Fan-in/Fan-out device

A Fan-in/Fan-out device, comprising:

• a multi-core optical fiber which has a pillar shape, and includes a plurality of first cores extending along an axial direction, and a common cladding surrounding the plurality of first cores;
• a first lens having a first optical axis parallel to a center axis of the multi-core optical fiber and being arranged so as to correspond to the multi-core optical fiber, and from which light beams which have been emitted from the respective first cores and whose principal rays are parallel to each other exit so that the principal rays incline in predetermined directions, respectively;
• a group of second lenses including a plurality of spatially separated second lenses each having a second optical axis parallel to the first optical axis, the group of second lenses being configured to converge each of the light beams exiting from the first lens, which have been emitted from the respective first cores with each of the corresponding second lenses;
• and
• a group of single-core optical fibers including the same number of single-core optical fibers as the number of the second lenses, each single-core optical fiber having a pillar shape, and including one second core extending along the center axis and a cladding surrounding the second core, end faces of the respective single-core optical fibers being arranged at positions at which the light beams exiting from the corresponding second lenses, which have been emitted from the respective first cores converge on the respective second cores,
• wherein, the end face of each of the single-core optical fibers is obliquely polished so as to incline in a first inclination direction with respect to a plane orthogonal to the center axis thereof by a first polishing angle,
• wherein, oblique polishing directions of surrounding single-core optical fibers of the single-core optical fibers, where center axes of the surrounding single-core optical fibers are positioned at positions separated away from the first optical axis, are set so that the corresponding second lenses are positioned closer to the first optical axis or closer to the first lens compared to non-obliquely polished positions of the corresponding second lenses at the time when the surrounding single-core optical fibers are not obliquely polished, and
• wherein, the end face of freely-selected one of the surrounding single-core optical fibers not parallel to at least one end surface of the surrounding single-core optical fiber except the freely-selected surrounding single-core optical fiber.