| As we all know, the analog-to-digital converter (ADC) plays an important role in modern communication systems. While the electronic analog-to-digital converter (ADC) improved, the rate of improvement is so slow compared to that of digital signal processors (DSP). The performance of ADC has become the major bottleneck that cannot fulfill the sampling rate and input bandwidth requirements needed in today’s high-speed applications, such as high-definition television, medical imaging, radar, instrumentation, communications and other fields. Now, various excellent photonic techniques have been proposed to extend performance of conventional electronic ADCs and these methods have attracted much attention to overcome the disadvantages of electronic ADC. One of these excellent schemes is the time-stretch analog-to-digital converter proposed by the professor Jalali from UCLA. In this paper, a detailed analysis about the time-stretch system using dispersion elements and optimize this system with our new scheme and algorithm. The main contents of this paper are as follows.Firstly, analyzing the dispersion effect to the optical pulse in the fiber link, analyze the principle of time-stretch analog-to-digital system using the mathematical model.Secondly, analyzing the dispersion and nonlinearity of photonic crystal fibers (PCF) affected by its structure, design a new time-stretch system using PCF which will simplify the system.Thirdly, proposing an envelope removing algorithm to eliminate the envelope of the stretched electric signal.Fourthly, propose a phase-modulation time-stretch analog-to digital system and detailedly analyze this system with mathematical model. Compare the performance of the two time-stretch systems. The results show the output of the phase-modulation system has a higher power and this system is more accurate.After the research of the above aspects, we provide a foundation to the time-stretch analog-to-digital converter technique. |
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