A coupled all-optical microwave oscillator with large tuning range based on SBS

Abstract

A coupled all-optical microwave oscillator with large tuning range is proposed. Without optical–electrical–optical conversion components or any electrical microwave devices, microwave signals can be generated through a pure optical oscillation. In this system, a fiber ring laser provides a set of frequency references for frequency selection. Meanwhile, it also serves as a high-Q active resonator to optimize phase noise performance. By transferring the cavity modes to an optical carrier and selectively amplifying some of the modes via stimulated Brillouin scattering, the oscillation frequency is preliminarily selected. A semiconductor optical amplifier in the fiber ring laser is employed to accomplish the optical envelope detection and feedback modulation. Once the oscillation system is closed, good quality and high stability single-mode microwave signals are generated. By varying the wavelength of Brillouin pump light, a tuning range from 2 GHz to 26 GHz is demonstrated. Furthermore, the single side-band phase noise of these microwave signals are around −90 dBc/Hz@10 kHz.