Loop-length dependent sources of phase noise in optoelectronic oscillators

Optoelectronic oscillators are a promising source of spectrally pure, easily tunable microwave signals. These oscillators use a low-loss fiber optic delay line as a very high Q resonant cavity. However, length-dependent sources of phase noise prevent the full Q of the resonant cavity from being realized. Here we show evidence that this length-dependent phase noise is in part dependent upon the optical power and laser noise. This dependence is consistent with the conversion of laser noise to phase noise via the Kerr effect.