Light from a first excitation light source is incident on one facet of a first optical fiber. A core is doped with a first rare earth substance. A resonant section induces light resonance in the core to generate resonant light, thereby providing selected light at the other facet of the first optical fiber. An optical multi/demultiplexer reflects the light of the selected wavelength in a direction different from that of the first optical fiber. A second excitation light source supplies light to the resonant section of the first optical fiber via the optical multi/demultiplexer and the other facet of the first optical fiber. A second optical fiber guides the light of the selected wavelength from the optical multi/demultiplexer to an exterior.