To reduce the necessary number of distributed compensation fibers by performing the collective distributed compensation of signal beams obtained by branching a signal light, including plural different wavelengths multiplexed together into N pieces, according to the direction and quantity of the distributed compensation and the performing individually the prescribed distributed compensation to each wavelength included in the signal beams extracted.

Each of wavelengths λ1-λn of the wavelength divided multiplex transmission is branched by an optical coupler(CPL) 30, and a distributed compensation fiber(DCF) 50 connected to the next stage of the CPL 30 performs distributed compensation by a prescribed quantity to each of wavelengths λ1-λn included in the signal beams, which are inputted from the CPL 30. Then the signal beams are sent to an array waveguide lattice-type optically coupled demultiplexer (AWG) 20, which is connected to the subsequent stage. The AWG 20 extracts the prescribed one from among the wavelengths λ1-λn included in the signal beams and outputs the signal light which includes the extracted wavelength to the DCF 50 connected to the next stage to perform the distributed compensation.