Broadband Transient Waveform Digitizer Based on Photonic Time Stretch

Abstract

A broadband digitizer is proposed and experimentally demonstrated based on photonic time stretch (PTS). In this scheme, a complementary single-sideband modulation architecture in combination with successive digital difference operation and phase compensation are employed to simultaneously eliminate dispersion-induced power fading problem, remove dynamic pulse envelope, suppress modulation nonlinearity impairment and maintain broadband waveform fidelity. In the proof-of-concept experiment, a PTS preprocessor with a stretch factor of 8.77 and a time window of 1.8 ns is realized, where the maximum power degradation in the frequency range up to 25 GHz is 5 dB. By using this preprocessor, single-tone microwave signals in the frequency range of 2 to 25 GHz are digitized with effective number of bits larger than 3.4 bits. For single-tone input microwave signals at 12 and 15 GHz, the 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> -order harmonic suppression ratios are enhanced by 11.51 and 16.86 dB, respectively. For a two-tone microwave signal at 8 and 10 GHz, the synthetic waveform fidelity after time stretch is maintained by carrying out phase compensation.