An optical waveguide is a form of a dielectric waveguide, that is capable of guiding an optical signal. The optical waveguide can be used as an component in integrated optical circuit or as a transmission medium in local or long haul communication systems.

Optical waveguides can be classified according to their geometry (planar, strip or fiber waveguides), mode structure (single-mode, multi-mode), refractive index distribution (step or gradient index) and material (glass, polymer, semiconductor).