Phase-preserving multilevel amplitude regeneration using a modified nonlinear amplifying loop mirror

Optimization of NALM parameters for phase-preserving amplitude regeneration of a multilevel star8-QAM signal was performed in numerical simulations. A Q-factor improvement of 5 dB for each amplitude level was shown. Possibilities of performance improvement using a power-dependent nonlinear phase shift and a nonlinear amplifier gain were investigated. A Q-factor improvement up to 11 dB for each level was obtained.