Non-Uniform Sub-Nyquist Optical Sampling by Acousto-Optic Delay Modulation

This paper presents an optical sampler based on the combination of a mode-locked laser and external acousto-optic delay modulator, and demonstrates its use in a non-uniformly sub-sampled photonic link. Delay modulation of the laser's uniformly spaced pulse sequence produces a non-uniformly spaced optical pulse train, which subsequently sub-samples the microwave input of the photonic link. Using this non-uniform sub-sampler, microwave frequencies spanning a range exceeding 200 Nyquist zones are aliased to a single zone, with modulation sidebands added that uniquely identify the input frequency. This enables wideband spectral folding and frequency disambiguation, using a single sampler that is based on a high-stability pulsed laser.