Flexible microwave pulses regulation in self-mode-locking optoelectronic oscillator

The mode-locking characteristic and microwave pulses regulation based on a self-mode-locking optoelectronic oscillator (SML-OEO) are analyzed and experimentally demonstrated. The oscillating modes in the SML-OEO cavity can be phase-coherent by means of the inherent oscillatory characterization via the opto-electronic loop. A self-excited microwave frequency comb (MFC) with the characteristics of a periodic rectangular pulse is generated. The phenomenon of nonlinear dynamical bifurcation in the SML-OEO, which leads to an amplification of the time scale in the system, where a single-cycle oscillatory pulse with a period of τ evolves into an oscillatory pulse with a period of 2τ. On this basis, by injecting a microwave signal with a period of 2τ/N (N is an integer) into the OEO loop, the gain in the OEO cavity is regulated so that the SML-OEO forms a new mode-locked state. The temporal domain characteristic forms a periodic rectangular pulse with a period of 2τ/N. The experiment results show that the microwave pulse of SML-OEO can be effectively regulated from 30 ns to 3.75 ns as N is set from 3 to 8.