Optical amplifier, and optical transmission system including the optical amplifier

An optical amplifier that is provided in a transmitting station of an optical transmission system to amplify a signal light and perform ALC (Automatic Level Control) of output power by means of a variable optical attenuator, wherein;

• the optical amplifier updates a target attenuation value for the variable optical attenuator in accordance with a current target attenuation value set to the variable optical attenuator for ALC and a difference between its own target output value and measured output value;
• the target attenuation value is updated at intervals of time exceeding output convergence time by ALC;
• and
• the difference between own target output value and measured output value of the optical amplifier is transmitted to a downstream optical amplifier as an expected control volume.

An optical amplifier that is provided in a receiving station of an optical transmission system to amplify a signal light and perform ALC (Automatic Level Control) of output power by means of a variable optical attenuator, wherein:

• the optical amplifier receives a difference between a target output value and measured output value of an upstream optical amplifier as an expected control volume;
• the optical amplifier updates a target attenuation value for the variable optical attenuator in accordance with a current target attenuation value set to the variable optical attenuator for ALC, a difference between its own target output value and measured output value, and the expected control volume;
• and
• the target attenuation value is updated at intervals of time exceeding output convergence time by ALC.

An optical transmission system that is provided with an optical amplifier in a transmitting station, a repeater station, and a receiving station, the optical transmission system amplifies an signal light and performs ALC (Automatic Level Control) of output power by means of a variable optical attenuator, wherein:

• the optical amplifier of the transmitting station
• updates a target attenuation value for the variable optical attenuator in accordance with a current target attenuation value set to the variable optical attenuator for ALC and a difference between its own target output value and measured output value, while updating the target attenuation value at intervals of time exceeding output convergence time by ALC, and
• transmits the difference between its own target output value and measured output value to a downstream optical amplifier as an expected control volume;
• the optical amplifier of the repeater station
• receives the difference between the target output value and measured output value of an upstream optical amplifier as the expected control volume,
• updates the target attenuation value for the variable optical attenuator in accordance with the current target attenuation value set to the variable optical attenuator for ALC, the difference between its own target output value and measured output value, and the expected control volume, while updating the target attenuation value at intervals of time exceeding output convergence time by ALC, and
• adopts the difference between its own target output value and measured output value as the expected control volume of the downstream optical amplifier;
• and
• the optical amplifier of the receiving station
• receives the difference between the target output value and measured output value of the upstream optical amplifier as the expected control volume, and
• updates the target attenuation value for the variable optical attenuator in accordance with the current target attenuation value set to the variable optical attenuator for ALC, the difference between its own target output value and measured output value, and the expected control volume, while updating the target attenuation value at intervals of time exceeding output convergence time by ALC.