Photonic analog-to-digital converters A tutorial

Each new bit of ADC resolution requires an increase in signal-to-noise-and-distortion ratio (SNDR) of 6 dB • ENOB without noise bandwidth is meaningless • Decreasing the noise bandwidth by a factor of 4 increases ADC resolution by 1 ENOB - e.g. the Tektronix 50 GS/s digital oscilloscope has • 5 ENOB over 16 GHz • 7 ENOB over 1 GHz • Every time you sneeze, you lose a few 1/10´s of an ENOB • Optical photons are very energetic compared to RF photons - Shot noise is irrelevant for electronic ADCs - Shot noise is a fundamental limit in photonic ADCs • Photonic ADCs usually contain a microwave photonic link - Standard analysis gives the SNR/CNR - Max ENOB over a given noise bandwidth readily estimated • If commercialized, photonic ADCs will resemble data conversion modules and digital oscilloscopes rather than single chip ADCs