Abstract:We have experimentally observed a new operating state of a regular pulse train in a narrow-band optoelectronic oscillator system, where the DC bias of the Mach-Zehnder modulator is set at the maximum value of the transmission transfer function instead of the usual quadrature point. The observed quasi-steady-state pulse train is distinctly periodic, with a period of 10.5 ?s and a center frequency of 10 GHz, and resembles a mode-locked optoelectronic oscillator in its waveform. The formation of regular pulses here may arise from the dynamic balance of non-linearity and narrowband filter effects, with the transient characteristics of the pulses arising mainly from instabilities between the gain and cavity loss. Our results are of great importance for deepening the understanding of the non-linear dynamical processes in OEO systems.