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Abstract: The performance of analog-to-digital converter (ADC) can be greatly enhanced by preprocessing the ultrafast analog signal using the photonic time-stretch technique. In the previous time-stretch ADC, the amplitude modulation is adopted. The amplitude of stretched signal has nonuniformity after the time-stretch preprocessing and the power of stretched signal is very weak, this will influence on recovering distortionless stretched signal, increase the difficult of detector and sampling. In this paper, we propose the photonic time-stretch ADC employing the phase modulation and the optical coherent detection to eliminate the nonuniformity phenomenon on the amplitude and increase power of stretched signal by adjusting the local oscillation (LO) power. The sampling rate of the ADC can reach 1.56TSa/s by using large dispersion photonic crystal fiber (PCF). [Copyright &y& Elsevier]