To efficiently gather information required for maintaining an optical transmission system from respective optical repeaters in the optical transmission system of a wavelength multiplex system.

The repeater 210-1 of this optical repeater 200 analyzes the wavelength, transmission direction and transmission line identification number, etc., of optical signals λ1-λq' by using an optical multiplexer/demultiplexer 211, spectroscopes 212 and 213, O/E converters 214-1 to 214-p and 215-1 to 215-q and decoders 216-1 to 216-p and 217-1 to 217-q. A control part 220 sends out analyzed results and the information relating to a light amplifier 218 to an optical terminal station equipment as supervisory and control signals.