Temporal-Talbot-effect-based preprocessing for pattern-effect reduction in all-optical clock recovery using a semiconductor-optical-amplifier-based fiber ring laser

We propose and experimentally demonstrate the temporal-Talbot-effect (TTE)-based preprocessing for the pattern-effect reduction in the all-optical clock recovery using a semiconductor-optical-amplifier (SOA)-based fiber ring laser (SOA-FRL). The TTE-based preprocessing successfully reduced the pattern effects of the recovered clock pulses, so that the 10-GHz clear optical clock pulses were recovered from a 10-Gbit/s return-to-zero on–off keying (RZ-OOK) pseudo-random bit sequence (PRBS) optical signal. “Peak variation” and “Pattern-dependent intensity noise (PDIN)” were proposed and were utilized as parameters to quantitatively evaluate the pattern effects, from which recovered clock pulses suffer, in the temporal domain and the frequency domain, respectively. Peak variation was reduced from 77.2% to 36.2%, and PDIN was improved from −103 dBc/Hz to −110 dBc/Hz with the aid of the TTE-based preprocessing. Furthermore, we examined the tolerance of the proposed technique by intentionally deviating the input signal’s bit-rate by ±190 Mbit/s (±2% of the bit-rate) from the optimum condition for the TTE. As compared with the PDIN value for the pulse train obtained by the direct injection of the non-processed signal into the SOA-FRL, the PDIN of the recovered clock pulses using the preprocessed signal indicated improvements over the entire measurement range of ±190 Mbit/s, which corresponds to the wavelength-dispersion deviation of ±56 ps/nm (±4% of the wavelength-dispersion applied to the input signal) from the optimum value.