Optical transmission system including optical repeaters with selectively enabled gain equalizers contained therein and including an add/drop apparatus with a plurality of individually selectable filters

An optical transmission system comprising:

• an optical fiber transmission line;
• a plurality of optical repeaters arranged along the transmission line;
• and
• a plurality of gain equalizers, each gain equalizer being arranged along the transmission line after an integer number of optical repeaters, each gain equalizer equalizing the gain of upstream optical repeaters, wherein each optical repeater comprises
• an optical amplifier which amplifies a light signal travelling along the transmission line and through the optical repeater,
• a gain equalizer, and
• a connection mechanism having a first state and a second state so that
• when the connection mechanism is in the first state, the gain equalizer of the optical repeater equalizes the gain of upstream optical repeaters, and
• when the connection mechanism is in the second state, the gain equalizer of the optical repeater does not equalize the gain of upstream optical repeaters,
• the connection mechanism of each optical repeater being in either the first state or the second state to provide the plurality of gain equalizers arranged along the transmission line.

An optical repeater, comprising:

• an optical amplifier which amplifies a light signal;
• a gain equalizer;
• and
• a connection mechanism having a first state and a second state so that
• when the connection mechanism is in the first state, the gain equalizer of the optical repeater performs an equalization process on the light signal, and
• when the connection mechanism is in the second state, the gain equalizer of the optical repeater does not perform an equalization process on the light signal.

An optical transmission system comprising:

• an optical fiber transmission line;
• a plurality of optical repeaters arranged along the transmission line, each optical repeater including
• a gain equalizer, and
• a connection mechanism having a first state and a second state so that
• when the connection mechanism is in the first state, the gain equalizer of the optical repeater equalizes the gain of upstream optical repeaters, and
• when the connection mechanism is in the second state, the gain equalizer of the optical repeater does not equalize the gain of upstream optical repeaters, the connection mechanism of each optical repeater being in either the first state or the second state to provide a plurality of gain equalizers arranged along the transmission line, each gain equalizer being arranged along the transmission line after an integer number of optical repeaters.

An optical transmission system comprising:

• an optical fiber transmission line;
• a plurality of optical repeaters arranged along the transmission line, each optical repeater including
• an optical amplifier which amplifies a light signal travelling along the transmission line and through the optical repeater,
• a gain equalizer, and
• a connection mechanism having a first state and a second state so that
• when the connection mechanism is in the first state, the gain equalizer of the optical repeater equalizes the gain of upstream optical repeaters, and
• when the connection mechanism is in the second state, the gain equalizer of the optical repeater does not equalize the gain of upstream optical repeaters, the connection mechanism of each optical repeater being in either the first state or the second state to provide a plurality of gain equalizers arranged along the transmission line, each gain equalizer being arranged along the transmission line after an integer number of optical repeaters.