Demonstration of a 40 gigasample/s real-time photonic analog-to-digital converter

A novel interferometric scheme for photonic analog-to-digital conversion (ADC) is experimentally demonstrated at a real-time sample rate of 40 gigasamples/s. The input signal in the experiment was a 1.25 GHz sinusoidal tone and the resolution 21 digital levels with an effective number of bits (ENOB) of 3.6. The major benefits of this scheme are that only one standard phase modulator is required and that the phase swing does not have to be larger than ±π to reach the full digital value space.