The Bit Error Performance Analysis Of Two Dimension Optical Code-division Multiple Access Systems

Optical code division multiplexing access(OCDMA) is one of the possible resolutions for future all optical communication network, which is a hot topic in optical communication research. Compared with other multiplexing technologies, it is still at the state of infancy.In two dimension OCDMA system, the code is encoded in time and wavelength or time and space domain, so the performance of two dimension OCDMA system is better than one dimension OCDMA system. The basic principle, the key technologies and system schemes are simply introduced. And the development, research status and trends of OCDMA technologies are also summarized. The sorts and architectures of two dimension OCDMA systems are investigated. Especially Optical Fast Frequency-Hop(FFH) CDMA system based on encoder/decoder of FBG is analyzed.With the performance of two dimension OCDMA system analyzed, The upper-bounds on BER of OCDMA system using the FFH codes is investigated with or without using the optical hard limiter. The thorough investigation and analysis on the performances of the system is performed by simulation and it gets some valuable results. Considering kinds of the receiver noise and users' multiplex access interference (MAI) in two dimension asynchronous OCDMA systems, the receiver with double optical hard-limiters (OHL) is proposed for improving system's transfer performance. The relations of the user number, received laser power, threshold and its performance of the system's bit error probability are numerical analyzed.Group velocity mismatch effect, nonlinear interference and effect of source extinction ratio are analyzed in two dimension OCDMA system. The thesis analyzes effect of group velocity and nonlinear interference in this system by using a relatively simple method. For improving system's transfer performance, the adjusting decision threshold of optical decoder according to extinction ratios was presented.