A comparative analysis of doubled-pass erbium doped fiber amplifiers considering different signal-return schemes

In this work, an experimental comparative analysis of doubled-pass erbium doped fiber amplifiers with different signal-return approaches is presented. The amplifier performance was investigated in terms of gain and noise figure as the signal under amplification was reflected back towards the erbium doped fiber by a mirror, filter, or circulator arrangement. Also, a semiconductor laser under single-facet optical injection locking was tried as an equivalent reflexive element. In particular, the regenerative characteristics provided by the injection locking process were able to provide considerably high gain and low noise figure levels for the amplifier, especially for considerably low input signal power.