An autonomous magnetic sleeve for a riser is provided. The first and second shoes are moved into engagement with a drum by a force applied to an actuator by a cable assembly. The plurality of semiconductor optical amplifiers operable to perform an optical switching operation on at least one of the optical signal wavelengths. When the ceramic bar is depressed against the lapping surface, a specific portion of the ceramic bar is deformed or strongly deformed through the elastic member by these actuators to thereby make it possible to perform the lapping in response to each element.