Optical CDMA Systems And Their Key Techniques

There are three multiple-access techniques mainly in optical communication, including WDM, TDM and CDMA. Optical CDMA techniques were proposed in mid-1970s, now, have attracted much attention. Using CDMA techniques in optical communications not only keep combating interference, security, soft capacity and simply network protocol, but also make use of the huge bandwidth of fiber, so, the combination of CDMA techniques with optical communication has advantages.This dissertation is around the study of optical CDMA systems and their key techniques. In the paper, we will make a theoretical analyse on key techniques of optical CDMA, propose several new address codes, propose some new schemes to improving system's performance. At the same time, we will make the experiment research on spread-time incoherent OCDMA system. The paper contains nine chapters, the main contents can be outlined as follows.1 Summary of the development and recent success in the optical communication and optical CDMA.2 Establish the mathematical model of optical CDMA, discuss the key techniques on optical CDMA.3 Study the address codes. Construct some two-dimensional time-spreading/frequency-hopping codes based on OOCs and Prime codes, propose the coders and decoders to implementing them, prove the correlation performance and capacity.4 Study the optical CDMA systems.(a) Analyze the performance of spreading time incoherent OCDMA system and scheme to improving the system's performance.(b) Study the spectral amplititude system, analyze the performance limit to noise. Propose new scheme to transmitting 1 and 0 based on multiple Bragg gratings, improving the system's performance.(c) Propose the scheme to implementing the coder and deoder ofoptical time-spreading/frequency-hopping, By assigning two orthogonal codes for one user and using these two codes to encoding 1 and 0 respectively, differential detection can be adopted. Not only improves system performances in BER, but also resists the interference such as MAI, and doesn't need any control devices to evaluate the optimum decisive threshold. By introducing OPPM(Overlap pulse position modulation), the system's performances are improved also.5 Study wireless optical CDMA system.(a) Analyze the free space optical CDMA communication system.(b) Propose the multiple apertures system based on analysis of channel performance of atmospheric channel.(c) Propose RAKE receiver in indoor diffuse channel based on analysis of channel performance.6 Study channel code, multi-user detection and other detection techniques of optical CDMA.7 Study of optical CDMA network.8 Finish the experiment on time-spreading incoherent optical CDMA system.9 Summary of all the paper.