Optical sensing system for determining the position and/or shape of an associated object

The present invention relates to an optical sensing system (1) for determining the position and/or shape of an associated object (O), the system comprises an optical fibers (10) having one or more optical fiber cores (9) with one or more fiber Bragg gratings (FBG, 8) extending along the full length where the position and/or shape is be to determined of said object (O). A reflectometer (REFL, 12) measures strain at a number of sampling points along the optical fiber cores, and a processor (PROC, 14) determines the position and/or shape based on said measured strains from the plurality of optical fiber cores. The fiber Bragg grating(s) (FBG, 8) extends along the full length of said optical fiber cores (9), the fiber core having a spatially modulated reflection (r) along the said full length of the optical fiber core so that the corresponding reflection spectrum is detectable in said wavelength scan. Thus, the fiber Bragg grating(s) may be effectively continuous along the optical fiber leaving no gaps so that ev