Band-expanding method for optical amplifiers and optical transmission apparatus

An optical signal transmission apparatus, comprising:

• optical amplifying means provided with first and second transmission bands;
• multiplexing means for supplying a pump laser to said optical amplifying means;
• first and second pump laser sources;
• and
• controlling means for controlling the output of each of said first and second pump laser sources;
• wherein the output of each of said first and second pump laser sources is controlled using a predetermined transition during a transition add-on period when said second pump laser source is changed from a non-pumping state to a pumping state, to substantially maintain an approximation of a gain characteristic of said first transmission band in real-time throughout the transition add-on period of said second transmission band.

An optical signal transmission apparatus, comprising:

• an optical amplifier provided with first and second transmission bands;
• a multiplexer to multiplex a pump laser to said optical amplifying means;
• first and second pump laser sources;
• and
• a controller to control the output of each of said first and second pump laser sources;
• wherein the output of each of said first and second pump laser sources is controlled using a predetermined transition during a transition add-on period when said second pump laser source is changed from a non-pumping state to a pumping state, to substantially maintain an approximation of a gain characteristic of said first transmission band in real-time throughout the transition add-on period of said second transmission band.