Phase-preserving NALM regenerator with lower input power by optimizing the nonreciprocal phase shifter

摘要

We propose a new nonlinear amplifying loop mirror (NALM)-based phase-preserving amplitude regenerator (socalled NP-NALM) by introducing a nonreciprocal phase shifter to further improve the regeneration performance. The theoretical model of the NP-NALM structure and the amplitude regeneration and phase-preserving conditions are presented. It is shown that the optimal working point power reduces with the increase of the nonreciprocal phase shift in the available range and the first working point power can be as low as 115 mW by optimizing the nonreciprocal phase shifter. We also investigate the cascaded NP-NALM transmission system for quadrature phase-shift keying signals with amplified spontaneous emission noise and the output error vector magnitude (EVM) can reduce to 23% from the EVM limit of 30%, corresponding to bit error ratio of 10(-3) for the cascaded system without regeneration. (C) 2021 Optical Society of America