Phase noise suppression in a DPSK transmission system by the use of an attenuation-imbalanced NOLM

► Performance improvement of phase-encoded long distance transmissions systems. ► Nonlinear phase noise suppression by phase-preserving amplitude regeneration. ► Passive, phase-preserving NOLM-based amplitude regenerator. ► Comparison of different phase-preserving NOLM-based amplitude regenerators.