Discussion of HS formulation using equivalent current theory [optical fibre theory]

The coupled mode formulation of Hardy and Streifer (HS) (1985) is currently under discussion. The author derives the HS formulation by the equivalent current theory of optical waveguide coupling, and hence show that the HS formulation is based upon the same principles of the common coupling equation and is correct only under weakly coupling condition. By making this clear and defining the weakly coupling condition quantitatively, the debate may be closed