Scintillation Characteristics of Annular Beam Array in Underwater Optical Links

Abstract

Underwater optical wireless communication systems offer a promising alternative to traditional acoustic methods for achieving high data rate transmission. However, the propagation of optical waves in underwater environments is severely impacted by oceanic turbulence, leading to intensity fluctuations and consequent performance degradation. In this work, we employ a laser beam array to model transmit spatial diversity for suppressing these fluctuations. The model uses annular-shaped lasers at the transmitter as a representation of beam shaping for turbulence mitigation, with a point detector assumed at the receiver. Through the use of the Huygens-Fresnel principle, we derive two key optical parameters: the average received intensity and the average of the intensity squared. We subsequently determine the scintillation index for this model. Our findings demonstrate reductions in scintillation under varying system parameters. For instance, increasing the number of beams in the array, the ring radius, and the secondary field amplitude of the annular beam leads to a lower scintillation index.