The far-field expansion of the Green's function in a 3-D optical waveguide

In this paper we find the far-field expansion of the outgoing Green's function in a three-dimensional cylindrical optical waveguide. As model for the field propagation we use the Helmholtz equation. We compare our results with the related paper (J. Inst. Math. Appl. 21(3) (1978), 315–330).