Controller which controls a variable optical attenuator to control the power level of a wavelength-multiplexed optical signal when the number of channels are varied

An optical communication system for transmitting, through an optical transmission line, a first light signal having a variable number of channels associated with different wavelengths, comprising:

• a terminal station which sends, through the optical transmission line, a second light signal indicating initiation of changing the number of channels in the first light signal;
• and
• an optical repeater which receives the first and second light signals, the optical repeater including
• an optical amplifier which amplifies the first light signal, and
• a controller which receives the second light signal and, upon receipt of the second light signal, controls the optical amplifier to amplify the first light signal with an approximately constant gain during a process of changing the number of channels and produces the third light signal indicating that the process is ready to be completed, the optical repeater transmitting the first and third light signals.

An optical communication system comprising:

• a terminal station which sends first and second light signals through an optical transmission line, the first light signal having a variable number of channels associated with different wavelengths, and the second light signal indicating completion of changing the number of channels in the first light signal;
• and
• an optical repeater which receives the first and second light signals, the optical repeater including
• an optical amplifier which amplifies the first light signal, and
• a controller which receives the second light signal and, upon receipt of the second light signal, completes a first mode in which the optical amplifier is controlled to amplify the first light signal with an approximately constant gain during a process of changing the number of channels.

An optical communication system comprising:

• a terminal station which sends first and second light signals through an optical transmission line, the first light signal having a variable number of channels associated with different wavelengths, and the second light signal indicating initiation of changing the number of channels in the first light signal;
• and
• an optical repeater which receives the first and second light signals, the optical repeater including
• a controller which receives the second light signal and, upon receipt of the second light signal, starts preparation of changing the number of channels, and
• an optical amplifier which is controlled by the controller to amplify the first light signal with an approximately constant gain during the preparation of changing the number of channels.

An optical communication system for transmitting, through an optical transmission line, a first light signal having a variable number of channels associated with different wavelengths, comprising:

• a terminal station which sends, through the optical transmission line, a second light signal indicating initiation of changing the number of channels in the first light signal;
• and
• an optical repeater which receives the first and second light signals, the optical repeater including
• a controller which receives the second light signal and, upon receipt of the second light signal, starts preparation of changing the number of channels and produces a third light signal indicating that the preparation is ready to be completed, and
• an optical amplifier which is controlled by the controller to amplify the first light signal with an approximately constant gain during the preparation of changing the number of channels, the optical repeater transmitting the first and third light signals.

An optical communication system comprising:

• a terminal station which sends first and second light signals through an optical transmission line, the first light signal having a variable number of channels associated with different wavelengths, and the second light signal indicating completion of changing the number of channels in the first light signal;
• and
• an optical repeater which receives the first and second light signals, the optical repeater including
• a controller which receives the second light signals and, upon receipt of the second light signal, finishes preparation of changing the number of channels, and
• an optical amplifier which is controlled by the controller to amplify the first light signal with an approximately constant gain during the preparation of changing the number of channels.

A method comprising:

• transmitting a first light signal through an optical transmission line, the first light signal having a variable number of channels associated with different wavelengths;
• transmitting a second light signal to an optical amplifier, the second light signal indicating initiation of changing the number of channels in the first light signal;
• starting preparation of changing the number of channels upon receipt of the second light signal by the optical amplifier;
• and
• controlling the optical amplifier to amplify the first light signal with an approximately constant gain during the preparation of changing the number of channels.

A method comprising:

• transmitting a first light signal through an optical transmission line, the first light signal having a variable number of channels associated with different wavelengths;
• amplifying the transmitted first light signal with an optical amplifier;
• changing the number of channels in the first light signal;
• transmitting a second light signal to the optical amplifier, the second light signal indicating completion of changing the number of channels in the first light signal;
• upon receipt of the second signal by the optical amplifier, controlling the optical amplifier to maintain a power level of the amplified first light signal at an approximately constant level in accordance with the number of channels in the first light signal.

An optical communication network, comprising:

• an optical transmission line;
• terminal stations, each connected to the optical transmission line, for transmitting and receiving, through the optical transmission line, a first light signal having a variable number of channels associated with different wavelengths and a second light signal indicating initiation of changing the number of channels in the first light signal;
• an optical repeater which receives the first and second light signals through the optical transmission line, the optical repeater including
• a controller which receives the second light signal and, upon receipt of the second light signal, starts preparation of changing the number of channels, and
• an optical amplifier which is controlled by the controller to amplify the first light signal with an approximately constant gain during the preparation of changing the number of channels.

An optical communication network, comprising:

• an optical transmission line;
• terminal stations, each connected to the optical transmission line, for transmitting and receiving, through an optical transmission line, a first light signal having a variable number of channels associated with different wavelengths and a second light signal indicating completion of changing the number of channels;
• and
• an optical repeater receiving the first and second light signals, the optical repeater including
• a controller which receives the second light signal and, upon receipt of the second light signal, finishes preparation of changing the number of channels, and
• an optical amplifier which is controlled by the controller to amplify the first light signal with an approximately constant gain during the preparation of changing the number of channels.