Patent ID: 7400443

Claim:
An optical amplifying apparatus, comprising: an optical amplifying device operating in one of a gain threshold mode and a constant gain mode, wherein the gain threshold mode is configured to deliver one of constant output power and constant pump power to suppress relatively small in magnitude input power variations, and wherein the constant gain mode is configured to track input power due to relatively large in magnitude input power variations; a controlling device configured for operating said optical amplifying device in one of the gain threshold mode and the constant gain mode responsive to input power and output power to the optical amplifying device, said controlling device further configured for switching the optical amplifying device from operating in the gain threshold mode to operating in the constant gain mode when an absolute value of a gain error exceeds a gain threshold, wherein the gain error is a difference between a target gain and a gain of the optical amplifying device, wherein the gain comprises the difference between input and output power measured by a measuring device, said controlling device further configured for switching the optical amplifying device back and forth between the gain threshold mode and the constant gain mode utilizing a control loop, and said controlling device further configured for switching the optical amplifying device from the constant gain mode to the gain threshold mode when no transient events occur during a lockout period; and said measuring device configured to measure power levels on a plurality of points within said optical amplifying device including at least an input power (P IN ) and an output power (P OUT ) of the optical amplifying device, said measuring device also configured to communicate with said controlling device to provide said input power and output power for the control loop.