All-optical clock recovery from NRZ data with simple NRZ-to-PRZ converter based on self-phase modulation of semiconductor optical amplifier

The feasibility of all-optical clock recovery (CR) from non-return-to-zero (NRZ) data with a simple NRZ-to-pseudo-RZ (PRZ) converter based on the self-phase modulation (SPM) of a semiconductor optical amplifier (SOA) is empirically presented. The SPM induces a frequency chirp at every leading edge of the NRZ data passing through the SOA. The SPM-induced chirp component is extracted by an optical grating bandpass filter and then transformed to PRZ data with a low polarisation dependency of ~0.7 dB. By transmitting the PRZ data into a mode-locked Er-doped fibre laser, all-optical CR has been achieved at 2.5 Gbit/s