Comparison of nonlinear fiber-based approaches for all-optical clock recovery at 40Â Gb/s

We compare two different nonlinear fiber-based approaches for all-optical clock recovery (AOCR) at 40 Gb/s. Both involve mode-locking a semiconductor fiber laser (SFL); one is based on the use of a nonlinear optical loop mirror (NOLM) while the second exploits nonlinear polarization rotation (NPR). We assess the impact of input signal characteristics on the RMS timing jitter and power fluctuation of the recovered clock. We also investigate the possibility for wavelength tunable operation. The results show that both approaches are capable of recovering a good quality clock signal over a large range of operating parameters. While the NPR-based approach has slightly better performance in terms of reduced power fluctuation and wavelength tunability, it is more sensitive to polarization. We also discuss the approaches for polarization-insensitive operation.