Mitigation of turbulences induced by air bubbles and performance enhancement in 112 Gbps UWOC link with coherent detection MIMO PDM-QPSK and advanced digital signal processing

The UWOC link range is significantly limited by the severity of the turbulent nature of the ocean. The present study investigates the performance of a high-speed spectrally efficient UWOC link incorporating polarization division multiplexing based quadrature phase-shift keying modulation scheme operating at a data rate of 112 Gbps. To alleviate the absorption, scattering, and turbulence induced by air bubbles, a digital signal processing aided coherent detection system is deployed at the receiver node along with spatial diversity techniques. It is observed that the operational link range under pure seawater is 195 m for single input single output configuration. The link length extends to 215 m for 3 × 3 repetition coding multiple-input multiple-output configuration. Considering the dynamic nature of the oceanic medium, the maximum link range feasibility analysis is also verified using Monte Carlo yield estimation. The received power improvement of 5.02 dBm is observed for 3 × 3 MIMO over 1 × 1 SISO configuration. Thus, the proposed MIMO technique reduces the impact of underwater turbulence on the propagating beam and as a result, it increases the reliable communication range for all the water scenarios.