Optical transmission device, method for manufacturing optical transmission device, and optical cable system

Abstract

The present invention makes it possible, in the production of an optical transmission device to be applied to an optical transmission system using a multicore fiber, to easily connect the multicore fiber and the optical transmission device. To this end, an optical transmission device, which is to be connected to an optical cable that comprises a first multicore fiber including a plurality of cores, comprises an optical processing means including a multicore fiber interface which comprises a second multicore fiber including a plurality of cores that can be fusion-spliced to an end part of the first multicore fiber and at least one optical component which is to be connected to the multicore fiber interface to perform a prescribed process on light beams that are to be respectively coupled to the plurality of cores of the multicore fiber interface.

Description

Technical Field

[0001] The present invention relates to an optical transmission device, a method for manufacturing an optical transmission device, and an optical cable system, and particularly to an optical transmission device connectable to a multi-core fiber and the like.

Background Art

[0002] In a submarine cable system that transmits optical signals using an optical submarine cable, optical transmission devices such as optical repeaters and optical branching devices are installed on the seabed. In recent years, in order to increase the transmission capacity, a multi-core fiber (MCF) in which a plurality of cores are arranged in a single optical fiber has been increasingly adopted in submarine cable systems. On the other hand, an optical fiber in which only one core is arranged in a single optical fiber is also called a single core fiber (SCF).

[0003] General optical components such as optical attenuators and optical amplifiers are connected to single core fibers. Therefore, in order to individually connect each core of the multi-core fiber to the optical component, optical components called fan-in and fan-out are used. Fan-in combines the light output from the cores of a plurality of single core fibers with the cores of the multi-core fiber. Fan-out combines the light output from a plurality of cores of the multi-core fiber with different single core fibers, respectively. An optical component having an interface connectable to a single core fiber and an interface connectable to a multi-core fiber may be used as a fan-in or a fan-out. Hereinafter, unless particularly distinguished, fan-in and fan-out are collectively referred to as "FIFO".

[0004] FIG. 22 is a block diagram showing the configuration of a general optical transmission device 900 connected to a multi-core fiber. The optical transmission device 900 includes an optical circuit 910. The optical circuit 910 includes a Wavelength Selective Switch (WSS) 901, an Optical Switch (OSW) 902, and a Variable Optical Attenuator (VOA) 903. The optical transmission device 900 is connected to the outside of the optical transmission device 900 by 4-core MCFs 921-923. The optical circuit 910 is connected to the MCFs 921-923 by FIFOs 911-913. The internal optical components of the optical circuit 910 and the optical circuit 910 and the FIFOs 911-913 are connected by single-core fibers.

[0005] In relation to the present invention, Patent Document 1 describes a technique related to an optical path switching device in a multi-fiber network. Further, Patent Documents 2 and 3 describe techniques related to an optical branching device used in a submarine cable system.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] As described with reference to FIG. 22, in an optical transmission system using a multi-core fiber, there are cases where it is necessary to connect an optical transmission device including an optical circuit using general optical components to a multi-core fiber. In such cases, it is necessary to provide a FIFO in the optical transmission device and connect the multi-core fiber outside the optical transmission device and the single-core fiber of the optical circuit using the FIFO. For this reason, the manufacturer of the optical transmission device had to newly prepare a FIFO for connecting the optical circuit and the multi-core fiber during the manufacture of the optical transmission device. Further, the manufacturer had to connect each core of the optical circuit and the multi-core fiber using the FIFO.

[0008] (Object of the Invention) An object of the present invention is to provide a technique for easily connecting a multi-core fiber and an optical transmission device when manufacturing an optical transmission device applied to an optical transmission system using a multi-core fiber.

Means for Solving the Problems

[0009] The optical transmission device of the present invention is an optical transmission device connected to an optical cable including a first multi-core fiber including a plurality of cores, including an optical processing means including a multi-core fiber interface composed of a second multi-core fiber including a plurality of cores that can be fusion-connected to an end of the first multi-core fiber, and at least one optical component connected to the multi-core fiber interface and performing a predetermined process on each light combined with the plurality of cores of the multi-core fiber interface.

[0010] The manufacturing method of the optical transmission device of the present invention is a manufacturing method of an optical transmission device connectable to a first multi-core fiber including a plurality of cores provided in an optical cable, An optical processing means including a multi-core fiber interface composed of a second multi-core fiber including a plurality of cores connectable to an end of the first multi-core fiber, and at least one optical component connected to one end of the multi-core fiber interface and performing a predetermined process on each light combined with the plurality of cores of the multi-core fiber interface. The method includes a procedure of fusion-splicing and connecting to the optical cable at the other end of the multi-core fiber interface.

Advantages of the Invention

[0011] The present invention enables easy connection between a multi-core fiber and an optical transmission device during the manufacture of the optical transmission device.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] Embodiments of the present invention will be described below with reference to the drawings. The directions of the arrows shown in the drawings are illustrative and are not intended to limit the directions indicated by each arrow. In each embodiment and the drawings, the same names and reference numerals are given to the elements already shown, and redundant explanations are omitted.

[0014] (First Embodiment) FIG. 1 is a block diagram showing a configuration example of a multi-core fiber transmission device (hereinafter referred to as "MCF transmission device") 100 of the present invention. The MCF transmission device 100 is an optical transmission device connected to the outside by an optical cable. The optical cable is, for example, an optical fiber cable for connecting between optical transmission devices laid on land or under the sea. That is, the optical transmission device 100 is used in an onshore optical cable system and an undersea optical cable system (undersea cable system). The optical cable includes a multi-core fiber having a plurality of cores. The MCF transmission device 100 includes an optical component 121 and an MCF interface 131.

[0015] The MCF interface 131 is connected to the optical component 121. The MCF interface 131 is a multi-core fiber composed of a plurality of cores, and can be fusion-connected to the end of the multi-core fiber of the optical cable for each core. The MCF interface 131 is, for example, an MCF pigtail fiber optically connected to the optical component 121. The optical processing unit 110 is an optical circuit including the optical component 121 and the MCF interface 131, and the optical processing unit 110 is a form of optical processing means.

[0016] The optical component 121 executes a predetermined process for each of the lights coupled to the plurality of cores of the multi-core fiber via the MCF interface 131. The predetermined process is, for example, attenuation, amplification, branching, coupling, filtering, wavelength multiplexing, and wavelength separation. However, the processes executed by the optical component 121 are not limited to these. The optical component 121 independently executes a predetermined process for each of the lights coupled to the plurality of cores of the multi-core fiber outside the MCF transmission device 100 connected to the MCF interface 131.

[0017] FIG. 2 is a block diagram showing a configuration example of an MCF transmission device 100 to which an MCF201 is connected. The MCF201 is a multi-core fiber connected to the MCF interface 131 from outside the MCF transmission device 100. The optical component 121 processes the light input / output between the MCF transmission device 100 and the outside thereof via the MCF interface 131 for each core of the MCF201 through which the light propagates. For example, the optical component 121 executes a predetermined process on each of the lights that have propagated through the cores of the MCF201 and are input from the MCF interface 131. Alternatively, the optical component 121 executes a predetermined process on the light generated by the optical component 121 and outputs the light to the MCF interface 131. The predetermined processes for the lights input / output to and from the MCF201 may be different for each core corresponding to each light, or some or all of them may be the same.

[0018] The optical component 121 may be a plurality of light-emitting components or a plurality of light-receiving components arranged in parallel in the same number as the number of cores of the MCF201. In FIG. 2, the optical processing unit 110 may include an electrical circuit electrically connected to the optical component 121. For example, the electrical circuit drives the light-emitting component to emit light. Alternatively, the electrical circuit amplifies the received light current output from the light-receiving component.

[0019] (First Modification of the First Embodiment) FIG. 3 is a block diagram showing a configuration example of an MCF transmission device 101 to which MCF201 and 202 are connected. The MCF transmission device 101 is a first modification of the MCF transmission device 100. The MCF201 is a multi-core fiber connected to the MCF interface 131, and the MCF202 is a multi-core fiber connected to the MCF interface 132. The optical processing unit 111 is different from the optical processing unit 110 in FIG. 2 in that the optical component 122 includes the MCF interface 132.

[0020] The optical component 122 processes the light that the MCF transmission device 101 inputs and outputs to / from the outside thereof via at least one of the MCF interfaces 131 and 132, for each of the lights propagating through the cores of the MCFs 201 and 202. For example, the optical component 122 executes predetermined processing on each of the lights that have propagated through the core of the MCF 201 and are input from the MCF interface 131, and outputs the processed lights to the MCF interface 132. As the optical component 122, an optical switch, an optical amplifier, an optical attenuator, an optical filter, or an optical wave shaper can be used. The optical wave shaper is an optical component having a function of changing the wavelength band and intensity of the input light.

[0021] For example, in the optical component 122, a plurality of optical switches are arranged in parallel. Each of the plurality of optical switches controls the connection between each core of the MCF 201 and each core of the MCF 202. The optical processing unit 111 may include a control unit for setting, for the light input from each core of the MCF 201, the core that is the output destination in the MCF 202, in the optical switch.

[0022] For example, in the optical component 122, a plurality of variable optical attenuators are arranged in parallel. Each variable optical attenuator controls the attenuation amount between each core of the MCF 201 and each core of the MCF 202. The optical processing unit 111 may include a control unit for setting, for each light input from each core of the MCF 201, the attenuation amount in the variable optical attenuator.

[0023] Further, the optical component 122 may be an optical matrix switch. The optical matrix switch controls the connection relationship between each core of the MCF 201 and each core of the MCF 202. For example, when the number of cores of the MCFs 201, 202 and the MCF interfaces 131, 132 are all four, a 4×4 optical matrix switch can be used as the optical component 122. The optical matrix switch is optically coupled to each core of the MCF interface 131 and the MCF interface 132, and the connection between each core of the MCF interface 131 and each core of the MCF interface 132 may be controlled from the outside.

[0024] Also, the cores of MCF201 and MCF interface 131 may be M, and the cores of MCF202 and MCF interface 132 may be N. In this case, an M×N optical matrix switch can be used as the optical component 122. Here, M and N are integers of 2 or more. M and N may be the same or different. The optical matrix switch may be realized by, for example, an LCOS having an MCF interface. LCOS (liquid crystal on silicon) is an optical device that performs processes such as switching and filtering of light using liquid crystals.

[0025] (Second modification of the first embodiment) FIG. 4 is a block diagram showing a configuration example of the MCF transmission device 102 to which MCF201-203 are connected. FIG. 5 is a block diagram showing a more specific configuration example of the MCF transmission device 102. The MCF transmission device 102 is a second modification of the MCF transmission device 100.

[0026] In FIG. 4, the optical processing unit 112 of the MCF transmission device 102 includes optical components 123-125. The optical component 123 is connected to MCF201 and 203 via MCF interfaces 133 and 137, respectively. The optical component 123 and the optical component 124 are connected by an MCF interface 134. The optical component 124 and the optical component 125 are connected by an MCF interface 135. The optical component 125 is connected to MCF202 via an MCF interface 136. Between the optical component 123 and the optical component 124, and between the optical component 124 and the optical component 125, they may be connected by fusing the MCF interfaces provided in the respective optical components.

[0027] As shown in FIG. 5, for example, the optical component 123 is a wavelength selective switch (WSS), the optical component 124 is an optical switch (optical SW), and the optical component 125 is a variable optical attenuator (VOA).

[0028] As shown in FIGS. 1-4, the MCF transmission devices 100-102 are provided with MCF interfaces 131-137, enabling direct connection between an external multi-core fiber and the optical processing units 110-112 without using a FIFO. Therefore, when manufacturing an optical transmission device applied to an optical transmission system using MCF, the manufacturer of the optical transmission device does not need to prepare a FIFO. As a result, the MCF transmission devices 100-102 of the present embodiment have the effect of easily connecting a multi-core fiber and an optical transmission device. Thereby, the manufacturing of the optical transmission devices 100-102 becomes easier.

[0029] In this embodiment, the case where the MCF transmission device is connected to a 4-core multi-core fiber has been described as an example. However, the number of cores in the multi-core fiber is not limited to 4. In the present embodiment and the following embodiments to which the configuration of the present embodiment is applicable, the number of cores of the MCF interface and the configuration of the optical components can be selected according to the number of cores of the multi-core fiber connected to the MCF transmission device. Even in such a case, regardless of the number of cores of the multi-core fiber connected from outside the MCF transmission device, the effect of easily connecting the MCF transmission device and the multi-core fiber can be obtained.

[0030] (Second Embodiment) FIG. 6 is a block diagram showing a configuration example of the MCF transmission device 103 according to the second embodiment of the present invention. The MCF transmission device 103 includes an optical processing unit 113. The optical processing unit 113 includes MCFs 311 and 312, and a connection unit 301. The MCF 311 is a multi-core fiber connected to the MCF 201, and the MCF 312 is a multi-core fiber connected to the MCF 202. The connection unit 301 brings the cross section of the MCF 311 and the cross section of the MCF 312 close to each other and directly connects the cores of both. Such a connection is also called a butt joint. By the connection unit 301, some or all of the cores of the MCF 201 and some or all of the cores of the MCF 202 can be optically connected. The connection unit 301 of the present embodiment corresponds to the optical component 122 in FIG. 3. Also, the MCFs 311 and 312 each include the functions of the MCF interfaces 131 and 132 in FIG. 3.

[0031] As the connection unit 301, a general rotary joint for optical fibers can be used. The rotary joint includes a mechanism for rotating one or both of two optical fibers connected by a butt joint on one central axis around the central axis.

[0032] FIG. 7 is a diagram showing an example of the cross section of the MCF 311. The cross section of the MCF 311 is circular, and the MCF 311 has four cores a-d. The cores a-d are arranged at equal intervals on a circle centered on the central axis X of the cross section of the MCF 311. That is, the distance between core a and core b, the distance between core b and core c, the distance between core c and core d, and the distance between core d and core a are equal. In this case, the angle formed by two adjacent cores with the central axis X is 90 degrees. The MCF 312 is also a multi-core fiber having the same cross section as the MCF 311.

[0033] Figures 8A - 8C, 9A - 9B, and 10A - 10B are diagrams for explaining an example of the connection between the core of MCF311 and the core of MCF312 in the connection part 301. These diagrams schematically show the cross - sections of MCF311 and 312 in the connection part 301. That is, in these diagrams, the order of cores a - d of MCF312 is reverse to the order of cores a - d of MCF311.

[0034] Figure 8A shows an example of the initial state of the positional relationship between the core of MCF311 and the core of MCF312 in the connection part 301. Cores a - d of MCF311 are respectively combined with cores a - d of MCF312. Figure 8B shows an example when the connection part 301 is rotated 90 degrees in the arrow direction from the initial state (the rotation amount is 0 degrees) around the central axis of MCF312. Such rotation can be performed by controlling the rotation amount of the rotary joint. In Figure 8B, cores a, b, c, d of MCF311 are respectively combined with cores b, c, d, a of MCF312. Figure 8C shows the case when the connection part 301 is rotated 180 degrees in the arrow direction from the initial state around the central axis of MCF312. In Figure 8C, cores a, b, c, d of MCF311 are respectively combined with cores c, d, a, b of MCF312. Similarly, when MCF312 is rotated 270 degrees in the arrow direction from the initial state around the central axis, cores a, b, c, d of MCF311 are respectively combined with cores d, a, b, c of MCF312. Therefore, when MCF311 and 312 are 4 - core multi - core fibers, by rotating MCF312 in 90 - degree steps, the optical processing unit 113 can function as an optical switch.

[0035] Thus, in the MCF transmission device 103 of the second embodiment, the optical processing unit 113 can function as an optical switch.

[0036] (The first modification of the second embodiment) Figures 9A-9B show an example in the MCF transmission device 103 shown in FIG. 6 where the rotation amount of the MCF 312 is set to 45 degrees instead of 90 degrees. FIG. 9A shows the initial state before rotation. Similar to FIG. 8A, the cores a-d of the MCF 311 are respectively coupled to the cores a-d of the MCF 312. FIG. 9B shows the case where the connection part 301 rotates the MCF 312 by 45 degrees from the initial state around the central axis. At the position where the MCF 312 is rotated by 45 degrees from the initial state, the positions of the respective cores a-d of the MCF 312 are greatly separated from any of the positions of the cores a-d of the MCF 311, and the cores a-d of the MCF 311 are not optically coupled to any of the cores a-d of the MCF 312. That is, by rotating the MCF 312 from the initial state by an angle (for example, 45 degrees, 135 degrees, 225 degrees, etc.) at which each core of the MCF 311 and each core of the MCF 312 are not optically coupled, the optical processing unit 113 can function as an optical shutter. An optical shutter is an optical component capable of controlling the transmission or blocking of light. Also, from the state of FIG. 9B, by further rotating the MCF 312 by 45 degrees, an effect as an optical switch similar to FIG. 8B can be obtained. Therefore, when the MCFs 311 and 312 are the 4-core multi-core fibers exemplified in FIG. 7, by setting the rotation amount of the MCF 312 from the initial state in 45-degree steps, the optical processing unit 113 can function as an optical switch and an optical shutter.

[0037] (Second Modification of the Second Embodiment) Figures 10A and 10B show an example in the MCF transmission device 103 shown in FIG. 6 when the rotation amount of the MCF 312 is made very small. FIG. 10A shows the initial state before rotation. Similar to FIGS. 8A and 9A, the cores a-d of the MCF 311 are respectively coupled to the cores a-d of the MCF 312. FIG. 10B shows the case where the connection part 301 rotates the MCF 312 slightly around the central axis. In FIG. 10B, at the position where the MCF 312 is rotated slightly from the initial state, the optical axes of the cores a-d of the MCF 311 and the optical axes of the cores a-d of the MCF 312 do not coincide. However, the amount of deviation of the optical axis between the cores a-d of the MCF 311 and the cores a-d of the MCF 312 is small. Therefore, in FIG. 10B, different from FIG. 9B, the coupling loss between the cores a-d of the MCF 311 and the cores a-d of the MCF 312 increases, but the optical connection between them is not blocked. In other words, the cores a-d of the MCF 311 and the cores a-d of the MCF 312 are optically loosely coupled. And the coupling loss between the MCF 311 and the MCF 312 is the smallest before the rotation of the MCF 312 (initial state). And as the MCF 312 rotates, the amount of axial deviation between the cores increases, so the coupling loss initially increases with the rotation amount of the MCF 312. And when the rotation amount reaches the angle at which the optical coupling between the cores of the MCF 311 and the cores of the MCF 312 that were initially opposed is blocked, the coupling loss becomes the maximum. Therefore, by finely controlling the rotation amount of the MCF 312, the optical processing unit 113 can function as a variable optical attenuator (VOA). Such a variable optical attenuator can adjust the attenuation amount of the light propagating between each core of the MCF 311 and each core of the MCF 312 by controlling the rotation amount of the MCF 312. Note that the functions of the optical switch, the optical shutter, and the variable optical attenuator described in FIGS. 8A-8C, FIGS. 9A-9B, and FIGS. 10A-10B are all obtained by rotating the MCF 312 around the central axis. Therefore, by controlling the rotation amount of the MCF 312, the optical processing unit 113 can realize any function of the optical switch, the optical shutter, and the variable optical attenuator.

[0038] As described above, the MCF transmission device 103 of the second embodiment can realize the functions of an optical switch, an optical shutter, and a variable optical attenuator by opposing the MCFs 311 and 312 and rotating the MCF 312 around the central axis. The MCFs 311 and 312 can be easily connected to the MCFs 201 and 202, respectively, using a general fusion device for multi-core fibers. As a result, the MCF transmission device 103 can easily connect the MCFs 201 and 202 to the MCF transmission device 103 including the optical processing unit 113.

[0039] In this embodiment, the operations of an optical switch and the like using the four-core multi-core fiber illustrated in FIG. 7 have been described. However, the number of cores of the MCFs 311 and 312 is not limited to four cores. Even when the cores are arranged at equal intervals on a circle centered on the central axis (that is, the angles formed by the central axis and two adjacent cores on the circle are all equal), the connection portion 301 exhibits the same functions as in this embodiment. In such a multi-core fiber, the plurality of cores of the MCF 311 are arranged at equal intervals on a circle centered on the central axis X of the MCF 311. The MCF 312 has the same core arrangement as the MCF 311.

[0040] For example, the MCFs 311 and 312 may be six-core multi-core fibers in which six cores are arranged at equal intervals on a circle centered on the central axis X. In this case, the angle formed by the central axis X and two adjacent cores is 60 degrees. When such a multi-core fiber is used as the MCFs 311 and 312, the function of the optical switch can be obtained by a rotation of 60-degree steps from the initial state, and the function of the optical shutter can be obtained by a rotation of 30 degrees each.

[0041] (Third Embodiment) An example in which the optical component 123 illustrated in FIG. 4 is a WSS (wavelength selective switch) will be described.

[0042] FIG. 11 is a diagram showing a configuration example of the WSS501. The WSS501 has the functions of two sets of 2-input 1-output WSSs that input and output six single-core fibers (SCF511 - 516). The WSS501 includes one LCOS (Liquid Crystal on Silicon) 517. The LCOS is an optical device that irradiates light onto a silicon substrate having a liquid crystal layer and performs processes such as optical switching and filtering using the reflection and refraction of light at that time. The WSS501 functions as a first WSS that inputs and outputs SCF511 - 513 and a second WSS that inputs and outputs SCF514 - 516. The first WSS and the second WSS operate independently.

[0043] FIG. 12 is a diagram showing an example of the allocation of usage areas on the surface of the LCOS517 included in the WSS501. The area surrounded by the dashed line shows an example of the area where light can be processed in the LCOS517. The area 518 is optically coupled to the SCF511 - 513 and processes the light input and output between the SCF511 - 513 and the WSS501. The area 519 is optically coupled to the SCF514 - 516 and processes the light input and output between the SCF514 - 516 and the WSS501. By dividing the processing area in this way inside the LCOS517, the LCOS517 can provide the functions of two independent WSSs.

[0044] FIG. 13 is a diagram showing a configuration example of the WSS601. The WSS601 has the functions of four sets of 2-input 1-output WSSs. The WSS601 includes one LCOS631. The LCOS631 is an optical device that performs processes such as optical switching and filtering using liquid crystals and inputs and outputs twelve single-core fibers (SCF611 - 622). The LCOS631 functions as a first WSS that inputs and outputs SCF611 - 613, a second WSS that inputs and outputs SCF614 - 616, a third WSS that inputs and outputs SCF617 - 619, and a fourth WSS that inputs and outputs SCF620 - 622. The first to fourth WSSs operate independently. That is, the WSS601 has the functions equivalent to two WSS501s described in FIG. 11.

[0045] WSS601 includes FIFOs 641 - 643 and MCFs 644 - 646. Each of MCFs 644 - 646 is a 4 - core multi - core fiber. FIFO 641 connects each core of MCF 644 to SCFs 611, 614, 617, and 620 respectively. FIFO 642 connects each core of MCF 645 to SCFs 612, 615, 618, and 621 respectively. FIFO 643 connects each core of MCF 646 to SCFs 613, 616, 619, and 622 respectively. MCFs 644 - 646 function as the MCF interfaces described in the first embodiment.

[0046] Using WSS601, the optical processing unit described in the first and second embodiments may be configured. For example, WSS601 may be used as an optical processing unit including the optical component 123 and MCF interfaces 133, 134, 137 described in FIG. 4. In this case, MCFs 644 - 646 function as MCF interfaces 133, 137, 134 in FIG. 4. MCF 644 is fusion - spliced to MCF 201, and MCF 645 is fusion - spliced to MCF 203. Also, MCF 646 is connected to the optical component 124 via the MCF interface 134.

[0047] FIG. 14 is a diagram showing an example of the allocation of the usage area on the surface of LCOS631. The area surrounded by the broken line shows an example of the area where light can be processed in LCOS631. By rearranging the area of LCOS517 shown in FIG. 12, LCOS631 can utilize four areas 632 - 635 with a single LCOS while using the same optical device as LCOS517.

[0048] Region 632 is optically coupled to SCF611 - 613 in FIG. 13 and processes the light input and output between SCF611 - 613 and LCOS631. Region 633 is optically coupled to SCF614 - 616 and processes the light input and output between SCF614 - 616 and LCOS631. Region 633 is optically coupled to SCF617 - 619 and processes the light input and output between SCF617 - 619 and LCOS631. Region 634 is optically coupled to SCF620 - 622 and processes the light input and output between SCF620 - 622 and LCOS631. In this way, LCOS517 can provide the functions of four independent WSSs.

[0049] For the WSS601 with such a configuration, since MCF644 - 646 can be used as the MCF interface, it is easy to connect to other multi - core fibers. Therefore, when WSS601 is installed in an optical transmission device, it is easy to connect to the multi - core fiber connected to the outside of the optical transmission device or to other optical processing units equipped with an MCF interface. That is, WSS601 enables easy connection of the multi - core fiber and the optical transmission device during the manufacture of the optical transmission device.

[0050] Note that the number of cores of MCF644 - 646 is not limited to 4 cores. For example, by using an MCF with 5 or more cores for MCF644 - 646 and further using an LCOS with 5 or more used regions, WSS601 can be applied to an MCF transmission device with an even larger number of cores.

[0051] (The Fourth Embodiment) The configuration of WSS601 illustrated in FIG. 13 can be modified and applied to an optical processing unit with other functions. FIG. 15 is a block diagram showing a configuration example of the optical processing unit 700 according to the fourth embodiment. The optical processing unit 700 includes an optical function device 710 having four sets of inputs and outputs, FIFOs 711 and 712, MCFs 731 and 732, and SCFs 721 - 728. The optical processing unit 700 is a form of the optical processing unit 111 described with reference to FIG. 3.

[0052] In this embodiment, MCF731 and 732 are each 4-core multi-core fibers. SCF721 - 728 are single-core fibers. FIFO711 connects each core of MCF731 to each core of SCF711 - 724 respectively. FIFO712 connects each core of MCF732 to SCF725 - 728 respectively. MCF731 and 732 are also used as MCF interfaces 131 and 132 described in FIG. 3.

[0053] The optical function device 710 processes the light input from SCF721 - 724 and outputs the processed light to SCF725 - 728. The optical function device 710 is, for example, an optical wave shaper having 4 sets of inputs and outputs, or 4 active optical filters arranged in parallel. The optical wave shaper is an optical device having a function of changing the wavelength band and intensity of the input light. The active optical filter is an optical device capable of dynamically controlling the transmission characteristics of the spectrum of the input light. The optical wave shaper and the active optical filter may be realized by an LCOS631 having 4 regions 632 - 635 illustrated in FIG. 14. In this case, regions 632 - 635 independently process the light input from SCF711 - 714. And the light processed in each region is output to SCF725 - 728 respectively.

[0054] Alternatively, the optical function device 710 may be composed of optical passive components such as an optical coupler, an optical isolator, and a passive optical filter. For example, the optical function device 710 may be a 4×4 optical star coupler. In this case, one set of the two sets of 4-way branches of the 4×4 optical star coupler may be connected to SCF721 - 724, and the other set may be connected to SCF725 - 728. Also, the optical coupler may be two sets of 2×2 optical couplers.

[0055] Furthermore, the optical functional device 710 may be four optical isolators arranged in parallel. In this case, the light propagating through the SCFs 721 - 724 passes through different optical isolators respectively and is output to the SCFs 725 - 728. The light passing directions of the four optical isolators do not have to be the same. Furthermore, the optical functional device 710 may be four sets of passive optical filters. In this case, the light propagating through the SCFs 721 - 724 passes through different passive optical filters respectively and is output to the SCFs 725 - 728. A passive optical filter is an optical filter with fixed transmission characteristics.

[0056] Note that the functions of the optical functional device 710 described above are examples, and the functions of the optical functional device 710 and the optical devices constituting the optical functional device 710 are not limited to the above-described optical wave shaper, optical coupler, etc. Also, the MCF 731 or 732 may be connected to the MCF interface of other optical functional devices.

[0057] The optical processing unit 700 connects the optical functional device 710 to the single-core fiber sides of the FIFOs 711 and 712, and uses the multi-core fiber sides of the FIFOs 711 and 712 as the MCF interface. The optical processing unit 700 having such a configuration can use the MCFs 731 and 732 as the MCF interface, so it is easy to connect to other multi-core fibers. Therefore, when the optical processing unit 700 is mounted on an optical transmission device, it becomes easy to connect to the multi-core fiber connected to the outside of the optical transmission device or to other optical processing units having an MCF interface. That is, the optical processing unit 700 enables easy connection of the multi-core fiber and the optical transmission device during the manufacture of the optical transmission device.

[0058] Note that the number of cores of the MCFs 731 and 732 is not limited to four cores. Also, the number of inputs and outputs of the optical functional device 710 may be increased or decreased according to the number of cores of the MCFs 731 and 732. For example, by using multi-core fibers with five or more cores for the MCFs 731 and 732 and further using an optical functional device 710 having five or more sets of inputs and outputs, the optical processing unit 700 can be applied to an MCF transmission device connected to an external MCF with five or more cores.

[0059] (Fifth Embodiment) FIG. 16 is a block diagram showing a configuration example of the undersea cable system 80 of the present invention. The undersea cable system 80 includes terminal stations 801-806, undersea cables 811-815, and branching devices 821-824. The undersea cable 811 is an optical cable including a single-core fiber and a multi-core fiber. Also, the undersea cables 812-813, 815 are optical cables including multi-core fibers. The undersea cable 814 is an optical cable including a single-core fiber. The terminal stations 801-806 are station buildings installed on land. The terminal stations 801-806 are connected to be mutually communicable based on the specifications of the undersea cable system 80, and each includes an optical communication device that terminates an optical signal transmitted through the connected undersea cable. The branching devices 821-824 are MCF transmission devices 102 to which three multi-core fibers can be connected, for example, as described with reference to FIG. 4.

[0060] FIG. 17 is a cross-sectional view schematically showing an example of the optical fibers included in the undersea cable 811. The undersea cable 811 connects the terminal station 801 and the terminal station 806 via the branching devices 821-824. The black dots in FIG. 17 indicate the cores of the respective fibers. The undersea cable 811 includes MCFs 831-834, each of which is a multi-core fiber with 2 cores, an MCF 835 which is a multi-core fiber with 4 cores, and SCFs 836-837, each of which is a single-core fiber. The undersea cables 812 and 813 each include two multi-core fibers with 2 cores. The undersea cable 814 includes four single-core fibers. The undersea cable 815 includes two multi-core fibers with 4 cores.

[0061] FIG. 18 is a diagram showing a connection example of submarine cables 811 and 812 in the branching device 821. Inside the branching device 821, each core of the MCF834 is connected to each core of two multi-core fibers of the submarine cable 812. For example, the MCF834 and the submarine cable 812 are connected to the MCF interface of an optical processing unit (for example, the optical processing unit 112 illustrated in FIG. 4) provided in the branching device 821. The optical processing unit provided in the branching device 821 sets a connection relationship between the MCF834 and the MCF included in the submarine cable 812.

[0062] FIG. 19 is a diagram showing a connection example of submarine cables 811 and 813 in the branching device 822. Inside the branching device 822, each core of the MCF833 is connected to each core of two multi-core fibers of the submarine cable 813. For example, the MCF833 and the submarine cable 813 are connected to the MCF interface of an optical processing unit (for example, the optical processing unit 112 illustrated in FIG. 4) provided in the branching device 822. The optical processing unit provided in the branching device 822 sets a connection relationship between the MCF833 and the MCF included in the submarine cable 813.

[0063] FIG. 20 is a diagram showing a connection example of submarine cables 811 and 814 in the branching device 823. Inside the branching device 823, each core of the SCF836 and the SCF837 is connected to each core of the submarine cable 814. The SCF836 and 837 may be directly connected to optical components of an optical processing unit provided in the branching device 823. The optical processing unit provided in the branching device 823 sets a connection relationship between the SCF836 and 837 and the SCF included in the submarine cable 814.

[0064] FIG. 21 is a diagram showing an example of connection between the undersea cable 811 and the undersea cable 815 in the branching device 824. Inside the branching device 824, each core of the MCF835 is connected to each core of the undersea cable 815. For example, the MCF835 and the undersea cable 815 are connected to the MCF interfaces provided in the branching device 824 (for example, the MCF interfaces 133, 136, and 137 in FIG. 4). The optical processing unit provided in the branching device 824 sets the connection relationship between the MCF835 and the MCF included in the undersea cable 815.

[0065] The undersea cable system 80 having such a configuration includes the branching devices 821-824. And since the branching devices 821-824 are provided with MCF interfaces, it is easy to connect to an undersea cable including a multi-core fiber. Therefore, the branching devices 821-824 facilitate the connection to the undersea cable when constructing the undersea cable system 80.

[0066] Also, as illustrated in FIG. 17, the undersea cable 811 has a configuration combining a single-core fiber, a two-core multi-core fiber, and a four-core multi-core fiber. Thereby, the undersea cable 811 can be branched or combined in units of multi-core fibers or single-core fibers in each branching device according to the configuration of the undersea cable system 80. As a result, the connection work of the undersea cable in the branching devices 821-824 becomes easy.

[0067] Note that the embodiments of the present invention can also be described as follows in the appended claims, but are not limited thereto.

[0068] (Appended Claim 1) An optical transmission device connected to an optical cable including a first multi-core fiber including a plurality of cores, An optical processing means comprising a multi-core fiber interface composed of a second multi-core fiber including a plurality of cores that can be fusion-connected to the end of the first multi-core fiber, and at least one optical component connected to the multi-core fiber interface and performing a predetermined process on each light that is combined with the plurality of cores of the multi-core fiber interface. Optical transmission device.

[0069] (Appendix 2) The optical processing means includes a plurality of the optical components. The plurality of the optical components each include the multi-core fiber interface. The plurality of the optical components are connected to each other via their respective multi-core fiber interfaces. The optical transmission device according to Appendix 1.

[0070] (Appendix 3) The optical processing means comprises a first multi-core fiber interface and a second multi-core fiber interface, which are the multi-core fiber interfaces. The first multi-core fiber interface can connect a multi-core fiber having M cores. The second multi-core fiber interface can connect a multi-core fiber having N cores. The optical component is an M×N optical matrix switch capable of externally controlling the connection between the cores of the first multi-core fiber interface and the cores of the second multi-core fiber interface. M and N are integers of 2 or more. The optical transmission device according to Appendix 1 or 2.

[0071] (Appendix 4) The optical component comprises a third multi-core fiber, a fourth multi-core fiber, and a rotating means. The cross-section of the third multi-core fiber and the cross-section of the fourth multi-core fiber face each other on the same central axis, The rotating means controls the amount of rotation around the central axis of the fourth multi-core fiber. The optical transmission device according to appended note 1 or 2.

[0072] (Appended note 5) The rotating means controls the connection relationship between the plurality of opposing cores by controlling the amount of rotation. The optical transmission device according to appended note 4.

[0073] (Appended note 6) The rotating means controls the connection loss between the plurality of opposing cores by controlling the amount of rotation. The optical transmission device according to appended note 4.

[0074] (Appended note 7) The plurality of cores of the third multi-core fiber are arranged at equal intervals on a circle centered on the central axis of the first multi-core fiber, and the fourth multi-core fiber has the same core arrangement as the third multi-core fiber. The optical transmission device according to any one of appended notes 4 to 6.

[0075] (Appended note 8) The optical component includes a FIFO and an optical function device optically coupled to each core of the FIFO. The optical transmission device according to appended note 1 or 2.

[0076] (Appended note 9) The optical transmission device according to any one of appended notes 1 to 8, A plurality of terminal stations each connected to the optical transmission device via a different optical cable, An optical cable system comprising the same.

[0077] (Appended note 10) The optical transmission device has a function of branching the optical cable. The optical cable includes a multi-core fiber composed of the same number of cores as the number of cores branched in the optical transmission device. The optical cable system according to Supplementary Note 9.

[0078] (Supplementary Note 11) A method for manufacturing an optical transmission device connectable to a first multi-core fiber including a plurality of cores provided in an optical cable, An optical processing means including a multi-core fiber interface composed of a second multi-core fiber including a plurality of cores connectable to an end of the first multi-core fiber, and at least one optical component connected to one end of the multi-core fiber interface and performing a predetermined process on each light combined with the plurality of cores of the multi-core fiber interface. A method for manufacturing an optical transmission device, wherein the optical cable is fusion-connected at the other end of the multi-core fiber interface.

[0079] Although the present invention has been described with reference to the embodiments above, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0080] In addition, the configurations described in the respective embodiments are not necessarily mutually exclusive. The operations and effects of the present invention may be realized by a configuration combining all or part of the above-described embodiments.

Explanation of Reference Numerals

[0081] 80 Submarine cable system 100 - 103 MCF transmission device 110 - 113 Optical processing unit 121 - 125 Optical components 131 - 137 MCF interface 201 - 203 MCF 301 Connection part 311 - 312 MCF 501 WSS 511 - 516, 611 - 622 SCF 518 - 519, 632 - 635 regions 517, 631 LCOS 601 WSS 641 - 643, 711, 712 FIFO 644 - 646, 731, 732 MCF 700 Optical processing unit 710 Optical functional device 721 - 728 SCF 801 - 806 Central offices 801 - 803 MCF 806 Central office 811 - 815 Submarine cables 821 - 824 Branching devices 831 - 834 2 - core MCF 835 4 - core MCF 836 - 837 SCF 900 Optical transmission device 901 Wavelength - selective switch 902 Optical switch 903 Variable optical attenuator 910 Optical circuit 921 - 923 MCF

Claims

1. An optical transmission device connected to an optical cable including a first multi-core fiber including a plurality of cores, comprising an optical processing means including a multi-core fiber interface composed of a second multi-core fiber including a plurality of cores that can be fusion-connected to an end of the first multi-core fiber, and at least one optical component connected to the multi-core fiber interface and performing a predetermined process on each light combined with the plurality of cores of the multi-core fiber interface. The optical processing means includes a first multi-core fiber interface and a second multi-core fiber interface, which are the multi-core fiber interfaces, The first multi-core fiber interface can connect a multi-core fiber having M cores, The second multi-core fiber interface can connect a multi-core fiber having N cores, The optical component is an M×N optical matrix switch whose connection between the cores of the first multi-core fiber interface and the cores of the second multi-core fiber interface can be controlled from the outside, M and N are integers of 2 or more, Optical transmission device.

2. An optical transmission device connected to an optical cable including a first multi-core fiber including a plurality of cores, comprising an optical processing means including a multi-core fiber interface composed of a second multi-core fiber including a plurality of cores that can be fusion-connected to an end of the first multi-core fiber, and at least one optical component connected to the multi-core fiber interface and performing a predetermined process on each light combined with the plurality of cores of the multi-core fiber interface. The optical component includes a third multi-core fiber, a fourth multi-core fiber, and a rotating means. The cross-section of the third multi-core fiber and the cross-section of the fourth multi-core fiber face each other on the same central axis. The rotation means is an optical transmission device that controls the amount of rotation around the central axis of the fourth multi-core fiber. **Claim 3** The rotation means controls the connection relationship between the plurality of opposing cores by controlling the amount of rotation. The optical transmission device according to claim 2. **Claim 4** The rotation means controls the connection loss between the plurality of opposing cores by controlling the amount of rotation. The optical transmission device according to claim 2. **Claim 5** The plurality of cores of the third multi-core fiber are arranged at equal intervals on a circle centered on the central axis of the first multi-core fiber, and the fourth multi-core fiber has the same core arrangement as the third multi-core fiber. The optical transmission device according to any one of claims 2 to 4. **Claim 6** The optical processing means includes a plurality of the optical components. The plurality of the optical components each include the multi-core fiber interface. The plurality of the optical components are connected to each other via their respective multi-core fiber interfaces. The optical transmission device according to any one of claims 1 to 5. **Claim 7** An optical transmission device according to any one of claims 1 to 6, and a plurality of end stations each connected to the optical transmission device via a respective different optical cable. An optical cable system comprising the same. **Claim 8** The optical transmission device has a function of branching the optical cable. The optical cable includes a multi-core fiber composed of the same number of cores as the number of cores branched in the optical transmission device. The optical cable system according to claim 7. A method for manufacturing an optical transmission device connectable to an optical cable including a first multi-core fiber including a plurality of cores, wherein the optical transmission device includes a multi-core fiber interface including a second multi-core fiber including a plurality of cores that can be fusion-connected to an end of the first multi-core fiber, the multi-core fiber interfaces, i.e., a first multi-core fiber interface and a second multi-core fiber interface, at least one optical component connected to the multi-core fiber interface and performing a predetermined process on each light beam that is coupled to the plurality of cores of the multi-core fiber interface, and includes optical processing means, wherein the optical component is an M×N optical matrix switch, and M and N are integers of 2 or more, by the optical processing means, a multi-core fiber having M cores is connected to the first multi-core fiber interface, and a multi-core fiber having N cores is connected to the second multi-core fiber interface, by the M×N optical matrix switch, the connection between the cores of the first multi-core fiber interface and the cores of the second multi-core fiber interface is controlled, a method for manufacturing an optical transmission device. A method for manufacturing an optical transmission device connectable to an optical cable including a first multi-core fiber including a plurality of cores, wherein the optical transmission device includes a multi-core fiber interface including a second multi-core fiber including a plurality of cores connectable to an end of the first multi-core fiber, and Comprising a third multi-core fiber and a fourth multi-core fiber, connected to one end of the multi-core fiber interface, and including at least one optical component that performs a predetermined process on each light that is coupled to the plurality of cores of the multi-core fiber interface. The optical processing means is fusion-connected to the optical cable at the other end of the multi-core fiber interface, opposing the cross-section of the third multi-core fiber and the cross-section of the fourth multi-core fiber on the same central axis, controlling the amount of rotation around the central axis of the fourth multi-core fiber, A method for manufacturing an optical transmission device.

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