The radar's principle of operation relies on a contrast between an emitted microwave and the corresponding echo which is scaterred/reflected back by a given target. The resolution of a radar is therefore tightly related to the spectral purity of the emitted microwave, and the generation of ultra-pure radio-frequencies is still a important challenge in microwave technology.
Few years ago, a new device referred to as "optoelectronic oscillator" (OEO) was proposed to generate such high spectral purity microwaves, and it mainly consists on a semiconductor laser whose output light is subjected to nonlinear modulation and delay. The aim of this talk will be to present a model which can accurately describe the dynamical behavior of OEOs. In particular, the model predicts that as the gain of the oscillator is increased, the ultra-pure single-mode solution becomes unstable beyond a precise critical value. Experimental measurements confirm this scenario with an excellent precision, thus validating the model. An extension to the stochastic and multimode dynamics of the OEO will also be proposed. At last, the consequences of these nonlinear phenomena on the performances of OEO-based systems will be discussed.