There are provided an optical connector having one or more protruding portions protruding and one or more recessed portions depressed relative to a reference plane corresponding to a reference face of a coupling of a standard optical connector in a connecting end face of a coupling into which a housing receiving a ferrule is inserted, a connector adapter to which the optical connector can be inserted and coupled, an optical fiber line using the optical connector and the connector adapter to connect optical fibers, and an optical communication system.