A Simulation Study on Clock Recovery of a Minimum Bandwidth Signal

Jitter and BER performance of non-linear clock recovery circuits are evaluated for a minimum bandwidth signal. To investigate the effect of bandwidth in optical transmission, BER performance of MB810 and NRZ signals with various types of timing recovery circuits are compared for a 40 Gbit/s optical link. Among the systems adopting non-linear timing recovery circuits, the MB810 signal employing an absolute value rectifier shows superior performance. We show that timing recovery without a non-linear circuit is also possible, and compare its BER performance with that of the others. Jitter performance of the fourth-law rectifier and that of the absolute-value rectifier is made for a minimum bandwidth signal. The mathematical derivation of the timing wave is also carried out for the clock recovery of the fourth-law rectifier. The result shows that the derived timing wave is expressed as a function of a pulse shape entering the timing path and the band-pass filter tuned to the pulse repetition rate.