  Transformation optics is used to prove that a spherical waveguide filled with
an isotropic material with radial refractive index n=1/r has radial polarized
modes (i.e. the electric field has only radial component) with the same perfect
focusing properties as the Maxwell Fish-Eye lens. The approximate version of
that device using a thin waveguide with a homogenous core paves the way to
experimentally prove perfect imaging in the Maxwell Fish Eye lens.
