Stable and Tunable Optoelectronic Oscillator With External Stimulated Brillouin Beat Note Injection

Broadband and tunable microwave signals are widely used in modern communication systems and sensing systems. In this work, we demonstrate a stable and tunable optoelectronic oscillator (OEO) scheme based on external low-power beat note injection of the stimulated Brillouin signal and a phase modulation sideband of the original pump signal. The injection-locked system reduces the high-frequency disturbance induced by the beat note signal, and thus the power required only meets the OEO locking threshold requirement. In addition, the external stimulated Brillouin signal generator avoids the excessive length of the resonant cavity and guarantees the frequency stability, especially the mode stability in the OEO with a total path length of similar to 12 m. By varying the stimulated Brillouin signal frequency and selecting different pump modulation sidebands, a continuously tuned beat note is generated, and a beat note injected OEO with a maximum frequency up to 11.5 GHz is achieved, which is the intrinsic upper frequency limit of the devices used, even for an injection beat frequency power as low as -14 dBm (similar to 40 mu W). Our work provides an important solution for the realization of widely tunable microwave systems.