Multilevel polarization shift keying modulation for turbulence-robust underwater optical wireless communication.

Turbulence is an intractable issue for underwater optical wireless communication (UOWC). Most literature has been mainly focused on the modeling of turbulence channels and performance analysis rather than mitigation of the turbulence effect, especially from the experimental aspects. In this paper, a multilevel polarization shift keying (PolSK) modulation based UOWC system is established utilizing a 15 m-long water tank, and the system performance is investigated under specific temperature gradient-induced turbulence and various transmitted optical powers. Experimental results show the feasibility of the PolSK in alleviating the effect of turbulence, and the bit error rate performance significantly outperforms traditional intensity-based modulation schemes which have difficulty in obtaining an optimal decision threshold in a turbulence channel.