Coherent Dual-Tone Microwave Signal Generation by OEO Based on Intra-Cavity Mutual Injection Locking

An approach to generating coherent dual-tone microwave signals via an optoelectronic oscillator (OEO) is proposed and demonstrated based on intra-cavity frequency mixing mutual injection locking. In the OEO cavity, two potential oscillation modes are selected by using an electrical dualpassband filter, and they are mixed with each other to generate a differential frequency signal. The self-generated differential frequency signal is then injected back into the OEO cavity to lock the phase relationship between the two oscillation modes via a mutual injection locking process, which breaks the mode competition effect. As a result, a coherent dual-tone microwave signal can be generated. In the experiment, a coherent dual-tone microwave signal with frequencies of 10 GHz and 10.1 GHz is generated, where the side-mode suppression ratios (SMSRs) and the phase noise reach 70 dB and -134.8 dBc/Hz@10 kHz, respectively. This scheme provides a pathway to generate coherent dual-tone microwave signals from an OEO without the requirement of external injection locking.