Photonic time stretch preprocessor employing coherent detection in analog-to-digital converter

Abstract

The performance of analog-to-digital converter (ADC) can be greatly enhanced by preprocessing the high-speed RF signal using the photonic time stretch technique. In order to accumulate more dispersion to stretch the optical pulses in time domain, we used the large dispersion photonic crystal fiber (PCF) as the stretched medium. However, the length of used fiber is so long, the optical signal becomes the weak signal before the digitizer as a result. We propose a new implementation of the time stretch analog-to-digital conversion system that overcomes the disadvantage from the direct detection. It is shown that the weak signal can be recovered by using the coherent optical detection and the conversion gain is very high. Real-time analog-to-digital conversion at 1.56TSa/s is demonstrated.