  In a water-air optical wireless communication (OWC) channel, dynamic ocean
waves may significantly deflect the light beam from its original direction,
thus deteriorating the communication performance. In this letter, a beam
tracking system to mitigate wave-induced communication degradation is
experimentally demonstrated. By employing the beam tracking on the PAM6 system,
a maximum of 486% improvement (from 140 Mb/s to 820 Mb/s) in throughput is
realized at a 1.2-m air distance for an average wave slope changing rate of
0.34 rad/s. For PAM4 signals, the packet loss rate reduces significantly from
75% to 11%, and a maximum throughput of 1.25 Gb/s is achieved.
