Frequency stabilization of the coupled opto-electronic oscillator

The coupled opto-electronic oscillator (COEO) is a system that couples an optical oscillator with the microwave oscillator. The COEO can be modeled as a photonic microwave oscillators using a mode-locked laser as the high-Q resonator, and has been shown to be capable of generating ultra-low phase noise microwave signals [N. Yu et al, Opt Lett. V. 30, 1231 (2005)]. This configuration also provides the opportunity to link the stability of the two oscillators. In this paper, we will describe our recent phase-noise measurements of photonic microwave oscillators. We will also discuss our investigation of the frequency stability link between the optical and microwave frequencies in the coupled oscillator. This link is established by stabilizing the optical frequency to an atomic transition, the stability of which is transfered to the microwave signal. This system represents a unique architecture for drawing a stable microwave signal from the optical oscillator