All-optical clock recovery for 40 Gbaud NRZ-QPSK signals using amplified feedback DFB laser diode

An all-optical clock recovery scheme based on monolithic amplified feedback DFB laser (AFL) diode is proposed for nonreturn-to-zero (NRZ) quadrature phase shift keying (QPSK) format signals. By using a preprocessing stage, clock recovery (CR) is successfully demonstrated for 40-Gbaud NRZ-QPSK signals based on this scheme. The dependence of the timing jitter of the recovered clock on the optical power of the injected signal is investigated. A minimum timing jitter of 362.8 fs (integrated within a frequency range from 10 Hz to 10 MHz) is obtained.