Controller, fusion connection device, connector connecting device, and control program

Abstract

To properly align a multicore fiber.SOLUTION: A controller (10) comprises a processor (10a). The processor (10a) executes an identification process for identifying a core position and a marker position of a multicore fiber, and an alignment process for aligning the multicore fiber by controlling an alignment mechanism so that the core position and marker position on an end surface of the multicore fiber satisfy a predetermined condition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a control device and a control program for controlling an aligning mechanism that aligns a multi-core fiber, and also to a fusion splicer and a connector connecting device equipped with such a control device. [Background technology]

[0002] In the field of optical communications, multicore fibers having multiple cores are widely used. Examples of documents disclosing multicore fibers include Patent Document 1. Multicore fiber connectors in which multiple multicore fibers are connected are also widely used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2019-152866 Summary of the Invention [Problem to be solved by the invention]

[0004] Some multicore fibers have multiple cores arranged symmetrically with respect to an axis, and also have markers arranged so that their centers do not overlap with the axis. With such markers, it is possible to uniquely identify multiple cores by the distance from the marker, etc.

[0005] In the alignment of a multicore fiber, it becomes necessary to newly consider things that have not been considered in the alignment of a single-core fiber. For example, when connecting two multicore fibers with matching core arrangements, it is necessary to align the marker of one multicore fiber so that it is located at an appropriate position relative to the marker of the other multicore fiber. Here, matching core arrangements of two multicore fibers means that when an end face of one multicore fiber is overlapped with an end face of the other multicore fiber, each core of one multicore fiber can be overlapped with any core of the other multicore fiber. Alternatively, it is necessary to align the position of the marker of the multicore fiber so that it is located at an appropriate position relative to the key or the like of a connector part. However, a technology for appropriately aligning a multicore fiber while taking such points into consideration has not been realized.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to realize a technique for appropriately aligning a multicore fiber, for example, such that a marker of a multicore fiber is disposed at an appropriate position relative to a marker of another multicore fiber, or such that a marker of a multicore fiber is disposed at an appropriate position relative to a key or the like of a connector part. [Means for solving the problem]

[0007] A control device according to one embodiment of the present invention includes a measurement control unit that identifies a marker position of a multicore fiber, and an alignment control unit that aligns the multicore fiber by controlling an alignment mechanism so that the marker position on an end face of the multicore fiber satisfies a predetermined condition. Effect of the Invention

[0008] According to one aspect of the present invention, a technique for properly aligning a multicore fiber can be realized. For example, a technique for aligning a multicore fiber such that a marker of the multicore fiber is disposed at a proper position relative to a marker of another multicore fiber, or such that a marker of the multicore fiber is disposed at a proper position relative to a key of a connector part, can be realized. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing a configuration of a control device according to a first embodiment and a second embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart showing the flow of a fusion splicing method according to the first embodiment. [Diagram 3] 3A to 3C are perspective views showing the state of the multi-core fiber in each step of the fusion splicing method shown in FIG. 2. [Figure 4] FIG. 2 is a diagram showing a multi-core fiber as an example of an optical fiber to which the fusion splicing method shown in FIG. 1 is applied, where (a) is a side view of the multi-core fiber, (b) is a front view of one end face of the multi-core fiber seen from a line of sight E1 direction, and (c) is a front view of the other end face of the multi-core fiber seen from a line of sight E2 direction. [Diagram 5] Fig. 1 shows the connection point of two normally connected optical fibers, where (a) is a side view of the two optical fibers, (b) is a front view of one end face of the two optical fibers as viewed from the line of sight E2, and (c) is a front view of the other end face of the two optical fibers as viewed from the line of sight E1. [Figure 6] Fig. 1 shows the fusion splice portion of two non-normally spliced ​​optical fibers, where (a) is a side view of the two optical fibers, (b) is a front view of one end face of the two optical fibers as viewed from the line of sight E2, and (c) is a front view of the other end face of the two optical fibers as viewed from the line of sight E1. [Figure 7]Fig. 1 shows the fusion splice portion of two non-normally spliced ​​optical fibers, where (a) is a side view of the two optical fibers, (b) is a front view of one end face of the two optical fibers as viewed from the line of sight E2, and (c) is a front view of the other end face of the two optical fibers as viewed from the line of sight E1. [Figure 8] Fig. 1 shows the fusion splice portion of two non-normally spliced ​​optical fibers, where (a) is a side view of the two optical fibers, (b) is a front view of one end face of the two optical fibers as viewed from the line of sight E2, and (c) is a front view of the other end face of the two optical fibers as viewed from the line of sight E1. [Figure 9] Fig. 1 shows the fusion splice points of two optical fibers that are reverse-spliced ​​(reverse-spliced ​​with respect to axis L1), where (a) is a side view of the two optical fibers, (b) is a front view of one end face of the two optical fibers as viewed from the line of sight E2, and (c) is a front view of the other end face of the two optical fibers as viewed from the line of sight E1. [Figure 10] Fig. 1 shows the fusion splice portion of two optical fibers that are reverse-spliced ​​(reverse-spliced ​​with respect to axis L3), where (a) is a side view of the two optical fibers, (b) is a front view of one end face of the two optical fibers as viewed from the line of sight E2, and (c) is a front view of the other end face of the two optical fibers as viewed from the line of sight E1. [Figure 11] Fig. 1 shows the fusion splice portion of two optical fibers that are inverted (inverted with respect to axis L2), where (a) is a side view of the two optical fibers, (b) is a front view of one end face of the two optical fibers as viewed from the line of sight E2, and (c) is a front view of the other end face of the two optical fibers as viewed from the line of sight E1. [Figure 12] Fig. 1 shows the fusion splice points of two optical fibers that have been reverse-spliced ​​(reverse-spliced ​​with respect to axis L4), where (a) is a side view of the two optical fibers, (b) is a front view of one end face of the two optical fibers as viewed from the line of sight E2, and (c) is a front view of the other end face of the two optical fibers as viewed from the line of sight E1. [Figure 13]FIG. 11 is a flowchart showing the flow of a connector connecting method according to a second embodiment of the present invention. [Figure 14] 1A is a side view of a multi-core fiber to which a connector housing is attached via a ferrule, and FIGS. 1B and 1C are cross-sectional views of the multi-core fiber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [First embodiment] (Control device configuration) A control device 10 according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a block diagram showing the configuration of the control device 10.

[0011] 1, the control device 10 includes a processor 10a, a primary memory 10b, a secondary memory 10c, a communication interface 10d, and a bus 10e. The processor 10a, the primary memory 10b, the secondary memory 10c, and the communication interface 10d are connected to each other via the bus 10e.

[0012] The secondary memory 10c stores a control program P that controls an alignment mechanism for aligning a multi-core fiber. The processor 10a loads the control program P stored in the secondary memory 10c onto the primary memory 10b. The processor 10a then controls the alignment mechanism according to instructions included in the control program P loaded onto the primary memory 10b.

[0013] An example of a device that can be used as the processor 10a is a CPU (Central Processing Unit). An example of a device that can be used as the primary memory 10b is a semiconductor RAM (Random Access Memory). An example of a device that can be used as the secondary memory 10c is a HDD (Hard Disk Drive).

[0014] The communication interface 10d is an interface for communicating with other devices via a network. The processor 10a uses the communication interface 10d to receive detection results from the photodetector 12 (described later) and to transmit control signals to the alignment mechanism described above.

[0015] (Flow of fusion splicing method) A flow of the fusion splicing method S1 according to the present embodiment will be described with reference to Fig. 2 and Fig. 3. The fusion splicing method S1 is a method of fusion splicing a multi-core fiber MF2 to a multi-core fiber MF1 using a fusion splicing device 1. The multi-core fibers MF1 and MF2 are multi-core fibers having the same core arrangement. Fig. 2 is a flow diagram showing the flow of the fusion splicing method S1, and Fig. 3 is a perspective view showing the state of the multi-core fibers MF1 and MF2 in each step included in the fusion splicing method S1. Note that in this embodiment, the multi-core fibers MF1 and MF2 are assumed to be multi-core fibers having a cladding, a plurality of cores formed inside the cladding, and a single marker formed inside the cladding. Specific examples of the multi-core fibers MF1 and MF2 will be described later with reference to different drawings.

[0016] As shown in Fig. 2, the fusion splicing method S1 includes a preparation step S11, a measurement step S12, an alignment step S13, a butting step S14, and a fusion step S15. As shown in Fig. 3, the fusion splicing device 1 includes a light source 11, a photodetector 12, a heating source 13, an alignment mechanism (not shown), and a control device 10. The alignment mechanism can perform translational movement in the x-axis direction and the y-axis direction, and rotational movement about the z-axis as the rotation axis, for each of the multi-core fibers MF1 and MF2. The control device 10 functions as a measurement control unit for performing the measurement step S12, an alignment control unit for performing the alignment step S13, a butting control unit for performing the butting step S14, and a fusion control unit for performing the fusion step S15. Here, the heat source 13 is not particularly limited as long as it is a mechanism for heating the end of the multi-core fiber, and examples thereof include a laser and an electrode.

[0017] The preparation step S11 is a step in which a user sets the multi-core fibers MF1 and MF2 in the fusion splicing apparatus 1. The multi-core fibers MF1 and MF2 are each held so that their central axes are parallel to the z-axis by an aligning mechanism of the fusion splicing apparatus 1. The state of the multi-core fibers MF1 and MF2 after carrying out the preparation step S11 is shown in (a) of Fig. 3.

[0018] When the preparation step S11 is completed, the measurement step S12 is performed. The measurement step S12 is a step in which the fusion splicing device 1 measures the core positions and the marker positions of the multi-core fibers MF1 and MF2 before fusion. In the measurement step S12, the processor 10a of the control device 10 controls the aligning mechanism of the fusion splicing device 1 so as to move the multi-core fiber MF1 in the negative direction of the z-axis. As a result, the end of the multi-core fiber MF1 is positioned between the light source 11 and the photodetector 12. The processor 10a of the control device 10 also controls the aligning mechanism of the fusion splicing device 1 so as to move the multi-core fiber MF2 in the positive direction of the z-axis. As a result, the end of the multi-core fiber MF2 is positioned between the light source 11 and the photodetector 12. As a result, the distance d between the end face of the multi-core fiber MF1 and the end face of the multi-core fiber MF2 is, for example, about 20 μm. The distance d is arbitrary within a range in which the following detection process or imaging process can be performed, and is not limited to 20 μm.

[0019] Then, the processor 10a of the control device 10 detects (1) the intensity I1 of light emitted from the light source 11 and transmitted through an end of the multi-core fiber MF1 (hereinafter referred to as the transmitted light intensity I1), and (2) the intensity I2 of light emitted from the light source 11 and transmitted through an end of the multi-core fiber MF2 (hereinafter referred to as the transmitted light intensity I2), using the photodetector 12. The processor 10a of the control device 10 repeats this detection process while rotating the multi-core fibers MF1 and MF2 about the z-axis as the rotation axis, or while rotating the light source 11 and the photodetector 12 about the z-axis as the rotation axis, by controlling the alignment mechanism of the fusion splicer 1. In this way, the processor 10a of the control device 10 obtains the directional dependency of the transmitted light intensity I1 of the multi-core fiber MF1 and the directional dependency of the transmitted light intensity I2 of the multi-core fiber MF2. Then, the processor 10a of the control device 10 executes an identification process to identify a core position and a marker position of the multi-core fiber MF1 based on the directional dependency of the transmitted light intensity I1 of the multi-core fiber MF1, and to identify a core position and a marker position of the multi-core fiber MF2 based on the directional dependency of the transmitted light intensity I2 of the multi-core fiber MF2. The states of the multi-core fibers MF1 and MF2 during the measurement step S12 are shown in (b) of FIG.

[0020] The above-mentioned detection process is based on the assumption that the photodetector 12 is a photodiode. In this case, data representing the transmitted light intensities I1 and I2 obtained by each detection process is a luminance value representing the intensity of light detected by the photodiode. Moreover, data representing the directional dependency of the transmitted light intensities I1 and I2 obtained by repeating the detection process is a one-dimensional array of luminance values ​​representing the intensity of light detected by the photodiode. On the other hand, when a camera is used as the photodetector 12, the above-mentioned detection process is composed of an imaging process for imaging the ends of the multi-core fibers MF1 and MF2, and a calculation process (e.g., an integration process, an average process, or a weighted average process) for deriving the transmitted light intensities I1 and I2 from the image obtained by the imaging process. In this case, data obtained by each imaging process is a two-dimensional array (i.e., an image) of luminance values ​​representing the intensity of light detected by each cell constituting the image sensor of the camera, and data representing the transmitted light intensities I1 and I2 of the multi-core fibers MF1 and MF2 obtained by each calculation process is, for example, an integrated value, an average value, or a weighted average value of the intensity of light detected by each cell constituting the image sensor of the camera. In addition, the data representing the directional dependency of the transmitted light intensities I1 and I2 obtained by repeating the detection process (imaging process and calculation process) is, for example, a one-dimensional array of the integrated value, average value, weighted average value, etc. of the light intensity detected by each cell constituting the image sensor of the camera.

[0021] When the measurement step S12 is completed, the alignment step S13 is performed. The alignment step S13 is a step in which the fusion splicer 1 aligns the multi-core fiber MF2 with respect to the multi-core fiber MF1. In this embodiment, the reference for determining the core position and marker position of the multi-core fiber MF2 is the core position and marker position of the multi-core fiber MF1. In the alignment step S13, the processor 10a of the control device 10 controls the alignment mechanism of the fusion splicer 1 to execute an alignment process for aligning the multi-core fiber MF2 with respect to the multi-core fiber MF1 such that the core position at the end face of the multi-core fiber MF2 relative to the core position at the end face of the multi-core fiber MF1 and the marker position at the end face of the multi-core fiber MF2 relative to the marker position at the end face of the multi-core fiber MF1 satisfy a predetermined condition. Here, the conditions that the core position and the marker position at the end face of the multi-core fiber MF2 should satisfy will be described later with reference to a different drawing. The state of the multi-core fibers MF1 and MF2 during the alignment step S13 is shown in FIG.

[0022] In this embodiment, the measuring step S12 is performed once, and then the aligning step S13 is performed once, but the present invention is not limited to this. For example, the measuring step S12 and the aligning step S13 may be alternately and repeatedly performed to advance the aligning work in stages.

[0023] When the aligning step S13 is completed, the butting step S14 is performed. The butting step S14 is a step in which the fusion splicer 1 butts the end face of the multi-core fiber MF1 with the end face of the multi-core fiber MF2. In the butting step S14, the processor 10a of the control device 10 controls the aligning mechanism of the fusion splicer 1 to move the multi-core fiber MF1 in the negative direction of the z axis by d / 2 (about 10 μm in this embodiment). In addition, the processor 10a of the control device 10 controls the aligning mechanism of the fusion splicer 1 to move the multi-core fiber MF2 in the positive direction of the z axis by d / 2 (about 10 μm in this embodiment). The state of the multi-core fibers MF1 and MF2 after performing the butting step S14 is shown in (d) of FIG. 3.

[0024] Note that pre-discharge may be performed in the butting process S14. Pre-discharge is a process for softening the tips of the multi-core fibers MF1, MF2. By butting the tips of the multi-core fibers MF1, MF2 after performing pre-discharge, it is possible to more reliably bring the tips of the multi-core fibers MF1, MF2 into close contact with each other. In this case, it is preferable to set the movement amount of the multi-core fibers MF1, MF2 to d / 2+ε. ε is an additional movement amount for overlapping the tips of the optical fibers OF1, OF2, and is, for example, 10 μm.

[0025] When the butting step S14 is completed, the fusion step S15 is performed. The fusion step S15 is a step in which the fusion splicing device 1 fuses the multi-core fiber MF1 and the multi-core fiber MF2. In the fusion step S15, the processor 10a of the control device 10 controls the heating source 13 (electrodes in this case) to generate an arc discharge, and heats and melts the ends of the multi-core fiber MF1 and the multi-core fiber MF2. When the heated and melted ends of the multi-core fiber MF1 and the multi-core fiber MF2 are solidified by natural cooling, the multi-core fiber MF1 and the multi-core fiber MF2 are fused to each other. The state of the multi-core fibers MF1 and MF2 after the fusion step S15 is performed is shown in (e) of FIG. 3.

[0026] In the above-mentioned alignment step S13, alignment may be performed so that a correlation coefficient (overlap integral) indicating the degree of correlation between the waveform of the luminance distribution of the multicore fiber that has already been measured (reference waveform) and the waveform of the luminance distribution of the multicore fiber that has actually been measured is increased. In this case, the type of the end face of the multicore fiber may be determined depending on whether the position of the peak corresponding to the marker is on the left or right side, based on the midpoint between the positions of the peaks corresponding to two adjacent cores. In addition, when the above-mentioned alignment step S13 is realized by the end-view method, alignment may be performed so that a correlation coefficient indicating the degree of correlation between an image of the end face of the multicore fiber that has already been photographed (reference image) and an image of the end face of the multicore fiber that has actually been photographed is increased. Here, the above-mentioned waveform and correlation coefficient can be defined as feature quantities. That is, the control device may be configured such that the measurement control unit further identifies a marker position on an end face of another multi-core fiber, and the alignment control unit aligns the multi-core fiber with respect to the other multi-core fiber based on a predetermined feature value or a feature value determined before alignment so that the marker position on the end face of the multi-core fiber relative to the marker position on the end face of the other multi-core fiber satisfies a predetermined condition.

[0027] (Example of multi-core fiber) A specific example of two multi-core fibers MF1 and MF2 will be described with reference to Fig. 4. Here, two multi-core fibers MF1 and MF2 having the same core arrangement and marker arrangement are considered, and each of these two multi-core fibers MF1 and MF2 is simply referred to as a multi-core fiber MF. In Fig. 4, (a) is a side view of the multi-core fiber MF, (b) is a front view of one end face σ1 of the multi-core fiber MF seen from the line of sight E1 direction, and (c) is a front view of the other end face σ2 of the multi-core fiber MF seen from the line of sight E2 direction. Note that the two multi-core fibers MF1 and MF2 having the same core arrangement and marker arrangement are merely one example of an application target of the present invention. The position, shape, and size of the markers in each of the two multi-core fibers MF1 and MF2 are arbitrary, and the two multi-core fibers MF1 and MF2 do not need to have the same marker arrangement.

[0028] The multi-core fiber MF includes n cores a1 to an and a cladding b (n is a natural number of 2 or more). The cladding b is a cylindrical member. The cladding b is made of, for example, silica glass. Each core ai (i is a natural number of 1 to n) is a cylindrical region provided inside the cladding b, has a higher refractive index than the cladding b, and extends in the same direction as the cladding b. Each core ai is made of, for example, silica glass doped with an up-dopant such as germanium. Note that the cladding b may have any cross-sectional shape as long as it is cylindrical. The cross-sectional shape of the cladding b may be, for example, a polygonal shape such as a square or a hexagon, or a barrel shape.

[0029] At the end faces σ1 and σ2, the cores a1-an are arranged line-symmetrically with respect to an axis L1 perpendicular to the central axis L0 of the multi-core fiber MF. Moreover, at the end faces σ1 and σ2, the cores a1-an are arranged so as to avoid the axis L1. In other words, at the end faces σ1 and σ2, the cores a1-an are arranged at positions other than the axis L1.

[0030] The multi-core fiber MF further includes a marker c. The marker c is a columnar region provided inside the cladding b, has a different refractive index from that of the cladding b, and extends in the same direction as the cladding b. The cross-sectional shape of the marker c is arbitrary, for example, a circular shape, a triangular shape, a rectangular shape, etc. The marker c is made of, for example, silica glass doped with a down dopant such as fluorine or boron. In this case, the refractive index of the marker c is lower than that of the cladding b. The marker c is alternatively made of silica glass doped with an up dopant such as germanium, aluminum, phosphorus, or chlorine. In this case, the refractive index of the marker c is higher than that of the cladding b. The marker c can be formed by, for example, a hole drilling method or a stack and draw method. The outer diameter of the marker c is usually smaller than the outer diameter of the core ai.

[0031] On the end faces σ1 and σ2, the center of the marker c is disposed so as to avoid the axis L1. In other words, on the end faces σ1 and σ2, the center (geometric center) of the marker c is disposed at a position other than the axis L1. Note that the marker c only needs to be disposed so that its center avoids the axis L1, and it does not matter if a part of the marker c overlaps with the axis L1.

[0032] The cores a1 to a4 of the multi-core fiber MF illustrated in Fig. 4 may be regarded as being arranged line-symmetrically with respect to the axis L2, may be regarded as being arranged line-symmetrically with respect to the axis L3, or may be regarded as being arranged line-symmetrically with respect to the axis L4. Here, the axis L2 is an axis that is orthogonal to both the central axis L0 and the axis L1. The axes L3 and L4 are also orthogonal to the central axis L0 and form an angle of 45 degrees with the axis L1.

[0033] Here, the cores a1 to an are considered as four cores a1 to a4 arranged on the vertices of a square, and the axis of line symmetry is considered as an axis L1 to L4 that does not pass through these four cores a1 to a4, but the present invention is not limited to this. The number n of the cores a1 to an is arbitrary, and the axis of line symmetry may pass through the cores a1 to an or may not pass through the cores a1 to an. For example, when n is an even number, it is possible to consider n cores a1 to an arranged on the vertices of a regular n-gon, n / 2 axis of line symmetry passing through the vertices of the regular n-gon facing each other, and n / 2 axis of line symmetry passing through the midpoints of the sides of the regular n-gon facing each other. In addition, when n is an odd number, it is possible to consider n cores a1 to an arranged on the vertices of a regular n-gon, and n axis of line symmetry passing through the vertices of the regular n-gon and the midpoints of the sides facing the vertices. In addition to these cores a1 to an, one more core may be present at the center of the multi-core fiber MF (the center of a regular n-gon with the cores a1 to an arranged on its vertices).

[0034] Furthermore, the cores a1 to an do not have to be arranged on the vertices of a regular n-gon. For example, in the multi-core fiber MF shown in FIG. 4, a multi-core fiber MF obtained by moving the cores a1 and a4 in a direction approaching the axis L1 and moving the cores a2 and a3 in a direction away from the axis L1, that is, a multi-core fiber MF in which the cores a1 to a4 are arranged on the vertices of an isosceles trapezoid, can be considered. In this case, the axis L1 becomes the axis of line symmetry. Also, a multi-core fiber MF can be considered in which, considering two line segments that are parallel to each other in the cross section of the multi-core fiber MF and equidistant from the center of the cross section of the multi-core fiber MF, four of the eight cores a1 to a8 are arranged on one line segment at equal intervals, and the remaining four cores a5 to a8 are arranged on the other line segment at equal intervals. Here, the interval between adjacent cores in the cores a1 to a4 and the interval between adjacent cores in the cores a5 to a8 are equal. Also, the two cores a1 and a5, the two cores a2 and a6, the two cores a3 and a7, and the two cores a4 and a8 are each positioned on a line perpendicular to the two lines described above. In this case, the axis L1 parallel to the two lines described above and the axis L2 perpendicular to the two lines described above are axes of line symmetry.

[0035] (Examples of multi-core fiber splices) Specific examples of the connection points of the multi-core fibers MF1 and MF2 will be described with reference to FIGS.

[0036] The connection modes of the multi-core fibers MF1 and MF2 include dissimilar end face connection, which connects one end face σ1 to the other end face σ2, and homogeneous end face connection, which connects both end faces σ1 or both end faces σ2. The heterogeneous end face connection includes normal connection and non-normal connection. Moreover, the homogeneous end face connection includes inversion connection with respect to each of the axis L1 to L4 of line symmetry of the cores a1 to a4. These connection modes will be described below.

[0037] 5 is a diagram showing connection points of a normal connection, where (a) is a side view of multicore fibers MF1 and MF2, (b) is a front view of an end face σ2 of the multicore fiber MF1 seen from the line of sight E2 direction, and (c) is a front view of an end face σ1 of the multicore fiber MF2 seen from the line of sight E1 direction. A connection point of a normal connection is a connection point that connects an end face σ2 of the multicore fiber MF1, which are dissimilar end faces, to an end face σ1 of the multicore fiber MF2, or a connection point that connects an end face σ1 of the multicore fiber MF1, which are dissimilar end faces, to an end face σ2 of the multicore fiber MF2 (FIG. 5 shows the former). A connection point of a normal connection satisfies the following conditions.

[0038] Condition 1: Each of the cores a1 to an of the end face σ1 of the multicore fiber MF2 overlaps with one of the cores a1 to an of the end face σ2 of the multicore fiber MF1. Specifically, (1) the core a1 of the end face σ1 of the multicore fiber MF2 overlaps with the core a1 of the end face σ2 of the multicore fiber MF1, (2) the core a2 of the end face σ1 of the multicore fiber MF2 overlaps with the core a2 of the end face σ2 of the multicore fiber MF1, (3) the core a3 of the end face σ1 of the multicore fiber MF2 overlaps with the core a3 of the end face σ2 of the multicore fiber MF1, and (4) the core a4 of the end face σ1 of the multicore fiber MF2 overlaps with the core a4 of the end face σ2 of the multicore fiber MF1.

[0039] Condition 2a: The marker c on the end face σ1 of the multi-core fiber MF2 overlaps with the marker c on the end face σ2 of the multi-core fiber MF1.

[0040] In short, the normal connection is a connection between different types of end faces, in which the cores a1 to an are optically coupled and the markers c are connected.

[0041] Note that only a part of the marker c of the multicore fiber MF2 may be connected to a part of the multicore fiber MF1 other than the marker c, or only a part of the marker c of the multicore fiber MF1 may be connected to a part of the multicore fiber MF2 other than the marker c. For example, when this configuration is realized by moving the marker c in the multicore fibers MF1 and MF2 in a direction away from the core a1, it is possible to suppress deformation of the core a1 that may occur during manufacturing of the multicore fiber MF1 due to the proximity of the marker c, and characteristic deterioration that occurs during use of the multicore fiber MF due to the proximity of the marker c.

[0042] The positions of the markers c in the multi-core fibers MF1 and MF2 may be determined as follows.

[0043] Condition β1: At the end face of the first multi-core fiber MF1, the marker c overlaps with an imaginary perpendicular bisector of an imaginary line segment connecting the center of the core a1 that is closest to the marker c and the center of the second closest core a4, among the cores a1 to a4 of the first multi-core fiber MF1.

[0044] Condition β2: At the end face of the second multi-core fiber MF2, the marker c overlaps with an imaginary perpendicular bisector of an imaginary line segment connecting the center of the core a1 that is closest to the marker c and the center of the second closest core a4, among the cores a1 to a4 of the second multi-core fiber MF2.

[0045] When condition β1 or condition β2 is satisfied, in the first multicore fiber MF1, the marker c can be further separated from at least the core a1 closest to the marker c, and in the second multicore fiber MF2, the marker c can be further separated from at least the core a1 closest to the marker c. Therefore, it is possible to suppress the characteristic degradation problem that occurs when the marker c approaches at least the core a1 in the first multicore fiber MF1 and when the marker c approaches at least the core a1 in the second multicore fiber MF2.

[0046] Moreover, the above-mentioned condition β1 may be the following condition β1', and the condition β2 may be the following condition β2'. In this case, the marker c can be further separated from the cores a1 to a4 in the first multicore fiber MF1, and the marker c can be further separated from the cores a1 to a4 in the second multicore fiber MF2. Therefore, it is possible to further suppress the characteristic degradation problem that occurs when the marker c approaches the cores a1 to a4 in the first multicore fiber MF1, and when the marker c approaches the cores a1 to a4 in the second multicore fiber MF2.

[0047] Condition β1': At the end face of the first multi-core fiber MF1, the center of the marker c overlaps with a virtual perpendicular bisector of a virtual line segment connecting the center of the core a1 closest to the marker c and the center of the second closest core a4 among the cores a1 to a4 of the first multi-core fiber MF1. In this case, the distance from the marker c to the core a1 is equal to the distance from the marker c to the core a2. Therefore, "the center of the core a1 closest to the marker c and the second closest core a4" here refers to the two cores a1 and a4 closest to the marker c. Even if the distance from the marker c to the core a1 is equal to the distance from the marker c to the core a2, it is possible to distinguish the core a1 from the core a2 as long as the cross-sectional structure of the first multi-core fiber MF1 is asymmetric with respect to the axis L1.

[0048] Condition β2': Furthermore, at the end face of the second multi-core fiber MF2, the center of the marker c overlaps with an imaginary perpendicular bisector of an imaginary line segment connecting the center of the core a1 closest to the marker c and the center of the second closest core a4 among the cores a1 to a4 of the second multi-core fiber MF2. In this case, the distance from the marker c to the core a1 is equal to the distance from the marker c to the core a2. Therefore, "the center of the core a1 closest to the marker c and the second closest core a4" here refers to the two cores a1 and a4 closest to the marker c. Even if the distance from the marker c to the core a1 is equal to the distance from the marker c to the core a2, it is possible to distinguish the core a1 from the core a2 as long as the cross-sectional structure of the second multi-core fiber MF2 is asymmetric with respect to the axis L1.

[0049] Moreover, the positions of the markers c in the multi-core fibers MF1 and MF2 may be determined so as to satisfy the following condition γ1 or γ2.

[0050] Condition γ1: At the end face of the first multi-core fiber MF1, the center of the marker c does not overlap with the imaginary perpendicular bisector of an imaginary line segment connecting the center of the core a1 that is closest to the marker c and the center of the next closest core a4, among the cores a1 to a4 of the first multi-core fiber MF1.

[0051] Condition γ2: At the end face of the second multi-core fiber MF2, the center of the marker c does not overlap with the imaginary perpendicular bisector of an imaginary line segment connecting the center of the core a1 that is closest to the marker c and the center of the next closest core a4, among the cores a1 to a4 of the second multi-core fiber MF2.

[0052] In this case, the center of the marker c of the first multi-core fiber MF1 or the center of the marker c of the second multi-core fiber MF2 is shifted from the above-mentioned imaginary perpendicular bisector. Therefore, it becomes easier to distinguish between the end face of the first multi-core fiber MF1 and the end face of the second multi-core fiber MF2, or to distinguish the core number of the first multi-core fiber MF1 or the core number of the second multi-core fiber MF2, compared with the case where the marker c of the first multi-core fiber MF1 and the marker c of the second multi-core fiber MF2 completely overlap each other or the case where the center of the marker c of the first multi-core fiber MF1 and the center of the marker c of the second multi-core fiber MF2 overlap with the above-mentioned imaginary perpendicular bisector. This can facilitate the connection of the first multi-core fiber MF1 or the second multi-core fiber MF2 to an external transceiver or an external fan-in / fan-out device.

[0053] In addition, when the multi-core fibers MF1 and MF2 are the multi-core fibers MF exemplified in FIG. 4, possible connection modes for connecting the end face σ2 of the multi-core fiber MF1 and the end face σ1 of the multi-core fiber MF2 include the connection mode shown in FIG. 6, the connection mode shown in FIG. 7, and the connection mode shown in FIG. 8, in addition to the normal connection.

[0054] Fig. 6 shows a connection mode in which a core a1 of a multi-core fiber MF1 is connected to a core a2 of a multi-core fiber MF2. In Fig. 6, (a) is a side view of the multi-core fibers MF1 and MF2, (b) is a front view of an end face σ2 of the multi-core fiber MF1 seen from a line of sight E2 direction, and (c) is a front view of an end face σ1 of the multi-core fiber MF2 seen from a line of sight E1 direction.

[0055] Fig. 7 shows a connection mode in which a core a1 of a multi-core fiber MF1 is connected to a core a3 of a multi-core fiber MF2. In Fig. 7, (a) is a side view of the multi-core fibers MF1 and MF2, (b) is a front view of an end face σ2 of the multi-core fiber MF1 seen from a line of sight E2 direction, and (c) is a front view of an end face σ1 of the multi-core fiber MF2 seen from a line of sight E1 direction.

[0056] Fig. 8 shows a connection mode in which a core a1 of a multi-core fiber MF1 is connected to a core a4 of a multi-core fiber MF2. In Fig. 8, (a) is a side view of the multi-core fibers MF1 and MF2, (b) is a front view of an end face σ2 of the multi-core fiber MF1 seen from a line of sight E2 direction, and (c) is a front view of an end face σ1 of the multi-core fiber MF2 seen from a line of sight E1 direction.

[0057] The connection modes shown in Figures 6 to 8 satisfy condition 1 but do not satisfy condition 2a. For this reason, the connection modes shown in Figures 6 to 8 are called non-normal connections rather than normal connections.

[0058] 9 is a diagram showing a connection point of an inverted connection, where (a) is a side view of multi-core fibers MF1 and MF2, (b) is a front view of an end face σ2 of the multi-core fiber MF1 seen from a line of sight E2 direction, and (c) is a front view of an end face σ2 of the multi-core fiber MF2 seen from a line of sight E1 direction. The connection point of an inverted connection is a connection point that connects an end face σ2 of the multi-core fiber MF1 and an end face σ2 of the multi-core fiber MF2, which are homogeneous end faces, or a connection point that connects an end face σ1 of the multi-core fiber MF1 and an end face σ1 of the multi-core fiber MF2, which are homogeneous end faces (the former is shown in FIG. 9). The connection point of an inverted connection satisfies the following conditions.

[0059] Condition 1: Each of the cores a1 to an of the end face σ2 of the multi-core fiber MF2 overlaps with one of the cores a1 to an of the end face σ2 of the multi-core fiber MF1. Specifically, (1) the core a1 of the end face σ2 of the multi-core fiber MF2 overlaps with the core a4 of the end face σ2 of the multi-core fiber MF1, (2) the core a2 of the end face σ2 of the multi-core fiber MF2 overlaps with the core a3 of the end face σ2 of the multi-core fiber MF1, (3) the core a3 of the end face σ2 of the multi-core fiber MF2 overlaps with the core a2 of the end face σ2 of the multi-core fiber MF1, and (4) the core a4 of the end face σ2 of the multi-core fiber MF2 overlaps with the core a1 of the end face σ2 of the multi-core fiber MF1.

[0060] Condition 2b: The marker c of the end face σ2 of the multi-core fiber MF2 overlaps with a region x that is line-symmetric with the marker c of the multi-core fiber MF1 with respect to the axis L1 at the end face σ2 of the multi-core fiber MF1.

[0061] In short, the inverted connection is a connection form of homogeneous end face connection in which the cores a1 to an are optically coupled and the markers c are not connected.

[0062] In addition, when the multi-core fibers MF1 and MF2 are the multi-core fibers MF exemplified in FIG. 4, possible connection modes for connecting the end face σ2 of the multi-core fiber MF1 and the end face σ2 of the multi-core fiber MF2 include the connection mode shown in FIG. 10, the connection mode shown in FIG. 11, and the connection mode shown in FIG. 12 in addition to the inverted connection shown in FIG. 9.

[0063] Fig. 10 shows a connection mode in which a core a1 of a multicore fiber MF1 is connected to a core a3 of a multicore fiber MF2. In Fig. 10, (a) is a side view of the multicore fibers MF1 and MF2, (b) is a front view of an end face σ2 of the multicore fiber MF1 seen from a line of sight E2 direction, and (c) is a front view of an end face σ1 of the multicore fiber MF2 seen from a line of sight E1 direction. The connection mode shown in Fig. 10 satisfies condition 1 and also satisfies condition 2b when the axis L1 is replaced with the axis L3. For this reason, the connection mode shown in Fig. 9 is called a reversal connection with respect to the axis L3.

[0064] Fig. 11 shows a connection mode in which a core a1 of a multi-core fiber MF1 is connected to a core a2 of a multi-core fiber MF2. In Fig. 11, (a) is a side view of the multi-core fibers MF1 and MF2, (b) is a front view of an end face σ2 of the multi-core fiber MF1 seen from the line of sight E2 direction, and (c) is a front view of an end face σ1 of the multi-core fiber MF2 seen from the line of sight E1 direction. The connection mode shown in Fig. 11 satisfies condition 1 and also satisfies condition 2b when the axis L1 is replaced with the axis L2. For this reason, the connection mode shown in Fig. 11 is called a reversal connection with respect to the axis L2.

[0065] Fig. 12 shows a connection mode in which a core a1 of a multicore fiber MF1 is connected to a core a1 of a multicore fiber MF2. In Fig. 12, (a) is a side view of the multicore fibers MF1 and MF2, (b) is a front view of an end face σ2 of the multicore fiber MF1 seen from a line of sight E2 direction, and (c) is a front view of an end face σ1 of the multicore fiber MF2 seen from a line of sight E1 direction. The connection mode shown in Fig. 12 satisfies condition 1 and also satisfies condition 2b when axis L1 is replaced with axis L4. For this reason, the connection mode shown in Fig. 12 is called a reversal connection with respect to axis L4.

[0066] (Predetermined conditions) As described above, in the aligning step S13, the processor 10a of the control device 10 aligns the multi-core fibers MF1 and MF2 so that the core position and marker position of the multi-core fiber MF2 relative to the core position and marker position of the multi-core fiber MF1 satisfy the "predetermined condition."

[0067] In this embodiment, the above-mentioned condition 1 is considered as the "predetermined condition" that the core position of the multi-core fiber MF2 should satisfy with respect to the core position of the multi-core fiber MF1. In this case, the following eight positional relationships are considered as the relationship of the marker position of the multi-core fiber MF2 with respect to the marker position of the multi-core fiber MF1.

[0068] Relation 1: A positional relationship between the marker c of the multi-core fiber MF1 and the marker c of the multi-core fiber MF2 that occurs in the connection mode (normal connection) shown in Fig. 5. That is, a positional relationship in which the center of the marker c of the multi-core fiber MF1 and the center of the marker c of the multi-core fiber MF2 coincide with each other.

[0069] Relationship 2: Positional relationship between the marker c of the multi-core fiber MF1 and the marker c of the multi-core fiber MF2 occurring in the connection mode (non-normal connection) shown in FIG.

[0070] Relationship 3: Positional relationship between the marker c of the multi-core fiber MF1 and the marker c of the multi-core fiber MF2 occurring in the connection mode (non-normal connection) shown in FIG.

[0071] Relationship 4: Positional relationship between the marker c of the multi-core fiber MF1 and the marker c of the multi-core fiber MF2 occurring in the connection mode (non-normal connection) shown in FIG.

[0072] Note that relations 2 to 4 can be expressed as positional relations in which one of the normally connected multi-core fibers MF1, MF2 is rotated by i×360° / 4 (i=1, 2, 3). In general, when the cores a1 to an of the multi-core fibers MF1, MF2 have m-fold symmetry, there are m-1 connection modes in which one of the normally connected multi-core fibers MF1, MF2 is rotated by i×360° / m (i=1, 2, ..., m-1) as non-normal connections.

[0073] Relationship 5: Positional relationship between the marker c of the multi-core fiber MF1 and the marker c of the multi-core fiber MF2 occurring in the connection mode shown in FIG. 9 (reverse connection with respect to the axis L1).

[0074] Relationship 6: Positional relationship between the marker c of the multi-core fiber MF1 and the marker c of the multi-core fiber MF2 occurring in the connection mode shown in FIG. 10 (reverse connection with respect to the axis L3).

[0075] Relationship 7: Positional relationship between the marker c of the multi-core fiber MF1 and the marker c of the multi-core fiber MF2 occurring in the connection mode shown in FIG. 11 (reverse connection with respect to the axis L2).

[0076] Relationship 8: Positional relationship between the marker c of the multi-core fiber MF1 and the marker c of the multi-core fiber MF2 occurring in the connection mode shown in FIG. 12 (reverse connection with respect to the axis L4).

[0077] Note that relations 6 to 8 can be expressed as positional relations in which one of the multi-core fibers MF1, MF2 invertedly connected with respect to the axis L1 is rotated by i×360° / 4 (i=1, 2, 3). In general, when the cores a1 to an of the multi-core fibers MF1, MF2 have m-fold symmetry, there are m-1 connection modes in which one of the invertedly connected multi-core fibers MF1, MF2 is rotated by i×360° / m (i=1, 2, ..., m-1) as other inverted connections.

[0078] It can be said that the relations 1 and 5 are relations in which, among two core pairs selected from the cores a1 to a4 of the multi-core fiber MF1, the pair of the core a1 closest to the marker c and the second closest core a4 is connected to the pair of the core a1 closest to the marker c and the second closest core a4 among two core pairs selected from the cores a1 to a4 of the multi-core fiber MF2. In this case, it is possible to concentrate the effect of reducing inter-core crosstalk on the pair of the core a1 closest to the marker c and the second closest core a4. On the other hand, it can be said that the relations 2 to 4 and the relations 6 to 8 are relations in which, among two core pairs selected from the cores a1 to a4 of the multi-core fiber MF1, the pair of the core a1 closest to the marker c and the second closest core a4 is connected to a pair other than the pair of the core a1 closest to the marker c and the second closest core a4 among two core pairs selected from the cores a1 to a4 of the multi-core fiber MF2. In this case, it is possible to distribute the effect of reducing inter-core crosstalk.

[0079] In this embodiment, regarding dissimilar end face connection, Relation 1 is considered as the "predetermined condition" that the marker position of the multicore fiber MF2 should satisfy relative to the marker position of the multicore fiber MF1. Also, in this embodiment, regarding homogeneous end face connection, Relations 5 to 8 are considered as the "predetermined condition" that the marker position of the multicore fiber MF2 should satisfy relative to the marker position of the multicore fiber MF1. This makes it possible to obtain a multicore fiber connection body connected by normal connection or inverted connection.

[0080] The control device 10 may set the relationship specified by the user as the "predetermined condition" that the marker position of the multi-core fiber MF2 should satisfy with respect to the marker position of the multi-core fiber MF1. Alternatively, the control device 10 may set the relationship automatically selected by the control device 10 as the "predetermined condition" that the marker position of the multi-core fiber MF2 should satisfy with respect to the marker position of the multi-core fiber MF1. A method in which the control device 10 automatically selects the "predetermined condition" from the relationships 1 to 8 is, for example, as follows.

[0081] That is, the control device 10 (alignment control unit) judges whether the connection target end faces of the multi-core fibers MF1, MF2 are end faces σ1 or σ2 based on the core positions and marker positions of the multi-core fibers MF1, MF2 measured in the measurement step S12. When the connection target end faces of the multi-core fibers MF1, MF2 are both end faces σ1, or when the connection target end faces of the multi-core fibers MF1, MF2 are both end faces σ2, the control device 10 judges that the connection to be made is homogeneous end face connection. On the other hand, when the connection target end face of one of the multi-core fibers MF1, MF2 is the end face σ1 and the connection target end face of the other of the multi-core fibers MF1, MF2 is the end face σ2, the control device 10 judges that the connection to be made is heterogeneous end face connection. When the connection to be made is heterogeneous end face connection, the control device 10 selects the relationship 1 as the "predetermined condition". On the other hand, if the connection to be made is a homogeneous end face connection, the control device 10 selects one of the relationships 5 to 8 as a predetermined relationship. Note that which of the relationships 5 to 8 is selected when the connection to be made is a homogeneous end face connection may be determined in advance or may be determined based on a user instruction.

[0082] The position of the marker c may vary depending on the manufacturing lot or manufacturer. Even in such a case, when the cores a1 to a4 identified by the distance from the marker c at the end face σ2 of the first multi-core fiber MF1 and the end face σ1 of the second multi-core fiber MF2 are connected as shown in Fig. 5, it is considered to be a normal connection. Also, when the cores a1 to a4 identified by the distance from the marker c at the end face σ2 of the first multi-core fiber MF1 and the end face σ1 of the second multi-core fiber MF2 are connected as shown in Figs. 9 to 12, it is considered to be a reverse connection.

[0083] Furthermore, when one end face of the first multi-core fiber MF1 and one end face of the second multi-core fiber MF2 are butted against each other, alignment may be performed so as to satisfy the following condition η.

[0084] Condition η: At one end face of the first multi-core fiber MF1 or one end face of the second multi-core fiber MF2, an imaginary line connecting the center of the marker c of the first multi-core fiber MF1 and the center of the marker c of the second multi-core fiber MF2 is parallel to an imaginary line connecting the center of the core a1 closest to the marker c of the first multi-core fiber MF1 and the center of the next closest core a4 at the end face of the first multi-core fiber MF1, or an imaginary line connecting the center of the core a1 closest to the marker c of the second multi-core fiber MF2 and the center of the next closest core a4 at the end face of the second multi-core fiber MF2.

[0085] In this case, similarly to the above-mentioned effect, it becomes easy to distinguish between the end face of the first multi-core fiber MF1 and the end face of the second multi-core fiber MF2, or to distinguish the core number of the first multi-core fiber MF1, or to distinguish the core number of the second multi-core fiber MF2. This can facilitate connection of the first multi-core fiber MF1 or the second multi-core fiber MF2 to an external transceiver or an external fan-in / fan-out device. Furthermore, compared with the case where the virtual straight lines connecting the two markers c are arranged non-parallel, at least one of the two markers c may be separated from the outer periphery of the cladding b, so that an effect can be achieved that an increase in the thickness of the cladding b or deformation of the cladding b during manufacturing, etc. can be suppressed.

[0086] When one end face of the first multi-core fiber MF1 and one end face of the second multi-core fiber MF2 are butted against each other, alignment may be performed so as to satisfy the following condition δ1 or condition δ2.

[0087] Condition δ1: The entire marker c of the second multi-core fiber MF2 is connected to the portion of the first multi-core fiber MF1 other than the marker c (such as the cladding b of the first multi-core fiber MF1).

[0088] Condition δ2: The entire marker c of the first multi-core fiber MF1 is connected to a portion of the second multi-core fiber MF2 other than the marker c (such as the cladding b of the second multi-core fiber MF2).

[0089] The stress applied to the marker c of the first multi-core fiber MF1 can be reduced (alleviated) by connecting the marker c of the first multi-core fiber MF1 only to the clad b of the second multi-core fiber MF2 having a relatively large area, rather than connecting the marker c of the first multi-core fiber MF1 having a relatively small area to the marker c of the second multi-core fiber MF2 having a relatively small area, or connecting the marker c of the first multi-core fiber MF1 across the marker c and the clad b of the second multi-core fiber MF2. This can suppress damage to the marker c of the first multi-core fiber MF1. The same can be said for the marker c of the second multi-core fiber MF2.

[0090] Furthermore, when one end face of the first multi-core fiber MF1 and one end face of the second multi-core fiber MF2 are butted against each other, alignment may be performed so as to satisfy the following condition ε1 or condition ε2.

[0091] Condition ε1: At the end face of the first multicore fiber MF1, the center of the marker c of the second multicore fiber MF2 is aligned so as to be connected to a region including the cores a1 and a4 (hereinafter also referred to as region B), which is between (1) an imaginary circumscribing circle that circumscribes the core a1 that is closest to the marker c and the next closest core a4 among the multiple cores a1 to a4 of the first multicore fiber MF1, and is located inside an imaginary circumscribing circle that is centered on the center of the cladding b of the first multicore fiber MF1; (2) an imaginary bisector of the angle made by an imaginary line passing through the center of the core a1 that is closest to the marker c and the center of the next closest core a4, and an imaginary line passing through the center of the core a1 and the center of the cladding b; and (3) an imaginary bisector of the angle made by an imaginary line passing through the center of the core a1 and the center of the core a4, and an imaginary line connecting the center of the core a4 and the center of the cladding b.

[0092] Condition ε2: At the end face of the second multicore fiber MF2, the center of the marker c of the first multicore fiber MF1 is aligned so as to be connected to a region including the cores a1 and a4 (hereinafter also referred to as region C), which is between (1) an imaginary circumscribing circle that circumscribes the core a1 that is closest to the marker c and the next closest core a4 among the multiple cores a1 to a4 of the second multicore fiber MF2, and is located inside an imaginary circumscribing circle that has its center at the center of the cladding b of the second multicore fiber MF2; (2) an imaginary bisector of the angle made by an imaginary line passing through the center of the core a1 that is closest to the marker c and the center of the next closest core a4, and an imaginary line passing through the center of the core a1 and the center of the cladding b; and (3) an imaginary bisector of the angle made by an imaginary line passing through the center of the core a1 and the center of the core a4, and an imaginary line connecting the center of the core a4 and the center of the cladding b.

[0093] In this case, the first multicore fiber MF1 can achieve both the former effect and the latter effect described above, but in particular, compared with the case of condition ζ1 or condition ζ2 described below, since the marker c of the second multicore fiber MF2 is connected to a position spaced apart from the outer periphery of the cladding b, an increase in the thickness of the cladding b or deformation of the cladding b during manufacturing or the like can be suppressed, and therefore, in particular, the latter effect can be made even greater. The same can be said about the second multicore fiber MF2.

[0094] Furthermore, when one end face of the first multi-core fiber MF1 and one end face of the second multi-core fiber MF2 are butted against each other, alignment may be performed so as to satisfy the following condition ζ1 or condition ζ2.

[0095] Condition ζ1: At the end face of the first multicore fiber MF1, the center of the marker c of the second multicore fiber MF2 is aligned so as to be connected to a region (hereinafter also referred to as region D) sandwiched between: (1) a virtual circumscribing circle that circumscribes the core a1 that is closest to the marker c and the next closest core a4 among the multiple cores a1 to a4 of the first multicore fiber MF1, and is located outside a virtual circumscribing circle that has its center at the center of the cladding b of the first multicore fiber MF1; (2) a virtual bisector of the angle made by a virtual line passing through the center of the core a1 that is closest to the marker c and the center of the next closest core a4, and a virtual line passing through the center of the core a1 and the center of the cladding b; (3) a virtual bisector of the angle made by a virtual line passing through the center of the core a1 and the center of the core a4, and a virtual line connecting the center of the core a4 and the center of the cladding b; and (4) the outer periphery of the cladding b.

[0096] Condition ζ2: At the end face of the second multicore fiber MF2, the center of the marker c of the first multicore fiber MF1 is aligned so as to be connected to a region sandwiched between: (1) a virtual circumscribing circle that circumscribes the core a1 that is closest to the marker c and the next closest core a4 among the multiple cores a1 to a4 of the second multicore fiber MF2, and has its center at the center of the cladding b of the second multicore fiber MF2; (2) a virtual bisector of the angle made by a virtual line passing through the center of the core a1 that is closest to the marker c and the center of the next closest core a4, and a virtual line passing through the center of the core a1 and the center of the cladding b; (3) a virtual bisector of the angle made by a virtual line passing through the center of the core a1 and the center of the core a4, and a virtual line connecting the center of the core a4 and the center of the cladding b; and (4) the outer periphery of the cladding b, which is in contact with the core a1 and the core a4 (hereinafter also referred to as region E).

[0097] In this case, the first multicore fiber MF1 can achieve both the former and latter effects described above, but in particular, compared with the case of condition ε1 or condition ε2, the marker c of the second multicore fiber MF2 is connected to a position spaced apart from the core a1 or a4, and therefore deformation of the core a1 or a4 can be suppressed, so that the former effect in particular can be made even greater. The same can be said about the second multicore fiber MF2.

[0098] In addition, for condition ε1, condition ε2, condition ζ1, or condition ζ2, a configuration in which at least a part of the marker c of the second multicore fiber MF2 is connected to region B or region D (hereinafter also referred to as configuration 1), a configuration in which the entirety of the marker c of the second multicore fiber MF2 is connected to region B or region D (hereinafter also referred to as configuration 2), or a configuration in which at least a part of the marker c of the second multicore fiber MF2 is connected across the boundary between region B and region D (hereinafter also referred to as configuration 3) can also be adopted at the end face of the first multicore fiber MF1. All of configurations 1 to 3 can achieve the former effect and the latter effect. However, in particular in the case of configuration 2, the configuration in which the entirety of the marker c of the second multicore fiber MF2 is connected to region B can achieve the latter effect more effectively than the configuration in which the entirety of the marker c is connected to region D in configuration 2 and configuration 3, since the marker c of the second multicore fiber MF2 is connected to a position spaced apart from the outer periphery of the cladding b. Moreover, in particular in the case of configuration 2, the configuration in which the entire marker c of the second multi-core fiber MF2 is connected to region D is more advantageous than the configuration in which the entire marker c of the second multi-core fiber MF2 is connected to region B in the case of configuration 2 or configuration 3, since the marker c of the second multi-core fiber MF2 is connected to a position spaced apart from the core a1 or a4. Moreover, in particular in configuration 3, the marker c of the second multi-core fiber MF2 is connected to the outer periphery of the cladding b and to a position spaced apart from the core a1 or a4, and therefore the former effect and the latter effect can be achieved in a well-balanced manner. Similarly, at the end face of the second multi-core fiber MF2, it is also possible to adopt a configuration in which at least a part of the marker c of the first multi-core fiber MF1 is connected to region C or region E, a configuration in which the entire marker c of the first multi-core fiber MF1 is connected to region C or region E, or a configuration in which at least a part of the marker c is connected to the boundary between region C and region E. The effect obtained in this case is similar to the effect obtained in the first multi-core fiber MF1 described above.

[0099] Note that, at both end faces of the multicore fiber connector obtained by connecting the multicore fibers MF1 and MF2, alignment may be performed so that the cores used for inputting optical signals are arranged diagonally, and the cores used for outputting optical signals are arranged diagonally. In this case, crosstalk between the cores used for inputting optical signals and crosstalk between the cores used for outputting optical signals can be reduced.

[0100] Furthermore, when performing two or more fusion splices in sequence to manufacture a multi-core fiber splice consisting of three or more multi-core fibers MF, the fusion splicing device 1 may store the state of fusion splicing (fusion splicing conditions) every time a fusion splice is performed, and may determine the p-th fusion splice by referring to the states of the fusion splices up to the p-1th fusion splice. Furthermore, when manufacturing a multi-core fiber splice consisting of three or more multi-core fibers MF, splicing conditions may be determined in advance, and each fusion splice may be performed under those splicing conditions.

[0101] The fusion splicing apparatus 1 may manufacture a multi-core fiber connection body in which the multi-core fiber MF1, the multi-core fiber MF2, and the multi-core fiber MF3 are connected in this order by connecting the multi-core fibers MF1 to MF3 that satisfy the conditions A1 and A2 so as to satisfy the condition B.

[0102] Condition A1: The number of cores in the multi-core fiber MF1 and the number of cores in the multi-core fiber MF3 are each n (n is a natural number of 2 or more).

[0103] Condition A2: (1) The ordinal numbers of the cores in the multicore fiber MF1 can be identified according to the arrangement of the cores such that the core closest to the marker c is numbered first and the core next closest to the marker c is numbered second; (2) The ordinal numbers of the cores in the multicore fiber MF2 can be identified according to the arrangement of multiple cores such that the core closest to the marker c is numbered first and the core next closest to the marker c is numbered second; and (3) The ordinal numbers of the cores in the multicore fiber MF3 can be identified according to the arrangement of multiple cores such that the core closest to the marker c is numbered first and the core next closest to the marker c is numbered second.

[0104] Condition B: The i-th (i is a natural number equal to or greater than 1 and equal to or less than n) core of the multi-core fiber MF3 is connected to a core, among the multiple cores of the multi-core fiber MF2, that is connected to the i-th core of the multi-core fiber MF1.

[0105] According to the above configuration, it is possible to manufacture a multicore fiber connector in which each core on one end face is connected to a core with the same ordinal number on the other end face.

[0106] Furthermore, the fusion splicing apparatus 1 may manufacture a multi-core fiber connection body by connecting L multi-core fibers so as to satisfy the following condition C1.

[0107] Condition C1: Among the L-1 connection points, there is an even number of inverted connection points.

[0108] According to the above configuration, when numbers are assigned to cores at both end faces of a multicore fiber connector according to the distance from the marker, if an inversion connection that satisfies the same relationship is adopted at these even numbered connection points, a multicore fiber connector can be manufactured in which each core at one end face is connected to a core with the same number at the other end face. Even if inversion connection points that satisfy different relationships are mixed, the same effect can be obtained as long as the number of inversion connection points that satisfy each relationship is an even number. For example, if there are two inversion connection points that satisfy relationship 5, zero inversion connection points that satisfy relationship 6, six inversion connection points that satisfy relationship 7, and four inversion connection points that satisfy relationship 8, the same effect can be obtained.

[0109] Furthermore, the fusion splicing apparatus 1 may manufacture a multi-core fiber connection body by connecting L multi-core fibers so as to satisfy the following condition C2.

[0110] Condition C2: Among the L-1 connection points, there is an odd number of inverted connection points.

[0111] According to the above configuration, when numbers are assigned to the cores at both end faces of a multicore fiber connector according to the distance from a marker, it is possible to manufacture a multicore fiber connector in which each core at one end face is connected to a core with a different number at the other end face. For example, it is possible to manufacture a multicore fiber connector in which core number 1 at one end face is connected to core number 2 at the other end face, and core number 2 at one end face is connected to core number 1 at the other end face.

[0112] Second Embodiment Although the embodiment in which the multi-core fiber MF2 is connected to the multi-core fiber MF1 has been described above, the present invention is not limited thereto. For example, an embodiment in which the multi-core fiber MF is connected to a connector housing CH is also included in the scope of the present invention. Hereinafter, a form in which the multi-core fiber MF is connected to a connector housing CH will be described. Note that the control device according to this embodiment is configured similarly to the control device 10 according to the first embodiment, and therefore description thereof will be omitted.

[0113] (Connector connection method) A flow of the connector connecting method S2 according to this embodiment will be described with reference to Fig. 13. The connector connecting method S2 is a method of bonding a multi-core fiber MF2 to a connector C using a connector connecting device. Fig. 13 is a flow diagram showing a flow of the connector connecting method S2. Note that in this embodiment, a multi-core fiber MF having a cladding, a plurality of cores formed inside the cladding, and a single marker formed inside the cladding is assumed. A specific example of the multi-core fiber MF is the same as that described in the first embodiment.

[0114] As shown in Fig. 13, the connector connecting method S2 includes a preparation step S21, a measurement step S22, an alignment step S23, an insertion step S24, and an adhesion step S25. The connector connecting device is a device for connecting a connector part to a multicore fiber, and includes a light source, a photodetector, an alignment mechanism, a gripping mechanism (a mechanism for gripping the connector part or the multicore fiber), and a control device 10. The alignment mechanism is capable of performing translational movement in the x-axis direction and the y-axis direction, and rotational movement about the z-axis as the rotation axis, for the multicore fiber MF. The control device 10 functions as a measurement control unit for performing the measurement step S22, an alignment control unit for performing the alignment step S23, an insertion control unit for performing the insertion step S24, and an adhesion control unit for performing the adhesion step S25.

[0115] The preparation step S21 is a step of setting the multi-core fiber MF, the coating of which has been removed from the end portion, in an alignment mechanism. The multi-core fiber MF is held by the alignment mechanism so that its central axis is parallel to the z-axis.

[0116] When the preparation step S21 is completed, the measurement step S22 is performed. The measurement step S22 is a step of measuring the core position and the marker position of the multi-core fiber MF. In the measurement step S22, the processor 10a of the control device 10 controls the alignment mechanism to move the multi-core fiber MF in the negative direction of the z-axis. As a result, the end of the multi-core fiber MF is positioned between the light source and the photodetector. Then, the processor 10a of the control device 10 (1) detects the intensity I of the light emitted from the light source and transmitted through the end of the multi-core fiber MF (hereinafter, referred to as the transmitted light intensity I) using the photodetector. The processor 10a of the control device 10 repeats this detection process by controlling the alignment mechanism while rotating the light source and the photodetector around the z-axis as the rotation axis. As a result, the processor 10a of the control device 10 obtains the directional dependency of the transmitted light intensity of the multi-core fiber MF. Then, the processor 10a of the control device 10 executes a specification process for specifying the core positions and marker positions of the multi-core fiber MF based on the directional dependency of the transmitted light intensity I of the multi-core fiber MF.

[0117] When the measurement step S22 is completed, the alignment step S23 is performed. The alignment step S23 is a step in which the connector connecting device aligns the multi-core fiber with respect to the connector housing CH. In this embodiment, a reference for determining the core position and marker position of the multi-core fiber MF is the key position of the connector housing CH. In the alignment step S23, the processor 10a of the control device 10 controls the alignment mechanism to execute an alignment process for aligning the multi-core fiber MF with respect to the connector housing CH such that the core position and the marker position at the end face of the multi-core fiber MF with respect to the key position of the connector housing CH satisfy a predetermined condition. Here, the condition that the core position and the marker position at the end face of the multi-core fiber MF should satisfy will be described later with reference to a different drawing.

[0118] In this embodiment, the measuring step S22 is performed once, and then the aligning step S23 is performed once, but the present invention is not limited to this. For example, the measuring step S22 and the aligning step S23 may be alternately and repeatedly performed to advance the aligning work in stages.

[0119] When the alignment step S23 is completed, the insertion step S24 is performed. The insertion step S24 is a step of attaching a ferrule to an end of the multi-core fiber MF from which the coating has been removed, and further inserting the end of the multi-core fiber MF with the ferrule attached into the connector housing CH. In the insertion step S24, the processor 10a of the control device 10 moves the multi-core fiber MF in the z-axis direction by, for example, controlling the alignment mechanism so that the end of the multi-core fiber MF is inserted into the connector housing CH.

[0120] When the insertion step S24 is completed, the bonding step S25 is performed. The bonding step S25 is a step of bonding an end of the multi-core fiber MF to the connector housing. The bonding step S25 may be performed by a user or by the processor 10a of the control device 10 controlling a syringe.

[0121] Here, the flow of attaching a ferrule to the multi-core fiber MF after alignment has been described, but the present invention is not limited to this. A ferrule may be attached to the multi-core fiber MF before alignment. In this case, since the side-view measurement method as described above cannot be used to identify the core positions and the marker positions, the core positions and the marker positions are identified using an end-view measurement method. Also, instead of attaching the multi-core fiber MF with the ferrule attached to the connector housing, a configuration may be adopted in which the multi-core fiber MF is inserted into the connector housing with the ferrule attached.

[0122] In addition, although the reference for aligning the multi-core fiber MF is the connector housing key position here, the present invention is not limited to this. When a key is formed on the ferrule, the multi-core fiber MF may be aligned using the key as a reference. When a key is formed on a connector or a jig for fixing the ferrule, the multi-core fiber MF may be aligned using the key as a reference. Furthermore, the multi-core fiber MF may be aligned with respect to the fiber holder using the key position of the fiber holder as a reference. In this case, the user can fix the multi-core fiber MF fixed to the fiber holder to the connector housing so that the key position of the fiber holder and the key position of the connector housing match. Furthermore, when aligning the multi-core fiber MF and the ferrule using a key other than the above-mentioned key, the following may be performed. When the manufacturing device is placed on a flat surface so that the holding mechanism holding the ferrule and the holding mechanism holding the MCF face each other, the multi-core fiber MF may be aligned so that the relationship between the ferrule reference surface corresponding to the key position when connecting the connector housing to the ferrule and the marker of the multi-core fiber MF is in an appropriate position. From the above, when the connector housing CH and the ferrule are collectively defined as connector parts, the control device may be configured so that the alignment control unit aligns the multi-core fiber with respect to the connector parts based on a reference that is predetermined or determined before alignment so that the marker position of the multi-core fiber with respect to the key position of the connector housing satisfies a predetermined condition.

[0123] (Predetermined conditions) As described above, in the alignment step S23, the processor 10a of the control device 10 aligns the multi-core fiber MF so that the core positions and marker positions of the multi-core fiber MF relative to the key positions of the connector housing CH satisfy the "predetermined condition." This "predetermined condition" will be described with reference to Fig. 14. In Fig. 14, (a) is a side view of the multi-core fiber MF to which the connector housing CH is attached via a ferrule F, and (b) and (c) are cross-sectional views of the multi-core fiber MF.

[0124] In this embodiment, as a "predetermined condition" that the core position of the multicore fiber MF should satisfy with respect to the key position of the connector housing CH, a condition is considered in which the symmetry axis L1 of the core at the end face of the multicore fiber MF overlaps with the axis L0 of the connector housing CH determined from the position of the key K of the connector housing CH. Here, the axis L0 determined from the position of the key K of the connector housing CH refers to, for example, an axis passing through the center of the key K among the axes of the connector housing CH in a cross section perpendicular to the insertion direction of the multicore fiber MF.

[0125] In this case, the positional relationships between the key K of the connector housing CH and the marker C of the multi-core fiber MF are relationship 1, in which the marker c is closer to the key K than relationship 2, as shown in (b) of Figure 14, and relationship 2, in which the marker c is farther from the key K than relationship 1, as shown in (c) of Figure 14.

[0126] In this embodiment, as the "predetermined condition" that the marker position of the multi-core fiber MF should satisfy with respect to the key position of the connector housing CH, either Relation 1 or Relation 2 is considered. In this manner, by aligning the relationship of the marker position of the multi-core fiber MF with the key position of the connector housing CH in all multi-core fibers, when connecting two multi-core fibers MF, either the normal connection or the inverted connection described above can be performed by simply aligning the key positions of the two multi-core fibers MF without measuring the marker positions.

[0127] 〔summary〕 The control device according to aspect 1 of the present invention includes a measurement control unit that identifies a marker position of a multicore fiber, and an alignment control unit that aligns the multicore fiber by controlling an alignment mechanism so that the marker position on the end face of the multicore fiber satisfies a predetermined condition.

[0128] A control device according to a second aspect of the present invention is the control device according to the first aspect, wherein the measurement control unit further identifies a marker position on an end face of another multi-core fiber, and the alignment control unit aligns the multi-core fiber with respect to the other multi-core fiber such that the marker position on the end face of the multi-core fiber relative to the marker position on the end face of the other multi-core fiber satisfies a predetermined condition.

[0129] A control device according to a third aspect of the present invention is the control device according to the second aspect, wherein the alignment control unit aligns the multi-core fiber with respect to the other multi-core fiber so that the connection between the multi-core fiber and the other multi-core fiber is a normal connection.

[0130] A control device according to a fourth aspect of the present invention is the control device according to the second aspect, wherein the alignment control unit aligns the multi-core fiber with respect to the other multi-core fiber so that the connection between the multi-core fiber and the other multi-core fiber is a reverse connection.

[0131] A control device according to a fifth aspect of the present invention is the control device according to the second aspect, wherein the alignment control unit determines whether the connection between the multicore fiber and the other multicore fiber is a homogeneous end face connection or a heterogeneous end face connection, and aligns the multicore fiber with respect to the other multicore fiber to achieve a normal connection if the connection is a homogeneous end face connection, and aligns the multicore fiber with respect to the other multicore fiber to achieve a reverse connection if the connection is a heterogeneous end face connection.

[0132] A control device according to a sixth aspect of the present invention is the control device according to the second aspect, wherein the alignment control unit aligns the multi-core fiber with respect to the connector housing so that a marker position of the multi-core fiber with respect to a key position of the connector housing satisfies a predetermined condition.

[0133] A control device according to a seventh aspect of the present invention is the control device according to the sixth aspect, wherein the alignment control unit aligns the multi-core fiber with respect to the connector housing so that the axis of symmetry of the cores at the end face of the multi-core fiber overlaps with the axis of the connector housing determined by the position of the key.

[0134] A control device according to an eighth aspect of the present invention is the control device according to the seventh aspect, wherein the alignment control unit aligns the multi-core fiber with respect to the connector housing so that a marker on an end face of the multi-core fiber is positioned closer to the key.

[0135] A fusion splicing apparatus according to a ninth aspect of the present invention includes the control apparatus according to any one of the second to fourth aspects and the aligning mechanism.

[0136] A connector connecting device according to a tenth aspect of the present invention includes the control device according to any one of the sixth to eighth aspects and the aligning mechanism.

[0137] A control program according to an eleventh aspect of the present invention is a control program for operating a computer as the control device according to any one of the first to eighth aspects, and causes the computer to function as the measurement control unit and the alignment control unit.

[0138] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the above-described embodiments are also included in the technical scope of the present invention.

[0139] In the present embodiment, the configuration in which the control device 10 realizes various controls by software has been described, but the present invention is not limited to this. Each unit of the control device 10 may be realized by software as described above, or may be realized by hardware such as a circuit. [Explanation of symbols]

[0140] 10 Control device 10a processor 10b Primary memory 10c Secondary Memory 10d Communication Interface 10e Bus P Control Program

Claims

1. a measurement control unit that identifies marker positions of a multicore fiber including a plurality of cores arranged in line symmetry and a marker arranged at a position other than the symmetric axis thereof, the marker being for identifying a first end face and a second end face, and a marker position of another multicore fiber having a core arrangement and a marker arrangement that are the same as those of the multicore fiber; an alignment control unit that controls an alignment mechanism to align the multi-core fiber with respect to the other multi-core fiber such that a marker position on an end face of the multi-core fiber with respect to a marker position on the end face of the other multi-core fiber satisfies a predetermined condition, when the end face of the multicore fiber and the end face of the other multicore fiber are homogeneous end faces that are the first end face or when the end face of the multicore fiber and the end face of the other multicore fiber are homogeneous end faces that are the second end face, the alignment control unit aligns the multicore fiber with respect to the other multicore fiber such that each core of the multicore fiber is optically coupled to each core of the other multicore fiber and a marker of the multicore fiber does not communicate with a marker of the other multicore fiber. A control device comprising:

2. a measurement control unit that identifies marker positions of a multicore fiber including a plurality of cores arranged in line symmetry and a marker arranged at a position other than the symmetric axis thereof, the marker being for identifying a first end face and a second end face, and a marker position of another multicore fiber having a core arrangement and a marker arrangement that are the same as those of the multicore fiber; an alignment control unit that controls an alignment mechanism to align the multi-core fiber with respect to the other multi-core fiber such that a marker position on an end face of the multi-core fiber with respect to a marker position on the end face of the other multi-core fiber satisfies a predetermined condition, the alignment control unit determines whether a connection between the multi-core fiber and the other multi-core fiber is a homogeneous end face connection that connects the first end face of one fiber to the first end face of the other fiber, or the second end face of one fiber to the second end face of the other fiber, or a heterogeneous end face connection that connects the first end face of one fiber to the second end face of the other fiber, when the result of the determination is dissimilar end face connection, aligning the multicore fiber with respect to the other multicore fiber such that each core of the multicore fiber and each core of the other multicore fiber are optically coupled and a marker of the multicore fiber and a marker of the other multicore fiber are communicated with each other; when the result of the determination is homogeneous end face connection, aligning the multicore fiber with respect to the other multicore fiber such that each core of the multicore fiber and each core of the other multicore fiber are optically coupled and a marker of the multicore fiber and a marker of the other multicore fiber are not communicated with each other; A control device comprising:

3. a measurement control unit that identifies a marker position of a multi-core fiber including a marker for identifying an end face; an alignment control unit that controls an alignment mechanism to align the multi-core fiber with respect to the connector housing so that a marker position of the multi-core fiber with respect to a key position of the connector housing satisfies a predetermined condition, the alignment control unit aligns the multi-core fiber with respect to the connector housing so that an axis of symmetry of the cores at the end face of the multi-core fiber overlaps with an axis of the connector housing determined by the position of the key; the alignment control unit aligns the multi-core fiber with respect to the connector housing so that a marker on an end face of the multi-core fiber is disposed on a side closer to the key. A control device comprising:

4. a measurement control unit that identifies a marker position of a multi-core fiber including a marker for identifying an end face; an alignment control unit that controls an alignment mechanism to align the multi-core fiber with respect to the connector housing so that a marker position of the multi-core fiber with respect to a key position of the connector housing satisfies a predetermined condition, the alignment control unit aligns the multi-core fiber with respect to the connector housing so that an axis of symmetry of the cores at the end face of the multi-core fiber overlaps with an axis of the connector housing determined by the position of the key; the alignment control unit aligns the multi-core fiber with respect to the connector housing so that a marker on an end face of the multi-core fiber is disposed on a side farther from the key; A control device comprising:

5. The control device according to claim 1 or 2, the aligning mechanism, Equipped with A fusion splicing device comprising:

6. The control device according to claim 3 or 4, the aligning mechanism, Equipped with A connector connecting device comprising:

7. A control program for operating a computer as the control device according to any one of claims 1 to 4, the control program causing the computer to function as the measurement control unit and the alignment control unit. A control program comprising:

8. a measurement control unit that identifies marker positions of a multicore fiber including a plurality of cores arranged in line symmetry and markers arranged at positions other than the symmetric axis thereof, the markers being for identifying a first end face and a second end face, and marker positions of another multicore fiber having a core arrangement and a marker arrangement that are the same as those of the multicore fiber; an alignment control unit that controls an alignment mechanism to align the multicore fiber so that a marker position on an end face of the multicore fiber relative to a marker position on an end face of the other multicore fiber satisfies a predetermined condition, the alignment control unit aligns the multi-core fiber with respect to the other multi-core fiber so that a positional relationship selected by a user or the control device from a plurality of positional relationships in which each core of the multi-core fiber is optically coupled to any core of the other multi-core fiber is realized at an end face of the other multi-core fiber; The plurality of positional relationships include positional relationships that are realized when the end face of the multicore fiber and the end face of the other multicore fiber are both the first end face, or when the end face of the multicore fiber and the end face of the other multicore fiber are both the same type of end face that becomes the second end face, in which each core of the multicore fiber and each core of the other multicore fiber are optically coupled, and a marker of the multicore fiber and a marker of the other multicore fiber are not in communication with each other. A control device comprising:

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