To provide a patch panel, which is provided with a series of opening parts, and an adapter collar for installing an optical fiber coupler to the opening part.

A collar 11 is provided with two main body parts, and one of the main body parts is just fitted in an opening part 16, while the other supports a panel front face. A coupler 13, to which the opening part, 16 is inserted, is extended through the main body parts and is provided with a web inside. The web serves as a locking surface for the coupler 13. The collar 11 is installed and fitted in the opening part 16 by using a cantilever arm shifted on the outside from the main body part. A locking member 12 can be inserted between the arm and the main body part, so that the collar 11 is prevented from coming off from the panel accidentally/ carelessly.