Optical amplifier

An optical amplifier having a plurality of rare earth doped optical fibers in a multi-stage, comprising:

• a replaceable optical part between said rare earth doped optical fibers;
• one or more optical variable attenuator means;
• detecting means for detecting a temperature of the rare earth doped optical fibers themselves or an environmental temperature;
• and
• attenuation amount control means for changing an optical attenuation amount of said optical variable attenuator means on the basis of the temperature of said rare earth doped optical fibers or the environmental temperature detected by the detecting means.

An optical amplifier comprising:

• first and second rare earth doped optical fibers provided in first and second amplifying stages of the optical amplifier, respectively;
• at least one optical variable attenuator provided between the first and second rare earth doped optical fibers;
• and
• an attenuation amount controller configured to control the optical variable attenuator to adjust an optical attenuation amount of said optical variable attenuator on the basis of a value which represents temperature of at least one of the first and second rare earth doped optical fibers to compensate fluctuation of gain property of the optical amplifier.

An optical amplifier comprising:

• first and second rare earth doped optical fibers provided in first and second amplifying stages of the optical amplifier, respectively;
• a replaceable optical part provided between the first and second rare earth doped optical fibers;
• at least one optical variable attenuator provided between the first and second rare earth doped optical fibers;
• and
• an attenuation amount controller configured to control the optical variable attenuator to adjust an optical attenuation amount of said optical variable attenuator on the basis of a value which represents temperature of at least one of the first and second rare earth doped optical fibers to compensate fluctuation of gain property of the optical amplifier.

An optical amplifier comprising:

• first and second rare earth doped optical fibers provided in first and second amplifying stages of the optical amplifier, respectively;
• at least one externally controllable optical variable attenuator provided between the first and second rare earth doped optical fibers;
• an attenuation amount controller configured to control the optical variable attenuator to adjust an optical attenuation amount of said optical variable attenuator on the basis of intensity of input optical signal to the optical amplifier and intensity of output optical signal from the optical amplifier;
• and
• an optical attenuation amount table of the optical variable attenuator associated with the intensity of the input optical signal to the optical amplifier and the intensity of the output optical signal from the optical amplifier, and the optical attenuation amount is changed in accordance with said table.