Methods and systems for gain control in pulsed optical amplifiers
View Patent ↗A method of operating an amplifier system includes providing a pump signal at a pump wavelength. The pump signal is a function of a pump power. The method also includes providing an input signal at a signal wavelength and coupling the pump signal and the input signal to an optical amplifier. The optical amplifier includes a gain medium characterized by a gain value at the signal wavelength. The method further includes amplifying the input signal to provide an output signal, detecting a feedback signal related to the gain value, and modifying the pump power based on the detected feedback signal.
1. A method of operating an amplifier system, the method comprising:
providing a pump signal at a pump wavelength, wherein the pump signal is a function of a pump power;
providing an input signal comprising a first plurality of pulses;
coupling the pump signal and the input signal to an optical amplifier, wherein the optical amplifier comprises a gain medium characterized by a gain value at a signal wavelength;
amplifying the input signal to provide an output signal;
detecting a feedback signal related to the gain value; and
modifying the pump power based on the detected feedback signal, wherein the pump signal comprises a second plurality of pulses, each of the second plurality of pulses being characterized by a decreasing signal amplitude between at least a portion of a duration between consecutive pulses of the first plurality of pulses.
2. The method of claim 1 wherein providing a pump signal comprises producing an output from a semiconductor laser.
3. The method of claim 2 wherein the semiconductor laser comprises a multi-mode semiconductor laser.
4. The method of claim 1 wherein the optical amplifier comprises a core pumped fiber amplifier.
5. The method of claim 1 wherein the feedback signal comprises residual pump light.
6. The method of claim 1 wherein the feedback signal comprises ASE.
7. An amplifier system comprising:
a pump source adapted to receive a drive signal and output a pump signal;
an optical amplifier adapted to receive an input signal comprising a first plurality of pulses, the optical amplifier having an input coupled to the pump source and an output;
a wavelength demultiplexer coupled to the output of the optical amplifier;
a detector optically coupled to the wavelength demultiplexer; and
a feedback system coupled to the detector and adapted to modify the pump signal for the pump source, wherein the pump signal comprises a second plurality of pulses, each of the second plurality of pulses being characterized by a decreasing signal amplitude between at least a portion of a duration between consecutive pulses of the first plurality of pulses.
8. The amplifier system of claim 7 wherein the pump source comprises a semiconductor laser operating at a pump wavelength.
9. The amplifier system of claim 7 wherein the drive signal comprises a baseline signal and an adjustment signal.
10. The amplifier system of claim 7 wherein the optical amplifier comprises a fiber amplifier.
11. The amplifier system of claim 10 wherein the fiber amplifier comprises an ytterbium-doped fiber.
12. The amplifier system of claim 7 wherein the wavelength demultiplexer is adapted to separate light at an input signal wavelength and the pump wavelength.
13. The amplifier system of claim 7 wherein the wavelength demultiplexer is adapted to separate light at an input signal wavelength and ASE co-propagating in the optical amplifier.
14. An amplifier system comprising:
a pump source adapted to receive a drive signal and output a pump signal;
an optical amplifier adapted to receive an input signal comprising a first plurality of pulses, the optical amplifier having an input coupled to the pump source and an output;
a signal separator coupled to the input of the optical amplifier;
a detector optically coupled to the signal separator; and
a feedback system coupled to the detector and adapted to modify the pump signal for the pump source, wherein the pump signal comprises a second plurality of pulses, each of the second plurality of pulses being characterized by a decreasing signal amplitude between at least a portion of a duration between consecutive pulses of the first plurality of pulses.
15. The amplifier system of claim 14 wherein the pump source comprises a semiconductor laser operating at a pump wavelength.
16. The amplifier system of claim 14 wherein the drive signal comprises a baseline signal and an adjustment signal.
17. The amplifier system of claim 14 wherein the optical amplifier comprises a fiber amplifier.
18. The amplifier system of claim 14 wherein the sign separator is adapted to separate light at an input signal wavelength and ASE counter-propagating in the optical amplifier.
19. The amplifier system of claim 14 wherein the signal separator comprises a wavelength demultiplexer.
20. The amplifier system of claim 14 wherein the signal separator comprises an optical circulator.
21. The method of claim 1 wherein the input signal has a constant power for each of the first plurality of pulses such that the pump power has a constant pattern for each of the second plurality of pulses.
22. The amplifier system of claim 14 wherein the input signal has a constant power for each of the first plurality of pulses such that the pump power has a constant pattern for each of the second plurality of pulses.
23. The amplifier system of claim 14 wherein the feedback system is characterized by a bandwidth, the bandwidth being larger than a maximum pulsing rate of the input signal.