Research On Key Technologies Of Photonic Analog-to-digital Conversion

Since the birth of photonic analog-to-digital conversion(ADC)technology in the 1980s,numerous researchers have been committed to improving the performance of ADC,thus contributing to the development of digital information technology.This paper considers the technology of ADC as the research object.Firstly,it introduces the development history and research trends of the ADC technology,and then studies the principles and characteristics of some typical photonic ADC schemes.Meanwhile,the superiority and insufficient of the existing ADC schemes are analyzed.This paper studies and proposes two new schemes of photonic ADC from the perspective of simplifying the system structure and improving the bit resolution of the system.The two schemes simplify the system structure and improve the quantization level to a great extent.The main innovations and academic contributions of this paper are as follows:1.A scheme of photonic analog-to-digital conversion based on vector superposition and differential coding is proposed.The practicability of the proposed scheme is proved by theoretical research and principle verification experiment.The scheme uses vector superposition to realize differential coding output of input RF signal.The scheme is simple in structure and easy to be integrated.The conversion from analog signals to digital signals can be realized by cascading a delay line interferometer(DLI)with only one phase modulator(PM).The results of computer simulation show that the phase shifts among different transfer functions are realized by adjusting the signal intensity with the vector superposition module.It avoids the phase-drift problem caused by temperature or environmental changes based on the modulator scheme.The stability of the system is effectively improved.2.A scheme of photonic analog-to-digital conversion based on the principle of hierarchical quantization is proposed.The practicability of the proposed scheme is proved by theoretical research and principle verification experiment.In this scheme,a hierarchical quantization module is built and used to realize the two-stage quantization of the signal.Hence it can improve the quantization levels of the system with a relatively simple structure.The results of computer simulation show that the total quantization levels of the scheme will be increased from 6 to 6N,which is a qualitative leap compared with the traditional phase-shifting optical quantization scheme.