A prismatic reflection optical waveguide device having an input and an output optical waveguide segments and a reflection interface provided therebetween apt to convey a light beam from one direction to another, wherein the light beam is conveyed by a single reflection on the reflection interface. Such a prismatic reflection optical waveguide device may, for example, be used as an optical waveguide sensor for measuring the refractive index of a sample medium. The measuring range and/or the sensitivity of such an optical waveguide sensor may be adjusted according to a particular application. Such a prismatic reflection optical waveguide device may also be used as a generally lossless bent optical waveguide wherein the reflection interface works as a mirror for reflecting the light beam coming from the input segment to the output segment, thereby providing a generally lossless transmission.