Accuracy of directional coupler theory in fiber or integrated optics applications

Abstract

Based on the solution of a simplified canonical problem, the possible margin of error on the predicted coupling length according to the coupled-mode theory as applied to fiber and integrated optical guides is inferred. It was found that coupling length obtained according to the coupled-mode theory is usually accurate to within 20% of the actual value provided that the frequency of operation is above the cutoff frequency of the antisymmetric mode of the coupled structure.