Optical amplifiers and upgrade modules

An upgrade module for a fiber-optic communications network optical amplifier, wherein the amplifier has a first gain stage and at least one second gain stage that are used to amplify light, wherein the amplifier has an input and an output, wherein a span of transmission fiber is connected to the input when the amplifier is installed in a fiber-optic communications network, and wherein operation of the amplifier is controlled using a control unit that is electrically connected to the gain stages, comprising:

• a controller that communicates with the control unit;
• a Raman pump that produces pump light for optically pumping the span of transmission fiber;
• and
• a pump coupler that directs the pump light from the Raman pump to the span of transmission fiber when the upgrade module is used to upgrade the amplifier, wherein the pump coupler bypasses the first gain stage and directs data signals that are received from the transmission fiber span to the input of the at least one second gain stage when the amplifier is upgraded using the upgrade module.

An upgraded amplifier that has been formed by upgrading a given amplifier using an upgrade module that provides Raman amplification capabilities, comprising:

• a fiber input that is connected to a transmission fiber span when the amplifier is used to amplify optical signals in a fiber-optic communications network;
• a fiber output;
• at least first and second rare-earth-doped fiber gain stages;
• a control unit that controls the first and second rare-earth-doped fiber gain stages;
• a removable midstage module, wherein the removable midstage module is optically coupled between the first and second rare-earth-doped fiber gain stages;
• a Raman pump that produces pump light for the transmission fiber span;
• a controller that controls the Raman pump and that is electrically connected to the control unit;
• and
• a wavelength-division multiplexing coupler that directs pump light from the Raman pump to the transmission fiber span and that directs light from the transmission fiber span into the first gain stage, wherein the first and second gain stages, midstage module, and control unit were part of the given amplifier and wherein the Raman pump and controller were part of the upgrade module prior to upgrading the given amplifier with the upgrade module to form the upgraded amplifier.

An upgrade module for a fiber-optic communications network optical amplifier that has at least first and second gain stages that are used to amplify light, wherein the amplifier has an input and an output, wherein a span of transmission fiber is connected to the input when the amplifier is installed in a fiber-optic communications link, and wherein operation of the amplifier is controlled using a control unit that is electrically connected to the gain stages, comprising:

• a controller that communicates with the control unit when the optical amplifier is upgraded with the upgrade module;
• a Raman pump that produces pump light for optically pumping the span of transmission fiber;
• and
• a pump coupler that directs the pump light from the Raman pump to the span of transmission fiber when the upgrade module is connected to the amplifier;
• and
• a dynamic filter that is optically coupled between the first and second gain stages when the optical amplifier is upgraded with the upgrade module, wherein the Raman pump and dynamic filter are controlled using the controller.

An upgrade module for a fiber-optic communications network optical amplifier that has at least first and second gain stages that are used to amplify light and a dynamic spectral filter between the first and second gain stages, wherein the amplifier has an input and an output, wherein a span of transmission fiber is connected to the input when the amplifier is installed in a fiber-optic communications link, and wherein the first and second gain stages and dynamic filter in the amplifier are controlled using a control unit that is electrically connected to the gain stages, comprising:

• a controller that communicates with the control unit when the optical amplifier is upgraded with the upgrade module;
• a Raman pump that produces pump light for optically pumping the span of transmission fiber;
• and
• a pump coupler that directs the pump light from the Raman pump to the span of transmission fiber when the upgrade module is used to upgrade the amplifier, wherein the dynamic filter is adjusted when the amplifier is upgraded with the upgrade module to accommodate an increase in input power that results from Raman pumping the span of transmission fiber with the Raman pump.

An upgraded amplifier that has been formed by upgrading a given amplifier using an upgrade module, wherein the given amplifier has Raman amplification capabilities and amplifies light in a first wavelength band and wherein the upgrade module has Raman amplification capabilities and amplifies light in a second wavelength band that is different than the first wavelength band, the upgraded amplifier comprising:

• a fiber input connected to a transmission fiber span when the upgraded amplifier is used to amplify optical signals in a fiber-optic communications network;
• a fiber output;
• at least one first gain stage that provides optical gain in the first wavelength band;
• at least one second gain stage that provides optical gain in the second wavelength band;
• a first Raman pump that provides Raman pump light to the transmission fiber span to generate Raman gain in the first wavelength band;
• a second Raman pump that provides Raman pump light to the transmission fiber span to generate Raman gain in the second wavelength band;
• a control unit that is used in controlling the first gain stage and the first Raman pump;
• and
• a controller that is used in controlling the second gain stage and the second Raman pump, wherein the controller and control unit communicate when the given amplifier has been upgraded using the upgrade module, wherein the first gain stage, first Raman pump, and control unit were part of the given amplifier and wherein the second gain stage, second Raman pump, and controller were part of the upgrade module prior to upgrading the given amplifier with the upgrade module to form the upgraded amplifier.

An upgrade module for a fiber-optic communications network optical amplifier that has at least first and second rare-earth-doped fiber gain stages that are used to amplify light in a first wavelength band, wherein the amplifier has an input and an output, wherein a span of transmission fiber is connected to the input when the amplifier is installed in a fiber-optic communications link, and wherein operation of the amplifier is controlled using a control unit that is electrically connected to the gain stages, comprising:

• a controller that communicates with the control unit when the optical amplifier is upgraded with the upgrade module;
• a Raman pump that produces pump light for optically pumping the span of transmission fiber;
• and
• a pump coupler that directs the pump light from the Raman pump to the span of transmission fiber when the upgrade module is connected to the amplifier;
• and
• at least one Raman-pumped gain stage that is controlled by the controller, wherein the Raman pump and gain stage operate in a second wavelength band that is different than the first wavelength band.