PURPOSE: To protect optical fibers from external force and miniaturize the U-link by connecting the other ends of the two optical fibers which are mounted with optical connectors at one end to themselves, and providing the surplus length containing parts which contain the extra length portions of the optical fibers after the connection to a U-form tubular case having openings at both ends.

CONSTITUTION: An optical fiber mounted with an optical connector 24 at one end is inserted from one end part 21a of a U-form tubular case body 21 composed of synthetic resin or the like and an optical fiber 26b is taken out from the opening of a connected portion containing part 22. Similarly, the other optical fiber mounted with an optical connector 25 at one end is inserted from the end part 21b and is wound one turn in a surplus length portion containing part 23, after which the other end 27b is taken out from the opening of the connected portion containing part 22. The optical fibers 26b and 27b are connected to themselves by thermal fusion bonding or the like and are put in the V groove 221 of the containing part 22, thence a cover body 222 is mounted. After the surplus length portions are wound, a cover body 232 is mounted to a box part 231. Thereby, the optical fibers may be protected from external force and the U-link may be miniaturized.