Low cost optical fibre based Fabry Pérot strain sensor production

The production of Fabry-Pérot based optical fibre sensors has long been an iterative and labour intensive process. This paper demonstrates the production of Fabry-Pérot based optical fibre strain sensors using chemical etching techniques. Utilising hydrofluoric acid (HF) and singlemode optical fibres, a preferential etching mechanism was observed around the core portion of the fibres. These etched fibre ends were then spliced together successfully to form enclosed Fabry-Pérot cavities between 18 and 60 μm in length. These sensors have then been deployed for strain monitoring and have been subjected to strains of up to 1400 με on tensile test specimens. Etched Fabry-Pérot cavity lengths were monitored using a white light interferometry (WLI) system based on a CCD spectrometer and an 850 nm super luminescent diode (SLD). A linear and repeatable response to these strain tests has been shown with negligible sensitivity to temperature.