Layered coating applications for sensing telemetry are provided. An example method can include depositing an optical waveguide on an inner surface of a wellbore tool, the optical waveguide including a first layer of low refractive-index material, a second layer of high refractive-index material applied to a first surface of the first layer, and a third layer of low refractive-index material applied to a second surface of the second layer; configuring non-uniformities at one or more locations of the optical waveguide, the non-uniformities configured to reflect or scatter light at angles relative to a site of interaction between the light and the non-uniformities; determining a reflection and/or transmission pattern of light propagated through the optical waveguide and reflected or scattered by the non-uniformities; and based on the reflection and/or transmission pattern of the light, determining one or more conditions associated with of the wellbore tool.