An optical repeater comprising: first, second, third and fourth excitation means (102, LD1 to LD4) for generating an excitation light of a single wavelength band; coupling means for combining and splitting the excitation lights output from the first to fourth excitation means and generating first, second, third and fourth excitation lights; first optical amplification means that is excited by the first excitation light and of which an amplification band is a first wavelength band; second optical amplification means that is excited by the second excitation light and of which an amplification band is a second wavelength band different from the first wavelength band, the second optical amplification means being arranged parallel with the first optical amplification means; third optical amplification means that is excited by the third excitation light and of which amplification band is the first wavelength band; and fourth optical amplification means that is excited by the fourth excitation light and of which amplification band is the second wave length band, the fourth optical amplification means being arranged parallel with the third optical amplification means, wherein the coupling means comprises: a first coupler for splitting an excitation light generated by combining an excitation light output from the first excitation means with an excitation light output from the second excitation means; a second coupler for splitting an excitation light generated by combining an excitation light output from the third excitation means with an excitation light output from the fourth excitation means; a third coupler for generating the first excitation light and the second excitation light by splitting an excitation light generated by combining an excitation light from one output of the first coupler with the excitation light from one output of the second coupler; and a fourth coupler for generating the third excitation light and the fourth excitation light by splitting an excitation light generated by combining an excitation light from another output of the first coupler with an excitation light from another output of the second coupler. first, second, third and fourth excitation means (102, LD1 to LD4) for generating an excitation light of a single wavelength band; coupling means for combining and splitting the excitation lights output from the first to fourth excitation means and generating first, second, third and fourth excitation lights; first optical amplification means that is excited by the first excitation light and of which an amplification band is a first wavelength band; second optical amplification means that is excited by the second excitation light and of which an amplification band is a second wavelength band different from the first wavelength band, the second optical amplification means being arranged parallel with the first optical amplification means; third optical amplification means that is excited by the third excitation light and of which amplification band is the first wavelength band; and fourth optical amplification means that is excited by the fourth excitation light and of which amplification band is the second wave length band, the fourth optical amplification means being arranged parallel with the third optical amplification means, wherein the coupling means comprises: a first coupler for splitting an excitation light generated by combining an excitation light output from the first excitation means with an excitation light output from the second excitation means; a second coupler for splitting an excitation light generated by combining an excitation light output from the third excitation means with an excitation light output from the fourth excitation means; a third coupler for generating the first excitation light and the second excitation light by splitting an excitation light generated by combining an excitation light from one output of the first coupler with the excitation light from one output of the second coupler; and a fourth coupler for generating the third excitation light and the fourth excitation light by splitting an excitation light generated by combining an excitation light from another output of the first coupler with an excitation light from another output of the second coupler. a first coupler for splitting an excitation light generated by combining an excitation light output from the first excitation means with an excitation light output from the second excitation means; a second coupler for splitting an excitation light generated by combining an excitation light output from the third excitation means with an excitation light output from the fourth excitation means; a third coupler for generating the first excitation light and the second excitation light by splitting an excitation light generated by combining an excitation light from one output of the first coupler with the excitation light from one output of the second coupler; and a fourth coupler for generating the third excitation light and the fourth excitation light by splitting an excitation light generated by combining an excitation light from another output of the first coupler with an excitation light from another output of the second coupler.