Fabrication and evaluation of hybrid silica/polymer optical fibre sensors for large strain measurement

Silica-based optical fibre sensors are widely used in structural health monitoring systems for strain and deflection measurement. One drawback of silica-based optical fibre sensors is their low strain toughness. In general, silica-based optical fibre sensors can only reliably measure strains up to 2%. Recently, polymer optical fibre sensors have been investigated for large strain measurement. Because of their high optical losses, the length of the polymer optical fibres is limited to 100 m. In this paper, we present a novel economical technique to fabricate hybrid silica/polymer optical fibre sensors that are capable of measuring large strain. First, stress analysis of a surface-mounted optical fibre sensor is performed to understand the effect of mechanical properties on the load distribution between the optical fibre and the host structure. Next, the procedure for fabricating a tapered polymer sensing element between two silica optical fibres is explained. The experimental set-up and the Components used in the fabrication process are described in detail. Test results of the fabricated silica/polymer optical fibre strain sensor are presented.