Method for aligning multicore fiber, method for manufacturing multicore fiber connector, device for aligning multicore fiber, and multicore fiber fusion splicing machine

A method for aligning multicore fibers each having three or more cores disposed on a circumference centered on a central axis of a clad, each of the cores being disposed the same in each of a plurality of the multicore fibers, the method comprising:

• a parallel disposing step of disposing the plurality of multicore fibers in parallel along a direction substantially perpendicular to a longitudinal direction of one of the plurality of multicore fibers;
• a first imaging step of capturing images of side surfaces of each of the plurality of multicore fibers before and after rotating each of the plurality of multicore fibers disposed in parallel by P° a number of times (N) rounded up such that N=360/P is an integer, wherein
• in each of the multicore fibers, a plurality of corners are defined by adjacent line segments that connect a center of the clad to each of the cores, the plurality of corners including:
• a first corner with a size of P° and two or more consecutive positions in a circumferential direction,
• and at least one second corner with a size different from P°, and
• for each of the N times, each of the plurality of multicore fibers is rotate about the central axis, and
• a first similarity determining step of determining, for each of the multicore fibers, a similarity between an image before a rotation by P° and an image after the rotation by P° for each of the N times the multicore fiber is rotated by P°;
• a first rotation position determining step of determining, for each of a set of second multicore fibers other than one specific first multicore fiber among the plurality of multicore fibers, specific relative rotation positions of each of the set of second multicore fibers with respect to the first multicore fiber in which a cross-correlation between a plurality of columns of similarities of the second multicore fiber and a plurality of columns of similarities of the first multicore fiber becomes highest;
• and
• a first rotation step of rotating, relatively, each of the set of second multicore fibers with respect to the first multicore fiber about the central axis such that the cross-correlation between the second multicore fiber and the first multicore fiber has a relationship of the specific relative rotation positions.

A device for aligning multicore fibers each having three or more cores disposed on a circumference centered on a central axis of a clad, each of the cores being disposed the same in each of a pair of the multicore fibers, the device comprising:

• a rotating portion that rotates each of the pair of multicore fibers about the central axis;
• a camera that captures images of side surfaces of each of the pair of multicore fibers;
• and
• a processor;
• wherein
• in each of the multicore fibers, a plurality of corners are defined by adjacent line segments that connect a center of the clad to each of the cores, the plurality of corners including:
• a first corner with a size of P° and two or more consecutive positions in a circumferential direction, and
• a second corner with a size different from P°,
• the rotating portion rotates each of the pair of multicore fibers by P° a number of times (N) rounded up such that N=360/P is an integer, wherein
• for each of the N times, the rotating portion rotates each of the pair of multicore fibers in a state in which end surfaces of the pair of multicore fibers face each other such that the central axis of each of the pair of multicore fibers coincide with each other,
• the camera captures a first set of images of the side surfaces of each of the pair of multicore fibers before and after each of the pair of multicore fibers is rotated by P°,
• the processor determines, for each of the pair of multicore fibers, a similarity between an image from the first set of images captured before a rotation and an image from the first set of images captured after the rotation for each of the N times the multicore fiber is rotated by P°,
• the processor determines specific relative rotation positions of the pair of multicore fibers in which a cross-correlation between a plurality of columns of similarities of one multicore fiber and a plurality of columns of similarities of an other multicore fiber becomes highest, and
• the rotating portion rotates at least one of the pair of multicore fibers such that one multicore fiber and the other multicore fiber have a relationship of the specific relative rotation positions.