Enhancing UWOC link performance using a hybrid OFDM/SAC-OCDMA system

This study proposes a novel UWOC system that combines Orthogonal Frequency Division Multiplexing (OFDM) with Spectral Amplitude Coding-Optical Code Division Multiple Access (SAC-OCDMA). The integration of these technologies aims to enhance various quantitative parameters, including the number of simultaneous users, effective power, spectral occupancy, and quality of service. The system adopts m-Quadrature Amplitude Modulation (m-QAM) as the modulation scheme for OFDM, along with the utilization of the Latin Square Code (LSC) as the signature code for SAC-OCDMA. To prove the performance of the hybrid OFDM/SAC-OCDMA system, both analytical and numerical evaluations are investigated for different water types such as; pure seawater, clear ocean water, and coastal ocean water. The system’s performance is assessed in terms of Bit Error Rate (BER) as a function of UWOC link range, transmitted power, number of simultaneous users, data rate, QAM constellations, inclination angle, and divergence angles of the optical beam. The results demonstrate that the implementation of the OFDM technique within the SAC-OCDMA system significantly enhances system performance by achieving impressive bit rates, reaching 860 Gbps in pure seawater, 736 Gbps in clear ocean water, and 7 Gbps in coastal water for 15 users, all while maintaining a BER of \(10^{-9}\). Additionally, the study identifies the minimal power levels at 15.27, 15.6 and 25.8 dBm for pure seawater, clear ocean water, and coastal ocean water, respectively. These findings highlight the superiority of the OFDM/SAC-OCDMA system over conventional SAC-OCDMA in terms of performance and capacity.