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A highly linear broadband photonic-assisted analog-to-digital converter (ADC) based on high-frequency optical sampling utilizing a dual output Mach–Zehnder modulator operating with signal frequencies up to 50 GHz is presented. The pulses employed in the optical sampling were generated by a cavity-less pulse source operated at 10 GHz in preference to conventional mode-locked lasers. The optical sampling front-end greatly extends the operational frequency range of the Nyquist limited electronic digitization back-end. The performance of the sampling system is characterized with 7.1 effective number of bits (ENOBs) at 40 with 5 GHz fully accessible bandwidth, and greater than 99 dB·Hz^2/3 spurious free dynamic range for the 30–40 GHz frequency range. Furthermore, more than 8 ENOB was achieved by reducing the effective bandwidth to 1 GHz with a digital filter, demonstrating the additional advantage of …