| 摘要 |
An optical amplifier comprises: at least first and second amplifier stages, each stage comprising a doped fiber and a pump source for providing pump light to the fiber. The input and output power of the amplifier is measured to enable automatic gain control. The input and output power is processed in order to derive target pump source levels for achieving a substantially constant gain, and the temporal response of the gain control loop is varied in dependence on the target pump source levels. The response time of the gain control loop is thus matched to the open loop gain of the amplifier, taking into account the combination and settings of the amplifier stages.
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