Method for connecting multicore fiber and multicore fiber connecting device

Abstract

To provide a method for connecting multicore fiber and a multicore fiber connecting device capable of suppressing variation in connection loss between cores.SOLUTION: The method includes a fusing step S2 of performing discharge by a pair of high-voltage discharge electrodes 61a and 61b facing each other across a butt joint position of multicore fibers 2a and 2b, and fusing the multicore fibers 2a and 2b together. In the fusing step S2, after the discharge is started and before the discharge is terminated, the pair of multicore fibers 2a and 2b are moved in a direction perpendicular to the longitudinal direction of the multicore fiber 2.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a multi-core fiber splicing method and a multi-core fiber splicing device. [Background technology]

[0002] A multicore fiber splicing device is a device used to splice a pair of multicore fibers, and includes, as its main components, an alignment device for accurately aligning the parts to be spliced, and a heater unit for generating heat to fuse the ends of the multicore fibers together. As the heater unit, for example, a pair of opposing high-voltage discharge electrodes is used.

[0003] When connecting multi-core fibers, rotational alignment is performed to make the cores of the respective multi-core fibers face each other. Patent Document 1 listed below discloses a method for aligning a multi-core fiber when the core positions do not have rotational symmetry.

[0004] Patent Document 2 listed below discloses a technique for fusing rotationally aligned multi-core fibers by discharge between a pair of opposing high-voltage discharge electrodes. In this fusion splicing, the ends of the aligned multi-core fibers are butted together, and a high voltage is applied to the discharge electrodes to cause an arc discharge, which melts the glass portion of the optical fiber with the generated heat, thereby fusing the fibers. Fusion splicing by discharge forms a physically strong joint, and a stable connection is maintained for a long period of time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-4685 [Patent Document 2] International Publication No. 2019 / 163150 Summary of the Invention [Problem to be solved by the invention]

[0006] In the case of fusion splicing by discharge, uneven temperature distribution may occur during arc discharge. One cause of temperature unevenness is that glass fume generated by the heat of arc discharge accumulates on the discharge electrode and becomes a resistor. Because the accumulation of glass fume is not uniform at each location on the high-voltage discharge electrode, uneven discharge occurs, resulting in the uneven temperature distribution. This causes uneven melting of each core, which increases the variation in the connection state between cores and may increase the variation in connection loss between cores.

[0007] Therefore, an object of the present invention is to provide a multi-core fiber splicing method and a multi-core fiber splicing device that can suppress variations in splice loss between cores. [Means for solving the problem]

[0008] A first aspect of the present invention is a method for connecting a pair of multicore fibers, comprising a fusion step of performing discharge between a pair of high-voltage discharge electrodes facing each other across a butt-joint position of each of the multicore fibers, and fusing the multicore fibers together, wherein in the fusion step, the pair of multicore fibers are moved in a direction perpendicular to the longitudinal direction of the multicore fibers from the start of the discharge to the end of the discharge.

[0009] According to aspect 1, since the pair of multi-core fibers are moved in a direction perpendicular to the longitudinal direction of the multi-core fibers from the start of discharge to the end of discharge, heating of each core can be averaged more than when the multi-core fibers are not moved, and the difference in thermal history of each core can be reduced. Therefore, according to aspect 1, the variation in the connection state of each core can be reduced, and the variation in connection loss between cores can be reduced.

[0010] A second aspect of the present invention is the method for connecting multi-core fibers according to the first aspect, characterized in that the discharge is composed of a plurality of pulse discharges, and the pair of multi-core fibers is moved between the pulse discharges.

[0011] According to the second aspect, it is possible to lengthen the period between pulse discharges, so that the pair of multi-core fibers can be moved accurately, and the reproducibility of heating can be improved, thereby reducing the difference in thermal history of each core.

[0012] A third aspect of the present invention is the method for connecting multi-core fibers according to the second aspect, characterized in that each core in the multi-core fiber is arranged in an N-fold rotational symmetry with the central axis of the cladding as the center of symmetry, the pulse discharge is performed M times where M is a number that is a multiple or divisor of N, and the pair of multi-core fibers are moved between the pulse discharges so that a distance between a midpoint of a line segment connecting the central axis of the cladding and tips of a pair of high-voltage discharge electrodes is constant and the line connecting the midpoint and the central axis of the cladding rotates 360° / M around the midpoint.

[0013] According to the third aspect, when the cores of the multi-core fiber are arranged in N-fold rotational symmetry with the central axis of the cladding as the center of symmetry, heating suitable for the rotational symmetry becomes possible.

[0014] A fourth aspect of the present invention is the method for connecting multi-core fibers according to the first aspect, wherein the pair of multi-core fibers is moved during the discharge.

[0015] According to the fourth aspect, since discharge and movement can be performed simultaneously, the difference in thermal history can be reduced in a short time, and fusion splicing of the multi-core fiber can be completed.

[0016] A fifth aspect of the present invention is a multi-core fiber splicing device that splices a pair of multi-core fibers, the multi-core fiber splicing device comprising: an alignment device that can adjust the position of each of the multi-core fibers; a fusion splicer that generates discharge between a pair of high-voltage discharge electrodes facing each other across a butt-joint position of the multi-core fibers and can fuse the multi-core fibers together; and a control device, wherein the control device controls the fusion splicer to generate discharge and fuse the multi-core fibers together, and controls the alignment device to move the pair of multi-core fibers in a direction perpendicular to the longitudinal direction of the multi-core fibers from the start of the discharge to the end of the discharge.

[0017] According to aspect 5, since the pair of multi-core fibers is moved in a direction perpendicular to the longitudinal direction of the multi-core fibers from the start of discharge to the end of discharge, the state of heating due to discharge changes, the heating of each core can be averaged, and the difference in thermal history of each core can be reduced. Therefore, according to aspect 5, it is possible to reduce the variation in the connection state of each core and the variation in connection loss between cores. [Effects of the Invention]

[0018] As described above, according to the present invention, a multi-core fiber splicing method and a multi-core fiber splicing device that can suppress variations in splice loss between cores are provided. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram schematically showing a cross section perpendicular to the longitudinal direction of a multi-core fiber. [Figure 2] FIG. 2 is a diagram schematically illustrating a multi-core fiber splicing device according to an embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing a method for connecting multi-core fibers using the multi-core fiber connection device according to the embodiment of the present invention. [Figure 4]FIG. 4 is a diagram showing a schematic view of the fusion step. [Figure 5] FIG. 5 is a view similar to FIG. 4 showing the fusion step according to the first modified example of the embodiment. [Figure 6] FIG. 6 is a view similar to FIG. 4 showing the fusion step according to the second modified example of the embodiment. [Figure 7] FIG. 7 is a view similar to FIG. 4 showing the fusion step according to the third modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments for carrying out a method for connecting multicore fibers 2 and a multicore fiber connecting device 1 according to the present invention will be illustrated with reference to the accompanying drawings. The embodiments illustrated below are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention can be modified and improved from the following embodiments within the scope of the claims without departing from the spirit thereof. Furthermore, in this specification, the dimensions of each component may be exaggerated to facilitate understanding.

[0021] First, the multi-core fiber 2 to be connected by the multi-core fiber connection device 1 according to this embodiment will be described.

[0022] FIG. 1 is a diagram schematically showing a cross section perpendicular to the longitudinal direction of a multicore fiber 2. The multicore fibers 2 connected to each other have the same configuration. The multicore fiber 2 includes a plurality of cores 21a to 21d, claddings 22 surrounding the outer peripheral surfaces of the cores 21, markers 23, an inner protective layer 24 covering the outer peripheral surface of the cladding 22, and an outer protective layer 25 covering the outer peripheral surface of the inner protective layer 24. The number of cores 21 is not limited to four. In this specification, when the cores 21a, 21b, 21c, 21d, etc. are not to be distinguished from each other, they are referred to as cores 21. Note that in FIG. 1, the central axis CC of the core 21 is shown only for one core 21a, and the central axes CC of the cores 21 are not shown for the other cores 21b to 21d. The cores 21a to 21d in this embodiment are located on the vertices of a square whose center is the central axis C of the cladding 22. Therefore, the cores 21a to 21d are arranged in four-way rotation symmetry around the central axis C of the cladding 22.

[0023] Next, the configuration of the multi-core fiber splicing device 1 according to this embodiment will be described.

[0024] 2 is a diagram schematically illustrating the multicore fiber splicing device 1. The multicore fiber splicing device 1 mainly includes an alignment device 40 that adjusts the positions of the multicore fibers 2a and 2b, a fusion splicer 60 that fuses the multicore fibers 2a and 2b together, and a control device 30.

[0025] The configuration of the multicore fibers 2a and 2b is the same as that of the multicore fiber 2. Therefore, in this specification, when there is no need to distinguish between the multicore fibers 2a and 2b, they may be referred to as the multicore fiber 2. Furthermore, when there is no need to distinguish between the end faces 50a and 50b of the multicore fibers 2a and 2b that are fused to each other, they may be referred to as the end face 50.

[0026] The alignment device 40 includes XYZ position adjustment devices 41a and 41b that adjust the positions of the multicore fibers 2a and 2b in the XYZ directions, and rotary alignment devices 42a and 42b that rotate the multicore fibers 2a and 2b around the central axis C of the cladding 22.

[0027] The alignment device 40 includes an end face measuring device 70. The end face measuring device 70 measures the end faces 50a and 50b of the multi-core fibers 2a and 2b to obtain position information of each core 21 and the like.

[0028] Regarding the end face measuring device 70, when the distance between the end faces 50a, 50b is short and it is difficult to install an image acquiring device such as a camera, a reflecting mirror may be inserted between the end faces 50a, 50b, and a reflected image of the end faces 50a, 50b reflected in the reflecting mirror may be acquired by the image acquiring device, and position information and the like of each core 21 may be acquired from the acquired image. Also, images of the side faces of the multicore fibers 2a, 2b may be directly acquired by the image acquiring device, and position information and the like of each of the cores 21a to 21d may be acquired from the acquired image.

[0029] The fusion splicer 60 has a pair of fixed high-voltage discharge electrodes 61a, 61b, and generates an arc discharge by applying a high voltage between the pair of high-voltage discharge electrodes 61a, 61b to fuse the end faces 50a, 50b of the butted multi-core fibers 2a, 2b. Fixing the pair of high-voltage discharge electrodes 61a, 61b makes it possible to maintain the stability of the electric field. Note that in this embodiment, the fusion splicer 60 is configured so that the multi-core fibers 2a, 2b to be spliced ​​are respectively arranged horizontally. The fusion splicer 60 may be configured so that the tips of the high-voltage discharge electrodes 61a, 61b are moved by controlling the fusion splicer 60 by a control device 30 described later.

[0030] The control device 30 is composed of, for example, an integrated circuit such as a microcontroller, an IC (Integrated Circuit), an LSI (Large-scale Integrated Circuit), or an ASIC (Application Specific Integrated Circuit), or an NC (Numerical Control) device. Furthermore, when an NC device is used, the control device 30 may or may not use a machine learning device.

[0031] The control device 30 executes a program to control the alignment device 40, the fusion splicer 60, and the end face measuring device 70 as follows. The program and the like are stored in a memory (not shown) provided in the control device 30.

[0032] The control device 30 calculates control information for controlling the alignment device 40 and the fusion splicer 60 based on position information such as the central axis C of each core 21 and cladding 22 of the end face 50 measured by the end face measuring device 70. The control information may be stored in advance in a memory (not shown).

[0033] The control device 30 controls the fusion splicer 60 based on the above control information, etc., to generate a discharge between a pair of high-voltage discharge electrodes 61a, 61b possessed by the fusion splicer 60, thereby fusing the pair of multi-core fibers 2a, 2b that are butted together and rotationally aligned.

[0034] The control device 30 controls the XYZ position adjusting device 41 of the alignment device 40 based on the above control information etc., to adjust the axial position of each of the pair of multi-core fibers 2 a, 2 b. Furthermore, the control device 30 controls the rotary aligners 42 a, 42 b based on the above control information etc., to rotate and align each of the pair of multi-core fibers 2 a, 2 b around the central axis C of the cladding 22.

[0035] Next, a method for connecting the multi-core fibers 2 using the multi-core fiber connecting device 1 will be described.

[0036] 3 is a flowchart showing a method for connecting a pair of multi-core fibers 2a and 2b. The method for connecting a pair of multi-core fibers 2a and 2b mainly comprises an aligning step S1 and a fusion splicing step S2.

[0037] <Alignment step S1> This step is a step of setting the multicore fiber 2 in the fusion splicer 60 so that the end faces 50a, 50b of the multicore fibers 2a, 2b to be connected to each other face each other with a predetermined gap between them. In this step, the control device 30 controls the XYZ position adjustment device 41 of the alignment device 40 to adjust the position in the XYZ axis directions of each of the pair of multicore fibers 2a, 2b, and align the central axes C of the claddings 22 of the respective multicore fibers 2a, 2b.

[0038] First, a plurality of multi-core fibers 2 shown in Fig. 1 are prepared. Before each of the multi-core fibers 2a, 2b is set in the fusion splicer 60, the inner protective layer 24 and the outer protective layer 25 are peeled off near the end faces 50a, 50b to be spliced ​​of each of the multi-core fibers 2a, 2b.

[0039] Next, as shown in Fig. 2, each of the multicore fibers 2 is set in a fusion splicer 60 in a state where the end faces 50 of the multicore fibers 2a, 2b to be spliced ​​face each other with a predetermined gap therebetween. Then, the central axes C of the clads 22 of the multicore fibers 2a, 2b are made to coincide with each other. That is, the multicore fibers 2a, 2b are arranged so that the central axes C of the clads 22 of the multicore fibers 2a, 2b are positioned on the same straight line. Note that, to align the central axes C of the clads 22 of the multicore fibers 2a, 2b, for example, each of the multicore fibers 2a, 2b may be observed from the side to ensure that the outer circumferential surfaces of the clads 22 of the multicore fibers 2a, 2b are flush with each other.

[0040] Next, the control device 30 controls the rotation aligners 42a, 42b of the alignment device 40 based on the image of the end face 50 measured by the end face measuring device 70, and rotationally aligns the multicore fibers 2a, 2b so that the cores 21a to 21d of the multicore fibers 2a, 2b face each other. It is preferable that the angle formed between the end face 50a of one multicore fiber 2a and the end face 50b of the other multicore fiber 2b is 0.5° or less. Note that when aligning the central axes C of the claddings 22 of the pair of multicore fibers 2a, 2b or when performing rotational alignment, for example, the side faces of the multicore fibers 2a, 2b may be observed with an image acquiring device (not shown) and the alignment may be performed based on the acquired images of the side faces of the multicore fibers 2a, 2b.

[0041] In this way, the multi-core fibers 2a and 2b are aligned.

[0042] <Fusing step S2> This step is a step in which discharge is generated by the pair of high-voltage discharge electrodes 61a, 61b to fuse the pair of multi-core fibers 2a, 2b. In this step, the control device 30 controls the fusion splicer 60 to generate discharge by the pair of high-voltage discharge electrodes 61a, 61b to fuse the respective multi-core fibers 2a, 2b. Also, in this step, the control device 30 controls the alignment device 40 to move the pair of multi-core fibers 2a, 2b in a direction perpendicular to the longitudinal direction of the multi-core fibers 2a, 2b from the start of discharge to the end of discharge.

[0043] Here, an example of the relationship between the discharge in the fusion step S2 and the movement of the pair of multi-core fibers 2a and 2b will be shown.

[0044] FIG. 4 is a timing chart of the fusion step S2. Here, an example is given in which the multicore fiber 2 has four cores 21a to 21d as shown in FIG. 1. In FIG. 4, the vertical axis represents the discharge intensity, and the horizontal axis represents the time. In this example, the discharge is composed of a plurality of pulse discharges. Four periods, namely, pulse discharge periods P1, P2, P3, and P4, are provided as periods in which pulse discharge is performed. The pulse discharge periods P1, P2, P3, and P4 are equal to one another, and the power of each pulse discharge is equal to one another. In addition, a non-discharge period Q1 is provided between the pulse discharge period P1 and the pulse discharge period P2 as a period in which pulse discharge is not performed, and a non-discharge period Q2 is provided between the pulse discharge period P2 and the pulse discharge period P3 as a period in which discharge is not performed. In addition, a non-discharge period Q3 is provided between the pulse discharge period P3 and the pulse discharge period P4 as a period in which discharge is not performed.

[0045] The schematic diagram at the bottom of FIG. 4 will be explained. The line segment connecting the tips of the high-voltage discharge electrodes 61a, 61b is denoted as line segment L. Furthermore, the perpendicular bisector of line segment L in a plane perpendicular to the longitudinal direction of the pair of multi-core fibers 2a, 2b is denoted as line segment V. Here, assuming coordinate axes with the line including line segment L as the X-axis and line V as the Y-axis, the intersection of the X-axis and Y-axis is defined as origin O. Therefore, origin O is the midpoint of the line segment connecting the tips of the pair of high-voltage discharge electrodes 61a, 61b. The schematic diagram at the bottom of FIG. 4 shows the positional relationship between the end face 50 of the multi-core fiber 2 and the tips of the pair of high-voltage discharge electrodes 61a, 61b. Note that in this example, line segment L and line V do not overlap with the cladding 22.

[0046] The control device 30 controls the XYZ position adjusting devices 41a and 41b to move the pair of multi-core fibers 2a and 2b in a state in which the respective multi-core fibers 2a and 2b are aligned. Specifically, the control device 30 places the respective multi-core fibers 2a and 2b in the fourth quadrant as shown in the leftmost schematic diagram at the bottom of FIG. 4 by the start of the pulse discharge period P1. In this embodiment, the respective multi-core fibers 2a and 2b are placed so that a line segment connecting the respective central axes CC of the cores 21a and 21b and the respective central axes CC of the cores 21c and 21d are parallel to the X-axis. In this embodiment, the multi-core fibers 2a and 2b are not rotated about the central axis C of the cladding 22, and a state in which the position of the marker 23 is always located at the upper right part of the cladding 22 on the page is maintained. Thereafter, the control device 30 controls the fusion splicer 60 to perform pulse discharge during the pulse discharge period P1.

[0047] Next, in the non-discharge period Q1, the control device 30 controls the XYZ position adjustment devices 41a and 41b to move the multicore fibers 2a and 2b to the state shown in the second schematic diagram from the left in Fig. 4. That is, in the non-discharge period Q1, the control device 30 controls the XYZ position adjustment devices 41a and 41b to move the multicore fibers 2a and 2b to the third quadrant, and at the start of the pulse discharge period P2, the state shown in the second schematic diagram from the left at the bottom in Fig. 4 is achieved. Thereafter, the control device 30 controls the fusion splicer 60 to perform pulse discharge during the pulse discharge period P2.

[0048] Next, in a non-discharge period Q2, the control device 30 controls the XYZ position adjusters 41a and 41b to move the multi-core fibers 2a and 2b to the second quadrant, and sets them to the state shown in the schematic diagram second from the right at the bottom of Fig. 4. Thereafter, the control device 30 controls the fusion splicer 60 to perform pulse discharge during a pulse discharge period P3.

[0049] Finally, in the non-discharge period Q3, the control device 30 controls the XYZ position adjusters 41a and 41b to move the multi-core fibers 2a and 2b to the first quadrant, and set them in the state shown in the rightmost schematic diagram at the bottom of Fig. 4. Thereafter, the control device 30 controls the fusion splicer 60 to perform pulse discharge during the pulse discharge period P4.

[0050] In this embodiment, in each state where the multi-core fibers 2a, 2b are located in the fourth quadrant, the third quadrant, the second quadrant, or the first quadrant, the distance between the origin O of the coordinate axes and the central axis C of the cladding 22 is W, and the angle that the line connecting the origin O and the central axis C of the cladding 22 forms with the X-axis is 45°. Therefore, when the multi-core fibers 2a, 2b move to the fourth quadrant, the third quadrant, the second quadrant, or the first quadrant, the line connecting the origin O and the central axis C of the cladding 22 rotates by 90° from before the movement to after the movement. In order to avoid complicating the drawing, the distance W is shown only in the state where the multi-core fibers 2a, 2b are located in the fourth quadrant. As described above, in the multi-core fibers 2a, 2b, the cores 21a to 21d are arranged in a four-fold rotational symmetry manner with the central axis C of the cladding 22 as the center of symmetry, and when the number of cores 21 is N, N=4. For this reason, in this example, when the number of pulse discharges is M, M=4, and the multi-core fibers 2a and 2b are moved such that, for each movement, the distance between the origin O and the central axis C of the cladding 22 is constant and the line connecting the origin O and the central axis C of the cladding 22 rotates 360° / M around the origin O. Therefore, the multi-core fibers 2a and 2b are moved M−1 times.

[0051] In this way, the multi-core fibers 2a and 2b are connected to each other.

[0052] In the present embodiment, an example has been shown in which the control device 30 controls the XYZ position adjustment devices 41a and 41b to move the multicore fibers 2a and 2b in the non-discharge periods Q1, Q2, and Q3, that is, an example in which the pair of multicore fibers 2a and 2b is moved between successive pulse discharges in the fusion step S2. However, the multicore fibers 2a and 2b may be moved in each of the pulse discharge periods P1, P2, P3, and P4. In the present embodiment, the multicore fibers 2a and 2b are moved in both the X-axis direction and the Y-axis direction. Alternatively, they may be moved only in the X-axis direction or only in the Y-axis direction. Furthermore, the multicore fibers 2a and 2b are moved so that the central axes C of the claddings 22 describe a rectangle in the XY plane. However, this is not limiting. For example, the central axes C of the claddings 22 may be moved so that they describe an arc in the XY plane with the origin O as the center.

[0053] Furthermore, in the present embodiment, an example has been described in which the line segment L and the straight line V do not overlap with the cladding 22, but this is not limiting. For example, at least one of the line segment L and the straight line V may overlap with the cladding 22 on the side opposite to the central axis C of the cladding 22 from the line segment connecting the predetermined cores 21 adjacent to each other at the shortest distance. The predetermined cores 21 adjacent to each other at the shortest distance may be, for example, a combination of core 21a and core 21b or a combination of core 21a and core 21d, but not a combination of core 21a and core 21c or a combination of core 21b and core 21d located diagonally. Furthermore, at least one of the line segment L and the straight line V may overlap with any of the cores 21a to 21d. Furthermore, at least one of the line segment L and the straight line V may overlap with the cladding 22 on the side closer to the central axis C of the cladding 22 than the line segment connecting the predetermined cores 21 adjacent to each other at the shortest distance.

[0054] Furthermore, in the present embodiment, an example in which the number of cores 21 is four has been shown, but this is not limiting. For example, the number of cores 21 may be three or six. Furthermore, in the above example, the angle between the X-axis and the line connecting the origin O and the central axis C of the cladding 22 is always 45°, but this is not limiting. Furthermore, this angle may be changed for each discharge. It is preferable not to change the distance between the origin O and the central axis C of the cladding 22, but this is not limiting. Furthermore, in the present embodiment, the multi-core fibers 2a, 2b are moved four times, but the number of times of movement is not limited to this.

[0055] In the above embodiment, the central axes CC of the cores 21 are arranged with the central axis C of the cladding 22 as the center of symmetry, the arrangement of the cores 21 has four-fold rotational symmetry, N = 4 and M = 4, and each multi-core fiber 2a, 2b is moved so that the distance between the central axis C of the cladding 22 and the origin O, which is the midpoint of the line segment connecting the tips of the pair of high-voltage discharge electrodes 61a, 61b, is constant and the line connecting the origin O and the central axis C of the cladding 22 rotates 360° / M, i.e., 90°, around the origin O for each pulse discharge. However, M may be a multiple of N. For example, when M is twice N, the multi-core fibers 2a, 2b may be moved so that the line connecting the origin O and the central axis C of the cladding 22 rotates 360° / 8, i.e., 45° for each pulse discharge. When the arrangement of the cores 21 has six-fold rotational symmetry, N = 6, and M may be 6 or 12. Furthermore, when the arrangement of the cores 21 has eight-fold rotational symmetry, N=8, and M may be 8, for example, 16. M does not have to be equal to N, and does not have to be a multiple of N. Furthermore, the number of cores 21 may be unrelated to N and M.

[0056] Furthermore, for example, when the arrangement of the cores 21 in the multicore fiber 2 has six-fold rotational symmetry, N=6. In this case, the multicore fibers 2a and 2b may be moved so that the line connecting the origin O and the central axis C of the cladding 22 rotates by 360° / 6=60° per movement. However, since one of the divisors of 6 is 2, the control device 30 may control the fusion splicer 60 to perform discharge twice, and the control device 30 may control the XYZ position adjustment devices 41a and 41b to move the multicore fibers 2a and 2b so that the line connecting the origin O and the central axis C of the cladding 22 rotates by 360° / 2, that is, 180°, between each discharge. Furthermore, since another divisor of 6 is 3, the control device 30 may control the fusion splicer 60 to perform three discharges, and the control device 30 may control the XYZ position adjustment devices 41a and 41b to move the multi-core fibers 2a and 2b so that the lines connecting the origin O and the central axis C of the cladding 22 rotate 360° / 3, or 120°, between each discharge.

[0057] That is, in the multicore fibers 2a, 2b, when the cores 21 are arranged with N-fold rotational symmetry around the central axis C of the cladding 22, discharge may be performed M times, where M is a multiple or sub-multiple of N. In this case, between successive discharges, each of the multicore fibers 2a, 2b may be moved such that the distance between the central axis C of the cladding 22 and the midpoint of the line segment connecting the tips of the pair of high-voltage discharge electrodes 61a, 61b remains constant, and the line connecting the midpoint and the central axis C of the cladding 22 rotates 360° / M around the midpoint.

[0058] Next, a modification of this embodiment will be described.

[0059] FIG. 5 is a diagram similar to FIG. 4 showing a first modified example of this embodiment. In the fusion step S2, the control device 30 controls the XYZ position adjustment devices 41a and 41b to place the pair of multi-core fibers 2a and 2b in the fourth quadrant. In this modified example, the distance between the origin O of the coordinate axes and the central axis C of the cladding 22 is W, and the angle between the X axis and the line connecting the origin O and the central axis C of the cladding 22 is 45°. Thereafter, the control device 30 controls the fusion splicer 60 to perform discharge during a pulse discharge period P1. Next, during a non-discharge period Q1, the control device 30 controls the XYZ position adjustment devices 41a and 41b to move the multi-core fibers 2a and 2b to the state shown in the schematic diagram on the right of FIG. 5. That is, during the non-discharge period Q1, the control device 30 controls the XYZ position adjustment devices 41a and 41b to move the multi-core fibers 2a and 2b to the second quadrant. In this modification, the distance between the origin O of the coordinate axes and the central axis C of the cladding 22 is W, and the angle between the X-axis and the line connecting the origin O and the central axis C of the cladding 22 is 45° and is not changed. Thereafter, the control device 30 controls the fusion splicer 60 to cause discharge during the pulse discharge period P2.

[0060] FIG. 6 is a diagram similar to FIG. 4 showing a second modified example of this embodiment. The control device 30 controls the XYZ position adjustment devices 41a and 41b to move the pair of multi-core fibers 2a and 2b, so that at the start of the pulse discharge period P1, they are positioned as shown in the left schematic diagram at the bottom of FIG. 6, that is, so that the central axis C of the cladding 22 is positioned between the fourth and third quadrants on the Y axis. In this modified example, the cladding 22 and the line segment L overlap. Then, the control device 30 controls the fusion splicer 60 to perform pulse discharge during the pulse discharge period P1. Next, during the non-discharge period Q1, the control device 30 controls the XYZ position adjustment devices 41a and 41b to move the multi-core fibers 2a and 2b, so that they are positioned as shown in the right schematic diagram of FIG. 6. That is, during the non-discharge period Q1, the control device 30 controls the XYZ position adjustment devices 41a and 41b to move the multi-core fibers 2a and 2b on the Y axis so that they are positioned between the second and first quadrants. The direction of the line connecting the origin O and the central axis C of the cladding 22 is kept consistent with the direction of the Y axis. Furthermore, the distance between the origin O of the coordinate axes and the central axis C of the cladding 22 is made the same before and after the movement. Next, the control device 30 controls the fusion splicer 60 to cause discharge during the pulse discharge period P2. Note that, although the pair of multi-core fibers 2a and 2b are moved on the Y axis here, this is not limiting.

[0061] In the method for connecting the multi-core fibers 2 of this embodiment, the discharge is made up of a plurality of pulse discharges, and the pair of multi-core fibers 2a and 2b is moved between the pulse discharges.

[0062] In this way, heating of each core 21 can be averaged, and the difference in thermal history of each core 21 can be reduced. Therefore, the variation in the connection state of each core 21 can be reduced. As a result, the variation in connection loss between cores 21 can be reduced.

[0063] Furthermore, since the period between pulse discharges can be lengthened, the pair of multi-core fibers 2a, 2b can be moved accurately, and the reproducibility of heating can be improved. Therefore, the difference in thermal history of each core 21 can be reduced. Therefore, the variation in the connection state of each core 21 can be reduced, and the variation in connection loss between the cores 21 can be reduced.

[0064] Although the above example shows a case where discharge occurs multiple times, discharge may occur only once.

[0065] FIG. 7 is a diagram similar to FIG. 4 showing a third modified example of the present embodiment. In this modified example, discharge is performed once. The control device 30 controls the XYZ position adjustment devices 41a and 41b to move the multicore fibers 2a and 2b and position them between the third and fourth quadrants as shown in the schematic diagram on the left at the bottom of FIG. 7 by the start of the discharge period R. In this modified example, the line connecting the origin O and the central axis C of the cladding 22 coincides with the Y axis. Thereafter, the control device 30 controls the fusion splicer 60 to perform discharge during the discharge period R. The control device 30 controls the XYZ position adjustment devices 41a and 41b to move the multicore fibers 2a and 2b at the same speed from the start to the end of the discharge period R. In other words, the control device 30 moves the multicore fibers 2a and 2b in an aligned state until they reach the state shown in the schematic diagram on the right of FIG. 7. For example, the multicore fibers 2a and 2b are moved so that when half of the discharge period R indicated by the dashed dotted line in Fig. 7 has elapsed, the positions of the multicore fibers 2a and 2b become the state shown in the schematic diagram shown in the center at the bottom of Fig. 7. The multicore fibers 2a and 2b are moved between the first and second quadrants so that when the discharge period R ends, the positions of the cores 21 of the multicore fibers 2a and 2b become the state shown in the schematic diagram on the right of Fig. 7.

[0066] In this modification, an example has been shown in which, in the fusion step S2, the control device 30 controls the XYZ position adjustment device 41 to continuously move the multi-core fibers 2a and 2b during the discharge period R, but the present invention is not limited to this. That is, the multi-core fibers 2a and 2b may be moved discretely during the discharge period R.

[0067] In the method of connecting the multi-core fibers 2a and 2b in this embodiment, the pair of multi-core fibers 2a and 2b are moved during discharge.

[0068] In this way, discharge and movement can be performed simultaneously, which reduces the difference in thermal history in a short time, thereby reducing the variation in the connection state of each core 21 and the variation in connection loss between cores.

[0069] In the above-described embodiment and modified example, the movement of the multicore fibers 2a, 2b moves the central axis C of the cladding 22 from one side to the other side of the line segment L connecting the pair of high-voltage discharge electrodes 61a, 61b. However, the multicore fibers 2a, 2b may be moved in a state in which the central axis C of the cladding 22 is located on one side of the line segment L. In this case, the multicore fibers 2a, 2b may be moved in a direction perpendicular to the line segment L in a state in which the central axis C of the cladding 22 is located on one side of the line segment L.

[0070] Furthermore, even when the multi-core fibers 2a, 2b move so that the central axis C of the cladding 22 straddles the line segment L, it is preferable that the distance between the central axis C of the cladding 22 and the line segment L when the central axis C of the cladding 22 is located above the line segment L is greater than the distance between the central axis C of the cladding 22 and the line segment L when the central axis C of the cladding 22 is located below the line segment L.

[0071] As described above, the method for connecting multi-core fibers 2 in this embodiment includes a fusion step S2 in which discharge is generated by a pair of high-voltage discharge electrodes 61a, 61b to fuse the respective multi-core fibers 2 together, and in the fusion step S2, the pair of multi-core fibers 2a, 2b are moved in a direction perpendicular to the longitudinal direction of the multi-core fibers 2a, 2b from the start of discharge to the end of discharge.

[0072] Moreover, the multicore fiber splicing device 1 of this embodiment is a multicore fiber splicing device 1 that splices a pair of multicore fibers 2a, 2b, and includes an alignment device 40 that can adjust the position and rotational position of each of the multicore fibers 2a, 2b, a fusion splicer 60 that generates discharge using a pair of high-voltage discharge electrodes 61a, 61b that face each other across the butt joint position of the multicore fibers 2a, 2b and can fuse the multicore fibers 2a, 2b together, and a control device 30, and the control device 30 controls the fusion splicer 60 to fuse the multicore fibers 2a, 2b together, and moves the pair of multicore fibers 2a, 2b in a direction perpendicular to the longitudinal direction of the multicore fibers 2a, 2b from the start of discharge to the end of discharge.

[0073] According to such a method for connecting the multi-core fibers 2 and the multi-core fiber connecting device 1, the multi-core fibers 2 are moved from the start of discharge to the end of discharge, so that heating of each core 21 can be averaged and differences in thermal history of each core 21 can be reduced. Therefore, variations in the connection state of each core 21 can be reduced. As a result, variations in connection loss between the cores 21 can be reduced.

[0074] Although the present invention has been described above using the embodiments as examples, the present invention is not limited to these. [Explanation of symbols]

[0075] 1. Multi-core fiber splicing device 2. Multicore fiber 21 Cores 22 Clad 30. Control device 40 Alignment device 60···Fusion splicer 61 High-voltage discharge electrode C: Central axis of cladding S2: Fusion step

Claims

1. A method for connecting a pair of multi-core fibers, comprising: a fusion step of generating discharge between a pair of high-voltage discharge electrodes facing each other across the butted position of each of the multi-core fibers, and fusing the multi-core fibers together; Equipped with In the fusion step, the pair of multi-core fibers are moved in a direction perpendicular to the longitudinal direction of the multi-core fibers from when the discharge is started to when the discharge is ended. A method for connecting multi-core fibers.

2. The discharge is constituted by a plurality of pulse discharges, and the pair of multi-core fibers is moved between the pulse discharges. The multi-core fiber splicing method according to claim 1 .

3. the cores in the multicore fiber are arranged in N-fold rotational symmetry with the central axis of the cladding as the center of symmetry, The pulse discharge is performed M times, where M is a number that is a multiple or sub-number of N, Between the pulse discharges, the pair of multi-core fibers are moved so that a distance between a center axis of the clad and a midpoint of a line segment connecting the tips of the pair of high-voltage discharge electrodes is constant, and the line connecting the midpoint and the center axis of the clad rotates 360° / M around the midpoint. The multi-core fiber splicing method according to claim 2 .

4. The pair of multi-core fibers is moved during the discharge. The multi-core fiber splicing method according to claim 1 .

5. A multi-core fiber splicing device for splicing a pair of multi-core fibers, an alignment device capable of adjusting the position of each of the multi-core fibers; a fusion splicer capable of fusing the multi-core fibers together by generating discharge between a pair of high-voltage discharge electrodes facing each other across a butted position of the multi-core fibers; a control device; Equipped with The control device controls the fusion splicer to cause discharge and fuse the multi-core fibers together, and controls the alignment device to move the pair of multi-core fibers in a direction perpendicular to the longitudinal direction of the multi-core fibers from the start of the discharge to the end of the discharge. A multi-core fiber splicing device.

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