Optical fiber bundle and optical switch

An optical fiber bundle comprising:

• four or more multi-core fibers;
• and
• a ferrule bundling and holding the four or more multi-core fibers,
• wherein in a cross section where, among the four or more multi-core fibers, a first multi-core fiber, a second multi-core fiber, a third multi-core fiber, and a fourth multi-core fiber are cut along a plane perpendicular to a direction in which each multi-core fiber extends, lines connecting center positions of each of the multi-core fibers are arranged to form a square shape,
• wherein, in the cross section, the first multi-core fiber and the second multi-core fiber are aligned in this order along a first direction,
• wherein the first multi-core fiber and the fourth multi-core fiber are aligned in this order along a second direction perpendicular to the first direction, and
• wherein the fourth multi-core fiber and the third multi-core fiber are aligned in this order along the first direction,
• wherein, in the cross section, arrangement of cores of the first multi-core fiber and arrangement of cores of the second multi-core fiber are the same as each other, and
• wherein arrangement of cores of the third multi-core fiber and arrangement of cores of the fourth multi-core fiber are the same as each other, and
• wherein the arrangement of the cores of the first multi-core fiber when the first multi-core fiber is rotated 180° in a circumferential direction of the first multi-core fiber is the same as the arrangement of the cores of the fourth multi-core fiber.