Undersampling a photonic analog-to-digital converter containing an optical hybrid combiner

A self-coherent optically-sampled analog-to-digital converter using a 90° optical hybrid coupler is experimentally demonstrated. It leverages practical, commercially available components and is used for high-resolution undersampling at 50 Msps of up to 20 GHz carrier frequencies. The measured ADC resolution is 9 effective bits for a 10 GHz carrier frequency and shows little carrier frequency dependence from 6 to 20 GHz.