Sub-threshold optoelectronic oscillator for selective amplification of RF signals

We present an experimental and numerical investigation of a sub-threshold optoelectronic oscillator (OEO) subject to injection from an external RF signal. A time-delayed numerical model is introduced and the agreement with experiments is discussed. The sub-threshold OEO exhibits frequency selective RF amplification. The OEO sensitivity is investigated for different subthreshold internal gain values. As the internal gain of the system increases and the oscillation threshold is approached, the OEO exhibits larger amplification of an injected RF signal. When the injected RF signal is on resonance, the OEO exhibits a maximum RF gain of approximately 28 dB near 0.5% below threshold. Furthermore, the injected RF signal frequency is scanned, and the amplified response is measured. Finally, we highlight the role of the intrinsic time-delay within the OEO’s temporal response to a pulsed, injected RF signal.