Study On Coding Theory And Technology Of Improving Data Security In Optical Transmission

Optical Code Division Multiple Access (OCDMA) is a hot topic of the researches on the all-optic access network since it exhibits attractive features like excellent anti-interference, asynchronous access, dynamic bandwidth assignment, soft capacity and etc. In addition, researchers think that security is an inherent characteristic of OCDMA system. Thus, there are few papers present any analysis of the degree of security that can be expected from OCDMA techniques. The security performance analysis of OCDMA systems and policies or mechanisms to enhance the security performance become the key issues since the development of OCDMA technology. This thesis focuses on the security of OCDMA, and research its performance by simulation. The works are as follows:1,Proposed a framework for security analysis, pointed out the parameters which related to security in address codes, analysed the securiyt performance from the perspective of two common eavesdropping methods, deduced the time eavesdropper required when taped single-signals from multiple users and the ability to tap a single user and multiple users. The result shows that the main performance related with address codes are capacity and cross-correlation, and the bit correct interception possibilities were decrease as code length/weight and number of simultaneous increase and increase with eavesdropper's SNR.2,OCDMA address codes are researched as focus. Beginning at the analysis of 1-D OCDMA codes and 2-D OCDMA codes, the encoding/decoding theories and systematic performance theories for prime codes, optical orthogonal codes , PC/OOC and OOC/OOC are analyzed. The BER curves are simulated using MATLAB and the performances of different address codes are compared.3,Construction of 2-D MLVW Latin/OOC is proposed. And its performance is calculate in theory. The BER curves are simulated using MATLAB. Calculation shows that the codes have good auto-correlation and intra-correlation, but its inter-correlation isn't as good as OOC. Overall, this code can be applied to future OCDMA communication system.