WDM system

A system comprising:

• a first optical transmission path for transmitting a first wavelength-multiplexed light;
• a second optical transmission path for transmitting a second wavelength-multiplexed light;
• and
• an optical transmission unit, including:
• a wavelength demultiplexing unit for wavelength-demultiplexing the first wavelength-multiplexed light which is transmitted through the first optical transmission path, into a plurality of light signals;
• and
• a wavelength multiplexing unit for transmitting to the second optical transmission path the second wavelength-multiplexed light which is produced by multiplexing each of the plurality of light signals which are obtained by demultiplexing;
• a supervisory control unit for causing supervisory control signal information transmitted to the second optical transmission path with the second wavelength-multiplexed light to carry information of the supervisory control signal transmitted through the first optical transmission path with the first wavelength-multiplexed light, wherein
• the supervisory control unit calculates an amount of transmitting ASE light from the wavelength-demultiplexing unit to the wavelength-multiplexing unit based on a characteristic of a filter of the wavelength-demultiplexing unit from an optical SN ratio of each wavelength in output of a reception amplifier at a preceding stage of the wavelength demultiplexing unit, a bandwidth of a filter in a wavelength-multiplexing unit and a wavelength demultiplexing unit, and output power of a transmission amplifier of the wavelength-multiplexing unit, and reflects the amount of transmitting ASE light to the supervisory control information transmitted to the second optical path.

A optical transmission method, comprising:

• wavelength-demultiplexing a first wavelength-multiplexed light which is transmitted through a first optical transmission path, into a plurality of light signals;
• transmitting to a second optical transmission path a second wavelength-multiplexed light which is produced by multiplexing each of the plurality of light signals which are obtained by demultiplexing;
• causing supervisory control signal information transmitted to the second optical transmission path with the second wavelength-multiplexed light to carry information of the supervisory control signal transmitted through the first optical transmission path with the first wavelength-multiplexed light;
• calculating an amount of transmitting ASE light on the first optical transmission path based on a characteristic of a filter used in the wavelength-demultiplexing from an optical SN ratio of each wavelength in output of a reception amplifier at a preceding stage of the wavelength demultiplexing, a bandwidth of a filter in the transmitting and the wavelength demultiplexing, and output power of a transmission amplifier of the transmitting, and reflects the amount of transmitting ASE light to the supervisory control signal information transmitted to the second optical transmission path.