Optical transmission network

An optical transmission network where a dense wavelength division multiplexing network is used to mutually connected between a plurality of coarse wavelength division multiplexing networks, and

• said dense wavelength division multiplexing network comprises:
• a set of terminal equipment;
• an optical transmission path which connects between said terminal equipment;
• and at least one repeater device having an optical amplifier for collectively amplifying dense wavelength division multiplexing light, and which is arranged on said optical transmission path, said optical transmission network comprising:
• a multiplexing section which is adjacent to one coarse wavelength division multiplexing network of said plurality of coarse wavelength division multiplexing networks, and is arranged on a light output terminal of either one of said terminal equipment and said repeater device, and which combines the optical signal of other than a usage wavelength band of said dense wavelength division multiplexing light, of the optical signals transmitted by said coarse wavelength division multiplexing network, on the optical transmission path of said dense wavelength division multiplexing network, and
• a de-multiplexing section adjacent to said terminal equipment or said repeater device in which said multiplexing section is arranged on the light output terminal, and arranged on a light input terminal of either one of said repeater device and said terminal equipment, and which branches an optical signal from said coarse wavelength division multiplexing network which is combined on said optical transmission path, via said multiplexing section, and applies the branched optical signal to another coarse wavelength division multiplexing network adjacent to the repeater device or the terminal equipment.