Stable and finely tunable optoelectronic oscillator based on stimulated Brillouin scattering and an electro-optic frequency shift

We demonstrate a stable and finely tunable optoelectronic oscillator (OEO) based on stimulated Brillouin scattering. In the proposed scheme, the optical carrier in the OEO loop and the Brillouin pump light is generated by a single laser source, which guarantees the frequency stability of the output microwave signal from the OEO. Frequency tuning is achieved by varying the pump frequency via an electro-optic frequency shifter composed of a dual-parallel Mach-Zehnder modulator (DPMZM) and an electrical 90° hybrid. Through subtly varying the frequency of the low-frequency microwave signal applied to the DPMZM, a finely tunable high-frequency microwave signal can be obtained from the OEO. In the proof-of-concept experiment, the output frequency of the OEO is tuned from 10.645 GHz to 12.645 GHz with a tuning resolution of 10 MHz. The stable performance of the OEO is also achieved, where the maximum frequency and power drifts at 11.145 GHz are measured to be 6.25 kHz (i.e., ∼0.6ppm) and 0.77 dB in a measurement time duration of 1000 s, respectively. Through using broadband devices in the OEO architecture, the proposed scheme can generate stable and finely tunable microwave signals up to 40 GHz or even higher.