130 Gsample/s photonic analog to digital converter

Digital processing of the received signals in radar systems leads to higher performance and the ability to rapidly reconfigure such systems. Typically, the analog-to-digital converter (ADC) is the major bottleneck in realizing the digital receiver. Time stretch (TS) preprocessing is a new photonic based approach that can potentially boost the capability of the available electronic ADCs (Coppinger et al, 1999; Bhushan et al, 2000). In this approach, the analog signal is imposed on a chirped optical carrier using an electro-optic modulator. This time to wavelength mapped signal is then dispersed and hence stretched in time prior to digitization by the electronic ADC. Time stretching increases the effective sampling rate and input bandwidth of the ADC. We demonstrate a photonic ADC with a time stretch preprocessor. The system has a sampling rate of 130 GSa/s and a signal-to-noise ratio exceeding 7 effective number of bits.