A Comparative Study of Asynchronous and Synchronous OCDMA Systems

This paper presents a detailed survey on both asynchronous and synchronous Optical Code-‎Division Multiple-Access (OCDMA) systems based on one dimensional (1-D), two dimensional (2-D), and three dimensional (3-D) codes, distinctively. Accordingly, different coding schemes along with their multiplexing capacity, correlation features, advantages and drawbacks are addressed and benchmarked. Additionally, different detection techniques such as direct and coherent detection and their capability to handle Multiple Access-Interference (MAI) are also discussed. Furthermore, the most pertinent OCDMA systems from the last two decades are summarized considering their coding schemes, performance, device components and applications. Therefore, a new comparative study in terms of spectral efficiency and system performance assuming both the binomial approach and Gaussian approach for 1-D, 2-D, 3-D asynchronous and synchronous OCDMA systems is carried out. On the one hand, numerical results shown that the asynchronous 3-D modified quadratic congruence/prime hop code (3D-MQC/PHC) stands out among the codes with superior spectral efficiency up to 24%. On the other hand, 3D-MD synchronous code outperforms both 3D-PD and 3D-MD/PD codes in terms of allowed bit rate by a percentage of 59% at 300 simultaneous network subscribers.