The decoupling of stepwise coupled modes

A decoupling algorithm is applied to the calculation of stepwise coupled modes. The stepwise coupled mode method solves the reduced wave equation in a discretely range-dependent environment. The solution contains both forward and backscattered energy and hence involves waves that decay and grow with range. Numerical difficulties can arise in trying to resolve both rapidly growing and decaying waves over many wavelengths. The decoupling algorithm described here solves the numerical problem and extends the applicability of the stepwise coupled mode method.