Research Of All-optical Ultra-wideband Signal Generation And Modulation Based On Semiconductor Optical Amplifiers

Ultra-wideband (UWB) technology has various advantages such as strong ability of anti-multipath interference, low complexity, low cost, low power consumption, high transfer rate and so on. Therefore, it has different applications in communication, location, radar and other fields. However, the transmission distance of UWB is only from meters to more than ten meters according to the quite low transmission power spectrum density. To further expand the coverage of the UWB signals, the UWB over fiber technology is proposed. The key technology of UWB-over-fiber contains the UWB signal source study and UWB modulation study. The optical generation and modulation technology of the UWB signals have attracted more and more attention in recent years. In this thesis, the optical generation and modulation technology of the UWB signals are studied. The research and analysis of the several schemes are also carried out in this paper. The main achievements and conclusions are listed as follows:(1) The development history of UWB technology is clarified. Based on classification, summarize the optical generation of UWB and modulation. And then it analyzes and compares the advantages and disadvantages of these programs.(2) The semiconductor optical amplifier (SOA) model is introduced. Then combined with OptiSystem software, the gain characteristics of SOA are studied by computer simulation. Analysis of the influence of the incident optical power, source wavelength and injection current of SOA on the gain. The way of two continuous light beams opposite is discussed, which changes the gain.(3) A new optical generation scheme for achieving doublet signal source based on cross-gain modulation (XGM) in SOA is proposed, which has various advantages such as simple structure, the output signal not sensitive to the wavelength and optical power, easy operation and so on. By OptiSystem simulation, the impacts of source power, source wavelength and injection current of SOA on doublet signal are studied, and the reference value of each parameter is proposed.(4) A new UWB pulse shape modulation (PSM) based on XGM in SOA is presented, which has various advantages such as simple structure, no time difference caused by dispersion medium and esay control. By OptiSystem simulation, the impacts of source power, modulation rate and source wavelength on the PSM signal and the transmission characteristics of PSM signal are investigated.(5)An improved UWB multifunctional modulator scheme in SOA is presented. PSM, PAM and BPM can be achived by simple preconding. By Opti System simulation, the impacts of source power, injection current of SOA and source wavelength on PSM, PAM and BPM modulation signal are studied, finally analyze the transmission characteristics of modulation signal on fiber.