Research On The Time-Delay Compensation In All-Optical Analog-To-Digital Conversion

With the development of science, the mankind have entered the information era, information storage, transmission and processing are carried out in the form of digital signals. However in the nature, all kinds of information are in the form of analog signals. Analog-to-digital convertion (ADC) is the communication bridge of analog world and digital world, also the core of modern information processing system. Traditional analog-to-digital conversion is carried out in the electric domain, however, because of the electronic bottleneck, the traditional ADC cannot meet the requirements of high-speed signal processing. At the same time, with the rapid development, all-optical signal processing technology has attracted the attention of experts and scholars from all over the world. All-optical ADC technology not only can overcome the limitation of electronic bottleneck, but also has great development potential. So it is the core of the signal processing, research in the future. All-optical quantization is the core of all-optical ADC, also is the key research object. Among all the optical quantization methods, soliton self-frequency shift has attracted the attention of many scholars and researchers because of the quick response, good effect and convenience to control. This paper focus on the time-delay compensation in all-optical ADC scheme based on soliton self-frequency shift, the research contents include the following aspects:(1) A brief introduction of the research background and significance of all-optical ADC and all-optical quantization is given. Then the review of the whole development history and research status of all-optical ADC in home and abroad is presented. Many kinds of technologies for dispersion compensation are introduced.(2) This paper researches on the all-optical quantization coding structure based on soliton self-frequency shift, and describes the derivation process of the generalized nonlinear schrodinger equation. Then the paper briefly introduces the numerical method to solve the generalized nonlinear schrodinger equation, which is split-step Fourier method. In addition, this paper introduces the method of moments which is used to describe the evolution of optical pulses in the optical fiber. Combine the method of moments and split-step Fourier method to solve the equation, it is helpful to find the factors which affect optical pulse center frequency and time delay. Then the time delay compensation mechanism is established. Two methods of time delay compensation scheme are put forward, the negative dispersion optical fiber and the chirped fiber Bragg grating.(3) The paper researches on the different types of negative dispersion optical fiber refractive index profile. Based on the time delay compensation mechanism, time delay compensation line is a straight line, and pulse time delay compensation line slope and pulse time delay line slope are the opposite. The rational selection of parameters used in negative dispersion fiber time delay compensation. Simulation results show that the maximum time difference is0.9ps. The maximum sampling rate this solution can support is555GSa/s, the output coding results is correct and effective.(4) The coupled-mode theory of optical fiber Bragg grating and the numerical method are studied, the single variable method analysis is used to get the influence of chirp variables, grating length, modulation depth and toe cutting technology on optical fiber Bragg grating reflective spectrum and time delay line. Comparative analysis, select the best parameters of the fiber Bragg grating for time delay compensation. Simulation results show that the maximum time difference is3.3ps, which can support the maximum sampling rate is151GSa/s, the output coding results is correct and effective.