Comparison of NLoS and LoS transmission techniques for UWOC using a 520 nm wavelength laser source

The paper presents an experimental demonstration of an underwater wireless optical communication (UWOC) system over a set distance of 1m using an on–off keying non-return-to-zero (OOK-NRZ) modulation technique. The optical transmitter source utilizes a laser diode (LD) with a wavelength of 520 nm, while the silicon PN photodiode serves as the receiver for the signal. Texts were transmitted through a channel in two cases: LOS and NLOS links at different concentrations of sodium chloride salt NaCl (10%, 20%, and 30%). We achieve a minimum attenuation coefficient of 0.265 dB/m and a lower BER of 1 × 10⁻² at the LOS link configuration in clear water, respectively. MATLAB software was used to calculate the received power and attenuation coefficient for both cases.