Long-haul microwave analog link with shot-noise-limited performance above the Stimulated Brillouin Scattering threshold

We have assembled and characterized a microwave frequency analog fiber link that offers shot-noise-limited performance at input powers above the stimulated Brillouin scattering threshold. The 20 km span of fiber consists of three pairs of alternating fibers, with each pair separated by isolators. The measured SBS threshold using the backscatter approach is 14 dBm; however, the measured relative intensity noise from 1-8 GHz remains at the shot-noise level until the input power exceeds 16 dBm. When compared to a single fiber link of the same length, the link gain, RF noise figure, and SFDR at 1 GHz all improve by 8.1 dB, 4.1 dB and 2.8 dB, respectively.