All-optical multilevel regeneration in nonlinear optical loop mirror

An all-optical multilevel amplitude regenerator is optimized based on the transmission response of a nonlinear optical loop mirror (NOLM). Three regenerative regions defined by the power-transfer-function (PTF) slope of less than 1 are obtained, and noise suppression is shown for a PAM4 signal. Using amplitude dithering we were able to experimentally characterize the transfer function slope and confirm the theoretical predictions.