Demonstration of Distortion Suppression in Photonic Time-Stretch ADC using Back Propagation Method

We experimentally demonstrate the performance of the recently proposed "OBP" algorithm based on optical phase retrieval by numerical back-propagation. Using this technique, distortion due to the modulator transfer function as well as the group velocity dispersion in a photonic time-stretch ADC (TS-ADC) can be suppressed, and frequency fading eliminated thanks to the use of a dual output "phase diverse" modulator. The algorithm was tested with a swept input signal frequency from 10 to 50 GHz. as well as with a two-tone signal, and is shown to recover the signal even in the presence of fading with a distortion suppression of up to 26 dB. These results also constitute the first experimental demonstration of channel combining in a phase diverse TS-ADC.