Investigation of an OFDR Fibre Braggs System for use in geotechnical scale modelling

A common challenge in experimental research is making measurements without unintentionally omitting data at key locations or altering the mechanical properties of the object of interest. In recent years fibre optic sensing systems have been used to overcome these challenges in both geotechnical field monitoring and full scale geotechnical laboratory experiments. However, fibre optics have found limited use in small scale modelling, typically for measuring the deformation of geosynthetics. In this paper we present an investigation into a fibre optics strain measurement technology that combines optical frequency domain reflectometry (OFDR) and Fibre Braggs Gratings (FBG) and could be beneficial to small scale geotechnical modelling, including centrifuge modelling. Specifically, this device has the capability of measuring over 2,000 points of strain at spatial increments of 6.35 mm over a single data acquisition channel and can measure 3D shape of a fibre bundle in real-time. The technology is evaluated using cantilever deflections tests, with comparison strain gauge measurements and 3-dimensional shape with visual comparison to the bending of a thin flexible rod.