Optical amplifiers with stable output power under low input power conditions

An optical amplifier that amplifies optical signals on a fiber-optic communications link, comprising:

• a first coil of rare-earth-doped fiber;
• a second coil of rare-earth-doped fiber;
• a 980 nm laser diode pump that optically pumps the first coil at a first pump power to provide optical gain for the optical signals;
• a 1480 nm laser diode pump that optically pumps the second coil at a second pump power to produce optical gain for the optical signals;
• and
• a control unit and at least one optical monitor that measure the optical signals in the amplifier, wherein the control unit controls the 980 nm and 1480 nm laser diode pumps based on the measured optical signals to suppress gain transients, and wherein at low measured optical signal powers the control unit uses only the 1480 nm laser diode pump to pump the second coil and controls the laser diode pumps to ensure that the first pump power is greater than the second pump power and to ensure that the first pump power is above a threshold level that minimizes mode partition noise effects in the 980 nm pump.

An optical amplifier that amplifies optical signals on a fiber-optic communications link, comprising:

• a first coil of rare-earth-doped fiber;
• a second coil of rare-earth-doped fiber;
• a first laser diode pump that produces pump light at a first pump power;
• a second laser diode pump that produces pump light at a second pump power that is provided to the second coil to optically pump the second coil;
• an optical splitter that is optically coupled to the first laser diode pump and that splits the pump light from the first laser diode pump into first and second portions, wherein the first portion of the first pump light is provided to the first coil to optically pump the first coil and wherein the second portion of the first pump light is provided to the second coil to optically pump the second coil;
• and
• a control unit and at least one optical monitor that measure the optical signals in the amplifier, wherein the control unit controls the first and second laser diode pumps based on the measured optical signals to suppress gain transients, wherein at some measured optical signal powers the control unit uses only the first pump to pump the first and second coils to minimize laser diode mode partition noise effects in the optical amplifier.

An optical amplifier that amplifies optical signals on a fiber-optic communications link, comprising:

• a first coil of rare-earth-doped fiber;
• a second coil of rare-earth-doped fiber;
• a first laser diode pump that produces pump light at a first pump power;
• a second laser diode pump that produces pump light at a second pump power that is provided to the second coil to optically pump the second coil;
• an optical splitter that is optically coupled to the first laser diode pump and that splits the pump light from the first laser diode pump into first and second portions, wherein the first portion of the first pump light is provided to the first coil to optically pump the first coil and wherein the second portion of the first pump light is provided to the second coil to optically pump the second coil;
• and
• a control unit and at least one optical monitor that measure the optical signals in the amplifier, wherein the control unit controls the first and second laser diode pumps based on the measured optical signals to suppress gain transients, wherein at low measured optical signal powers the control unit uses only the first pump to pump the first and second coils to minimize laser diode mode partition noise effects in the optical amplifier.

An optical amplifier that amplifies optical signals on a fiber-optic communications link, comprising:

• a first coil of rare-earth-doped fiber;
• a second coil of rare-earth-doped fiber;
• a first laser diode pump that produces pump light at a first pump power, wherein the pump light at the first pump power is provided to the first coil to optically pump the first coil, and wherein remnant pump light is left over after pumping the first coil with the pump light at the first pump power;
• a second laser diode pump that produces pump light at a second pump power that is provided to the second coil to optically pump the second coil;
• an optical fiber that provides the remnant pump light from the first coil to the second coil to optically pump the second coil;
• and
• a control unit and at least one optical monitor that measure the optical signals in the amplifier, wherein the control unit controls the first and second laser diode pumps based on the measured optical signals to suppress gain transients, wherein at some measured optical signal powers the control unit uses only the first pump to pump the first and second coils to minimize laser diode mode partition noise effects in the optical amplifier.

An optical amplifier that amplifies optical signals in a fiber-optic communications link, comprising:

• a first coil of rare-earth-doped fiber;
• a second coil of rare-earth-doped fiber;
• a first laser diode pump that produces pump light at a first pump power;
• a second laser diode pump that produces pump light at a second pump power;
• a coupler that receives the pump light from the first and second laser diode pumps and distributes the pump light to the first and second coils of rare-earth-doped fiber;
• and
• a control unit and at least one optical monitor that measure the optical signals in the amplifier, wherein the control unit controls the first and second laser diode pumps based on the measured optical signals to suppress gain transients, and wherein at low measured optical signal powers the control unit turns off the second pump while using the first pump to pump the coil to minimize the effects of laser diode mode partition noise on the optical amplifier.