Investigation of hybrid LD/LED system for UWOC link with depth variations

Abstract In this paper, An UWOC system using a hybrid LD/LED link is proposed. A simulation was assumed to study the quality of the received optical signal with different modulation schemes such as 64-PPM, 4-QAM, NRZ-OOK, and RZ-OOK. A total of 64-PPM modulation schemes have enhanced the distance link compared with other modulation schemes. PIN and APD PDs are employed to validate the quality of the received optical signal under different water depths. Various metrics of BER, Q. factor, and data rate was introduced to assess the reliability of the hybrid LD/LED link. The simulation results show the proposed system can be achieved a good link with different water depths. The attenuation coefficient of water varies with depth and restricted the performance link distance by hybrid LD/LED link. The 64- PPM is a suitable modulation scheme for getting a long-distance link. The photodetector APD PD outperforms the PIN PD when 64-PPM and 4-QAM are applied.