A material
medium that confines and guides a propagating
electromagnetic wave. (
188 )
Note 1: In the
microwave regime, a waveguide normally consists of a hollow metallic conductor, usually rectangular, elliptical, or circular in cross section. This type of waveguide may, under certain conditions, contain a solid or gaseous
dielectric material.
Note 2: In the optical regime, a waveguide used as a long
transmission line consists of a solid dielectric filament (
optical fiber), usually circular in cross section. In integrated optical circuits an
optical waveguide may consist of a thin dielectric film.
Note 3: In the rf regime, ionized layers of the stratosphere and refractive surfaces of the
troposphere may also act as a waveguide.