RF frequency analysis and separation by optical sampling

We demonstrate several schemes of RF frequency analysis by optical means. They are based on the sampling of RF signals in time-domain and subsequently translating them into the spatial domain where Fourier transformation and other signal processing operations are readily executed. The most general option introduces true-time delays in the form of optical fibers. A drawback of this method is the need to stabilize and control optical phases. We report the achievement of such control by closed-loop active phase stabilization.