Performance investigation of hybrid air and underwater wireless optical communication systems using RGB lasers under varying types of liquid and environment effect

Underwater wireless optical communication (UWOC) is a technology that enables high-speed data transmission through water using light, typically from lasers or light-emitting diodes (LEDs). In this research we propose a red, green and blue (RGB) of laser diodes (450 nm, 518 nm, and 655 nm) in UWOC system with a data rate of 2.5 Gbps over a distance of up to 17 m in a water-air medium. Moreover, the UWOC system was tested with various water types, including tap water, chlorine-treated water, and chlorophyll-containing water, across different levels of turbidity. The bit error rate (BER) values obtained using a blue laser diode were 1.12 × 10⁻⁸, 3.15 × 10⁻⁸, and 1.19 × 10⁻⁷, respectively under different water density. Furthermore, the effects of turbulence and temperature variations in the water environment were considered in this system. The turbulence caused scattering, diffraction, and refraction of the laser light, which results in increased signal distortion. The BER value of blue, green, and red laser can achieve up to 3.3 × 10⁻⁷, 5.8 × 10⁻⁶, and 4.6 × 10⁻⁴, respectively under turbulence influence. In contrast, variations in water temperature had minimal impact on the loss associated with each laser diode across different water types. However, temperature changes induced wavelength shifts in the laser light. The RGB laser source can achieve BER under the forward error correction (FEC) limit. This study can further improve the researcher design of their UWOC system for various applications.