Patent ID: 7254338

Claim:
A multi-wavelength light source unit for use in an optical communication system, comprising: a demultiplexer having an input port configured to receive a multiplexed light signal and a plurality of output ports configured to demultiplex the multiplexed light signal into a plurality of lights having different wavelengths and configured to output respective demultiplexed light with a predetermined wavelength; a multiplexer having a plurality of input ports configured to receive the demultiplexed lights and an output port configured to multiplex the demultiplexed lights into the multiplexed light signal and configured to output the multiplexed light signal, the plurality of input ports of the multiplexer being respectively port-to-port connectable to each one of the plurality of output ports of the demultiplexer; a plurality of semiconductor optical amplifiers each disposed between the output ports of the demultiplexer and the input ports of the multiplexer, the semiconductor optical amplifiers being configured to amplify the demultiplexed lights output form the demultiplexer; a plurality of beam splitters each disposed between the semiconductor optical amplifiers and the input ports of the multiplexer, the beam splitters being configured to split the amplified demultiplexed lights into two parts and being configured to provide the respective input ports of the multiplexer with a split part of the lights, while to transmit the other split part of the lights out of the beam splitters; an optical band-pass filter disposed between the input port of the demultiplexer and the output port of the multiplexer, the optical band pass filter being configured to pass to the demultiplexer the light signal only in a predetermined wavelength band of the multiplexed light signal from the multiplexer; and an optical isolator being disposed between the optical band-pass filter and the multiplexer, the optical isolator being configured to block the light signal component reflected to the multiplexer from the optical band-pass filter.