Analysis of Orbital Angular Momentum Laser Beams for Applications in Underwater Communication

Underwater communications present a challenge in the US Naval Undersea Community. During underwater operations, command and control requires effective communication on both a tactical (short-range) and strategic (long-range) level. One approach to address this issue would be the use of an optical beam to transmit underwater. This paper evaluates the use of an Orbital Angular Momentum (OAM) beam and their effectiveness in underwater transmissions as compared to a Gaussian beam. The normalized variance, or scintillation index is used as the metric for comparison. Additionally, an in-laboratory underwater turbulence emulator is used to generate and control various environmental parameters to include varying levels of salinity as well as temperature gradients. The goal of the emulation is to be able to simulate some of the scaled effects of various environments in order to better predict and gain intuition and understanding of the performance of an optical system in various environments. Results provided evaluate efficiency as a function of environmental conditions and scintillation index. Transmission in the 532 nm band is analyzed.