Analysis of Channel Models for Underwater Wireless Optical Communication Systems Using Eye Diagrams and BER

Underwater optical wireless communication (UWOC) stands out among other communication methods for its potential for high data rates and broad bandwidth. Reliably modelling the underwater channel is crucial to realising these advantages and optimising system performance. This paper investigates and analyses the performance of UWOC optical receivers by utilising the channel impulse response within its individual formulation criteria across four different channel models: Double Gamma Functions (DGF), Weighted Double Gamma Functions (WDGF), Combination of Exponential and Arbitrary Power Functions (CEAPF), and Beta Prime (BP). The study examines two water types (harbour and coastal) and two transmitted pulse shapes (rectangular and Gaussian). Two indicators for reviewing receiver performance are employed: (I) eye diagram (ED) analysis, both with and without inter-symbol interference (ISI), (II) BER in relation to signal-to-noise ratio (SNR), and (III) a range of transmitted pulse widths at half maximum (PWHM) from 0.1 to 0.7 to expand the ISI assessment. The results show that the rectangular pulse performs well across the investigated pulse-width range for the considered channel models, as indicated by the eye-diagram responses. For the investigated conditions, ISI generally increases the model-corresponding BER compared with the case without ISI for each model within its formulation environment. However, the magnitude of the increase varies among the channel models, water types, and pulse shapes. Depending on the pulse shape, the DGF and BP models exhibit high susceptibility to severe Inter-Symbol Interference (ISI), resulting in the highest absolute error floors. Conversely, the WDGF model demonstrates superior baseline accuracy, maintaining the lowest absolute BER across both rectangular and Gaussian signal waveforms in harbour water. Additionally, the results reveal that while all models experience extreme BER degradation in rectangular-pulse coastal environments, the CEAPF model demonstrates the highest overall structural resilience by minimising the average relative BER increase. The results provide an analytical assessment of how different channel impulse-response models affect UWOC receiver performance and provide a basis for future development of a machine-learning-based digital receiver decision unit.