Research On Ultra-high Speed Time-stretch Photonic Analog-to-digital Converter

Analog-to-digital converter(ADC)is an essential component in the digital signal processing(DSP)technique nowadays.Ultra-fast and highprecision ADC has an extremely important application in wireless communications,radar systems,measurements and biomedical imaging.However,the analog bandwidth and the sampling rate of the traditional electronic ADCs are limited by several factors,such as the sampling clock jitter and the setting time of the sample-and-hold circuit.Many attributes of photonics can complement electronic ADCs to improve their performance.For example,mode-locked lasers achieve at least an order of magnitude smaller timing jitter values compared to electronic clocks,which is advantageous in sampling ultrafast signals with high precision.Wide optical bandwidths and low-loss optical dispersive media also provide large delay capabilities.Photonic systems are also more resilient to channel-to-channel crosstalk and electromagnetic interference.These advantages have led to the development of a vast number of techniques over the past few decades that use photonics to achieve analog-to-digital conversion of wideband electrical signals.Photonics ADC based on Time-stretch method can achieve ultrawideband and ultra-high sampling frequency,while the high power dissipation will limit the effective number of bits.The focus of this paper is the high precision technology of the time stretch Photonics analog-to-digital converter(TS-PADC),including noise analysis of the TS-PADC system and channel mismatch,prototype realization and optimization of the TS-PADC system based on CFBG,and high precision verification experiment.Main contents of the thesis are summarized as follows:(1)Main methods for photonic-based analog-to-digital conversion technology are summarized,their advantages and disadvantages are also compared.By tracking the latest research situation and development tendency of TS-PADC technology,it is pointed out that he urgent problem that needs to be solved in TS-PADC is the problem of high precision.(2)The basic principle of TS-PADC system is studied.For afore mentioned high precision problem,the noise of the system are analyzed and simulated,channel mismatch of the back-end time interleaving structure is analyzed.At last,parameters of the system required to achieve high precision are proposed.(3)The concrete realization method of high-precision TS-PADC system is studied.A 2-channel experimental prototype based on CFBG is demonstrated and realized.The corresponding experiments are carried out to achieve high precision.