Frequency domain analysis of optoelectronic oscillators utilizing optical and RF resonators with arbitrary transfer functions

Abstract

Optoelectronic oscillators (OEOs) have attracted much attention for producing ultra-low phase-noise microwave/millimeter-wave oscillations. Traditional delay-based OEOs usually suffer from strong spurious peaks in their phase noise power spectral densities and possible mode-hopping phenomena. Some methods have been proposed in the literature such as using multi-loop architectures or injection locking to other OEOs or radio frequency (RF) oscillators to reduce these spurious peaks. In other approaches, optical filters/resonators other than optical fibers have been proposed to reduce or suppress these peaks and prevent the mode-hopping phenomenon, such as whispering gallery mode resonators (WGMRs), fiber Bragg gratings, and other forms of microwave photonic filters. Usually, approximate single-purpose approaches have been presented to analyze OEOs utilizing such resonators. Here a general framework for analyzing the performance of OEOs implementing RF and optical filters/resonators with arbitrary linear transfer functions is presented. Consequently, it can consider, for example, the most general dispersion models of the fibers as well as any OEO architecture using a combination of different optical resonators. It can also consider the noise transfer between any sidebands of the RF or optical signals and any kind of amplitude noise to phase noise transfers and vice versa. The non-idealities of the electro-optic modulators such as the chirping and finite extinction ratios can also be taken into account. The validity of the new approach is verified by comparing its results with those previously published in the literature. In particular, the case of a WGMR plus delay line OEO is considered for comparisons.