Numerical simulation of laser propagation in ocean turbulence with the nonuniform fast Fourier transform algorithm

Abstract

Our work studies the spatial distribution of ocean optical turbulence through numerical simulation. We used the ocean optical turbulence phase screen created by the ocean power spectrum to study the effect of varying the refractive index of water via a laser beam propagating through ocean optical turbulence. Because the intensity of ocean optical turbulence is much higher than that of atmospheric turbulence, when simulating the ocean phase screen, traditional methods based on the fast Fourier transform (FFT) algorithm introduce enormous errors in the low-frequency band. Some interpolation algorithms commonly used in atmospheric turbulence simulation can reduce these errors. However, their calculation complexity is always high, so the computational speed is slow. We combine a nonuniform sampling method based on variations in the ocean turbulent power spectrum and the nonuniform FFT algorithm to generate phase screens of ocean optical turbulence. The proposed algorithm can solve the deficiency of the long runtime of the traditional algorithm with even better accuracy. In addition to the traditional phase structure function, we measured the far-field distribution of the laser transmitting through water turbulence caused by temperature contrasts, and the experimental results have outstanding agreement with the simulated far-field image from our ocean phase screen. To the best of our knowledge, this is the first work to verify the accuracy of the phase screen by conducting far-field image experiments.