## 2 Related Works  
In recent years, there has been a growing body of research focused on advancing the field of UWOC, aiming to overcome the challenges of underwater connectivity and harness the potential of optical communication for seamless data transmission below the water's surface. Authors in 2021 [14] explored three schemes for achieving large-capacity underwater optical transmission systems: OFDM with LD, WDM transmission, and OAM transmission. These technologies offer advantages such as high-speed communication, resistance to interference, and increased transmission capacity. They hold promise for underwater inspection and exploration due to their sufficient bandwidth, reliability, and cost-effectiveness. In 2022 [15], authors proposed a quasi-cyclic low-density parity-checked (QC-LDPC) code with multiple-pulse-position modulation (MPPM) to address turbulence-induced fading in UWOC systems. MPPM offers a balance between power and bandwidth efficiency. Simplified LLR decoding is used, and closed-form expressions for BER are  
Figure 1: Underwater optical wireless communication link. derived. The reported results validate the efficacy of the proposed LDPC code in improving the performance of BER for different MPPM formats over fading channels. Another study in 2022 [16] analyzes the BER performance of UWOC systems with OOK modulation and APD detector with various oceanic turbulence distributions. A mathematical model is developed considering absorption, scattering, and turbulence effects. Closed-form expressions for BER are derived for different turbulence distributions, considering both high- and low-ISI scenarios. Theoretical analysis and simulations confirm the accuracy of the derived expressions, aiding the design and evaluation of UWOC systems. Authors [17] addresses the complexity issue of lookup table (LUT) predistortion in underwater wireless optical communication (UWOC) systems. A multi-modulus weighted strategy is proposed to reduce the size of the LUT while maintaining performance. Experimental results demonstrate significant reduction in LUT size, with the proposed MMW-RLUT accounting for a fraction of the full-size LUT across various QAM modulations without performance degradation. In 2023 [18], authors investigated the self-interference problem in NOMA-based underwater wireless optical communication systems. Their work proposes an ACPS coding scheme to eliminate decoding errors caused by self-interference within NOMA paired groups. Additionally, a GSPA algorithm was designed to optimize power allocation and reduce the bit error rate (BER) in turbulent environments. Simulation results show significant BER reduction in the ACPS-based UWOC-NOMA system compared to conventional systems, considering light-intensity scintillation. Another study in 2023 [19] demonstrates the effectiveness of a modified CNN model in addressing attenuation challenges in underwater optical wireless communication. The proposed CNN decoder significantly improves BER, SNR, and effective channel length compared to a conventional decoder. It achieves a decrease in BER by several orders of magnitude, increased channel length, and decreased SNR. The results make the CNN decoder an ideal substitute for ordinary underwater optical communication decoders. On the other hand, various multiplexing schemes, such as wavelength division multiplexing (WDM) [20,21], polarization division multiplexing (PDM) [22, 23, 24], and mode division multiplexing (MDM) [25, 26], have been proposed to enhance channel capacity in optical wireless communication. Among these, PDM has emerged as a valuable technique for optical communication systems, offering several advantages [27]. It enhances capacity, robustness, and signal quality by leveraging polarization diversity. PDM improves communication in turbid waters, enhances beam alignment and stability, addresses underwater geographical variations, and offers energy efficiency.