Document Type : Research Article
Authors
1
Department of Communications and Computers Engineering, Higher Institute of Engineering, El-Shorouk Academy, El-Shorouk City, Cairo Governorate, Egypt.
2
Department of Electrical Engineering, Faculty of Engineering, October 6 University,6th of October City, 12585, Giza, Egypt.
3
Higher Institute of Engineering and Technology, kafr El-Shiekh, Egypt
Abstract
Underwater Optical Wireless Communication (UOWC) is gaining prominence as a promising solution for high-speed data transmission in marine environments, offering a viable alternative to conventional acoustic and RF systems. This study investigates the performance of six widely used modulation schemes—OOK, PPM, PAM, DQPSK, 16-PSK, and 32-QAM—under varying underwater conditions. The evaluation is conducted across four representative water types: pure sea, clear ocean, coastal ocean, and turbid harbor, each characterized by different absorption, scattering, turbulence, and noise levels. A green LED-PS operating at 520 nm, optimal for coastal and turbid waters, is employed alongside a SiPM-PD with a high sensitivity of –53.4 dBm. Performance is assessed through key metrics including received optical power, BER, SNR, channel capacity, and communication distance. Results at a target BER of 10⁻⁶ show that the required transmitted power increases markedly with both turbidity and modulation complexity, ranging from –2.10 dBm (OOK, pure sea) to 80.63 dBm (32-QAM, turbid harbor), while SNR demands rise from 17.59 dB to 43.58 dB. Maximum channel capacity reaches 47.6 bps/Hz with 32-QAM in pure sea water but drops to nearly zero in turbid harbor conditions. Similarly, the maximum achievable distance drops from 81.1 m (OOK, pure sea) to just 3.99 m (32-QAM, turbid harbor). At fixed SNR = 30 dB and receiver sensitivity of –53.4 dBm, communication distances follow consistent trends, confirming the crucial influence of both environmental conditions and modulation . These findings offer valuable insights into optimal modulation selection for robust and energy-efficient UOWC system design in diverse environments.
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