Research On Enhancing Capacity Methods Of Optical Code Division Multiple Access (OCDMA)

Optical Code Division Multiple Access (OCDMA) technology is one of the three most important multiplexing/ multiple access technologies in the field of optical communication, whose advantages of the high bandwidth utilization and asynchronous access make it become one of the most important solutions in all-optical communication network. Around codes, system and technical integration, this paper puts forward to the methods of enhancing system capacity, in order to provide power basis for enhancing system capacity and lowering the multi-user interference through researching address codes, forming the scientific background about multi-system integration.First, this paper summarizes the characteristics of typical address codes and compares their relevant parameters to get their application circumstances. Paying more attention about the relationship of validity and reliability in communications systems, referencing the conception of energy efficiency rate in Sensor Networks, the paper presents inferior optimal orthogonal code by use of code weight, improving One-dimensional optimal orthogonal codes under a certain bit error rate (BER) , enhancing the code's capacity. And user-gain coefficient, freedom-gain and calculating complexity and so on become the standard in the method, which have some theoretical value.Second, utilizing the advantages in code capacity, correlation and bit error rate about two-dimensional address codes and integrating with the idea about hybrid code, this paper puts forward to the two-dimensional frequency-hopping address code coding method. This method gives an example: it using Walsh code as spread spectrum series which is generated by Hadamard matrix, and unipolar code as frequency-hopping series, improves the utilization of optical wave, at the same time, lowers the bit error rate .At last, the calculating result is given.Finally, taking into account of the development about all-optical communication network s, this paper presents OCWT system based on OCDMA,WDM,OTDM technologies in the basis of the previous studies, making the combination of the three multiplexing technologies become possible in principle. Finally, the paper gives the enhancing capacity and lowering BER simulation results in the ideal condition, while brings new challenge in system integration and synchronization and extends ideas for related researches.In order to increasing the number of optical user access, the paper considers that if we can integrate several enhancing capacity methods ,the system capacity can be further enhanced and improve the bandwidth utilization of fiber.