Research Of MAI Suppression And Combinatorial Encoding/Decoding Technology In Ocdma System

Optical code division multiple access (OCDMA), which introduces the concept of code division multiple access (CDMA) into optical fiber communication, provides the attractive features such as all optical process, asynchronous access, the soft capacity, the simple network protocol and high confidentiality. The design of the optical code, the structure of the optical encoder/decoder, the system trials study and the multiple access interference (MAI) suppression are all the key issues in OCDMA. The MAI suppression method and combined encoding/decoding scheme are investigated thoroughly in this thesis. The main work can be outlined as follows:The principle of fiber Bragg grating (FBG) and the architecture of the FBG encoder/decoder are introduced firstly. And then an incoherent two-dimensional OCDMA experimental platform employing the FBG encoder/decoder is built and a4×2.5Gb/s OCDMA transmission trial is achieved. The experimental results show that the FBG-based OCDMA system is a promising method for future high capacity optical networks.The MAI is one of the important factors that affect the performance of incoherent OCDMA system. To address this question, several MAI schemes have been proposed. In chapter3, we proposed a suppression method that employs the semiconductor optical amplifiers (SOA) as optical limited amplifier and made a theoretical analysis on it. Based on the SOA-based MAI suppression method, a multiuser OCDMA system is designed and simulated. The results show that the SOA-based MAI suppression method improves the quality of decoded signal and reduces MAI noise effectively.The design of the optical encoder/decoder is crucial in the OCDMA system performance. It is the first time to propose a combinatorial encoding/decoding scheme. The basic principle that includes the code generation and recognition, the architecture of encoder and decoder, and the design method of address code is investigated. Additionally, the novel OCDMA system is simulated in the software optisystem7.0. The results indicate that the proposed scheme provides a flexible and powerful way to process optical code sequences. Finally the potential application of the proposed encoding/decoding method in OCDMA-PON and Triple Play networks is discussed.