power feed lines of the tail cables 48a to 48c and the branch submarine cables 21a to 21c are connected in a configuration similar to the cable coupling. The cable coupling is described in the Background Art section.

[0143] The description of the branching unit 41 illustrated in FIG. 8 excluding the above-described point is the same as the description of FIG. 7.

[0144] FIG. 9 is a schematic diagram illustrating a third configuration example of the branching unit 41. The branching unit 41 illustrated in FIG. 9 differs from the ones illustrated in FIG. 7 and FIG. 8 in that the housing 47a to 47c that include mold units 44a to 44c are arranged outside the housing 47 and are connected to the housing 47 by universal couplings 49a to 49c. The branching unit 41 illustrated in FIG. 9 differs from the ones illustrated in FIG. 7 and FIG. 8 in that the boots 46a to 46c cover the housings 47a to 47c.

[0145] The optical wirings 50a to 50c illustrated in FIG. 9 are one of the LW core cables 51a to 51c illustrated in FIG. 7 and the tail cables 48a to 48c illustrated in FIG. 8. In the case of the optical wirings 50a to 50c are the LW core cables 51a to 51c illustrated in FIG. 7, the optical wirings 50a to 50c are connected to the branch submarine cables 21a to 21c in a manner that complies with the UJ specification, for example. On the other hand, when the optical wirings 50a to 50c are the tail cables 48a to 48c illustrated in FIG. 8, the optical wirings 50a to 50c are connected to the branch submarine cables 21a to 21c by the aforementioned cable couplings.

Effect

[0146] In the submarine cable system according to the present example embodiment, the landing cable includes a preliminary optical fiber and a preliminary power feed line for a case when it is necessary to additionally install another submarine cable. The preliminary wires are connected to the streamed-off branch submarine cable. Therefore, in the submarine cable system, by connecting a new submarine cable to the streamed-off branch submarine cable, another submarine cable can be additionally installed without conducting new landing construction. As a result, the submarine cable system may suppress the occurrence of cable landing construction.

Third Example Embodiment

[0147] The preliminary optical fiber of the landing cable according to the first and second example embodiments cannot be used for communication because they are not connected to the communication counterpart. However, the preliminary optical fiber can be applied to vibration or temperature sensing in a zone in which the landing cable is installed. This will be described as the third example embodiment.

[0148] First, optical fiber sensing is briefly described. An optical fiber, that is originally a medium of transferring a signal, can also carry information about the temperature and vibration of the environment in which it is placed on the light transmitted therein. Therefore, an optical fiber is increasingly being used for sensing purposes.

[0149] FIG. 10 is a schematic connection diagram illustrating a configuration example in which optical fiber sensing is applied to the submarine cable system 100 illustrated in FIG. 1.

[0150] An interrogator 70 periodically transmits pulse light to an optical fiber of the landing cable 121. Then, due to a back-scattering light phenomenon in the optical fiber, weak light returns from the optical fiber to the interrogator 70. By analyzing the light, the temperature and vibration information at each position on the optical fiber at the moment the pulse light passed can be obtained.

[0151] One of the features of optical fiber sensing is that only one optical fiber is required, and an electrical wire for power and signal transmission is not necessary. Therefore, optical fiber sensing can be applied to a preliminary optical fiber of the landing cable of one of the example embodiments, and thereby the landing cable 121 can be utilized for monitoring the temperature and vibration of the seabed in the zone up to the boundary point 119.

[0152] The optical fiber for optical fiber sensing may either be assigned for temporary usage until the start of communication usage in the future or assigned as a dedicated for sensing.

Minimum Example Embodiment of the Example Embodiments

[0153] FIG. 17 is a schematic diagram illustrating a configuration of a landing cable 321x that is a minimum configuration of the landing cable according to the example embodiment.

[0154] The landing cable 321x is a landing cable installed offshore from the cable landing position. The landing cable 321x includes an initially used optical fiber 56ax that is an optical fiber used since the start of the communication by the landing cable 321x and an initially used power feed line 54x that is a power feed line initially used from the start. In addition, the landing cable 321x includes a preliminary optical fiber 56bx that is a preliminary optical fiber.

[0155] The preliminary optical fiber 56bx connects an endpoint on a side of the cable landing position and a boundary point with a cable district not including the preliminary optical fiber 56bx. In the boundary point, a preliminary optical fiber endpoint that is an endpoint of the preliminary optical fiber 56bx is maintained in a future usable state.

[0156] The disposition of each of the initially used optical fiber 56ax, the preliminary optical fiber 56bx, and the initially used power feed line 54x is not limited to the case illustrated in FIG. 17 but is optional.

[0157] The preliminary optical fiber 56bx is preliminary, and the endpoint is maintained in a future usable state. Therefore, when the number of optical fibers of the submarine cable connected to the landing cable 321x increases, the preliminary optical fiber 56bx enables connecting a new optical fiber across the shoreline. As a result, the landing cable 321x may suppress the occurrence of new cable landing construction of a submarine cable.

[0158] Thus, the landing cable 321x has the effect described in the Advantageous Effects of Invention section, due to the above-described configuration.

[0159] Here, the landing cable 321x illustrated in FIG. 17 is the landing cable 21 illustrated in FIG. 1 or FIG. 3, for example.

[0160] The initially used power feed line 54x is one of the power feed line illustrated in FIG. 4, the power feed line included in the LW core cables 51a to 51f illustrated in FIG. 5, or the power feed lines 54a to 54e illustrated in FIG. 6 that is used since the start of communication.

[0161] The initially used optical fiber 56ax is an optical fiber included in the landing cable 21 connected to the optical fiber included in the submarine cable 22 illustrated in FIG. 1, for example. Alternatively, the initially used optical fiber 56ax is among the optical fibers included in the landing cable 121 illustrated in FIG. 2 which is connected to the optical fiber included in the tail cable 23, for example. Alternatively, the initially used optical fiber 56ax is an optical fiber included in the optical fiber included in the landing cable 21 connected to the optical fiber included in the branch submarine cable 21c illustrated in FIG. 3, for example.

[0162] The landing position is the landing position 97 illustrated in FIG. 1 or FIG. 3, for example.

[0163] The preliminary optical fiber 56bx is an optical fiber included in the optical fiber included in the landing cable 21 that is not connected to the optical fiber included in the submarine cable 22 illustrated in FIG. 1, for example. Alternatively, the preliminary optical fiber 56bx is an optical fiber whose proximity of the endpoint is stored in the optical fiber slack storage unit 31 illustrated in FIG. 2, for example. Alternatively, the preliminary optical fiber 56bx is an optical fiber included in the optical fiber included in the landing cable 21 connected to an optical fiber group included in the optical fiber included in the branch submarine cables 21a, 21b, and 21d illustrated in FIG. 3, for example.

[0164] The boundary point is the boundary point 119 illustrated in FIG. 1 or FIG. 10 or the boundary point 219 illustrated in FIG. 3, for example.

[0165] The preliminary optical fiber endpoint is an endpoint of an optical fiber included in the optical fiber included in the landing cable 21 that is stored in the optical fiber slack storage unit 31 illustrated in FIG. 2, for example. Alternatively, the preliminary optical fiber endpoint is an endpoint of an optical fiber included in the optical fiber included in the landing cable 21 connected to an optical fiber group included in the branch submarine cables 21a, 21b, and 21d illustrated in FIG. 3, for example.

[0166] While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these example embodiments, and various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims. For example, the configuration of an element illustrated in each diagram is merely an example for helping to understand the present invention and is not limited to the configuration illustrated in the diagrams.

[0167] The whole or part of the example embodiments disclosed above can be described as, but not limited to, the following supplementary notes.

(Supplementary Note 1)

[0168] A landing cable that is installed offshore from a cable landing position, the landing cable including

[0169] a preliminary optical fiber being a preliminary optical fiber in addition to an initially used optical fiber being an optical fiber used since start of communication by the landing cable and an initially used power feed line being a power feed line initially used from the start, in which

[0170] the preliminary optical fiber connects an endpoint on a side of the cable landing position and a boundary point with a district of a cable not including the preliminary optical fiber, and

[0171] a preliminary optical fiber endpoint being an endpoint of the preliminary optical fiber is maintained in a future usable state at the boundary point.

(Supplementary Note 2)

[0172] The landing cable according to supplementary note 1, in which the boundary point is located on a landward side of a cable coupling unit on a landward side of a first repeater or a piece of submarine equipment when being traced from the landing position.

(Supplementary Note 3)

[0173] The landing cable according to supplementary note 1 or 2, in which the boundary point is located outside territorial sea.

(Supplementary Note 4)

[0174] The landing cable according to any one of supplementary notes 1 to 3, in which the boundary point is located in at least one of an area exceeding a zone in which a cable burial method is necessary, an area exceeding a zone in which a horizontal directional drilling method is necessary, and an area exceeding a zone in which authorization acquisition of installation operation is necessary.

(Supplementary Note 5)

[0175] The landing cable according to any one of supplementary notes 1 to 4, further including a preliminary power feed line on an endpoint at a side of the landing position, in which:

[0176] the preliminary optical fiber and the preliminary power feed line are connected to the boundary point;

[0177] at the boundary point, the preliminary optical fiber endpoint and a preliminary power feed line endpoint being an endpoint of the preliminary power feed line are maintained in a future usable state, bundled into one, and provided with a cable branching unit at an end on an offshore side;

[0178] the landing cable is branched into an initially used submarine cable including the initially used optical fiber and the initially used power feed line, and a plurality of preliminary submarine cables having the preliminary optical fiber and the preliminary power feed line;

[0179] the preliminary optical fiber endpoint and the preliminary power feed line endpoint are maintained in a future usable state at a submarine endpoint within the preliminary submarine cable; and

[0180] the boundary point and the preliminary submarine cable are located in an area being landward side than a cable coupling unit on a landward side of a first repeater or the first submarine equipment when being traced from the landing position, outside territorial sea, in an area exceeding a zone in which a cable burial method is necessary, in an area exceeding a zone in which a horizontal directional drilling method is necessary, and in an area exceeding a zone in which authorization acquisition of installation operation is necessary.

(Supplementary Note 6)

[0181] The landing cable according to supplementary note 5, in which a streaming cable is connected to a submarine endpoint of the preliminary submarine cable, and

[0182] the boundary point, the preliminary submarine cable, and the streaming cable are arranged in an area being landward side than the cable coupling unit, outside the territorial sea, in an area exceeding a zone in which the cable burial method is necessary, in an area exceeding a zone in which the horizontal directional drilling method is necessary, and in an area exceeding a zone in which the authorization acquisition is necessary.

(Supplementary Note 7)

[0183] The landing cable according to supplementary note 5 or 6 that is a complex submarine cable made by compounding a plurality of armorless submarine cables, in which

the armorless submarine cable includes an optical fiber and a power feed line, and

[0184] the cable branching unit separates a cable that is made by compounding a plurality of the armorless submarine cables into units of the armorless submarine cable and the landing cable is connected by using an existing submarine cable connection part and connection technique.

(Supplementary Note 8)

[0185] The landing cable according to any one of supplementary notes 1 to 7, in which the preliminary optical fiber is connected as a loopback connection to another of the preliminary optical fiber at the boundary point.

(Supplementary Note 9)

[0186] The landing cable according to any one of supplementary notes 1 to 8, in which some of optical fibers that are connected to the boundary point are used for an optical fiber sensing purpose.

(Supplementary Note 10)

[0187] A partial landing cable that is all portions of the submarine cable according to any one of supplementary notes 1 to 9 in an area of a country in which the landing position is set, in which the boundary point is arranged outside the area or supposed to be arranged outside the area.

(Supplementary Note 11)

[0188] A landing cable including an optical fiber group including a plurality of optical fibers, and a power feed line group including a plurality of power feed lines, the landing cable being installed from a landing position, in which:

[0189] an endpoint that is not arranged at the landing position is arranged at a first repeater being a first repeater traced from the landing position or between the landing position and the first repeater;

[0190] the optical fiber group includes a first optical fiber group and a second optical fiber group;

[0191] the optical fiber of the first optical fiber group is the optical fiber connecting to a beyond-first-repeater submarine cable being a submarine cable after the first repeater;

[0192] the optical fiber of the second optical fiber group is the optical fiber that is preliminary and not connected to the beyond-first-repeater submarine cable; and

[0193] an endpoint of the optical fiber of the second optical fiber group is maintained in a usable state.

(Supplementary Note 12)

[0194] The landing cable according to supplementary note 11, in which the endpoint of the optical fiber is arranged in an area outside territorial sea.

(Supplementary Note 13)

[0195] The landing cable according to supplementary note 11 or 12, in which the endpoint of the optical fiber is located in at least one of an area exceeding a zone in which a cable burial method is necessary, an area exceeding a zone in which a zone in which a horizontal directional drilling method is necessary is necessary, and an area exceeding a zone in which authorization acquisition of installation operation is necessary.

(Supplementary Note 14)

[0196] The landing cable according to any one of supplementary notes 11 to 13, in which optical fibers included in the second optical fiber group are connected as a loopback connection.

(Supplementary Note 15)

[0197] The landing cable according to any one of supplementary notes 11 to 14, in which the optical fiber of the second optical fiber group is maintained in a usable state by retaining a seaward side optical fiber endpoint of an optical fiber including the optical fiber of the second optical fiber group in an optical fiber slack storage unit.

(Supplementary Note 16)

[0198] The landing cable according to supplementary note 15, in which the optical fiber of the second optical fiber group is supposed to be used when a number of beyond-first-repeater submarine cable optical fibers included in the beyond-first-repeater submarine cable increases.

(Supplementary Note 17)

[0199] The landing cable according to supplementary note 16, in which the endpoint on a seaward side of the optical fiber of the first optical fiber group is connected to the beyond-first-repeater submarine cable by a connection device, and the optical fiber slack storage unit is included in the connection device.

(Supplementary Note 18)

[0200] The landing cable according to supplementary note 17, in which the optical fiber slack storage unit is molded with resin.

(Supplementary Note 19)

[0201] The landing cable according to supplementary note 18, in which the resin is polyethylene.

(Supplementary Note 20)

[0202] The landing cable according to any one of supplementary notes 17 to 19, in which the connection device is included in the first repeater.

(Supplementary Note 21)

[0203] The landing cable according to any one of supplementary notes 11 to 14, further including a branching unit, in which a seaward side from the branching unit is split as a second plurality of branch submarine cables, some of the branch submarine cables are connected to the beyond-first-repeater submarine cable, and the optical fiber included in another of the branch submarine cable is the optical fiber of the second optical fiber group.

(Supplementary Note 22)

[0204] The landing cable according to supplementary note 21, in which the optical fiber of the second optical fiber group is supposed to be used when another submarine cable is added in future.

(Supplementary Note 23)

[0205] The landing cable according to supplementary note 21 or 22, in which streaming-off is performed on an endpoint of a branch submarine cable that is an endpoint of the some of the branch submarine cables that is not connected to the branching unit, and the endpoint of the optical fiber of the second optical fiber group included in the some of the branch submarine cables is maintained in the usable state because of the streaming-off.

(Supplementary Note 24)

[0206] The landing cable according to supplementary note 23, in which the streaming-off is connection of a dummy submarine cable or a rope to the branch submarine cable endpoint or sealing of the branch submarine cable endpoint.

(Supplementary Note 25)

[0207] The landing cable according to any one of supplementary notes 21 to 24, in which a number of the power feed lines is the plural number.

(Supplementary Note 26)

[0208] The landing cable according to any one of supplementary notes 21 to 25, further including a configuration in which a second plurality of armorless submarine cables without armor are bundled.

(Supplementary Note 27)

[0209] The landing cable according to any one of supplementary notes 21 to 25, further including a third plurality of combinations of the optical fiber and the power feed line that are equivalent to combinations of a beyond-first-repeater submarine cable optical fiber of the beyond-first-repeater submarine cable and a beyond-first-repeater submarine cable power feed line of the beyond-first-repeater submarine cable.

(Supplementary Note 28)

[0210] A partial landing cable that is all portions of the landing submarine cable according to any one of supplementary notes 11 to 27 in an area of a country in which the optical fiber endpoint on a landward side is arranged, in which the optical fiber endpoint on a seaward side is arranged outside the area, or is supposed to be arranged outside the area.

[0211] While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims.

[0212] This application is based upon and claims the benefit of priority from Japanese patent application No. 2019-110497, filed on Jun. 13, 2019, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

[0213] 100, 200 Submarine cable system [0214] 11 First repeater [0215] 16 Cable landing station [0216] 17 Beach manhole [0217] 18 Land cable [0218] 119, 219 Boundary point [0219] 121, 221 Landing cable [0220] 321x Landing cable [0221] 21a, 21b, 21c, 21d Branch submarine cable [0222] 23 Tail cable [0223] 24 Cable coupling unit [0224] 31 Optical fiber slack storage unit [0225] 33, 43a, 43b, 43c Tensile wire retaining unit [0226] 34 Mold unit [0227] 35 Storage unit [0228] 36 Bellows unit [0229] 37 Repeater housing [0230] 38, 45a, 46a, 46b, 46c Boot [0231] 39a, 39b, 39c Chip [0232] 41 Branching unit [0233] 42 Outer wire retaining unit [0234] 44a, 44b, 44c Mold unit [0235] 47, 47a, 47b, 47c Housing [0236] 48a, 48b, 48c Tail cable [0237] 49a, 49b, 49c Universal coupling [0238] 51 LW core cable [0239] 51a, 51b, 51c, 51d, 51e, 51n LW core cable [0240] 52 Outer armoring wire [0241] 54 Power feed line [0242] 54x Initially used power feed line [0243] 56 Optical fiber housing pipe [0244] 56ax Initially used optical fiber [0245] 56bx Preliminary optical fiber [0246] 61 Tensile wire [0247] 62, 62a, 62b, 62c, 62d, 62e Power feed line [0248] 621 Power feed conductor [0249] 622 Power feed line sheath [0250] 63, 63a, 63b, 63c, 63d, 63e Optical fiber housing pipe [0251] 70 Interrogator [0252] 97 Landing position