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This paper introduces a high transmission and secure Underwater Optical Wireless Communication (UOWC) system using Dual Polarization (DP) states, each of them carries three channels assigned with Optical Code Division Multiple Access (OCDMA) code; named, Fixed Right Shift (FRS). A comparison between different transmission powers is performed. The system performance is evaluated across five distinct water types; pure seawater (PS), clear ocean (CL), coastal ocean (CS), harbor I (HI), and harbor II (HII). Assessments encompass received power, Bit Error Rate (BER), eye diagrams, and Q-factor. Comparative analyses are conducted at data rates of 2.5, 5, and 10 Gbps across each water type. The results indicate that the Laser Diode (LD) sources with 15 dBm transmitted power yield higher received powers compared to that with 10 dBm. Additionally, the optimal system performance characterized by lower BER, higher Q-factor, and wider eye openings, is observed in water types with lower attenuation, such as PS and CL, and at lower data rates. Conversely, higher attenuation water types, like HI and HII, achieve lower performance metrics. Moreover, our model can successfully allow six channels, each delivering 10 Gbps data, propagate distances up to 35 m for PS, 22 m for CL, 13.6 m for CS, 7.1 m for HI, and 4.45 m for HII, demonstrating BER ∼ 10 - 4 and Q-factor of ∼ 4. [ABSTRACT FROM AUTHOR]

In this paper, three different modulation formats; namely non return to zero (NRZ), alternate mark inversion (AMI), and carrier compressed return to zero (CSRZ) are used in an underwater optical wireless communication (UOWC) system. A laser diode (LD) source operating at 532 nm is used. A comparison of transmission performance using these modulation schemes in the UOWC system are preferred in terms of received optical power, bit error rate (BER), Q-factor, and eye diagrams at 10 Gbps data rate. Additionally, real underwater environments such as pure sea (PS), clear ocean (CO), coastal sea (CS), harbor I (HI), and harbor II (HII) are considered. The simulation findings indicate that using the NRZ modulation scheme in UWOC system achieves the best performance, while the worst performance is observed when CSRZ is utilized. Further, the low attenuation caused by PS results in a longer underwater distance with higher received power and lower BER. At BER ∼ 10 - 9 , and received power of ∼ − 21 dBm, the underwater spans of 28 m for PS, 18.6 m for CO, 11.7 m for CS, and 4.06 m for HII are obtained when NRZ line coding is employed. Furthermore, at the same BER and received power, these underwater ranges are decreased to 26.3 m, 17.8 m, 11.3 m, and 3.96 m for PS, CO, CS, and HII, respectively, when CSRZ modulation format is used. [ABSTRACT FROM AUTHOR]

This paper proposes a novel 4 × 10 Gb/s underwater optical wireless communication system based on orbital angular momentum (OAM) multiplexed beams. The proposed transmission uses four OAM beams based on Laguerre-Gaussian profiles, each transporting data at 10 Gb/s at 532 nm operating wavelength. The system performance is evaluated for five different types of water environments, i.e., pure sea (PS), clear ocean (CO), coastal ocean (CS), harbor I (HI), and harbor II (HII) by measuring the received optical power (ROP), underwater transmission distance, bit error rate, beam divergence angle, eye-diagrams, and receiver aperture diameter. The obtained results show that the PS has the longest underwater propagation distance of 10 m, while HII has the shortest range of 2.62 m due to high attenuation at ROP of approximately −18 dBm. The underwater span achieved at the same ROP value for CO, CS, and HI are 8 m, 6.1 m, and 3.85 m, respectively. [ABSTRACT FROM AUTHOR]