US Patent 10222559 Ferrule and method of manufacturing optical-fiber-attached ferrule

A ferrule holds end portions of optical fibers and includes: a plurality of optical fiber holes arranged in a predetermined direction, wherein the optical fibers are inserted into the plurality of optical fiber holes; and an adhesive-filling section that is filled with an adhesive and internally includes an opening surface of the plurality of optical fiber holes and an opposed surface opposed to the opening surface. The adhesive-filling section includes an upper side opening and a lower side opening, the upper side opening opens on a top surface that is a surface on a side from which the adhesive is filled, and the lower side opening opens on a lower surface that is a surface on a side opposite to the top surface.