Self-excited Microwave Pulse Generation Based on Self-mode-locking Optoelectronic Oscillator

In this paper, a self-mode-locking optoelectronic oscillator (SML-OEO) is proposed and experimentally analyzed for self-excited microwave pulse generation. The SML-OEO shows the ability to realize phase coherence of the oscillating modes in the OEO cavity, thus generating a self-excited microwave frequency comb (MFC) with the characteristics of a periodic rectangular waveform in the temporal domain. On this basis, introducing broadband electric bandpass filters (EBFs) with different bandwidths in the SML-OEO loop provides flexibility in choosing the frequency band of the resulting MFCs, and the self-excited microwave pulses with tunable duty cycles can be realized by tuning the parameters of the proposed SML-OEO. In addition, by adjusting the gain in the SML-OEO cavity, the gain unevenness of the EBF can also be utilized to realize the frequency hopping output of two mutually coupled MFCs. In the proof-of-principle experiment, the self-excited microwave pulses with different bandwidths of 3-5 GHz and 5-9 GHz are realized, where the temporal waveforms are rectangular waveforms with the period of tens of ns and tunable duty cycle. And it realizes the mutual coupling of two MFCs with the same FSR in 5-9 GHz bandwidth, whose temporal-domain signal is the frequency-hopping outputs of two rectangular microwave pulses.