The role of material properties in the strain testing using microstructured Polymer Optical Fibres (mPOF)

Optical fibre sensors have conventionally been made of silica. Polymer optical fibres have a much lower Young's modulus, and higher elastic limit than silica, and can be incorporated into a large range of materials. Whilst these properties make them attractive for using in mechanical sensing, using polymers also brings complexity because of their viscoelastic response. In this work, we use long period gratings (LPG) in microstructured polymer optical fibre (mPOF) as an optical sensor. The effects of stress and strain on the sensor are decoupled and analyzed independently. It has been proposed that the relaxation of stress in the optical fibre during loading would have a significant effect on the interpretation of the optical sensor output. However through the experiments and modelling in this study it has been shown that the effect of stress is minimal.