Theoretical and experimental study of single and dual-loop optoelectronic oscillators

Optoelectronic oscillators (OEOs) are used to generate RF signals in the X-band region with a very low phase noise. These hybrid opto-electronic devices are based on a long optical fiber that forms a very high-Q RF cavity. We have studied theoretically and experimentally single-loop and dual-loop optoelectronic oscillators. Excellent agreement between theory and experiments was obtained. The results indicate that flicker noise limits the performance of long cavity OEOs at low frequencies (<500 Hz). We have also studied physical effects in dual-injection locked OEO. The locking of two OEOs with different cavity lengths enables the generation of signals with a very low noise and with very low spurs. We demonstrate theoretically that it is possible to reduce the first spur level by more than 20 dB in compare with that obtained in current experiments.