Optical amplifier

An optical amplifier comprising:

• a first optical amplifying unit which includes a first optical amplifying medium which inputs a first pumping light and a first signal light simultaneously and amplifies the first signal light by using energy of the first pumping light, a first light source which generates the first pumping light, and a first pumping light controller which controls power of the first pumping light;
• wherein said first pumping light controller provides in advance information on a first relation between power of an first output light of said first optical amplifying medium and power of the first pumping light on condition that a gain tilt arising through said first optical amplifying medium among individual signals of different wavelengths which form the first signal light based on wavelength division multiplex is virtually constant or virtually minimum, takes out a value of the power of the first pumping light from the first relation in response to a value of the power of the first output light resulting from amplification by said optical amplifying medium, and controls said first light source so that the generated first pumping light has the taken out value of the power of the first pumping light;
• a second optical amplifying unit which includes a second optical amplifying medium which inputs a second pumping light and a second signal light simultaneously and amplifies the second signal light by using energy of the second pumping light, a second light source which generates the second pumping light, and a second pumping light controller which controls power of the second pumping light;
• wherein said second pumping light controller provides in advance information on a second relation between power of an second output light of said second optical amplifying medium and power of the second pumping light on condition that a gain tilt arising through said second optical amplifying medium among individual signals of different wavelengths which form the second signal light based on wavelength division multiplex is virtually constant or virtually minimum, takes out a value of the power of the second pumping light from the second relation in response to a predetermined value of the power of the second output light, and controls said second light source so that the generated second pumping light has the taken out value of the power of the second pumping light;
• and
• optical attenuation means with variable degree of attenuation which is disposed between said first and second optical amplifying units.

An optical amplifier comprising:

• a first optical amplifying unit which includes a first optical amplifying medium which inputs a first pumping light and a first signal light simultaneously and amplifies the first signal light, a first light source which generates the first pumping light, and a first pumping light controller which controls power of the first pumping light;
• wherein said first pumping light controller provides in advance information on a first relation between power of an first output light of said first optical amplifying medium and power of the first pumping light on condition that a gain tilt arising through said first optical amplifying medium among individual signals of different wavelengths which form the first signal light based on wavelength division multiplex is virtually constant or virtually minimum, takes out a value of the power of the first pumping light from the first relation in response to a value of the power of the first output light resulting from amplification by said optical amplifying medium, and controls said first light source so that the generated first pumping light has the taken-out value of the power of the first pumping light;
• a second optical amplifying unit which includes optical amplifying mediums of n in number (where n is a natural number) connected tandem which input a second input light and pumping lights simultaneously and amplify the second input light, light sources of n in number which generate the pumping lights to supply them to said n optical amplifying mediums respectively, and a second pumping light controller which controls the pumping lights supplied to said n optical amplifying mediums to have power values which are expressed in terms of predetermined constants α1, α2, . . . , αn and a reference pumping power Pp to be a α1Pp, α2Pp, . . . , αnPp in the order of alignment;
• wherein said pumping light controller provides in advance with information on second relation between power of second output light of the last-stage optical amplifying medium of said optical amplifying unit and the reference pumping power Pp on condition that a gain tilt arising through said n optical amplifying mediums among individual signals of different wavelengths which form the second signal light based on wavelength division multiplex is virtually constant or virtually minimum, takes out a power of the reference pumping power Pp from the second relation in response to a predetermined value of the power of the second output light, and controls said n light sources so that the generated n pumping lights have the taken-out value of the reference pumping power Pp multiplied by the predetermined constants respectively;
• and
• optical attenuation means having a variable degree of attenuation which is disposed between said first and second optical amplifying units.