Research On Time Tensile Modulus Conversion Technology In Dispersive Fourier Transform

In the field of optics, ideal Fraunhofer diffraction system can visually show the spectrum of the original image in the image surface, which means that the Fraunhofer diffraction realizes the analog computation of two-dimensional dispersive Fourier transformation. This kind of method, that uses Fourier transformation to analyze the process in optics, has now developed into an important branch of modern optics—the Fourier optics. Dispersive Fourier transformation is a new type of measuring technique based on optic Fourier transformation. It uses chromatic dispersion to stretch the optical pulses which were modulated by external information, thus to reduce the bandwidth enabled to be captured by the slow detector. It overcomes the speed limitation of traditional optical device, and provides a new kind of high-speed measuring method. DFT has been applied in the fields such as optical sensing, spectroscopy, and optical imaging.Time-stretch analog to digital converter (TS-ADC), is a method that employing DFT to boost the bandwidth of electronic analog-to-digital converter (ADC). This method slows down the analog signal in time domain and compresses the bandwidth before the signal enters the electronic ADCs, thus to overcome the backend insufficient bandwidth and sampling rate, consequently improving the performance of system.This thesis focused on the following topics:1. Introduction of dispersive Fourier transformation (DFT) is presented, containing its meaning, background, principle, common method, and research progress in recent years.2. The process of dispersive Fourier transformation is theoretically analyzed. Based on the analytic results, the process is simulated. Results indicate that with dispersion increasing, frequency spectrum is mapped into temporal waveform, and higher-order GVD coefficients can have negative effects on mapping.3. Focusing on time-stretch analog to digital converting system based on DFT, specific mathematical analysis and experiments were tried. The copies of 5GHz-12.5GHz original signal are obtained and verified. Furthermore, accompanying distortion is also analyzed and corrected.4. To improve the performance of time-stretch analog to digital converting system, further study is made. The feasibility of applying wavelength division system is discussed and confirmed experimentally. More recommendations to improve the results are proposed.