Research On Optical Microwave Frequency Conversion By Cascade Intensity Modulators In RoF System

With the optical fiber communication and the microwave techniques development, two originally independent discipline begins to fuse, which is eventually forming an interdisciplinary technology area—Microwave Photonics. Microwave photonics studies the interaction between microwave and optical signals. The major functions of microwave photonics systems include photonic generation, processing, control and distribution of microwave and millimeter-wave signals. Typical application of microwave photonics is Radio-over-Fiber (RoF), which is a promising solution for future broadband wireless access in the millimeter-wave band, as it can increase the capacity, bandwidth and mobility to serve both fixed and mobile users. Optical millimeter-wave frequency convention schemes are essential for RoF and other applications, which have been the research topics of many scientific research institutions at home and abroad.In this thesis, we did many theoretical analysis about the optical frequency down conversion schemes based on the electrooptic modulators. Firstly, various of parameters were analysed on the effect of the properties of frequency conversion, We made detailed theoretical analysis and simulation verification for each parameter of the parts of Transmitting Terminal, Modulation Terminal and the Receiving Terminal. According to the analysis results, we proposed an optimized solution for the frequency conversion without any external devices. Sencendly, some optical devices such as EDFA and FBG were analysed on the effect of their effection for the system performance. By adjustmenting the working point of modulators and the modulation index,we can get the maximum gain of the frequency conversion schemes, at the same time, we can inhibit the IMD3distotion. In those systems, the maximum gain can reach to7.5dB, it was43dB more than the gain of the system without EDFA,and the maximum SFDR can reach to121dB/Hz4/5,it was20dB more than the SFDR of the system without FBG. According to the analysis results, a simple experiment had been done to verify the feasibility of the proposed schemes.The experiment provided us valuable experience to do more complex experiments in future.