Electro-Optically active Guided Wave Optical Components are only commercially available in Lithium Niobate substrate material. In this paper some examples of the applications of these components are given, along with a comparison between Lithium Niobate based components and those fabricated in other materials. The advantages of Lithium Niobate components in terms of cost and performance for both electro-optical, passive and non-linear optical waveguide devices are highlighted.