Optical amplifier output control based on change in detected input power

1. An optical amplifier comprising:

a light amplifying medium for receiving an input optical signal and outputting an output amplified signal;

a first measuring block for measuring a change in power of the input signal wherein measuring the change in input power includes calculating a difference between two detected input power levels separated by a specified time interval;

a pump laser for supplying pump light to the light amplifying medium; and

an electronic control for controlling the power of the pump light in response to the measured change in power of input signal to provide an output amplified signal having a substantially constant power following a transient period for one or more changes in the power of the input signal.

2. The optical amplifier of claim 1 , further comprising:

a second measuring block for measuring the level of power of the output signal, where the electronic control additionally controls the power of the pump light in response to the measured level of power of the output signal to provide the output amplified signal having the substantially constant power.

3. The optical amplifier of claim 1 , where the light amplifying medium is one or more erbium doped fibers.

4. The amplifier of claim 1 , where the input signal includes one or more channels, each channel having one or more distinct wavelengths.

5. The optical amplifier of claim 1 , where the first measuring block includes a first photo-detector, where the first photo-detector receives a tapped portion of the input optical signal.

6. A method of controlling the output power of an optical amplifier comprising:

measuring a change in input power where measuring the change in input power includes calculating a difference between two detected input power levels separated by a specified time interval; and

in response to the measured change in input power, controlling the optical amplifier such that a power of an output amplified signal is substantially constant for one or more changes in the input power.

7. The method of claim 6 , where controlling the optical amplifier includes controlling a power of a pump light supplied by a pump laser such that the power of the output amplified signal is returned to substantially a power prior to the change in input power.

8. The method of claim 7 , where controlling the optical amplifier includes decreasing the power of the pump light when the measured change in input power is an increase in input power and larger than a specified transient threshold.

9. The method of claim 7 , where controlling the optical amplifier includes increasing the power of the pump light when the measured change in input power is negative and an absolute value of the change is larger than a specified transient threshold.

10. The method of claim 6 , where controlling the optical amplifier further includes providing a short transient time for returning the output amplified signal to substantially a same power as before the change in input power.

11. The method of claim 6 , further comprising:

measuring a power of the output amplified signal; and

using both the power of the output amplified signal with the change in the input signal to control the power of pump light.

12. The method of claim 11 , where controlling the optical amplifier includes decreasing the power of the pump light when a measured power of the output amplified signal is larger than a calculated sum of a target output power and a specified tolerance value.

13. The method of claim 11 , where controlling the optical amplifier includes increasing the power of the pump light when a measured power of the output amplified signal is less than a calculated difference between a target output power and a specified tolerance value.

14. The method of claim 6 , further comprising:

using the pump laser to provide an amplifying light to a light amplifying medium, the light amplifying medium including one or more erbium doped fibers.

15. The method of claim 6 , where the input power is a total power of an input signal that includes one or more channels where each channel includes one or more distinct wavelengths.

16. A method comprising:

monitoring an input signal received at an optical amplifier;

monitoring a power of an output amplified optical signal;

detecting a change in a power of the input signal; and

using the detected change in the power of the input signal and monitored power of the output amplified signal to control the optical amplifier such that a power of an output amplified optical signal remains substantially constant following a transient period including modifying a power of a pump light based on a measured power of the output amplified signal relative to a calculated sum of a target output power and a specified tolerance value.

17. The method of claim 16 , where controlling the optical amplifier includes decreasing the power of a pump light when the measured change in input power is positive and larger than a specified transient threshold.

18. The method of claim 16 , where controlling the optical amplifier includes increasing the power of a pump light when the measured change in input power is negative and an absolute value of the change is larger than a specified transient threshold.

19. The method of claim 16 , where controlling the optical amplifier includes decreasing a power of a pump light when a measured power of the output amplified signal is larger than a calculated sum of a target output power and a specified tolerance value.

20. The method of claim 16 , where controlling the optical amplifier includes increasing a power of a pump light when a measured power of the output amplified signal is less than a calculated difference between a target output power and a specified tolerance value.

21. The method of claim 6 , where the change in input power is due to adding or dropping channels of an optical signal input to the optical amplifier.

22. The method of claim 6 , further comprising measuring changes in input power after subsequent specified time intervals according to a currently detected input power level after each time interval and a detected input power level before that time interval.