Low noise-figure gain-clamped L-band double-pass erbium-doped fiber ring lasing amplifier with an interleaver

A new design of all-optical gain-clamped L-band double-pass (DP) erbium-doped fiber amplifier (EDFA) has been proposed and demonstrated, in which the input port and the odd-channel output port of an interleaver are connected with the DP configuration EDF through a circulator to form lasing ring cavity for clamping gain, and the even port is utilized to export the amplified signals. The low noise figure can be achieved because the lasing power copropagates with the signals, and it is exported separately from the amplified signal thanks to interleaver. Meanwhile, the fiber Bragg grating incorporated in DP configuration suppresses the backward amplified spontaneous emission generation, and therefore improves efficiently the gain and lowers the noise figure. In such a way, the clamped gain of 16.3 dB with a variation below 0.2 dB and noise figure below 5 dB are achieved in the new L-band all-optical gain-clamped EDFA.