High speed acoustic communication with orbital angular momentum multiplexing

Abstract

Acoustic communication is critical for underwater application such as deep ocean scientific explorations, off-shore industrial controls, and ocean environment monitoring. This is because other techniques using electromagnetic waves such as RF communications are difficult for underwater applications due to the strong absorption of water in such a frequency. Optical communication, on another hand, suffers from the light scattering from micro-particles or marine life making long range underwater optical communication very challenging. Therefore, using acoustic waves to transmit information is currently the dominate technique for underwater applications including data collection and remote control of off-shore benthic stations. However, the low frequency bandwidth available for acoustic communication limits the data transmission rate and information capacity or content. We propose and experimentally demonstrate here a new approach using the orbital angular momentum (OAM) of acoustic vortex beams which provides a new and independent channel that enhances the data transmission rate by eight fold. The OAM multiplexing method demonstrated here will impact significantly on future underwater communications.

Acoustic metasurfaces

“…5d) can produce a metasurface with a first-order acoustic vortex with spiral phases and orbital angular momentum. Other set-ups have been proposed 28,[95][96][97] , and applications of acoustic vortices have been studied [98][99][100][101][102] .…”

Meta-neural-network for real-time and passive deep-learning-based object recognition

“…For further demonstrating the potential of our meta-neural-network to recognize very complicated object in real-time with compact footprint, we showcase a distinctive example in which one needs to accurately distinguish between different spatial patterns of wave field that are encoded with information and far more sophisticated than the scattered patterns produced by simple digit-shaped objects. As a representative case, the introduction of orbital angular momentum (OAM) opens a new degree of freedom for information encoding and dramatically improves the capacity of waves as information carriers 51,52 , which is of crucial significance particularly for acoustic waves that dominate underwater communications but innately bear no spin [53][54][55] . Such spatial multiplexing mechanism uses several twisted beams with different topological charges (TCs) to carry multiplexed information which, however, needs to be read out accurately from the complicated spatial pattern of this synthesized beam.…”

Perspective on using multiple orbital-angular-momentum beams for enhanced capacity in free-space optical communication links

“…Separate from using optical beams, free-space communication links can take advantage of mode multiplexing in many other carrier-wave-frequency ranges to increase system capacity. For example, OAM can be manifest in many types of electromagnetic and mechanical waves (see Figure 8), and interesting reports have explored the use of OAM in millimeter, acoustic, and THz waves [47][48][49][50][51][52][53][54][55].…”