All-optical gain control of remote optically pumped amplifier

An optical system for gain stabilization of a multichannel optical amplifier with remote forward pump (Forward Remote Optically Pumped Amplifier, F-ROPA) was experimentally investigated. To implement optical stabilization, a spectrally selective, within one channel, optical feedback is created. With unsaturated gain exceeding the losses in the feedback circuit, there occurs the generation, which ensures the stabilization of the gain at the level that exactly compensates the losses in the feedback circuit. It is established that the ROPA gain in the optical stabilization mode changes by no more than 0.17 dB when the pump laser power is varied within the range from 21.5 dBm to 29 dBm, and not more than 0.43 dB with the input signal power modulated from 2 dBm to 10 dBm, and not more than 0.24 dB when the ambient temperature changes within the range from -40 °С to +50 °С. It is shown that the optical gain stabilization does not lead to the distortion of the gain spectrum, and the gain can be controlled with high accuracy by changing the losses in the feedback cavity. The results obtained are promising for using F-ROPA optical gain stabilization in optical communication lines with long spans.