Optical CDMA code based on Diagonal Eigenvalue Unity (DEU)
In recent years, optical Code Division Multiple Access (optical CDMA) has become an interesting research area in optical communication technologies. Optical CDMA technology has obvious superiority for constructing the local area networks (LANs) and access networks in contrast to other multiplexing techniques. The need for transmission security in the developing of optical CDMA networks at the physical layer is becoming increasingly important. Spectral Amplitude Coding (SAC) is an encoding approach to implement optical CDMA networks. Although the system performance of SAC optical CDMA has been presented by many researchers, its security show has not presented widely. Therefore, there is a need to investigate the transmission security that can be provided by SAC optical CDMA. In this work, security performance of SAC optical CDMA schemes has been investigated. A new two dimensional Diagonal Eigenvalue Unity (2D-DEU) code is developed for the spectral/spatial optical code division multiple access (OCDMA) system. It has a lower cross correlation value compared to two dimensional diluted perfect differences (2D-DPD), two dimensional Extended Enhanced Double Weight (2DExtended-EDW) codes. Also, for the same code length, the number of users can be generated by the 2D-DEU code is higher than that provided by the others codes. The Bit Error Rate (BER) numerical analysis is developed by considering the effects of shot noise, phase induced intensity noise (PIIN), and thermal noise. The main result shows that BER is strongly affected by PIIN for the higher source power. The 2D-DEU code performance is compared with 2D-DPD, 2D-Extended-EDW and two dimensional multi-diagonals (2D-MD) codes. This comparison proves that the proposed 2D-DEU system outperforms the related codes.