SUMMARY

The use of vortex waves in multiple environments is of increasing interest for numerous applications including underwater acoustic communications; however, the underwater acoustic communication environment is both complex and challenging. While radio frequency waves meet the needs of high-speed communications in air, they attenuate rapidly underwater due to absorption and their propagation is limited to centimeters. Acoustic waves, on the other hand, are capable of propagating long distances in underwater environments. Even so, the available bandwidth is still limited severely to tens of kHz by attenuation for ranges of tens to hundreds of meters. This causes bottlenecks in underwater acoustics communications channels. Acoustic orbital angular momentum (OAM) has been demonstrated as an additional degree of freedom which may be used to alleviate this bottleneck, though the development of arrays capable of implementing OAM-based communications systems in underwater acoustic communications channels is largely unexplored. This study addresses the challenges of developing these systems through modelling, simulating, designing, and testing OAM-based acoustic communications arrays. Ray tracing tools are employed to simulate performance of these arrays in various complex environments over multiple ranges and explore the array processing implications of these systems. A prototype system is developed for lab and field testing.