Rayleigh-Scattering-Induced RIN and Amplitude-to-Phase Conversion as a Source of Length-Dependent Phase Noise in OEOs

Optoelectronic oscillators (OEOs) are hybrid RF-photonic oscillators that promise to be environmentally robust frequency sources with very low phase noise. Recent experiments have shown that the excess flicker phase noise in these systems grows with the length of the optical fiber loop. In this paper, we detail a mechanism for this length-dependent flicker noise in which Rayleigh-scattering-induced amplitude noise in the optical fiber combines with amplitude-to-phase noise conversion in the nonlinear electronic components. We derive an analytic model of the loop noise that includes these effects and verify this model by comparing it to numerical calculations and experimental results.