A novel zero cross correlation code for optical code division multiple access system

Abstract

Optical Code Division Multiple Access (OCDMA) techniques have shown outstanding capabilities in sharing multiple users simultaneously in access network. The purpose of this study was to develop a new spectral amplitude coding (SAC) in OCDMA code. In particular, we tried to minimize multiple access interference (MAI), consequently diminish the phase induced intensity noise (PIIN) by using this new code with the main characteristic of zero cross correlation in its property. This code was investigated and analyzed for its performance in the network system. Another aim was to find out the components and parameters used in order to optimize the performance of the code. Finally, the analysis was validated by comparing theoretical studies with the simulation results. The method of combinatorial matrix was applied in developing this zero cross correlation (ZCC) code. By using SAC incoherent OCDMA techniques, we were able to mitigate the PIIN effect in the system performance. The study of system performance methodology in ZCC code was conducted and used to generate the mathematical derivation for the code performance theoretically.The simulation was conducted with optimization of the parameters involved to obtain the best performance in the system. The validation of the theoretical results was confirmed through this simulation analysis. The great contribution of ZCC code was that there was no overlapping of bit ‘1’ among users and absolutely orthogonal for any number of users and weights. The code structure was very flexible especially in changing code parameter such as the number of users and the number of weight. The code demonstrated an excellence in signal security due to the random code structure. Our performance analysis showed ZCC code has a better performance compared to other codes in the same class of SAC. It could also accommodate a higher number of users simultaneously. This system could support 110 users simultaneously with a permissible bit error rate of 10-9. Power required was lower at the photo detector which means the detection system required less power by applying this code. Direct detection technique used in the ZCC coding system reduced the number of filters, thus led to less system cost. The results showed that employing ZCC coding technique achieved higher bit rates up to 10 Gigabits per second compared to other coding techniques. The principal conclusion was that by the invention of the new ZCC code, it contributed to the solution of many issues in OCDMA such as reduction of MAI, increased the number of users accommodated, increased effective power at the detector, higher bit rates being transmitted, enhanced security and reduced the complexity by using a direct detection technique.