Study of mutual injection-pulling between two mutually-coupled single-loop optoelectronic oscillators

Abstract This paper analyzes the injection-locking and injection-pulling behavior of two mutually coupled single-loop free-running OEOs with nearby frequencies. We derive the phase dynamics equations of two mutually-coupled OEOs considering weak RF signal injection and the phase stability of the mutually injection-locked system is studied. Also, we present compact closed form expressions for the oscillation frequencies of two mutually injection-pulled OEOs in terms of the injection-ratios and the phase shifts of the mutually injected RF signals. The beat frequency of the mutually injection-pulled system is calculated in terms of the injection ratios. The influence of mutual injection-pulling on the RF output power spectrums of two OEOs are studied. It is shown that the RF output power spectrums of two mutually injection-pulled OEOs are highly asymmetric and strongly depends on the injection ratios. The experimental results corroborating the theoretical findings are given.