Optical signal transmission for the visible light communication system through the water-air interface link

This article presents a theoretical method for assessing the impact of water depth on the water-air interface in a VLC system. Optical signals are sent using multiple input-multiple output (MIMO) technology and compared to a traditional single input-single output (SISO) method. We use modulation methods including RZ-OOK, NRZ-OOK, 32-PPM, and 4-QAM to superimpose information onto visible light for use in coastal waters. Bit error rate (BER) and data rate in relation to changing water depths are used to evaluate the system's efficiency. We also evaluate the stability of the MIMO strategy by taking into account obstacles like water attenuation and depth link impairments. Multiple limitations, such as water attenuation and the depth link, are taken into account to assess the MIMO approach's dependability. The findings indicate that the MIMO technique with a configuration of (4Tx/4Rx) has superior performance in terms of BER and data rate when compared to other techniques. Additionally, 32-PPM can perform better than other modulation schemes and is seen as the ideal choice for NLoS since it offers the best maximum depth at the lowest BER while also providing a high data rate. When comparing APD PD to PIN PD, it is seen that APD PD exhibits the capability to operate in J9C conditions and effectively detect optical signals with a high level of performance, specifically at 32 PPM.