Optical-fiber bundle structure, optical connection structure, and method of manufacturing optical-fiber bundle structure

A method of manufacturing an optical-fiber bundle structure, the method comprising:

• preparing a ferrule including a fiber accommodating portion formed in a hollow shape having a circular cross section, the fiber accommodating portion extending in a first direction and including a first accommodating portion and a second accommodating portion having an inner diameter larger than that of the first accommodating portion, and a plurality of optical fibers accommodated in the fiber accommodating portion, each of the plurality of optical fibers including a first diameter portion, a second diameter portion having a diameter larger than that of the first diameter portion, and a tapered portion connecting the first diameter portion and the second diameter portion to each other by a tapered surface having a tapered shape;
• pushing the plurality of optical fibers into the ferrule such that the first diameter portions of the plurality of optical fibers are inserted into the first accommodating portion;
• and
• pulling the plurality of optical fibers back in a direction opposite to a direction in which the plurality of optical fibers are pushed,
• wherein the second accommodating portion includes a plurality of regions divided by a plurality of imaginary planes perpendicular to the first direction, and
• wherein, in the pulling the plurality of optical fibers back, the plurality of optical fibers are pulled back in the direction opposite to the direction in which the plurality of optical fibers are pushed such that the second diameter portion of each of the plurality of optical fibers is located in the second accommodating portion and such that the tapered portions of the optical fibers adjacent to each other among the plurality of optical fibers are located in different regions among the plurality of regions while a state in which the first diameter portion of each of the plurality of optical fibers is located in the first accommodating portion is maintained.