Abstract: The FIFO device includes an MCF, a first lens having a first optical axis parallel to a center axis of the MCF, a group of second lenses including the same number of second lenses having a second optical axis parallel to the first optical axis as cores of the MCF, and a group of single-core optical fibers including the same number of single-core optical fibers as the second lenses. An end face of each single-core optical fiber is obliquely polished so as to incline in a predetermined inclination direction with respect to a plane orthogonal to the center axis by a predetermined polishing angle. Oblique polishing directions of surrounding single-core optical fibers are set so that the corresponding second lenses are positioned closer to the first optical axis or to the first lens compared to their positions at the time when the surrounding single-core optical fibers are not obliquely polished.

Abstract: An optical filter device includes: a first multi-core optical fiber including a plurality of first cores; a first lens; an optical filter which is rotated by a rotation angle about a rotation axis; a second lens; and an optical fiber including cores which the emission light beams from the second lens enter. When directions directed from a reference axis toward one side and another side with respect to the reference axis along an orthogonal axis orthogonal to an optical axis and the reference axis are defined as first and second orthogonal directions, respectively, a circumferential orientation of the first multi-core optical fiber is set so that a separation distance is minimized. The separation distance is a sum of distances from the reference axis to first cores that are most separated away from the reference axis in the first and second orthogonal directions, respectively.

Abstract: An optical component including an interference filter which is less likely to generate back reflected light, where the filter is accommodated in a hollow cylindrical housing and is tilted with respect to the optical axis. The housing has front and back openings. First and second collimator lenses respectively face the front and back openings. The housing includes a filter housing section and first and second cylindrical optical path sections extending in the front-back direction respectively from the front and back openings to the filter housing section while maintaining the shape of each opening. The diameter of the opening of the first optical path section is smaller than the apparent diameter of the first collimator lens. When light is input from the front along the optical axis, light of prescribed wavelengths is output to the back. Light reflected by the filter travels toward the inside of the first optical path section.

Abstract: An optical component including an interference filter which is less likely to generate back reflected light, where the filter is accommodated in a hollow cylindrical housing and is tilted with respect to the optical axis. The housing has front and back openings. First and second collimator lenses respectively face the front and back openings. The housing includes a filter housing section and first and second cylindrical optical path sections extending in the front-back direction respectively from the front and back openings to the filter housing section while maintaining the shape of each opening. The diameter of the opening of the first optical path section is smaller than the apparent diameter of the first collimator lens. When light is input from the front along the optical axis, light of prescribed wavelengths is output to the back. Light reflected by the filter travels toward the inside of the first optical path section.