Light amplification device, light transmission system, and light amplification method

A light transmission system comprising

• a light relay device including a light amplification device, and
• a network management device, wherein
• the light amplification device includes
• a wavelength demultiplexing unit configured to receive wavelength division multiplexed signal light including a plurality of pieces of signal light different in wavelength, demultiplex the wavelength division multiplexed signal light into a plurality of wavelength bands, and output a plurality of pieces of demultiplexed multiplex signal light;
• a plurality of light amplification media configured to amplify each of the plurality of pieces of demultiplexed multiplex signal light, and output each of a plurality of pieces of amplified demultiplexed multiplex signal light;
• a wavelength multiplexing unit configured to multiplex and output the amplified demultiplexed multiplex signal light;
• a plurality of excitation energy supply units configured to supply excitation energy to each of the plurality of light amplification media;
• and
• a control unit,
• the control unit includes a wavelength multiplexing/demultiplexing control unit configured to control the wavelength demultiplexing unit and the wavelength multiplexing unit in such a way that a starting wavelength serving as a starting point of the wavelength band and a wavelength number being a number of pieces of the signal light included in the wavelength band become an optimum starting wavelength and an optimum wavelength number that are the starting wavelength and the wavelength number when a sum of power consumption of the plurality of excitation energy supply units is minimized, and
• the network management device manages the plurality of pieces of signal light constituting the wavelength division multiplexed signal light in such a way that the pieces of signal light with a same modulation multi-level number are included in a same wavelength band.

A light amplification method comprising:

• receiving wavelength division multiplexed signal light including a plurality of pieces of signal light different in wavelength, demultiplexing the wavelength division multiplexed signal light into a plurality of wavelength bands, and generating a plurality of pieces of demultiplexed multiplex signal light;
• amplifying each of the plurality of pieces of demultiplexed multiplex signal light by a plurality of light amplification media, and generating each of a plurality of amplified demultiplexed multiplex signal light;
• multiplexing the amplified demultiplexed multiplex signal light;
• supplying excitation energy to each of the plurality of light amplification media;
• and
• demultiplexing the wavelength division multiplexed signal light into the plurality of wavelength bands in such a way that a starting wavelength serving as a starting point of the wavelength band and a wavelength number being a number of pieces of the signal light included in the wavelength band become an optimum starting wavelength and an optimum wavelength number that are the starting wavelength and the wavelength number when a sum of power consumption during generation of the excitation energy is minimized.