Optical fiber alignment method, alignment device, and connection device

Abstract

One embodiment of the present disclosure relates to an optical fiber alignment method that makes it possible to achieve highly accurate optical fiber alignment without the use of a complicated drive system. The alignment method includes rough alignment steps (ST1, ST2) and a fine alignment step (ST5) for aligning first and second optical fibers (10). The rough alignment steps (ST1, ST2) involve rough alignment of the first and second optical fibers (10) on the basis of the results of end surface observation. The fine alignment step (ST5) involves fine alignment of the first and second optical fibers (10) on the basis of side surface observation to increase the optical coupling efficiency between the first and second optical fibers (10).

Description

[Technical Field]

[0001] The present disclosure relates to an optical fiber alignment method, an alignment device, and a connection device. This application claims priority from Japanese Patent Application No. 2021-140350, filed on August 30, 2021, the contents of which are incorporated herein by reference in their entirety. [Background technology]

[0002] Patent Document 1 discloses a method for aligning two multi-core optical fibers (hereinafter referred to as "MCFs") to be optically connected (see paragraphs "0069" and "0070" and FIG. 8). Specifically, a mirror is placed in a space between the end faces of the two MCFs. The mirror has two reflective surfaces, each inclined at approximately 45° with respect to the central axes (fiber axes) of the two MCFs, and images of the end faces of the two MCFs are reflected onto a monitor. The monitor displays the arrangement of elements that make up the end faces, such as cores, cladding, and markers. Therefore, the alignment of the two MCFs can be achieved by rotating one or both of the two MCFs relative to each other so that the positions of these corresponding elements on the end faces coincide. In other words, the multiple cores of one MCF can be optically connected to the multiple cores of the other MCF. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-050695 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-12799 Summary of the Invention

[0004] The optical fiber aligning method disclosed herein comprises selecting both a first and a second optical fiber or the second optical fiber as an alignment target, and aligning the first and second optical fibers so that they are optically connected to each other, the method comprising a coarse alignment step and a fine alignment step. The first optical fiber has a plurality of first cores extending along a first central axis and arranged at predetermined positions on a first end face perpendicular to the first central axis. The second optical fiber has a plurality of second cores extending along a second central axis and arranged at positions equivalent to the predetermined positions on a second end face perpendicular to the second central axis.

[0005] The coarse alignment step is a step of coarsely aligning the first and second optical fibers based on the results of observing the end faces of the first and second optical fibers, and includes a first image acquisition substep, a measurement substep, and a first rotation substep. In the first image acquisition substep, end face images of the first and second optical fibers are acquired. In the measurement substep, dimensions and central positions of at least each of the multiple first cores and each of the multiple second cores are measured from the end face images of the first and second optical fibers as information regarding the first core arrangement on the first end face consisting of multiple first cores and the second core arrangement on the second end face consisting of multiple second cores. In the first rotation substep, the alignment target is rotated in a circumferential direction around the central axis of the alignment target based on the measurement results of the measurement substep. Meanwhile, the fine alignment step is a step of finely aligning the first and second optical fibers based on the results of observing the side faces of the first and second optical fibers so as to increase the optical coupling efficiency between the corresponding cores of the first and second optical fibers after the coarse alignment, and includes a second image acquisition substep and a second rotation substep. In the second image acquisition substep, side images of the first and second optical fibers are acquired. In the second rotation substep, the alignment state between the first and second optical fibers after the rough alignment is confirmed from the side image, and the alignment target is rotated in a circumferential direction around a central axis of the alignment target.

[0006] Furthermore, the coarse alignment of the first and second optical fibers in the first rotation substep is performed under a first condition or a second condition. The first condition is defined by both the first core arrangement and the second core arrangement having n-fold rotational symmetry, where n-fold rotational symmetry is 2 or more, and the second condition is defined by both the first core arrangement and the second core arrangement not having rotational symmetry. Under the first condition, the coarse alignment is performed so that a first angle formed between an orientation indicated by a first line defined on the first end face and extending from the center of the first end face to pass through the center of a specific first core among the multiple first cores, and an orientation indicated by a second line defined on the second end face and extending from the center of the second end face to pass through the center of a specific second core associated with the specific first core among the multiple second cores, is 360° / n or less. Under the second condition, the coarse alignment is performed so that a second angle formed between the orientation indicated by the first line and the orientation indicated by the second line is a minimum angle excluding zero. The minimum angle excluding zero is selected from the angle between a plurality of first radiating line elements defined on the first end face and extending radially from the center of the first end face so as to pass through the centers of the plurality of first cores, or the angle between a plurality of second radiating line elements defined on the second end face and extending radially from the center of the second end face so as to pass through the centers of the plurality of second cores. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 shows the appearance (including partial cutaway views) and cross-sectional structures of various optical fibers that can be applied to the optical fiber alignment method, etc., of the present disclosure (including fixing the optical fiber after alignment and connecting optical fibers arranged opposite each other). [Figure 2] FIG. 2 is a diagram showing various configuration examples of a fixing jig (included in the connection device of the present disclosure) for fixing (including temporarily fixing) the optical fiber after alignment. [Figure 3] FIG. 3 is a diagram showing various configurations (included in the splicing device of the present disclosure) for splicing two aligned and fixed optical fibers. [Figure 4]FIG. 4 is a diagram showing a simple example of an apparatus configuration for explaining the aligning operation in the optical fiber aligning method of the present disclosure. [Figure 5] FIG. 5 is a diagram showing the structure of various temporary fixing mechanisms. [Figure 6] FIG. 6 is a diagram for explaining each step of the optical fiber alignment method of the present disclosure. [Figure 7] FIG. 7 is a diagram showing an example of the configuration of an alignment device in steps ST2 and ST5 shown in FIG. [Figure 8] FIG. 8 is a diagram for explaining the rotation alignment accuracy in the rough alignment step and the fine alignment step as various examples of alignment operations between two MCFs each having rotationally symmetric core arrangements. [Figure 9] FIG. 9 is a diagram for explaining the rotation alignment accuracy in the coarse alignment step and the fine alignment step as an example of the alignment operation between two MCFs whose core arrangements do not have rotational symmetry. [Figure 10] FIG. 10 is a diagram illustrating the rotational alignment accuracy in the coarse alignment step and the fine alignment step as a modified example of the alignment operation between two MCFs each having rotationally symmetric core arrangements. [Figure 11] FIG. 11 is a diagram for explaining a specific case that makes marker detection difficult. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Problem to be solved by this disclosure] As a result of examining the above-mentioned conventional technology, the inventors have discovered the following problem. That is, to implement the conventional alignment method disclosed in the above-mentioned Patent Document 1, a complex drive system is required. For example, to achieve high alignment accuracy, it is necessary to arrange a drivable mirror for observing the end face. Furthermore, there is a problem that a high-precision fiber drive system (a drive system that moves and rotates the optical fiber to be aligned) is required that can butt the end faces of two MCFs, after the positions of the multiple elements (core, cladding, marker, etc.) that make up the end face have been adjusted (aligned) by observing the end face, without misaligning the adjusted element positions.

[0009] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an optical fiber alignment method, alignment device, and connection device that have a structure that enables high-precision alignment of optical fibers without the application of a complex drive system.

[0010] [Effects of this disclosure] According to the optical fiber alignment method of the present disclosure, a combination of coarse alignment operation by end face observation and fine alignment operation by side observation enables high-precision alignment of an optical fiber without applying a complex drive system.

[0011] [Description of the embodiments of the present disclosure] First, the contents of the embodiments of the present disclosure will be individually listed and described.

[0012] The optical fiber alignment method of the present disclosure includes: (1) A method for selecting both a first and a second optical fiber or the second optical fiber as an alignment target and aligning the first and second optical fibers so that they are optically connected to each other, the method comprising a coarse alignment step and a fine alignment step, wherein the first optical fiber has a plurality of first cores extending along a first central axis and arranged at predetermined positions on a first end face perpendicular to the first central axis, and the second optical fiber has a plurality of second cores extending along a second central axis and arranged at positions equivalent to the predetermined positions on a second end face perpendicular to the second central axis. The coarse alignment step is a step of coarsely aligning the first and second optical fibers based on the results of observing the end faces of the first and second optical fibers, and includes a first image acquisition substep, a measurement substep, and a first rotation substep. In the first image acquisition substep, end face images of the first and second optical fibers are acquired. In the measurement substep, dimensions and central positions of at least each of the multiple first cores and each of the multiple second cores are measured from the end face images of the first and second optical fibers as information regarding the first core arrangement on the first end face consisting of multiple first cores and the second core arrangement on the second end face consisting of multiple second cores. In the first rotation substep, the alignment target is rotated in a circumferential direction around the central axis of the alignment target based on the measurement results of the measurement substep. Meanwhile, the fine alignment step is a step of finely aligning the first and second optical fibers based on the results of observing the side faces of the first and second optical fibers so as to increase the optical coupling efficiency between the corresponding cores of the first and second optical fibers after the coarse alignment, and includes a second image acquisition substep and a second rotation substep. In the second image acquisition substep, side images of the first and second optical fibers are acquired. In the second rotation substep, the alignment state between the first and second optical fibers after the rough alignment is confirmed from the side image, and the alignment target is rotated in a circumferential direction around a central axis of the alignment target. Furthermore, the coarse alignment of the first and second optical fibers in the first rotation substep is performed under first conditions or second conditions. Note that the coarse alignment under the first condition and the coarse alignment under the second condition can be performed using a common device configuration. The first condition is defined by both the first core arrangement and the second core arrangement having n-fold rotational symmetry, where n-fold rotational symmetry is 2 or more, and the second condition is defined by both the first core arrangement and the second core arrangement not having rotational symmetry. Under the first condition, the coarse alignment is performed so that a first angle formed between an orientation indicated by a first line defined on the first end face and extending from the center of the first end face to pass through the center of a specific first core among the multiple first cores, and an orientation indicated by a second line defined on the second end face and extending from the center of the second end face to pass through the center of a specific second core associated with the specific first core among the multiple second cores, is 360° / n or less. Under the second condition, the coarse alignment is performed so that a second angle formed between the orientation indicated by the first line and the orientation indicated by the second line is a predetermined minimum angle excluding zero. The minimum angle excluding zero is selected from the angle between a plurality of first radiating line elements defined on the first end face and extending radially from the center of the first end face so as to pass through the centers of the plurality of first cores, or the angle between a plurality of second radiating line elements defined on the second end face and extending radially from the center of the second end face so as to pass through the centers of the plurality of second cores. As described above, the optical fiber alignment method of the present disclosure enables high-precision alignment of optical fibers without applying a complex drive system by combining a coarse alignment operation in which the end faces of two optical fibers are observed with the fibers spaced a certain distance apart, and a fine alignment operation in which the end faces of the two optical fibers are closely spaced with the fibers observed from the side. In other words, by combining the two types of alignment operations, it is possible to compensate for the decrease in alignment accuracy caused by the rotation of the optical fiber during each alignment operation and the movement of the optical fiber between alignment operations (suppression of alignment errors caused by the drive system).

[0013] (2) In the above (1), the alignment method may further include, prior to the fine alignment step, a moving step of moving at least the second optical fiber after coarse alignment of the first and second optical fibers along the second central axis so as to reduce a gap between a first end face of the first optical fiber after coarse alignment and a second end face of the second optical fiber after coarse alignment. By bringing the tip portions of the first and second optical fibers close to each other, the fine alignment step can be easily performed by side observation.

[0014] (3) In the above (1) or (2), in both or either of the coarse alignment step and the fine alignment step, the first core arrangement at the first end face of the first optical fiber may be fixed as an alignment target. In this way, by setting one of the first and second optical fibers to be optically connected as the alignment target, it is possible to suppress alignment errors caused by the drive system.

[0015] (4) In any of (1) to (3) above, the measurement substep involves measuring a rotation period, and the rotational alignment in the second rotation substep is performed by rotating the alignment target by a rotation angle equal to or less than the first angle or the second angle after the first rotation substep. Here, the "rotation period" is angular information expressing the rotational symmetry of the core arrangement consisting of multiple cores on the end face of each optical fiber. It is the rotation angle at which the pre-rotation and post-rotation core positions first overlap when the end face image is rotated around the central axis. For example, if the core arrangement on the end face has n (≧2)-fold rotational symmetry with respect to the end face center, the rotation period is given as 360° / n. Note that n=1 is not considered rotationally symmetric because all planar figures return to their original state (planar figures before rotation) by rotating 360°. This configuration avoids excessive rotation in the second rotation substep, enabling efficient alignment.

[0016] (5) In any of (1) to (3) above, the first optical fiber may include a marker extending along the first central axis, and the second optical fiber may include a marker extending along the second central axis. In this case, in the first rotation substep, the alignment target may be rotated to a position where a side image in which one of the plurality of first cores and the first marker overlap and one of the plurality of second cores and the second marker overlap is acquired in the second image acquisition substep. With this configuration, even if the markers cannot be observed during side observation, matching the core arrangements inevitably makes it possible to match the markers as well.

[0017] (6) In any of the above (1) to (5), each of the first and second optical fibers preferably includes either a multi-core optical fiber or a bundle fiber. These optical fibers have end faces that are composed of multiple elements (multiple cores, markers) in addition to the cladding, and can be the target of alignment by the alignment method of the present disclosure as optical fibers that require alignment by rotation.

[0018] The alignment device of the present disclosure comprises: (7) The optical fiber alignment method of the present disclosure defined in (1) to (6) above is realized. That is, the alignment device enables high-precision alignment of an optical fiber without using a complex drive system. Specifically, the alignment device of the present disclosure includes a coarse alignment unit and a fine alignment unit, and selects as alignment targets either a first optical fiber extending along a first central axis and having multiple first cores arranged at predetermined positions on a first end face perpendicular to the first central axis, or a second optical fiber extending along a second central axis and having multiple second cores arranged at positions equivalent to the predetermined positions on the first end face on a second end face perpendicular to the second central axis, and aligns the first and second optical fibers so that they are optically connected to each other. The coarse alignment unit coarsely aligns the first and second optical fibers based on the results of observation of the end faces of the first and second optical fibers. The fine alignment unit finely aligns the first and second optical fibers based on the results of observation of the side faces of the first and second optical fibers so as to increase the optical coupling efficiency between the corresponding cores of the first and second optical fibers roughly aligned by the coarse alignment unit. Here, the rough alignment unit includes a first image acquisition unit, a measurement unit, and a first rotation unit. , th and acquires end face images of the first and second optical fibers, respectively. The measurement unit measures the dimensions and center positions of each of the plurality of first cores and each of the plurality of second cores from the end face images of the first and second optical fibers, as information regarding the first core arrangement on the first end face consisting of a plurality of first cores and the second core arrangement on the second end face consisting of a plurality of second cores. The first rotation unit rotates the alignment target in a circumferential direction centered on the central axis of the alignment target, based on the measurement results of the measurement unit. The fine alignment unit also includes a second image acquisition unit and a second rotation unit. The second image acquisition unit acquires side images of the first and second optical fibers. The second rotation unit CoarseThe alignment state between the aligned first and second optical fibers is confirmed from a side image, and the alignment target is rotated in a circumferential direction around the central axis of the alignment target. Note that the first rotating part of the coarse alignment unit and the second rotating part of the fine alignment unit may be configured by a common alignment mechanism, or each may be configured by a different alignment mechanism. In particular, the first rotation unit rotates the first and second optical fibers under a first condition in which both the first core arrangement and the second core arrangement have n-fold rotational symmetry, where n is two or more times, so that a first angle formed between an orientation indicated by a first line defined on the first end face and extending from the center of the first end face to pass through the center of a specific first core among the plurality of first cores and an orientation indicated by a second line defined on the second end face and extending from the center of the second end face to pass through the center of a specific second core associated with the specific first core among the plurality of second cores is 360° / n or less. Further, the first rotation unit rotates the first and second optical fibers such that, under a second condition in which neither the first core arrangement nor the second core arrangement has rotational symmetry, a second angle between the orientation indicated by the first line and the orientation indicated by the second line is equal to or less than the smallest angle, excluding zero, of the angle formed between a plurality of first radiating line elements defined on the first end face and extending radially from the center of the first end face so as to pass through the centers of the plurality of first cores, or the angle formed between a plurality of second radiating line elements defined on the second end face and extending radially from the center of the second end face so as to pass through the centers of the plurality of second cores.

[0019] The connection device of the present disclosure includes: (8) For carrying out the optical fiber aligning method of the present disclosure defined in (1) to (6), a fusion device may be included that heat-fusion-splices the first and second optical fibers in a state where the first end face of the first optical fiber and the second end face of the second optical fiber that have been aligned by the aligning device defined in (7) are butted together. In this case, physical strength of the spliced ​​portion (including the end faces) between the optically connected first and second optical fibers can be obtained.

[0020] The connection device of the present disclosure includes: (9) The optical fiber aligning method of the present disclosure defined in (1) to (6) may include the aligning device defined in (7) above, and may further include a fixing jig for fixing the first and second optical fibers aligned by the aligning device in a state in which the first end face of the first optical fiber and the second end face of the second optical fiber face each other. The fixing jig preferably includes one of a temporary fixing mechanism for detachably holding the alignment target, a ferrule that constitutes part of an optical connector and is mounted on the tip end of the alignment target, including the end face, and a fiber array on which the tip ends of multiple optical fibers including the alignment target are mounted. This configuration is effective for aligning two optical fibers to be optically connected. It is also effective for aligning opposing array components (such as a fiber array) and bonding them together with an ultraviolet-curable resin. In particular, the temporary fixing jig can temporarily maintain the aligned state of the first and second optical fibers, making it effective when heat-fusion splicing the first and second optical fibers using the fusion splicing device.

[0021] (10) In the above (9), the fixing jig may include a mechanical splice element. This configuration is also effective for aligning two opposing optical fibers.

[0022] [Details of the embodiments of the present disclosure] The specific structures of the optical fiber alignment method, alignment device, and splicing device according to the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, in the description of the drawings, identical elements are given the same reference numerals, and duplicate explanations will be omitted.

[0023] The optical fiber alignment method of the present disclosure is applicable to an optical fiber having an internal bending such as an MCF (multi-core optical fiber). This method is suitable for aligning objects that have a refractive index change section and a structure in which the refractive index changes depending on the orientation around the fiber axis (central axis). Specific aligning targets include the above-mentioned MCF, as well as bundled fibers. It can also be applied to aligning ferrules (included in optical connectors) and fiber arrays, which require matching the core arrangement of two optical fibers to be optically connected.

[0024] Fig. 1 is a diagram showing the appearance (including a partially cutaway view) and cross-sectional structure of various optical fibers applicable to the optical fiber alignment method, etc., according to the present disclosure. The upper part of Fig. 1 shows an appearance view of MCF 10 and the cross-sectional structure of MCF 10 taken along line II shown in the appearance view. The lower part of Fig. 1 shows an appearance view of bundle fiber 30 and the cross-sectional structure of bundle fiber 30 taken along line III-III shown in the appearance view.

[0025] 1 includes a glass fiber 13 extending along a fiber axis AX (center axis) and a resin coating 14 provided on the outer circumferential surface of the glass fiber 13. The glass fiber 13 includes a plurality of cores 11 extending along the fiber axis AX and a common cladding 12 surrounding each of the plurality of cores 11. In a cross section of the MCF 10 perpendicular to the fiber axis AX, the fiber axis AX passes through the center of the cross section of the common cladding 12.

[0026] The fiber bundle 30 shown in the lower part of FIG. 1 includes a housing 31 and a plurality of single-core optical fibers 32 (hereinafter, referred to as "SCFs"). The housing 31 has a front end face 31A and a rear end face 31B opposite the front end face 31A. The housing 31 further includes a front opening 33 provided on the front end face 31A and a storage space 34 for storing the plurality of SCFs 32 with their tip ends bundled together. The resin coating has been removed from the tip ends (glass fibers 320) of the plurality of SCFs 32, and each end face of the plurality of SCFs 32 is located at the front opening 33. Therefore, the structure of the front end face 31A of the fiber bundle 30 is substantially similar to the end face structure of the MCF 10. Each of the plurality of SCFs includes a glass fiber 320 covered with a resin coating. The glass fiber 320 includes a core 321 and a cladding 322 surrounding the core 321.

[0027] FIG. 2 shows various configuration examples of a fixing jig (included in the splicing device of the present disclosure) for fixing (including temporary fixing) an optical fiber after alignment. The splicing device of the present disclosure includes a fixing jig for maintaining the arrangement of elements on the end face of the optical fiber after alignment. As an application example of the fixing jig, the upper part of FIG. 2 shows a state in which an MCF 10 is fixed to a temporary fixing mechanism 50 used in splicing work such as fusion splicing (denoted as "temporary fixing mechanism" in FIG. 2). The middle part of FIG. 2 shows a state in which an MCF 10 is fixed to a ferrule 60 constituting a part of an optical connector (denoted as "ferrule fixing" in FIG. 2). The lower part of FIG. 2 shows a state in which multiple MCFs 10 are fixed to a fiber array 70 (denoted as "fiber array fixing" in FIG. 2). Note that while FIG. 2 shows an MCF 10 as an example of an object to be fixed for alignment, the various optical fibers shown in FIG. 1 are applicable. The fixing jig shown in FIG. 2 can serve as an alignment reference for the MCF 10 and also functions as a member for maintaining the core arrangement in the MCF 10 after alignment.

[0028] 2, the tip portion of the MCF 10 (the portion where the glass fiber 13 is exposed by removing the resin coat 14) is held by the temporary fixing mechanism 50. The temporary fixing mechanism 50 includes a lower member 51 having a V-groove 51b in which the tip portion of the MCF 10 is placed, an upper member 52 that presses the tip portion of the MCF 10 against the V-groove 51b, and a hinge 53 for attaching the upper member 52 to the lower member 51 so that the upper member 52 can be opened and closed. After the MCF 10 is rotated around the fiber axis AX in the circumferential direction indicated by the arrow S1 (after alignment), the tip portion of the MCF 10 is fixed to the temporary fixing mechanism 50, and the core arrangement at the end face of the MCF 10 is held by the temporary fixing mechanism 50.

[0029] 2, a ferrule 60 constituting a part of an optical connector is fixed to the tip portion (glass fiber 13) of MCF 10 from which the resin coat 14 has been removed. After the MCF 10 is rotated in the circumferential direction indicated by arrow S2 around the fiber axis AX (after alignment), the ferrule 60 is adhesively fixed to the tip portion of MCF 10, thereby maintaining the core arrangement at the end face of the MCF 10 relative to the ferrule 60.

[0030] In the "fiber array fixation" shown in the lower part of FIG. 2, the tip portions of a plurality of MCFs 10, from which the resin coating 14 has been removed, are held in a fiber array 70. The fiber array 70 includes a lower member 71 having V-grooves 710 in which the glass fibers 13 of the plurality of MCFs 10 are respectively disposed, and an upper member 72 that presses each of the glass fibers 13 against the corresponding V-groove 710. Each of the plurality of MCFs 10 is rotated in the direction indicated by arrow S3 around the fiber axis AX (alignment). After alignment, each of the plurality of MCFs 10 is sandwiched between the V-groove 710 of the lower member 71 and the upper member 72, and is then adhesively fixed to the fiber array 70 with an adhesive such as ultraviolet-curable resin. As a result, the core arrangement at the end face of each of the plurality of MCFs 10 is maintained relative to the fiber array 70.

[0031] FIG. 3 is a diagram showing various configurations (included in the splicing device of the present disclosure) for connecting two aligned and fixed optical fibers. As an application example of the splicing device of the present disclosure, the top row of FIG. 3 shows a connection example using a fusion splicing device (denoted as "fusion splicing" in FIG. 3). The second row of FIG. 3 shows a connection example using an optical connector (denoted as "optical connector connection" in FIG. 3). The third row of FIG. 3 shows an example of connection between fiber arrays (denoted as "fiber array connection" in FIG. 3). The bottom row of FIG. 3 shows a connection example using a mechanical splice element (denoted as "mechanical splice connection" in FIG. 3). Note that in FIG. 3, the fixed-side optical fiber (the optical fiber excluded from the alignment target) is shown in the region indicated by reference symbol "A," and the alignment-side optical fiber (the optical fiber selected for the alignment target) is shown in the region indicated by reference symbol "B." However, the optical fiber in either region indicated by reference symbol "A" or "B" can be selected for the alignment target.

[0032] The "fusion splicing" shown in the top row of Figure 3 illustrates a simple configuration example of a fusion splicing device for fusion-splicing end faces of MCFs 10, each of whose tip portions is fixed to a temporary-fixing mechanism 50. The temporary-fixing mechanism 50 to which the MCF 10 on the fixed side A is fixed and the temporary-fixing mechanism 50 to which the MCF 10 on the alignment side B is fixed are installed in a guide groove 57. The temporary-fixing mechanisms 50 on the fixed side A and the alignment side B are brought close to each other along the guide groove 57, so that the end face of the MCF 10 on the fixed side A and the end face of the MCF 10 on the alignment side B are butted together between discharge electrodes 55A and 55B. An electric discharge generated between these discharge electrodes 55A and 55B fusion-splices the end face of the MCF 10 on the fixed side A and the end face of the MCF 10 on the alignment side B (reference numeral "56" in Figure 3 indicates a fusion portion).

[0033] The "optical connector connection" shown in the second row of Figure 3 shows a simple example of the configuration of an optical connector for optically connecting the end faces of MCFs 10, each having a ferrule 60 fixed to its tip. The ferrule 60 fixed to the MCF 10 on the fixed side A and the ferrule 60 fixed to the MCF 10 on the alignment side B are housed in a sleeve 62. At this time, the sleeve 62 holds the end faces 61 of the ferrules so that they abut or face each other with a predetermined distance between them. In this "optical connector connection," the end face of the MCF 10 on the fixed side A and the end face of the MCF 10 on the alignment side B may be in contact or may not be in contact.

[0034] The "fiber array connection" shown in the third row of Figure 3 illustrates a simple example of a configuration for optically connecting the end faces of MCFs 10, each of whose tip portions is fixed to a fiber array 70 on the fixed side A, with the end faces of MCFs 10, each of whose tip portions is fixed to a fiber array 70 on the alignment side B. The fiber array 70 on the fixed side A to which the MCFs 10 are fixed and the fiber array 70 on the alignment side B to which the MCFs 10 are fixed are installed on a guide member 73. The fiber arrays 70 on the fixed side A and the fiber arrays 70 on the alignment side B are brought close to each other along the guide member 73, and their end faces are bonded together using an adhesive 76 such as an ultraviolet-curable resin, forming a joint 75. In this "fiber array connection," the fiber arrays 70 on the fixed side A and the fiber arrays 70 on the alignment side B are positioned by the guide member 73, so that the end faces of the MCFs 10 on the fixed side A and the end faces of the MCFs 10 on the alignment side B are aligned with each other due to the bonding between these fiber arrays 70. Both the fiber arrays 70 on the fixed side A and the alignment side B include a lower member 71 having a V-groove 710 for holding the glass fiber 13 of the MCF 10 from which the resin coating 14 has been removed, and an upper member 72 for pressing the glass fiber 13 against the V-groove 710 of the lower member 71, and the MCF 10, lower member 71, and upper member 72 are fixed together with an adhesive 76 such as an ultraviolet-curing resin.

[0035] The "mechanical splice connection" shown at the bottom of FIG. 3 illustrates a simple example of a configuration for optically connecting end faces of MCFs 10, the portions of which covered with the resin coating 14 are fixed by temporary fixing mechanisms 50A. The end portions of the MCFs 10 fixed to the temporary fixing mechanisms 50A on the fixed side A and the end portions of the MCFs 10 fixed to the temporary fixing mechanisms 50A on the alignment side B are each housed within a mechanical splice element 80. The mechanical splice element 80 includes a lower member 81 having a groove 81a for holding the MCFs 10 on the fixed side A and the alignment side B in an optically connected state, and an upper member 82 having a groove 82a for similarly holding the MCFs 10 on the fixed side A and the alignment side B in an optically connected state. The end faces of the MCFs 10 on the fixed side A and the alignment side B housed within the mechanical splice element 80 are maintained optically connected via a refractive index matching material 83.

[0036] Fig. 4 is a diagram for explaining the alignment operation in the optical fiber alignment method of the present disclosure. The upper part of Fig. 4 shows a simple example of an apparatus configuration (coarse alignment unit) for explaining the coarse alignment operation (end face observation). The lower part of Fig. 4 shows a simple example of an apparatus configuration (fine alignment unit) for explaining the fine alignment operation (side surface observation). Furthermore, the upper and lower parts of Fig. 5 show a temporary fixing mechanism 50 (denoted as "Type 1" in Fig. 5) and a temporary fixing mechanism 50A (denoted as "Type 2" in Fig. 5) that are mechanisms for holding the optical fiber to be aligned (MCF 10 in the example shown in Fig. 4), and that hold the optical fiber during the alignment operation and fix the optical fiber after alignment.

[0037] The example of an apparatus configuration shown in the upper part of Fig. 4 is an apparatus for carrying out the optical fiber alignment method (coarse alignment operation by end face observation) of the present disclosure, and includes a light source 140A (referred to as "light source 1" in Fig. 4), a light source 140B (referred to as "light source 2" in Fig. 4), an alignment mechanism 130 (first rotation unit), a temporary fixing mechanism 50, a camera 100 (first image acquisition unit), and a control unit 120 that also functions as a measurement unit. Note that although Fig. 4 shows an MCF 10 as the alignment target, various optical fibers that require alignment such as those shown in Fig. 1 are applicable.

[0038] Light source 140A irradiates observation light into the rear end face of MCF 10, which is the target of alignment. Meanwhile, light source 140B irradiates observation light into the interior of MCF 10 from the side of MCF 10. Light irradiated from both light sources 140A and 140B is emitted from the front end face of MCF 10, and camera 100 captures an end face image 100A of MCF 10 (first image capture substep). That is, the light from light source 140A and light source 140B forms a light-dark pattern of parts with different refractive indices (multiple elements constituting the end face) within MCF 10. For example, the cladding and markers are displayed dark, and the core is displayed bright, making it possible to confirm the positions of the cladding, core, and marker from the light-dark pattern. Camera 100 captures this light-dark pattern as end face image 100A.

[0039] In the upper part of Figure 4, as an example, cores #1 to #8 are arranged at equal intervals with a center-to-center distance of 31 µm so as to surround the center of a cladding (center of the end face) with an outer diameter of 125 µm, and marker 111 is shown at a position shifted from the center of the cross section. Components of the end face include cores #1 to #8, marker 111, cladding (common cladding in the example of Figure 4), as well as parts displayed as a light and dark pattern in end face image 100A. Furthermore, the circle surrounding cores #1 to #8 and marker 111 corresponds to the outer periphery of the cladding.

[0040] As a rough alignment step, the control unit 120 controls the light sources 140A and 140B, which perform a first image acquisition substep, and the camera 100, which serves as a first image acquisition unit. Furthermore, the control unit 120, as a measurement unit, performs measurement (measurement substep) of elements constituting the end face of the MCF 10 (substantially the glass fiber 13), and controls a first rotation unit, which performs rotation (first rotation substep) of the MCF 10 in the circumferential direction about the fiber axis AX of the MCF 10. The control unit 120 preferably has a memory for recording measurement data (alignment target data) of another optical fiber to be optically connected to the alignment target (MCF 10 shown in FIG. 4), and the rotation control of the alignment target is performed so that the measurement data of the alignment target obtained in the measurement substep matches this alignment target data.

[0041] The upper part of FIG. 4 shows a simple configuration example of the alignment mechanism 130. However, for example, the alignment device disclosed in Patent Document 2 can be applied to this alignment mechanism 130, and Patent Document 2 is incorporated herein by reference in its entirety. In the "alignment device" shown in the upper part of FIG. 4, the alignment mechanism 130 includes a drive unit 131, a holding member 132 that holds the side of the MCF 10 to be aligned, and a rotating shaft 133 that rotates the holding member 132 around the fiber axis AX in the circumferential direction indicated by arrow S4 while holding the MCF 10. A thread groove is formed on the side of the rotating shaft 133, and a protrusion on the end face of the holding member 132 engages with the thread groove. When the drive unit 131 rotates the rotating shaft 133 by a predetermined amount in accordance with a control command from the control unit 120, the holding member 132 that holds the MCF 10 rotates in conjunction with this rotation in the circumferential direction indicated by arrow S4. This causes the alignment of the MCF 10. The driving unit 131 is, for example, a motor such as a stepping motor.

[0042] The device configuration example shown in the lower part of Fig. 4 is a device for carrying out the optical fiber alignment method (fine alignment operation by side observation) of the present disclosure, and includes a light source 140C (denoted as "light source 3" in Fig. 4), an alignment mechanism 130 (second rotation unit), a temporary fixing mechanism 50, a camera 100 (second image acquisition unit), and a control unit 120. Note that the lower part of Fig. 4 also shows an example in which an MCF 10 is applied as the alignment target.

[0043] The light source 140C irradiates the side of the MCF 10 (glass fiber 13 from which the resin coating 14 has been removed) to be aligned with light for observation. The light irradiated from the light source 140C is emitted from the side of the MCF 10 opposite the irradiated portion, and the camera 100 acquires a side image 100B of the MCF 10 (second image acquisition substep). That is, the light from the light source 140C forms a light-dark pattern of portions of the MCF 10 with different refractive indices. For example, the cladding and markers appear dark, and the core appears bright, making it possible to confirm the positions of the cladding, core, and marker from the light-dark pattern. The camera 100 acquires this light-dark pattern as the side image 100B. FIG. 4 also shows a luminance distribution 100C along the measurement axis shown in the side image 100B. In the luminance distribution 100C, the horizontal axis indicates the pixel position along the measurement axis shown in the side image 100B, and the vertical axis indicates the luminance of each pixel. When the fine alignment step of the two MCFs 10 is performed, the fine alignment of the two MCFs 10 is performed by pattern matching while checking the side image 100B of the two MCFs 10 arranged closely to each other.

[0044] In the example of the device configuration shown in the lower part of Fig. 4, the control unit 120 controls the light source 140C and the camera 100 as the second image acquisition unit to perform the second image acquisition substep as the fine alignment step. Furthermore, the control unit 120 controls the second rotation unit to rotate the MCF 10 to be aligned in the circumferential direction around the fiber axis AX based on pattern matching based on the side image 100B. In addition, when a side image of the alignment target (MCF 10 shown in Fig. 4) and a side image of another optical fiber to be optically connected to the alignment target are separately acquired, the control unit 120 preferably has a memory for recording the side image of the other optical fiber as alignment target data, and the rotation control of the alignment target is performed so that the side image of the MCF 10 to be aligned matches the side image of the other MCF 10. In addition, in the lower part of Fig. 4, to The alignment mechanism 130 shown is the same as the example of the device configuration shown in the upper part of FIG. 4 above.

[0045] In the device configuration examples shown in both the upper and lower parts of Fig. 4 described above, a temporary fixing mechanism 50 is disposed at the tip portion of the MCF 10. As shown in the upper part of Fig. 5, this temporary fixing mechanism 50 includes a lower member 51, an upper member 52, and a hinge 53 for attaching the upper member 52 to the lower member 51 in an openable and closable state. The lower member 51 has an abutting surface 51a, and a V-shaped groove 51b is formed in the abutting surface 51a to hold the tip portion (glass fiber 13) of the MCF 10 from which the resin coat 14 has been removed. On the other hand, the upper member 52 has an abutting surface 52a. During the alignment operation of the MCF 10, the abutment surface 51a of the lower member 51 and the abutment surface 52a of the upper member 52 are maintained apart, and after alignment, the abutment surface 52a of the upper member 52 is pressed against the abutment surface 51a of the lower member 51, thereby holding the arrangement of elements on the end face of the MCF 10 placed in the V-groove 51b with respect to the temporary fixing mechanism 50. Thereafter, the aligned MCF 10 is fusion-spliced ​​to another MCF 10 by the fusion device shown in the top row of FIG.

[0046] A temporary fixing mechanism 50A shown in the lower part of FIG. 5 can also be used to align and fix the MCF 10. This temporary fixing mechanism 50A functions as a means for holding the element arrangement on the end face of the MCF 10 so that the aligned MCF 10 can be installed on the mechanical splice element 80 shown in the bottom part of FIG. 3. The temporary fixing mechanism 50A includes a lower member 510, an upper member 520, and a hinge 530. The lower member 510 has an abutting surface 510a, and a groove 510b is formed in the abutting surface 510a for holding the side surface of the MCF 10 (the portion covered with the resin coat 14) that is to be aligned. Meanwhile, the upper member 520 has an abutting surface 520a, and a groove 520b is also formed in the abutting surface 520a for holding the side surface of the MCF 10. During the alignment operation of the MCF 10, the abutment surface 510a of the lower member 510 and the abutment surface 520a of the upper member 520 are maintained apart, and after alignment, the abutment surface 520a of the upper member 520 is pressed against the abutment surface 510a of the lower member 510, thereby holding the arrangement of elements on the end face of the MCF 10 placed in the groove 510b with respect to the temporary fixing mechanism 50A. Thereafter, the aligned MCF 10 is optically connected to another MCF 10 by the mechanical splice element 80 shown in the bottom row of FIG.

[0047] FIG. 6 is a diagram illustrating each step of the optical fiber alignment method of the present disclosure. The optical fiber alignment method of the present disclosure includes a coarse alignment step performed by observing the end face and a fine alignment step performed by observing the side face. The optical fiber alignment method of the present disclosure is suitable for aligning optical fibers such as MCFs, as illustrated in FIG. 1, which have a refractive index change portion therein and a structure in which the refractive index changes depending on the orientation. The following explanation focuses on the alignment operation of two MCFs. In the example of FIG. 6, two MCFs 10 are each targeted for alignment. However, as shown in FIG. 3, one of the two optical fibers may be set as the optical fiber on the fixed side A as the alignment target, and the other may be set as the optical fiber on the alignment side B.

[0048] (Rough alignment by observing the end face) In the rough alignment step, the left MCF 10 and the right MCF 10 are aligned based on the results of observing the end faces of the left MCF 10 and the right MCF 10 so that the correspondence between the multiple cores (first cores) arranged on the end face (first end face) of the MCF 10 arranged on the left side in Figure 6 (a first optical fiber extending along a first central axis, hereinafter referred to as the "left MCF") and the multiple cores (second cores) arranged on the end face (second end face) of the MCF 10 arranged on the right side (a second optical fiber extending along a second central axis, hereinafter referred to as the "right MCF") falls within an allowable range that allows for unique determination of the correspondence.

[0049] The maximum angle defining the allowable range is an angle set with respect to the angle (first angle) between the orientation indicated by a first line defined on the end face of the left MCF 10 and the orientation indicated by a second line defined on the end face of the right MCF 10, when both the core arrangement (first core arrangement) defined on the end face of the left MCF 10 and the core arrangement (second core arrangement) defined on the end face of the right MCF 10 have n-fold rotational symmetry (where n is two or more times) (first condition), as in the example shown in FIG. 8. Here, the first and second lines are straight lines defined on the end faces of the left MCF 10 and the right MCF 10, respectively, and refer to straight lines extending from the center of the end face so as to pass through the centers of specific cores among the multiple cores (e.g., line L shown in FIG. 8). The rotational period is angle information defining the rotational symmetry of the core arrangement consisting of multiple cores on the end face. For example, when the core arrangement on the end face has n (≧2)-fold rotational symmetry with respect to the end face center, the rotational period is given as 360° / n.

[0050] Furthermore, the maximum angle that defines the tolerance range is an angle set with respect to the angle (second angle) between the orientation indicated by line L (first line) defined on the end face of the left MCF 10 and the orientation indicated by line L (second line) defined on the end face of the right MCF 10 when neither the core arrangement (first core arrangement) of the left MCF 10 nor the core arrangement (second core arrangement) of the right MCF 10 has rotational symmetry (second condition), as in the example shown in Figure 9, and is less than or equal to the smallest angle, excluding zero, formed between radiating line elements extending from the center of the end face on the same end face. Here, the minimum angle excluding zero is the minimum angle between adjacent radiating line elements among the radiating line elements L1 to L4 defined on the end face of the left MCF 10 and extending radially from the center of the end face so as to pass through the centers of each of the cores #1 to #4, or the minimum angle between adjacent radiating line elements among the radiating line elements L1 to L4 defined on the end face of the right MCF 10 and extending radially from the center of the end face so as to pass through the centers of each of the cores #1 to #4, and corresponds to, for example, the angle θ shown in FIG. 9.

[0051] First, in the rough alignment step, as a first image acquisition sub-step, an end face image (bright and dark pattern as shown in FIG. 4) of the left MCF 10 is acquired by the camera 100 (step ST1). Between the left MCF 10 and the right MCF 10, a mirror 900 having a reflective surface inclined at 45° with respect to the respective fiber axes AX is arranged. When observation light is simultaneously incident on the rear end face and side face of the left MCF 10, this observation light is emitted from the front end face of the left MCF 10 (the surface directly facing the reflective surface of the mirror 900), and the camera 100 acquires the end face image via the mirror 900.

[0052] Once the end face image of the left MCF 10 is acquired, the mirror 900 is flipped in the direction indicated by the arrow S5, and an end face image of the right MCF 10 is acquired by the camera 100 in the same manner as for the left MCF 10. Once the end face images of the left MCF 10 and the right MCF 10 are acquired, a measurement substep and a first rotation substep are executed successively (step ST2). That is, in the measurement substep, at least the dimensions and center positions of each of a plurality of elements (cores, markers, cladding, etc.) are measured from each of the end face images of the left MCF 10 and the right MCF 10 as information regarding the element arrangement on the end face. For example, the control unit 120 determines the movement amount in the x-axis direction, the movement amount in the y-axis direction, and the rotation angle of each of the left MCF 10 and the right MCF 10 based on the measurement results of the left MCF 10 and the right MCF 10, and controls various drive systems for changing the attitudes of the left MCF 10 and the right MCF 10. This drive system In this control, rotational alignment (first rotation substep) is performed on the left MCF 10 and the right MCF 10 so that the correspondence between elements such as cores of the left MCF 10 and the right MCF 10 falls within an allowable range that makes it possible to uniquely determine the correspondence.

[0053] As described above, when the rough alignment step is completed, the mirror 900 moves in the direction indicated by the arrow S6. (Step ST3). Thereafter, the left MCF 10 and the right MCF 10 are moved along the z-axis so that the end faces of the left MCF 10 and the right MCF 10 are positioned close to each other (Step ST4: moving step). This moving step is also controlled by the control unit 120.

[0054] 7 shows an example of the configuration of an alignment device (coarse alignment unit) for performing the above-mentioned rough alignment steps (steps ST1 to ST3). This coarse alignment unit mainly includes an XYZ stage 800 for performing the rough alignment step in the above-mentioned step ST2, a camera 100 (first image acquisition unit), a memory 110, a control unit 120 that also functions as a measurement unit, an alignment mechanism 130A for the left MCF 10, and an alignment mechanism 130B for the right MCF 10. In this coarse alignment unit, the alignment mechanism 130A and the alignment mechanism 130B form a first rotation unit that can perform both the coarse alignment under the first condition and the coarse alignment under the second condition. Furthermore, the alignment device shown in the upper part of FIG. 7 includes a mirror 900 for guiding light for observing the end faces from the left MCF 10 and the right MCF 10 (light irradiated from light source 140A and light source 140B onto the rear end face and side face of MCF 10 as shown in the upper part of FIG. 4) to camera 100, a support shaft 920 for holding the mirror 900, and a mirror driver 910. The control unit 120 performs the above-mentioned measurement substeps and also controls the XYZ stage driver 810 for controlling the movement of the XYZ stage 800, the mirror driver 910 for controlling the attitude of the mirror 900, and the alignment mechanisms 130A and 130B. In the example shown in the upper part of FIG. 7, both the left MCF 10 and the right MCF 10 are held by temporary fixing mechanism 50A, but the temporary fixing mechanism 50 shown in the upper part of FIG. 5 may also be used. Both temporary fixing jigs can be moved to any position by the installed XYZ stage. Furthermore, when the left MCF 10 is fixed as an alignment target, a fixing jig such as the fiber array shown in FIG. 2 may be used instead of the temporary fixing mechanism shown in FIG.

[0055] The XYZ stage 800 is composed of a Z-axis stage 800A for moving the left and right MCFs 10 individually along the z-axis, a Y-axis stage 800B for moving the left and right MCFs 10 individually along the y-axis, and an X-axis stage 800C for moving the left and right MCFs 10 individually along the x-axis to enable position changes of the left and right MCFs 10. The mirror driver 910 rotates the support shaft 920 in the direction indicated by arrow S7 (switching the observation target) and moves the support shaft 920 in the direction indicated by arrow S8 (inserting and retracting the mirror 900). The alignment mechanism 130A rotates the left MCF 10 in the circumferential direction centered on the fiber axis AX, and the alignment mechanism 130B rotates the right MCF 10 in the circumferential direction centered on the fiber axis AX. Both alignment mechanisms 130A and 130B have the same structure as alignment mechanism 130 shown in the upper and lower parts of Fig. 4. After completion of step ST4 (movement step), the drive system of mirror 900 (mirror 900, mirror drive unit 910, support shaft 920) is replaced with light source 140C (light source 3) that emits light for side observation.

[0056] (Fine alignment by observing the side) After the end faces of the left MCF 10 and the right MCF 10 are positioned close to each other in the movement step (step ST4), a fine alignment step is performed (step ST5). The fine alignment step is an alignment step for increasing the optical coupling efficiency between the corresponding elements between the left MCF 10 and the right MCF 10 after the coarse alignment, and rotational alignment of the alignment targets (one or both of the left MCF 10 and the right MCF 10) is performed within the tolerance range set in the coarse alignment step described above. Specifically, after the movement of the left MCF 10 and the right MCF 10 in the z-axis direction after the coarse alignment is completed as described above (step ST4), the positions of the glass fiber 13 and the core 11 are adjusted by observing side images (bright and dark patterns visible due to light refracted by the glass fiber 13 and the core 11) of the tip portions (glass fiber 13 from which the resin coating 14 has been removed) of the left MCF 10 and the right MCF 10 to be aligned.

[0057] In step ST5, a fine alignment step, first, a light source 140C (light source 3) that emits light for side observation is placed in place of mirror 900. A light and dark pattern generated by light from light source 140C passing through glass fibers 13 of left MCF 10 and right MCF 10 is acquired by camera 100 as a side image of the left MCF 10 and right MCF 10 (corresponding to 100B shown in the lower part of FIG. 4) (second image acquisition substep). Based on this side image, rotational alignment of the left MCF 10 and the right MCF 10 is performed so that the end face positions of cores 11 in the left MCF 10 and the end face positions of cores 11 in the right MCF 10 overlap along the fiber axis AX (pattern matching), that is, so as to increase the optical coupling efficiency between the corresponding elements of the left MCF 10 and the right MCF 10 (preferably to maximize the coupling efficiency) (second rotation substep). When the rotational alignment of the left MCF 10 and the right MCF 10 is completed in step ST5, the left MCF 10 and the right MCF 10 are moved along the z-axis direction so that the end faces of the left MCF 10 and the right MCF 10 are butted together for fusion splicing or other operations (step ST6).

[0058] The lower part of FIG. 7 shows an example of the configuration of an alignment device (fine alignment unit) for performing the above-mentioned fine alignment step (step ST5). This fine alignment unit mainly includes an XYZ stage 800, a camera 100 (second image acquisition unit), a memory 110, a control unit 120, an alignment mechanism 130A for the left MCF 10, and an alignment mechanism 130B for the right MCF 10, all for performing the fine alignment step in the above-mentioned step ST5. In this fine alignment unit, the alignment mechanism 130A and the alignment mechanism 130B form a second rotation unit. Furthermore, instead of the drive system for the mirror 900 in the alignment device shown in the upper part of FIG. 7, a light source 140C (light source 3) is provided for obtaining a side image. To perform the above-mentioned fine alignment step of step ST5, the control unit 120 controls the drive of the XYZ stage driver 810, which controls the movement of the XYZ stage 800, and the alignment mechanisms 130A and 130B. The splicing device of the present disclosure may include a fixing jig in addition to the alignment device that performs the above-described coarse and fine alignment. The example shown in the lower part of FIG. 7 uses the temporary fixing mechanism 50A as the fixing jig, as in the example shown in the upper part of FIG. 7, but the temporary fixing mechanism 50 shown in the upper part of FIG. 5 may also be used. Both temporary fixing jigs can be moved to any position using an XYZ stage installed thereon, allowing for continuous operations from the coarse and fine alignment to the connection of the left MCF 10 and the right MCF 10 shown in FIG. 3. Furthermore, when fixing the left MCF 10 as the alignment target, a fixing jig such as the fiber array shown in FIG. 2 may be used instead of the temporary fixing mechanism shown in FIG. 5.

[0059] Similar to the alignment device shown in the upper part of FIG. 7 , the XYZ stage 800 is configured to change the positions of the left and right MCFs 10 by using a Z-axis stage 800A for moving the left and right MCFs 10 individually along the z-axis, a Y-axis stage 800B for moving the left and right MCFs 10 individually along the y-axis, and an X-axis stage 800C for moving the left and right MCFs 10 individually along the x-axis. The alignment mechanism 130A rotates the left MCF 10 in the circumferential direction about the fiber axis AX, and the alignment mechanism 130B rotates the right MCF 10 in the circumferential direction about the fiber axis AX. Both alignment mechanisms 130A and 130B have the same structure as the alignment mechanisms 130 shown in the upper and lower parts of FIG. 4 . After completion of step ST6 (moving step), the light source 140C is replaced with, for example, a discharge unit 550 including a pair of discharge electrodes 55A and 55B.

[0060] Next, the rotational alignment accuracy in the coarse alignment step and the fine alignment step will be described with reference to FIG. 8. FIG. 8 is a diagram illustrating the rotational alignment accuracy in the arrangement coarse alignment step and the fine alignment step as various examples of alignment operations between two MCFs whose respective core arrangements have rotational symmetry. In a normal alignment operation, a situation may arise in which the markers 111 of the left MCF 10 and the right MCF 10 cannot be detected in the fine alignment step (side observation). In the optical fiber alignment method of the present disclosure, even in such cases, in order to align the positions of these markers 111 in the fine alignment step, the coarse alignment step is performed with an accuracy to the extent that the rotational misalignment between the core arrangements of the left MCF 10 and the right MCF 10 falls within the angular range (tolerance) of the rotation period in which the core arrangements overlap, and further, the fine alignment step is preferably performed within the range of that period.

[0061] The left side of FIG. 8 shows the end face (two types: two-core arrangement and four-core arrangement) of the left MCF 10 during the fine alignment step (when observed from the side). In the example of FIG. 8, the light source 140C and the camera 100 are arranged on either side of the left MCF 10 as an apparatus configuration for side observation (fine alignment step). The left MCF 10 is fixed as an alignment target. Furthermore, the line L shown in FIG. 8 is a straight line (first line) that starts at the center of the end face (the point through which the fiber axis AX passes) and extends to pass through the center of a specific core for the left MCF 10, indicating the orientation for specifying the core arrangement in the left MCF 10, which is the alignment target. Similarly, in the case of the right MCF 10, it is a straight line (second line) that starts at the center of the end face (the point through which the fiber axis AX passes) and extends to pass through the center of a specific core, indicating the orientation for specifying the core arrangement in the right MCF 10, which is the alignment target.

[0062] In the case of a two-core arrangement, core #1, core #2, and marker 111 are covered by a common cladding on the end faces of the left MCF 10 and the right MCF 10, respectively, and a tolerance range (rotational range in the fine alignment step) is set in the measurement substep of the coarse alignment step. The two-core arrangement has two-fold rotational symmetry, resulting in a rotation period of 180° (=360° / 2). On the other hand, in the case of a four-core arrangement, core #1 to core #4 and marker 111 are covered by a common cladding on the end faces of the left MCF 10 and the right MCF 10, respectively, and a tolerance range (rotational range in the fine alignment step) is set in the measurement substep of the coarse alignment step. The four-core arrangement has four-fold rotational symmetry, resulting in a rotation period of 90° (=360° / 4). For core arrangements with n (≧2)-fold rotational symmetry, the rotation period is defined as 360° / n.

[0063] Therefore, in the case of a two-core arrangement, in the fine-alignment step, the rotation angle for rotational alignment is determined within the maximum angle range of -180° or more and +180° or less, centered on a rotation angle of 0° (the orientation indicating the core arrangement of the left MCF 10), as shown in the center and right side of Fig. 8, and in the case of a four-core arrangement, the rotation angle for rotational alignment is determined within the maximum angle range of -90° or more and +90° or less, centered on a rotation angle of 0°, as shown in the center and right side of Fig. 8. Note that when the left MCF 10 and the right MCF 10 are aligned, the images of their end faces reflected by a mirror and viewed from the same direction are oriented in a direction that is bent back along a straight line perpendicular to the fiber axis AX common to both optical fibers. Therefore, the rotational alignment in the first rotation sub-step in the rough alignment step is performed by rotating the alignment target (right MCF 10, when the left MCF 10 is fixed as in the example of FIG. 8) so that the deviation angle between the image of the right MCF 10 and the arrangement obtained by folding back the image of the left MCF 10 (the angle formed by line L (first line) indicating the orientation of the core arrangement in the left MCF 10 and line L (second line) indicating the orientation of the core arrangement in the right MCF 10) falls within the above-mentioned allowable range (the maximum angle range shown in the center and right of FIG. 8). With the above configuration, even if the marker 111 cannot be observed during side observation, it is possible to align the marker 111 by aligning the core arrangement.

[0064] FIG. 9 illustrates the rotational alignment accuracy in the coarse alignment step and the fine alignment step as an example of an alignment operation between two MCFs whose core arrangements do not have rotational symmetry. The core arrangements of the left MCF 10 and the right MCF 10 shown in FIG. 9 are four-core arrangements consisting of cores #1 to #4, similar to the example shown in the lower part of FIG. 8. However, they differ from the example shown in the lower part of FIG. 8 in that core #2 is positioned closer to the outer periphery of the common clad than the position shown in the lower part of FIG. 8. As a result, the core arrangements of the left MCF 10 and the right MCF 10 shown in FIG. 9 do not have rotational symmetry (when n = 1). Furthermore, on the left side of FIG. 9, a light source 140C and a camera 100 are arranged on either side of the left MCF 10 as an apparatus configuration for side observation (fine alignment step). The left MCF 10 is fixed as an alignment target. 9 are a group of straight lines (plurality of second radiating line elements) that extend radially from the end face center (the point through which the fiber axis AX passes) to pass through the centers of cores #1 to #4 in the case of the left-side MCF 10. Similarly, in the case of the right-side MCF 10, they are a group of straight lines (plurality of second radiating line elements) that extend radially from the end face center (the point through which the fiber axis AX passes) to pass through the centers of cores #1 to #4. Note that, in the case of the left-side MCF 10, the line L shown in FIG. 9 is a straight line (first line) that extends from the end face center (the point through which the fiber axis AX passes) to pass through the center of a specific core (core #1), and indicates the orientation that indicates the core arrangement in the left-side MCF 10, which is the alignment target. Similarly, in the case of the right MCF 10, it is a straight line (second line) that starts from the center of the end face (the point through which the fiber axis AX passes) and extends to pass through the center of a specific core (core #1), and indicates the orientation that indicates the core arrangement in the right MCF 10 that is the alignment target. Also, L1 to L4 shown on the end face of the left MCF 10 are radiating line elements that extend radially from the center of the end face of the left MCF 10 to pass through the centers of cores #1 to #4, respectively, and the angle between adjacent radiating line elements is all set to θ.9, on the end face of the left MCF 10, the minimum angle is θ, and line L coincides with radiating line element L1 passing through core #1. Similarly, L1 to L4 shown on the end face of the right MCF 10 are radiating line elements that extend radially from the center of the end face of the right MCF 10 to pass through the centers of cores #1 to #4, respectively, and the angle between adjacent radiating line elements is also θ. In the case of the right MCF 10, the minimum angle is also θ, and line L coincides with radiating line element L1 passing through core #1.

[0065] In the case of a four-core arrangement with four-fold rotational symmetry, as described above, cores #1 to #4 and markers 111 are covered by a common cladding on the end faces of the left MCF 10 and the right MCF 10, respectively, and a tolerance range (a rotational range in the fine alignment step) is set in the measurement sub-step of the coarse alignment step. Because the four-core arrangement has four-fold rotational symmetry, it has a rotation period of 90° (=360° / 4). However, in the case of a core arrangement without rotational symmetry, such as the example in FIG. 9, it becomes difficult to set the tolerance range in the coarse alignment step.

[0066] 9 as an example of a core arrangement without rotational symmetry, the tolerance range in the coarse alignment step is such that the angle between the orientation indicated by a line L defined on the end face of the left MCF 10 and extending from the center of the end face to pass through the center of a specific core among cores #1 to #4, and the orientation indicated by a line L defined on the end face of the right MCF 10 and extending from the center of the end face to pass through the center of a specific core associated with that specific core among cores #1 to #4 (core #1 of the left MCF 10) is equal to or less than a predetermined minimum angle excluding zero. Note that the minimum angle excluding zero is an angle θ selected from the angles formed between radiating line element L1 to radiating line element L4 at each of the end faces of the left MCF 10 and the right MCF 10. 9 (four-core arrangement without rotational symmetry), in the fine-alignment step, the rotation angle for rotational alignment is determined within the maximum angle range of -θ° to +θ° centered on a rotation angle of 0° (each of the four orientations indicating the core arrangement of the left MCF 10), as shown in the center and right of Fig. 9. Note that when the left and right MCFs 10 are aligned, the images of their end faces reflected by a mirror and viewed from the same direction are oriented in a direction that is bent back by a straight line perpendicular to the fiber axis AX common to both optical fibers. Therefore, the rotational alignment in the first rotation sub-step in the rough alignment step is performed by rotating the alignment target (the right MCF 10 when the left MCF 10 is fixed as in the example of FIG. 9) so that the deviation angle between the image of the left MCF 10 folded back and the image of the right MCF 10 (the angle between the line L indicating the orientation of the core arrangement in the left MCF 10 and the line L indicating the orientation of the core arrangement in the right MCF 10) falls within the above-mentioned allowable range (the angle range shown in the center and right of FIG. 9). Note that in the example of FIG. 9, no markers are placed on the end faces of the left MCF 10 and the right MCF 10, but if markers are placed, are Even in this case (even if the markers 111 cannot be observed during side observation), matching the core arrangements inevitably makes it possible to match the markers as well.

[0067] Furthermore, FIG. 10 is a diagram illustrating the rotational alignment accuracy in the coarse alignment step and the fine alignment step as a modified example of the alignment operation between two MCFs whose core arrangements have rotational symmetry. In the coarse alignment step in the example of FIG. 10, coarse alignment is performed using the positional relationship between marker 111 and one of cores #1 to #4. The core arrangements of the left MCF 10 and the right MCF 10 shown in FIG. 10 are four-core arrangements consisting of cores #1 to #4 and have four-fold rotational symmetry, similar to the example shown in the lower part of FIG. 8. On the left side of FIG. 10, a light source 140C and a camera 100 are arranged on either side of the left MCF 10 as an apparatus configuration for side observation (fine alignment step). The left MCF 10 is fixed as an alignment target. 10 is a straight line (first line) that starts from the center of the end face (the point through which the fiber axis AX passes) and extends to pass through the center of a specific core in the case of the left MCF 10, and indicates the orientation for indicating the core arrangement in the left MCF 10, which is the alignment target. Similarly, in the case of the right MCF 10, it is a straight line (second line) that starts from the center of the end face (the point through which the fiber axis AX passes) and extends to pass through the center of a specific core, and indicates the orientation for indicating the core arrangement in the right MCF 10, which is the alignment target.

[0068] 10, the left side shows the end face of the left MCF 10 (alignment target) that is roughly aligned so that the marker 111 and core #4 overlap along the side observation direction. Also, the center of FIG. 10 shows the end face of the right MCF 10 (alignment target) that is roughly aligned so that the marker 111 and core #4 overlap along the side observation direction, and the right side shows the end face of the right MCF 10 (alignment target) that is roughly aligned so that the marker 111 and core #1 overlap along the side observation direction. Note that in the example of FIG. 10, cores #1 to #4 and the marker 111 are covered by a common cladding on the end faces of the left MCF 10 and the right MCF 10, and the measurement substep of the coarse alignment step sets the tolerance range for the coarse alignment step (the rotational range for the fine alignment step). The four-core arrangement has four-fold rotational symmetry, resulting in a rotation period of 90° (=360° / 4).

[0069] In the example of Figure 10, the right MCF 10 shown in the center is roughly aligned so that the marker 111 overlaps with core #4 along the side observation direction, just like the left MCF 10 that is the alignment target. Here, the cross-sectional size of the marker 111 is smaller than the cross-sectional size of any of cores #1 to #4. Therefore, the core arrangement on the end face of the left MCF 10 does not necessarily match the core arrangement on the end face of the right MCF 10. Therefore, in the fine alignment step following the rough alignment step, the right MCF 10 (MiddleThe center of the left MCF 10 is then fine-aligned by a rotation angle equivalent to the core diameter (effectively, error correction). This rotation angle (correction range) is within the tolerance range (the range of rotation possible in the fine-alignment step) in the coarse-alignment step, and specifically, is equal to or less than the rotation period (=90°) obtained from the core arrangements of the left MCF 10 and the right MCF 10. Similarly, in the example of FIG. 10 , the right MCF 10 shown on the right is coarsely aligned so that the marker 111 overlaps with core #1 along the side observation direction, unlike the left MCF 10 that is the alignment target. In this case, in the fine-alignment step following the coarse-alignment step, the rotation angle for rotational alignment is determined within the maximum angle range (the rotation period of the core arrangement) of −90° to +90° centered on a rotation angle of 0° (the orientation indicating the core arrangement of the left MCF 10). Even if the marker 111 is roughly aligned so that it overlaps with core #2 or core #3 along the side observation direction, in the fine alignment step, the rotation angle for rotational alignment is determined within the maximum angle range (rotation period of the core array) of -90° or more and +90° or less, centered on a rotation angle of 0°.

[0070] In a typical alignment operation, after high-precision alignment is performed in step ST2 among the above-described steps ST1 to ST4, steps ST3 and ST4 are subsequently performed. Because this requires highly accurate and complex observation and drive systems, it is difficult to achieve sufficient alignment precision using a drive system with a readily available and simple structure. For example, steps ST1 to ST3 described above require a drive system capable of driving the position of mirror 900 with good reproducibility. Furthermore, step ST4 requires a drive system that precisely moves the two optical fibers that have been aligned in step ST2 (alignment in the x-axis direction, alignment in the y-axis direction, and rotation about the fiber axis AX) so as not to change the alignment state of the cores between the two optical fibers. In contrast, in the optical fiber alignment method disclosed herein, first, in the coarse alignment steps of steps ST1 to ST3 described above, alignment is limited to rough alignment by observing the end face, and then, in the fine alignment step of step ST5, precise alignment is performed by observing the side face. This reduces the precision required for controlling the drive system in the rough alignment step (end face observation).

[0071] The optical fiber alignment method disclosed herein not only mitigates the accuracy requirements for drive system control as described above, but also enables accurate alignment, including marker positioning, by combining end-face observation and side-face observation. In a typical MCF, the number of markers is fewer than the number of cores, and the dimensions of their refractive index change regions are often designed to be smaller than each core. Therefore, cases in which markers cannot be detected during side-face observation include, for example, when the marker is in the shadow of a core (Case 1) depending on the relative positions of the MCF and the camera, or when light refracted by the core and light refracted by the marker are measured by the same observation pixel of the camera (Case 2). In such cases, the light refracted by the marker becomes weak and becomes buried in the light refracted by the core, making it undetectable. Normally, when alignment is performed without marker detection, marker mismatch results in splicing cores other than the intended cores, necessitating re-fusion. Figure 11 illustrates specific cases that make marker detection difficult, as described above. That is, in the above case 1, the marker is placed in the circle 111A1 or 111A2 shown by the dashed line with respect to the core 11, and thus the marker is in the shadow of the core 11. On the other hand, in the above case 2, the marker is placed in the circle 111B1, circle 111B2, circle 111C1, or circle 111C2 shown by the dashed line with respect to the core 11, and thus the marker is in the shadow of the camera that measures the refracted light from the core 11. light This shows a state in which refracted light from the marker has reached the arrival area (observation pixel area). However, according to the optical fiber alignment method of the present disclosure, it is possible to avoid this marker misalignment. First, in the coarse alignment step using end face observation, the markers and cores between the two optical fibers are aligned until they roughly match, and then the fine alignment step using side observation is performed from that state. By aligning the corresponding end face elements between the two optical fibers based on the side image acquired after the coarse alignment even if the marker cannot be detected in the fine alignment step, it is possible to necessarily align the marker positions between the two optical fibers.

[0072] For the above reasons, in the optical fiber alignment method disclosed herein, in order to ensure stable alignment accuracy, in the first rotation sub-step of the coarse alignment step, it is possible to rotate the optical fiber to be aligned to a position where a side image is acquired in a state where light due to refraction at the core and light due to refraction at the marker are measured at different pixels of the camera, or where a side image is acquired in a state where one of multiple cores intentionally overlaps with the marker in the second image acquisition sub-step (improving the accuracy of core detection and alignment in the fine alignment step).

[0073] The alignment device and the connection device using the optical fiber alignment method of the present disclosure may combine the coarse alignment steps under both the first and second conditions described above. That is, the above description includes the features noted below. In the above example, the coarse alignment unit and the fine alignment unit in Note 1 below are described as the same alignment mechanisms 130A and 130B, but they may be separate components.

[0074] [Appendix 1] An optical fiber alignment device that selects, as an alignment target, either a first optical fiber having a plurality of first cores extending along a first center axis and arranged at predetermined positions on a first end face perpendicular to the first center axis, or a second optical fiber having a plurality of second cores extending along a second center axis and arranged at positions equivalent to the predetermined positions on a second end face perpendicular to the second center axis, and aligns the first and second optical fibers so as to be optically connected to each other, a coarse alignment unit (alignment mechanisms 130A, 130B) for coarsely aligning the first and second optical fibers based on the results of observation of the end faces of the first and second optical fibers; a fine alignment unit (alignment mechanisms 130A, 130B) that finely aligns the first and second optical fibers based on a result of side observation of the first and second optical fibers so as to increase the optical coupling efficiency between the corresponding cores of the first and second optical fibers that have been roughly aligned by the coarse alignment unit; Equipped with The rough alignment unit is a first image acquisition unit (camera 100) that acquires end face images of the first and second optical fibers, respectively; a measurement unit (control unit 120) that measures dimensions and center positions of each of the plurality of first cores and each of the plurality of second cores from the end face images of the first and second optical fibers, respectively, as information regarding a first core arrangement on the first end face that is composed of the plurality of first cores and a second core arrangement on the second end face that is composed of the plurality of second cores; a first rotating unit (alignment mechanisms 130A, 130B) that rotates the alignment target in a circumferential direction around a central axis of the alignment target based on a measurement result of a measuring unit; Including, The fine alignment unit is a second image acquisition unit (camera 100) that acquires side images of the first and second optical fibers; a second rotating unit (alignment mechanisms 130A, 130B) that confirms an alignment state between the first and second optical fibers that have been roughly aligned from the side image and rotates the alignment target in a circumferential direction around the central axis of the alignment target; Including, the first rotating unit rotates the first and second optical fibers under a first condition in which both the first core arrangement and the second core arrangement have n-fold rotational symmetry, where n-fold rotational symmetry is 2 or more, such that a first angle formed between an orientation indicated by a first line defined on the first end face and extending from the center of the first end face to pass through a center of a specific first core among the plurality of first cores and an orientation indicated by a second line defined on the second end face and extending from the center of the second end face to pass through a center of a specific second core associated with the specific first core among the plurality of second cores is 360° / n or less; the first rotation unit rotates the first and second optical fibers under a second condition in which neither the first core arrangement nor the second core arrangement has rotational symmetry, such that a second angle between an orientation indicated by the first line and an orientation indicated by the second line is equal to or less than a minimum angle, excluding zero, of an angle formed between a plurality of first radiating line elements defined on the first end face and extending radially from the center of the first end face so as to pass through the centers of the plurality of first cores, or an angle formed between a plurality of second radiating line elements defined on the second end face and extending radially from the center of the second end face so as to pass through the centers of the plurality of second cores. Optical fiber alignment device.

[0075] [Appendix 2] A splicing device for optical fibers aligned to be optically connected to each other, comprising: a first optical fiber extending along a first central axis and having a plurality of first cores arranged at predetermined positions on a first end face perpendicular to the first central axis; and a second optical fiber extending along a second central axis and having a plurality of second cores arranged at positions equivalent to the predetermined positions on a second end face perpendicular to the second central axis, selected as an alignment target; or the second optical fiber, a coarse alignment unit (alignment mechanisms 130A, 130B) for coarsely aligning the first and second optical fibers based on the results of observation of the end faces of the first and second optical fibers; a fine alignment unit (alignment mechanisms 130A, 130B) that finely aligns the first and second optical fibers based on a result of side observation of the first and second optical fibers so as to increase the optical coupling efficiency between the corresponding cores of the first and second optical fibers that have been roughly aligned by the coarse alignment unit; a fixing jig for maintaining the aligned state of the first and second optical fibers achieved by the coarse alignment unit and the fine alignment unit; Equipped with The rough alignment unit is a first image acquisition unit (camera 100) that acquires end face images of the first and second optical fibers, respectively; a measurement unit (control unit 120) that measures dimensions and center positions of each of the plurality of first cores and each of the plurality of second cores from the end face images of the first and second optical fibers, respectively, as information regarding a first core arrangement on the first end face that is composed of the plurality of first cores and a second core arrangement on the second end face that is composed of the plurality of second cores; a first rotating unit (alignment mechanisms 130A, 130B) that rotates the alignment target in a circumferential direction around a central axis of the alignment target based on a measurement result of a measuring unit; Including, The fine alignment unit is a second image acquisition unit (camera 100) that acquires side images of the first and second optical fibers; a second rotating unit (alignment mechanisms 130A, 130B) that confirms an alignment state between the first and second optical fibers that have been roughly aligned from the side image and rotates the alignment target in a circumferential direction around the central axis of the alignment target; Including, the first rotating unit rotates the first and second optical fibers under a first condition in which both the first core arrangement and the second core arrangement have n-fold rotational symmetry, where n-fold rotational symmetry is 2 or more, such that a first angle formed between an orientation indicated by a first line defined on the first end face and extending from the center of the first end face to pass through a center of a specific first core among the plurality of first cores and an orientation indicated by a second line defined on the second end face and extending from the center of the second end face to pass through a center of a specific second core associated with the specific first core among the plurality of second cores is 360° / n or less; the first rotation unit rotates the first and second optical fibers under a second condition in which neither the first core arrangement nor the second core arrangement has rotational symmetry, such that a second angle between an orientation indicated by the first line and an orientation indicated by the second line is equal to or less than a minimum angle, excluding zero, of an angle formed between a plurality of first radiating line elements defined on the first end face and extending radially from the center of the first end face so as to pass through the centers of the plurality of first cores, or an angle formed between a plurality of second radiating line elements defined on the second end face and extending radially from the center of the second end face so as to pass through the centers of the plurality of second cores. Connection device. [Explanation of symbols]

[0076] 10...MCF (multi-core optical fiber) 11, 321, #1 to #8…Core 12...Common clad 13, 320...glass fiber 14...Resin coating 322...Clad 30...Bundle fiber 31...Case 31A…Front end face 31B…Rear end face 32...Single-core optical fiber 33…Front opening 34...Storage space 50, 50A...Temporary fixing mechanism 51, 71, 81, 510...Lower members 52, 72, 82, 520...Upper members 55A, 55B...discharge electrode 56...Fusion part 57...Guide groove 51a, 52a, 510a, 520a...Abutment surface 51b, 710...V groove 81a, 82a, 510b, 520b...Groove 53, 530...hinge 60...Ferrule 61...Ferrule end face 62...Sleeve 70...Fiber array 73...Guide member 75…Joint part 76...Adhesive (UV curing resin) 80...Mechanical splice element 100...camera 100A...End face image 100B...Side image 100C…Luminance distribution 110...Memory 111...Marker 120...Control unit 130, 130A, 130B…Alignment mechanism 131...Drive unit 132...gripping member 133...Rotating shaft 140A, 140B, 140C...Light source 550...Discharge unit 800...XYZ Stage 800A...Z-axis stage 800B...Y-axis stage 800C...X-axis stage 810...XYZ stage drive unit 900...Mirror 910...Mirror drive unit 920...Support shaft A…Fixed side B…Alignment side AX...Fiber axis (center axis) L...Line L1 to L4...radiating line elements S1 to S8...arrows.

Claims

1. A method for aligning optical fibers, comprising selecting, as an alignment target, either a first optical fiber having a plurality of first cores extending along a first center axis and arranged at predetermined positions on a first end face perpendicular to the first center axis, or a second optical fiber having a plurality of second cores extending along a second center axis and arranged at positions equivalent to the predetermined positions on a second end face perpendicular to the second center axis, and selecting the second optical fiber as an alignment target, and aligning the first and second optical fibers so as to be optically connected to each other, a coarse alignment step of coarsely aligning the first and second optical fibers based on the results of observing the end faces of the first and second optical fibers; a fine alignment step of finely aligning the first and second optical fibers based on a result of side observation of the first and second optical fibers so as to increase optical coupling efficiency between the associated cores of the first and second optical fibers after the rough alignment; Equipped with The rough alignment step includes: a first image acquisition substep of acquiring end face images of the first and second optical fibers, respectively; a measurement substep of measuring dimensions and center positions of each of the plurality of first cores and each of the plurality of second cores from the end face images of the first and second optical fibers, respectively, as information regarding a first core arrangement on the first end face consisting of the plurality of first cores and a second core arrangement on the second end face consisting of the plurality of second cores; a first rotation sub-step of rotating the alignment target in a circumferential direction around a central axis of the alignment target based on a measurement result of the measurement sub-step; Including, The fine alignment step includes: a second image acquisition substep of acquiring side images of the first and second optical fibers; a second rotation sub-step of checking an alignment state between the first and second optical fibers after the rough alignment from the side image and rotating the alignment target in a circumferential direction around the central axis of the alignment target; Including, In the first rotating substep, the first and second optical fibers are The coarse alignment is performed such that, under a first condition in which both the first core arrangement and the second core arrangement have n-fold rotational symmetry, where n is two or more, a first angle formed between an orientation indicated by a first line defined on the first end face and extending from the center of the first end face to pass through the center of a specific first core among the plurality of first cores, and an orientation indicated by a second line defined on the second end face and extending from the center of the second end face to pass through the center of a specific second core associated with the specific first core among the plurality of second cores, is 360° / n or less; or, under a second condition in which neither the first core arrangement nor the second core arrangement has rotational symmetry, a second angle formed between the orientation indicated by the first line and the orientation indicated by the second line is equal to or less than the smallest angle, excluding zero, formed between a plurality of first radiating line elements defined on the first end face and extending radially from the center of the first end face to pass through the centers of the plurality of first cores, or an angle formed between a plurality of second radiating line elements defined on the second end face and extending radially from the center of the second end face to pass through the centers of the plurality of second cores. A method for aligning optical fiber.

2. and a moving step, prior to the fine alignment step, of moving at least the second optical fiber after coarse alignment along the second central axis so as to reduce a distance between the first end face of the first optical fiber after coarse alignment and the second end face of the second optical fiber after coarse alignment.

2. The method for aligning an optical fiber according to claim 1.

3. In both or either of the coarse alignment step and the fine alignment step, the first core arrangement at the first end face of the first optical fiber is fixed as an alignment target.

2. The method for aligning an optical fiber according to claim 1.

4. in the measurement sub-step, a rotation period defining a rotational symmetry of each of the first core arrangement on the first end face and the second core arrangement on the second end face is measured, and the rotational alignment in the second rotation sub-step is performed by rotating the alignment target by a rotation angle equal to or less than the first angle or the second angle after the first rotation sub-step.

2. The method for aligning an optical fiber according to claim 1.

5. the first optical fiber includes a first marker extending along the first central axis, and the second optical fiber includes a second marker extending along the second central axis; in the first rotation sub-step, the alignment target is rotated to a position where the side image in a state where any one of the plurality of first cores and the first marker overlap and any one of the plurality of second cores and the second marker overlap is acquired in the second image acquisition sub-step; 2. The method for aligning an optical fiber according to claim 1.

6. each of the first and second optical fibers is either a multi-core optical fiber or a bundle fiber; 2. The method for aligning an optical fiber according to claim 1.

7. An alignment device for carrying out the optical fiber alignment method according to any one of claims 1 to 6, a coarse alignment unit that coarsely aligns the first and second optical fibers based on the results of observation of the end faces of the first and second optical fibers; a fine alignment unit that finely aligns the first and second optical fibers based on a result of side observation of the first and second optical fibers so as to increase the optical coupling efficiency between the associated cores of the first and second optical fibers after the rough alignment; Equipped with The rough alignment unit is a first image acquisition unit that acquires end surface images of the first and second optical fibers; a measurement unit that measures dimensions and center positions of each of the plurality of first cores and each of the plurality of second cores from the end face images of the first and second optical fibers, respectively, as information regarding a first core arrangement on the first end face that is composed of the plurality of first cores and a second core arrangement on the second end face that is composed of the plurality of second cores; a first rotating unit that rotates the object to be aligned in a circumferential direction around a central axis of the object to be aligned based on a measurement result of the measuring unit; Including, The fine alignment unit is a second image acquisition unit that acquires side images of the first and second optical fibers; a second rotating unit that confirms an alignment state between the first and second optical fibers after rough alignment from the side image and rotates the alignment target in a circumferential direction around the central axis of the alignment target; Including, The first rotating portion rotates the first and second optical fibers, The rotation is performed such that, under a first condition in which both the first core arrangement and the second core arrangement have n-fold rotational symmetry, where n is two or more, a first angle formed between an orientation indicated by a first line defined on the first end face and extending from the center of the first end face to pass through the center of a specific first core among the plurality of first cores, and an orientation indicated by a second line defined on the second end face and extending from the center of the second end face to pass through the center of a specific second core associated with the specific first core among the plurality of second cores, is 360° / n or less; or, under a second condition in which neither the first core arrangement nor the second core arrangement has rotational symmetry, a second angle formed between the orientation indicated by the first line and the orientation indicated by the second line is equal to or less than the smallest angle, excluding zero, formed between a plurality of first radiating line elements defined on the first end face and extending radially from the center of the first end face to pass through the centers of the plurality of first cores, or an angle formed between a plurality of second radiating line elements defined on the second end face and extending radially from the center of the second end face to pass through the centers of the plurality of second cores. Alignment device.

8. The alignment device according to claim 7, a fusion device that heat-fuse the first and second optical fibers together while butting the first end face of the first optical fiber and the second end face of the second optical fiber that have been aligned by the alignment device.

9. The alignment device according to claim 7, a fixing jig that fixes the first and second optical fibers in a state in which the first end face of the first optical fiber and the second end face of the second optical fiber that have been aligned by the alignment device face each other.

10. The fixing jig is a mechanical splice element. The connection device according to claim 9.

Images