Polymer optical fiber specklegram strain sensor with extended dynamic range

A polymer optical fiber strain sensor with extended dynamic range is reported. The proposed algorithm resets the reference fiber status depending on the magnitude of the specklegram deviation so the correlation coefficient never saturates, yielding a continuous response over the full range for both positive and negative strains. The technique was evaluated on the measurement of axial strains using a ZEONEX core, poly(methyl methacrylate) cladding multimode fiber, presenting reproducible results with 3 × 10 − 3 μϵ − 1 sensitivity (∼15 μϵ resolution) within a 22,600 μϵ interval. In contrast to the available approaches, the presented method can retrieve the strain direction and does not require intensive image processing, thus providing a simple and reliable technique for mechanical measurements using multimode optical fibers.