Performance Analysis of Two-Level Asynchronous Optical CDMA Systems Utilizing Wrapped OPPM

In this paper the performance and the capacity of two-level asynchronous incoherent optical CDMA (OCDMA) systems employing wrapped overlapping pulse position modulation (WOPPM) and optical AND logic gate receiver are analyzed. These analyses are performed by considering the multiple access interference as the main limiting factor. Because of the power limitation in some laser sources, the same-symbol-power scheme for all users is assumed. Optical orthogonal codes with the same length are assigned to the users of each class. Considering the throughput as constraint, the effects of the number of users in each class and the weight of low-weight users on the performance of each class are examined and the results are compared with the same-mark-power case. Finally, the effect of WOPPM signaling parameters such as overlapping index and total number of symbols on the error probability of each class is investigated in the presence and in the absence of throughput constraint. Our results show that when the multilevel technique is employed in WOPPM OCDMA systems, one can find solutions for some design problems that cannot be handled by conventional one-level methods. In addition to this benefit, employing this technique leads to a less complex transceiver structure.