Research On The Application Of Combinatorial Encoding/Decoding Technology In OCDMA System

Multiple access is a technology which appeared in order to satisfy the multiple users to share the channel and high speed, large capacity communication requirement in the optical network. Among them, Optical code division multiple access (OCDMA) is a technology which to achieve the multiple users to share the transmission channel by giving each user allocate specific pseudo random code. Since its features of random asynchronous transmission, soft capacity, convenient network management and high flexibility, etc, it is becoming a hot research topic in the field of optical fiber communication. In addition, the user data is transmitted in the channel after its encoded into a pseudo random sequence of light code word, that make OCDMA technology has greater potential to enhance the system security. Therefore, the encoding and decoding technology has become one of the core research techniques in OCDMA system. This paper also focuses on the related research in OCDMA system.Firstly,the encoding technology of OCDMA system are discussed.The relevant theory and experiment of encoding technology was studied and verified,including the time domain codec technology of optical fiber delay line and spectral codec technology of FBG. In this paper, the two-dimensional OCDMA encoding and decoding system is designed in time and spectral domain with the fiber delay lines and FBGs, and two-users simulation experiment with code rate of 8Gchip/s has been successfully implemented based on optisystem7.0.Secondly, considering the serious problems such as low spectrum efficiency, dispersion compensation difficulties and multiple access interference in the OCDMA technology of all-optical signal processing, and it is difficult to overcome the bottleneck in a short time. Based on the optical domain codec and electrical domain codec of their respective advantages, this paper proposes a combination of electro-optic decoding scheme, and the theoretical formula is deduced. At the same time, the OCDMA simulation system based on the electro-optical combination codec is established, and the two user simulation experiment of the chip rate of 80Gchip/s is realized. In order to further verify the effectiveness and feasibility of the scheme, a OCDMA system experimental platform based on the combination of electro-optic codec experiment platform is built, and the verification experiment of single user data transmission with chip rate of 1 Gchip/s is successfully implemented.Finally,combined with the development trend of the highly integration of OCDMA system in future, this paper proposes a two-dimensional OCDMA system coding and decoding scheme based on two-dimensional photonic crystal(PC).The feasibility of two-dimensional codec based on PC is theoretical analysised with the characteristics of slow light and filter characteristics of PC. A four channel codec of the two-dimensional photonic crystal is designed by the Rsoft software, at the same time, the codec performance is simulated.