Efficient Mode-Coupling Calculation for Constant Depth Ocean with Range-Dependent Sound-Speed Fluctuation

In this paper, a criterion for efficient coupled-mode matrix calculation in a constant depth ocean with range-dependent sound-speed fluctuation is proposed. The usual stepwise coupled mode requires high computational power to calculate the mode-coupling matrix at each interface of the range segment. To reduce the computational complexity, the criterion for selecting appropriate mode pairs, which strongly affects the mode-coupling matrix, is derived from perturbation theory. This criterion determines the effective range of the modal beat wavenumber. Numerical examples indicate that compared with the full calculation of the mode-coupling matrix, for the calculation using the proposed criterion, the computational complexity is significantly reduced, while the accuracies of the mode-coupling matrix and acoustic field are maintained.