Research On Novel Photonic Analog-to-digital Conversion

It is widely recognized that the analog-to-digital converter(ADC) represents the key bottleneck in modern high-performance communication and radar systems.The use of optical technologies in ADCs has attracted great interest thanks to the inherent ultranarrow pulse width,high sampling rate and low timing jitter offered by optics.In this paper,a novel approach to perform photonic analog-to-digital conversion with improved bit resolution is proposed and investigated.Instead of using Mach-Zehnder modulators with geometrically-scaled half-wave voltages,the MZMs in the approach have identical half-wave voltages.To improve the bit resolution without increasing the number of MZMs,each MZM is connected with multiple comparators having multiple thresholds.The quantization and encoding are performed based on the symmetrical number system(SNS) technique.Three new quantization and encoding schemes based on the SNS are proposed and demonstrated.A 4 bit photonic analog-to-digital conversion based on the given schemes is investigated.For the given schemes,numerical simulations and experiments are performed.The effectiveness of the proposed schemes is verified.Both theoretical and experimental results confirm the feasibility of this proposed scheme.To clarify the relationship between the system noise and the ENOB degradation,we perform a computer simulation using the Monte Carlo method;the same method can also be used to show the sampling-jitter-induced ENOB degradation. Some limitations have been proposed,which give useful information for further research.