Multicore optical device, and method for manufacturing a multicore optical device

Abstract

To provide an optical attenuator using two multicore fibers. [Solution] A multicore optical device is provided, comprising a first multicore fiber having a first core and a second core, and a second multicore fiber having a third core and a fourth core, wherein the axes of the first core and the third core are offset, and the axes of the second core and the fourth core are offset, and the first multicore fiber and the second multicore fiber are connected.

Description

Technical Field

[0001] The present disclosure relates to a multi-core optical device and a method for manufacturing a multi-core optical device.

Background Art

[0002] Patent Document 1 describes that an optical loss section is inserted between single-core optical fibers that connect core sections having a high gain coefficient among the core sections of two multi-core fibers for amplification. As a result, since the maximum value of the core section having a high amplification gain over the entire length is reduced, the deviation of the amplification gain can be further suppressed. Patent Document 1 discloses that the optical loss section can be realized by fusion-connecting single-core optical fibers to be connected in each optical fiber bundle while shifting the optical axes by a predetermined amount.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique described in Patent Document 1, for example, problems in the case of realizing an optical attenuator by connecting two multi-core fibers in a specific manner have not been studied.

[0005] An object of the present disclosure is to provide an optical attenuator using two multi-core fibers in view of the above-described problems.

Means for Solving the Problems

[0006] A first aspect of the present disclosure provides a multicore optical device comprising a first multicore fiber having a first core and a second core, and a second multicore fiber having a third core and a fourth core, wherein the axes of the first core and the third core are offset, and the axes of the second core and the fourth core are offset, and the first multicore fiber and the second multicore fiber are connected.

[0007] Furthermore, a second aspect of the present disclosure provides a method for manufacturing a multicore optical device, which involves connecting a first multicore fiber having a first core and a second core with a second multicore fiber having a third core and a fourth core, by offsetting the axis of the first core with the axis of the third core and offsetting the axis of the second core with the axis of the fourth core. [Effects of the Invention]

[0008] From one perspective, an optical attenuator can be provided using two multicore fibers. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the configuration of a multicore optical device according to the embodiment. [Figure 2] This is a diagram showing an example configuration of an optical transmission system according to an embodiment. [Figure 3] This flowchart shows an example of a method for manufacturing a multicore optical device according to the embodiment. [Figure 4] This figure shows an example of a method for manufacturing a multicore optical device when the arrangement of each core in each MCF according to the embodiment is symmetrical in all directions (up, down, left, and right). [Figure 5] This figure shows an example of a method for manufacturing a multicore optical device when the arrangement of each core in each MCF according to the embodiment is symmetrical in all directions (up, down, left, and right). [Figure 6] This figure shows an example of a method for manufacturing a multicore optical device when at least one of the core arrangements of each MCF according to the embodiment is asymmetrical in the vertical, horizontal, and vertical directions. [Figure 7] This figure shows an example of a method for manufacturing a multicore optical device when at least one of the core arrangements of each MCF according to the embodiment is asymmetrical in the vertical, horizontal, and vertical directions. [Figure 8] This flowchart shows an example of a method for manufacturing a multicore optical device in which different types of cores are connected according to the embodiment. [Modes for carrying out the invention]

[0010] The principles of this disclosure will be described with reference to several exemplary embodiments. These embodiments are described for illustrative purposes only and should be understood as helping those skilled in the art to understand and implement this disclosure without implying any limitation on the scope of this disclosure. The disclosures described herein may be implemented in various ways other than those described below.

[0011] In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which this disclosure belongs.

[0012] Embodiments of the present disclosure will be described below with reference to the drawings. Each drawing is merely illustrative for illustrating one or more embodiments. Each drawing may be associated not only with one specific embodiment but also with one or more other embodiments. As those skilled in the art will understand, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps described in any of the drawings may be changed as appropriate.

[0013] (Embodiment 1) <Structure> Referring to FIG. 1, the configuration of the multi-core optical device 10 according to the embodiment will be described. FIG. 1 is a diagram showing an example of the configuration of the multi-core optical device 10 according to the embodiment. The multi-core optical device 10 has a first multi-core fiber (MCF) 11A and a second multi-core fiber 11B. Hereinafter, when it is not necessary to distinguish between the first multi-core fiber 11A and the second multi-core fiber 11B, they are simply referred to as "multi-core fiber 11" as appropriate.

[0014] The first multi-core fiber 11A has a first core 12A and a second core 13A. The second multi-core fiber 11B has a third core 12B and a fourth core 13B. In the multi-core optical device 10, the axis of the first core 12A and the axis of the third core 12B are shifted, and the axis of the second core 13A and the axis of the fourth core 13B are shifted, and the first multi-core fiber 11A and the second multi-core fiber 11B are connected at their ends. Thereby, an optical attenuator (multi-core attenuator) in the MCF can be realized. The multi-core optical device 10 of the present disclosure is Fan-in / Fan-out device (FIFO) -less and has the same size as a conventional optical attenuator in a single-core fiber (SCF). Therefore, the accommodation performance can be improved. Note that the number of cores in each MCF of the present disclosure may be two or more, and is not limited to the example where the number of cores is two.

[0015] Note that the MCF is an optical fiber in which a plurality of cores are arranged in one cladding. When using the MCF, different information can be transmitted for each core, so the amount of information (transmission capacity) that can be transmitted through one fiber can be increased. Note that the FIFO is a device that arranges the SCF according to the core-to-core pitch of the MCF in order to connect the single-core fiber (SCF) and the MCF.

[0016] (Embodiment 2) <System Configuration> Next, referring to FIG. 2, the configuration of the optical transmission system 1 according to the embodiment will be described. FIG. 2 is a diagram showing a configuration example of the optical transmission system 1 according to the embodiment. In the example of FIG. 2, the optical transmission system 1 includes a multi-core optical device 10, optical amplification repeaters (REP, repeaters) 20A, 20B, 20C, and communication stations 30A, 30B. Hereinafter, when there is no need to distinguish each of the optical amplification repeaters 20A, 20B, and 20C, they may be simply referred to as "optical amplification repeater 20" as appropriate. Also, hereinafter, when there is no need to distinguish each of the communication stations 30A and 30B, they may be simply referred to as "communication station 30" as appropriate. Note that the numbers of the multi-core optical device 10, the optical amplification repeater 20, and the communication station 30 are not limited to the example of FIG. 2.

[0017] Between the communication station 30A and the optical amplification repeater 20A, between the optical amplification repeater 20A and the optical amplification repeater 20B, and between the optical amplification repeater 20B and the multi-core optical device 10, they are respectively connected by MCF so that optical communication can be performed. Also, between the multi-core optical device 10 and the optical amplification repeater 20C, and between the optical amplification repeater 20C and the communication station 30B, they are respectively connected by MCF so that optical communication can be performed.

[0018] The multi-core optical device 10 realizes an optical attenuator in the MCF by connecting (for example, fusing or fixing and connecting with an instrument) while shifting the axes of one MCF and the other MCF. The multi-core optical device 10 may be housed in a specific housing (Joint Box). Note that the multi-core optical device 10 is used for various purposes in the optical transmission system 1. For example, the multi-core optical device 10 may be used for line adjustment when the distance between the optical amplification repeaters 20 deviates from the rated distance due to construction reasons. Also, the multi-core optical device 10 may be used for adjusting the tolerance of the optical components mounted in the device or the path difference, for example, when the input / output intensities of various optical transmission devices (for example, ROADM (reconfigurable optical add / drop multiplexer)) are defined by the standard.

[0019] The optical amplification repeater 20 is a device that amplifies and relays optical signals transmitted in each core of the MCF. The communication station 30 is a device that communicates optically with other communication stations 30 via the multicore optical device 10 and the optical amplification repeater 20. When communication is performed using an optical submarine cable laid on the seabed, the communication station 30 may be called, for example, a submarine cable landing station. The communication station 30 may, for example, convert optical signals received from other communication stations 30 into electrical signals and relay them to a network such as the Internet.

[0020] <Manufacturing method> Next, with reference to Figures 3 to 7, an example of a method for manufacturing the multicore optical device 10 according to the embodiment will be described. Figure 3 is a flowchart of an example of a method for manufacturing the multicore optical device 10 according to the embodiment. Figures 4 and 5 show an example of a method for manufacturing the multicore optical device 10 when the arrangement of each core in each MCF according to the embodiment is symmetrical in the vertical and horizontal directions. Figures 6 and 7 show an example of a method for manufacturing the multicore optical device 10 when at least one of the arrangements of each core in each MCF according to the embodiment is asymmetrical in the vertical and horizontal directions.

[0021] In step S101, each multicore fiber 11 is positioned (fixed) so that the central axes of each core in each multicore fiber 11 coincide. Here, a fusion splicer that fuses the first multicore fiber 11A and the second multicore fiber 11B may use image recognition or the like to align the positions so that the central axes of each core in the first multicore fiber 11A and each core in the second multicore fiber 11B coincide.

[0022] Alternatively, the fusion splicer may be used to shift the axes using rotational, vertical, and horizontal axis shifting functions, so that the position where the transmission power of each core is maximized is the position where the central axes of each core coincide. In this case, for example, light of the same intensity may be input to each core of the first multicore fiber 11A from each light source, and the position may be determined by the position where the intensity of each light output from each core of the second multicore fiber 11B, as expected by the light intensity meter, is maximized.

[0023] Furthermore, if each multicore fiber 11 is provided with alignment grooves or the like, the fusion splicer may be used to position each multicore fiber 11 so that the grooves of each multicore fiber 11 are aligned. This aligns the central axes of each core of the first multicore fiber 11A and each core of the second multicore fiber 11B so that they coincide.

[0024] Next, the central axis of each core in each multicore fiber 11 is shifted and positioned (fixed) (step S102). A specific example of the method for shifting the central axis of each core in each multicore fiber 11 will be described later.

[0025] Next, each multicore fiber 11 is connected (step S103). Here, the first multicore fiber 11A and the second multicore fiber 11B may be fused together using a fusion splicer. Below, a specific example of a method for shifting the central axis of each core in each multicore fiber 11 will be described.

[0026] <<Assuming the arrangement of each core in each MCF is symmetrical both vertically and horizontally>> If the first multicore fiber 11A and the second multicore fiber 11B are MCFs in which the cores are arranged symmetrically in the vertical and horizontal directions, the first multicore fiber 11A and the second multicore fiber 11B may be connected with their axes offset (rotated) in the direction of the rotation axis. This makes it possible to realize an optical attenuator in the MCF.

[0027] Figure 4 shows an example in which the first core 12A and the second core 13A of the first multicore fiber 11A are arranged symmetrically in the vertical and horizontal directions, and the third core 12B and the fourth core 13B of the second multicore fiber 11B are also arranged symmetrically in the vertical and horizontal directions. The first multicore fiber 11A and the second multicore fiber 11B are connected with their central axes 301 aligned and their axes offset in the rotation axis direction 302.

[0028] Figure 5 shows an example where the second multicore fiber 11B is connected to the first multicore fiber 11A after being rotated by an angle θ in the rotational direction, as viewed from above along the central axis of each multicore fiber 11. The central axes of the first multicore fiber 11A and the second multicore fiber 11B are at the same position 501. The third core 12B of the second multicore fiber 11B is connected to the first core 12A of the multicore optical device 10 with an angle θ offset in the rotational direction. Also, the fourth core 13B of the second multicore fiber 11B is connected to the second core 13A of the multicore optical device 10 with an angle θ offset in the rotational direction.

[0029] Furthermore, if the central axis of the second multicore fiber 11B is the origin (0,0) and the coordinates of a specific core are (X,Y), then the coordinates of the specific core after rotating the second multicore fiber 11B by θ [rad] are expressed as (Xcosθ + Ysinθ, -Xsinθ + Ycosθ). Therefore, the amount of axial displacement (distance) d when connected with an angle θ in the direction of rotation can be calculated by the following equation (1). TIFF2026115547000002.tif11150

[0030] Based on the amount of axial misalignment, the connection loss (attenuation) (dB) can be calculated. The value of the connection loss corresponding to the amount of axial misalignment may be calculated using a theoretical formula or by actual measurement.

[0031] <<If the core arrangement of at least one MCF is not symmetrical vertically or horizontally>> MCFs with asymmetrical core configurations are manufactured and sold. When MCFs with asymmetrical core configurations are connected with a rotational offset, the amount of offset for each core differs, resulting in a deviation in the amount of connection loss at each core.

[0032] Figure 6 shows an example in which the first core 12A and the second core 13A of the first multicore fiber 11A are arranged symmetrically in the vertical and horizontal directions, and the third core 12B and the fourth core 13B of the second multicore fiber 11B are arranged asymmetrically in the vertical and horizontal directions. The first core 12A and the third core 12B are connected by aligning their central axes 601 and then offsetting their axes on a plane perpendicular to the central axis. Similarly, the second core 13A and the fourth core 13B are connected by aligning their central axes 602 and then offsetting their axes on a plane perpendicular to the central axis.

[0033] Figure 7 shows an example in which the second multicore fiber 11B is connected to the first multicore fiber 11A with a distance d offset in the vertical and horizontal directions, when viewed from above along the central axis of each multicore fiber 11. The third core 12B of the second multicore fiber 11B is at a distance (d) from the first core 12A of the multicore optical device 10. 2 +d 2 ) 1 / 2 They are connected with a misalignment. Also, the fourth core 13B of the second multicore fiber 11B is at a distance (d) from the second core 13A of the multicore optical device 10. 2 +d 2 ) 1 / 2 They are connected with a misalignment.

[0034] If at least one of the first multicore fiber 11A and the second multicore fiber 11B is an MCF having a core arrangement that is not symmetrical vertically or horizontally, they may be connected by shifting their axes on a plane perpendicular to the central axis of the multicore fiber 11. In this case, for example, one multicore fiber 11 may be moved on a plane perpendicular to the central axis of each multicore fiber 11 and connected to the other multicore fiber 11. More specifically, the first multicore fiber 11A and the second multicore fiber 11B may be connected by the following procedure. This makes it possible to make the amount by which each core is shifted the same.

[0035] (Example of positioning using a fusion splicer) For example, a fusion splicer that fuses a first multicore fiber 11A and a second multicore fiber 11B may align the positions of each core of the first multicore fiber 11A and each core of the second multicore fiber 11B using image recognition or the like. Then, by following the procedure below, for example, the reduction in the connection area between the first multicore fiber 11A and the second multicore fiber 11B can be further reduced, making fusion splicing easier.

[0036] The fusion splicer may, for example, hold the first multicore fiber 11A and the second multicore fiber 11B in a position where each core is connected side by side in the lateral direction (hereinafter also referred to as "horizontal direction" as appropriate) or in the vertical direction (hereinafter also referred to as "vertical direction" as appropriate) on a plane perpendicular to the central axis of each multicore fiber 11. Then, as shown in Figure 7, the fusion splicer may shift the second multicore fiber 11B by the same amount (for example, distance d) in the vertical and lateral directions on a plane perpendicular to the central axis of each multicore fiber 11, and then fuse the first multicore fiber 11A and the second multicore fiber 11B.

[0037] Alternatively, the fusion splicer may, after aligning with each core, hold the first multicore fiber 11A and the second multicore fiber 11B such that, for example, each core is aligned in a 45-degree straight line on a plane perpendicular to the central axis of each multicore fiber 11. Then, the fusion splicer may shift the second multicore fiber 11B vertically or horizontally, and then fuse the first multicore fiber 11A and the second multicore fiber 11B.

[0038] (Example of positioning using a power monitor) Each multicore fiber 11 may be connected at a position where the transmission power of each core is equal, with the axis offset in at least one direction on a plane perpendicular to the central axis of each multicore fiber 11: horizontally, vertically, and in the direction of the rotation axis on a plane perpendicular to the central axis. In this case, for example, the first multicore fiber 11A and the second multicore fiber 11B may be fused at a position where the transmission power of each core is equal, while offsetting the axis using at least one of the rotational axis offset function, vertical axis offset function, and horizontal axis offset function of a fusion splicer. In this case, for example, light of the same intensity may be input to each core of the first multicore fiber 11A from each light source, and the fusion may be performed at a position where the intensity of each light output from each core of the second multicore fiber 11B, as expected by an optical intensity meter, is the same.

[0039] <<Example of implementing an optical attenuator with inter-core deviation>> The above example described a case where the multicore optical device 10 does not have core deviation (the attenuation due to the connection between the two cores is the same for each of the multicores). Below, we will describe a case where the multicore optical device 10 has intercore deviation (the attenuation due to the connection between the two cores is different for each of the multicores). Note that in the following, the arrangement of each core in each MCF may be symmetrical vertically and horizontally, or it may not be symmetrical vertically and horizontally.

[0040] In optical transmission system 1, for example, an MCF (Multi-Chip Function) may be used to configure both an uplink and a downlink path, resulting in a difference in path length between the uplink (e.g., from communication station 30A to communication station 30B) and the downlink (e.g., from communication station 30B to communication station 30A). This can occur, for example, when a specific core is bypassed by a FIFO (First-In, First-Out) or branching device (branching unit, switch, etc.) and then connected to the same MCF as other cores. In this case, it is conceivable that optical attenuators with different attenuation levels for each core may be required.

[0041] Furthermore, if the input / output strength of the transmission device is defined by a standard, and adjustments are needed for tolerances of optical components implemented within the device or for path differences, it is conceivable that optical attenuators with different attenuation amounts between each core may be required. Also, if there are differences in attenuation amounts among the cores of the MCF and it is necessary to adjust for path differences, it is conceivable that optical attenuators with different attenuation amounts between each core may be required.

[0042] (Example of positioning using a fusion splicer) For example, a fusion splicer that fuses a first multicore fiber 11A and a second multicore fiber 11B may align the positions of each core of the first multicore fiber 11A and each core of the second multicore fiber 11B using image recognition or the like. Then, using the rotational axis shifting function, vertical axis shifting function, and horizontal axis shifting function of the fusion splicer, the axes may be shifted by a specific amount in at least one of the rotational, vertical, and horizontal directions.

[0043] Let the coordinates C1 and C2 of each core before axis shifting be C1=(s,t) and C2=(u,v), respectively. Let the coordinates after axis shifting be C1'=(s',t') and C2'=(u',v'), and when the amount of shift in the X-axis direction is x[um], the amount of shift in the Y-axis direction is y[um], and the shift angle in the θ-axis direction (rotation direction) is θ[rad], then s',t',u',v' can be expressed as follows. Coordinates of C1': s'=(s+x)cosθ+(t+y)sinθ,t'=-(s+x)sinθ+(t+y)cosθ Coordinates of C2': u'=(u+x)cosθ+(v+y)sinθ,v'=-(u+x)sinθ+(v+y)cosθ

[0044] At this time, the axial misalignment d1 of C1 and the axial misalignment d2 of C2 can be calculated as follows. TIFF2026115547000003.tif875 TIFF2026115547000004.tif877

[0045] Therefore, by determining the core placement information and axial displacement amount of the MCF, it is possible to calculate the axial displacement amount of each core.

[0046] (Example of positioning using a power monitor) The first multicore fiber 11A and the second multicore fiber 11B may be fused together at a position where the transmission power of each core is a specific value different from the other, by shifting the axes using rotational axis shifting, vertical axis shifting, and horizontal axis shifting functions of the fusion splicer. In this case, for example, light of the same intensity may be input to each core of the first multicore fiber 11A from each light source, and the fusion may be spliced ​​together at a position where the intensity of each light emitted from each core of the second multicore fiber 11B, as expected by an optical intensity meter, is a specific value different from the other.

[0047] [An example where each core has different characteristics] Multi-Camera Filters (MCFs) with different loss characteristics for each core are manufactured and sold to reduce crosstalk. When using such MCFs, it is necessary to connect different types of cores in each MCF to adjust the attenuation and crosstalk levels for each path (for example, the path from communication station 30A to communication station 30B and the path from communication station 30B to communication station 30A) to similar values.

[0048] In this case, the second multicore fiber 11B is rotated by an angle corresponding to the number of cores in the first multicore fiber 11A and the second multicore fiber 11B, and then connected as in the examples described above. More specifically, if the number of cores in each multicore fiber 11 is n (where n is an integer of 2 or more), the second multicore fiber 11B may be rotated by 360 / n degrees. The first multicore fiber 11A and the second multicore fiber 11B may then be connected by one of the methods described above: "when the arrangement of each core in each MCF is symmetrical vertically and horizontally," "when the arrangement of each core in at least one of the MCFs is not symmetrical vertically and horizontally," or "an example of realizing an optical attenuator with intercore deviation."

[0049] In this case, the first core 12A of the first multicore fiber 11A has a first characteristic, and the second core 13A has a second characteristic that is different from the first characteristic. Also, the third core 12B of the second multicore fiber 11B has a second characteristic, and the fourth core 13B has a first characteristic. Furthermore, the axes of the first core 12A and the third core 12B are offset, and the axes of the second core 13A and the fourth core 13B are offset when they are connected.

[0050] <Manufacturing method> Next, with reference to Figure 8, an example of a method for manufacturing a multicore optical device 10 in which different types of cores are connected according to the embodiment will be described. Figure 8 is a flowchart showing an example of a method for manufacturing a multicore optical device 10 in which different types of cores are connected according to the embodiment.

[0051] In step S201, each multicore fiber 11 is positioned (fixed) so that the central axes of each core of each multicore fiber 11 coincide. This process may be the same as the process in step S101 in Figure 3.

[0052] Next, one of the multicore fibers 11 (for example, the second multicore fiber 11B) is rotated by an angle corresponding to the number of cores to be positioned (step S202).

[0053] Next, the central axis of each core in each multicore fiber 11 is shifted and positioned (fixed) (step S203). This process may be the same as the process in step S102 in Figure 3.

[0054] Next, each multicore fiber 11 is connected (step S204). This process may be the same as the process in step S103 in Figure 3.

[0055] [Example of implementing a loopback connection point] In laying submarine cables, there are limits to the length of cable that can be carried on a ship. Therefore, for long-distance systems, the laying work is carried out in multiple stages. In this case, the cable laid earlier may require monitoring of the optical line status until all cables have been laid. To address this, a loopback connection point is created where the ends of two parallel-laid MCFs are connected to each other. Then, an optical signal transmitted from communication station 30A is transmitted through one MCF, looped back at the loopback connection point, and transmitted through the other MCF, which is received by communication station 30A. This allows for remote monitoring of whether there are any abnormalities in the two MCFs. When the laying of MCFs from both directions is complete, the submerged loopback connection point is raised, and the MCF from communication station 30A and the MCF from communication station 30B are connected.

[0056] When a loopback connection is made after conversion to SCF using a FIFO, the housing space at the loopback point is constrained. On the other hand, the technology disclosed herein eliminates the need for a FIFO, making miniaturization possible.

[0057] In MCF systems, a method is often adopted in which opposing cores are used for transmission to suppress inter-core crosstalk. In this case, the first core 12A of the first multicore fiber 11A and the fourth core 13B of the second multicore fiber 11B are used for uplink transmission (transmission), and the second core 13A of the first multicore fiber 11A and the third core 12B of the second multicore fiber 11B are used for downlink transmission (reception). In this case, similar to the "example where each core has different characteristics" described above, the first core 12A of the first multicore fiber 11A used for transmission is connected to the third core 12B of the second multicore fiber 11B used for reception, and the fourth core 13B of the second multicore fiber 11B used for transmission is connected to the second core 13A of the first multicore fiber 11A used for reception.

[0058] <Other> In response to the recent increase in demand for communication capacity, multicore technology in optical transmission systems is attracting attention. While the multicore nature of transmission fibers is progressing, existing single-core (single-mode) optical devices are still being used. In this case, it is necessary to connect SCFs to each core of the MCF using a FIFO, and then connect each SCF to another MCF using another FIFO.

[0059] Therefore, the amount of optical devices required increases compared to conventional single-core systems. Consequently, there is a need to simplify or miniaturize the optical devices, for example, when there are limitations on the space available in the housing for these optical devices. According to this disclosure, an optical attenuator can be provided in which two multicore fibers are connected in a specific manner. Therefore, the optical attenuator can be miniaturized compared to the case where a FIFO is used.

[0060] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0061] Some or all of the embodiments described above may also be described as follows, but are not limited to the following. Some or all of the elements (e.g., configuration and function) described in each appendix dependent on Appendix 1 may also be dependent on other independent appendices of other categories in a similar manner. Some or all of the elements described in any appendix may be applicable to various hardware, software, recording means, systems, and methods for recording software. (Note 1) A first multicore fiber having a first core and a second core, A second multicore fiber having a third core and a fourth core, The axes of the first core and the third core are offset, and the axes of the second core and the fourth core are offset, and the first multicore fiber and the second multicore fiber are connected. Multicore optical device. (Note 2) The first core and the second core are arranged symmetrically in the first multicore fiber, both vertically and horizontally. The third core and the fourth core are arranged symmetrically in the second multicore fiber, both vertically and horizontally. The first multicore fiber and the second multicore fiber are connected with their axes offset in the direction of rotation. The multicore optical device described in Appendix 1. (Note 3) The first core and the second core are arranged asymmetrically in the first multicore fiber, The first multicore fiber and the second multicore fiber are connected with their axes offset on a plane perpendicular to the central axis. The multicore optical device described in Appendix 1. (Note 4) The first multicore fiber and the second multicore fiber are connected such that, from a position where each core is aligned horizontally or vertically on a plane perpendicular to the central axis, the second multicore fiber is offset by the same amount in the vertical and horizontal directions on a plane perpendicular to the central axis. The multicore optical device described in Appendix 3. (Note 5) The first multicore fiber and the second multicore fiber are connected by shifting the second multicore fiber vertically or horizontally on a plane perpendicular to the central axis, from a position where each core is aligned on a 45-degree straight line on a plane perpendicular to the central axis. The multicore optical device described in Appendix 3. (Note 6) The first multicore fiber and the second multicore fiber are connected at a position where their axes are offset in the lateral direction on a plane perpendicular to the central axis, in the lateral and vertical directions on a plane perpendicular to the central axis, and in the direction of the rotation axis, and the transmission power of each core is equal. The multicore optical device described in Appendix 3. (Note 7) The first multicore fiber and the second multicore fiber are connected such that the attenuation at the connection between the first core and the third core is different from the attenuation at the connection between the second core and the fourth core, with the axes of the first core and the third core offset, and the axes of the second core and the fourth core offset. The multicore optical device described in Appendix 1. (Note 8) The first core and the fourth core have a first characteristic, The second core and the third core have a second characteristic that is different from the first characteristic. The multicore optical device described in Appendix 1. (Note 9) The first core and the fourth core are transmitting cores, and the second core and the third core are receiving cores, forming a loopback connection point. The multicore optical device described in Appendix 1. (Note 10) A first multicore fiber having a first core and a second core, and a second multicore fiber having a third core and a fourth core, The first multicore fiber and the second multicore fiber are connected by offsetting the axes of the first core and the third core, and offsetting the axes of the second core and the fourth core. A method for manufacturing multicore optical devices. [Explanation of Symbols]

[0062] 1. Optical transmission system 10 Multicore Optical Devices 11 Multicore Fibers 11A First Multicore Fiber 11B Second Multicore Fiber 12A 1st Core 12B Third Core 13A Second Core 13B 4th Core 20 Optical Amplifier Repeater 30 Communications Stations

Claims

1. A first multicore fiber having a first core and a second core, A second multicore fiber having a third core and a fourth core, The axes of the first core and the third core are offset, and the axes of the second core and the fourth core are offset, and the first multicore fiber and the second multicore fiber are connected. Multicore optical device.

2. The first core and the second core are arranged symmetrically in the first multicore fiber, both vertically and horizontally. The third core and the fourth core are arranged symmetrically in the second multicore fiber, The first multicore fiber and the second multicore fiber are connected with their axes offset in the direction of rotation. The multicore optical device according to claim 1.

3. The first core and the second core are arranged asymmetrically in the first multicore fiber, The first multicore fiber and the second multicore fiber are connected with their axes offset on a plane perpendicular to the central axis. The multicore optical device according to claim 1.

4. The first multicore fiber and the second multicore fiber are connected such that, from a position where each core is aligned horizontally or vertically on a plane perpendicular to the central axis, the second multicore fiber is offset by the same amount in the vertical and horizontal directions on a plane perpendicular to the central axis. The multicore optical device according to claim 3.

5. The first multicore fiber and the second multicore fiber are connected by shifting the second multicore fiber vertically or horizontally on a plane perpendicular to the central axis, from a position where each core is aligned on a 45-degree straight line on a plane perpendicular to the central axis. The multicore optical device according to claim 3.

6. The first multicore fiber and the second multicore fiber are connected at a position where their axes are offset in the lateral direction on a plane perpendicular to the central axis, in the lateral and vertical directions on a plane perpendicular to the central axis, and in the direction of the rotation axis, and the transmission power of each core is equal. The multicore optical device according to claim 3.

7. The first multicore fiber and the second multicore fiber are connected such that the attenuation at the connection between the first core and the third core is different from the attenuation at the connection between the second core and the fourth core, with the axes of the first core and the third core offset, and the axes of the second core and the fourth core offset. The multicore optical device according to claim 1.

8. The first core and the fourth core have a first characteristic, The second core and the third core have a second characteristic that is different from the first characteristic. The multicore optical device according to claim 1.

9. The first core and the fourth core are transmitting cores, and the second core and the third core are receiving cores, forming a loopback connection point. The multicore optical device according to claim 1.

10. A first multicore fiber having a first core and a second core, and a second multicore fiber having a third core and a fourth core, The first multicore fiber and the second multicore fiber are connected by offsetting the axes of the first core and the third core, and offsetting the axes of the second core and the fourth core. A method for manufacturing multicore optical devices.

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