UV written planar waveguide sensors provide an integrated solution to refractive index sensors. The high sensitivity of the devices originate from their use of Bragg gratings which provide an accurate means of interrogating the local effective index. Conventionally the optical mode is made sensitive to an external refractive index by etching away the cladding and exposing it to an analyte. These devices have been used to sense liquid/solid phase changes and have displayed their potential for use as biological and chemical sensors. Recent results demonstrate sensitivities rivaling that of the highest specification Surface Plasmon Resonance (SPR) techniques. Here we introduce a new geometry which embraces the benefits of planar technology to realise new integrated devices. The geometry relies upon the use of a vertical trench or groove to produce an interface of optical quality which provides lateral access for an optical mode. The evanescent field interacts with the material within the groove and a Bragg grating in the region provides the means for interrogation. This reorientation of the sensor geometry provides additional flexibility to UV written devices, allowing several different sensors to be defined on the single substrate without multiple etching processes. These multiple sensors may offer complementary information such as the effective index as a function of penetration depth and interrogation wavelength for dispersion analysis. The paper also outlines the inherent feature benefits and fabrication advantages, including a reduction in return loss, spectral artefacts and stress induced birefringence.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.