Spatial-frequency-multiplexed optical fiber sensor array for structure monitoring

Abstract

A novel optical fiber sensor system suitable for monitoring the strain/stress distribution of mechanical structures is reported, in which an array of interferometric-type sensors is integrated based on a new spatial-frequency-multiplexing technique. It not only maintains the inherent advantage of the high dynamic range of interferometric sensors but also offers the additional benefits of simple robust system configuration, direct digital readout, and low building, installation, and maintenance cost. Preliminary experimental results on a suspension beam are reported.

<title>Composite-embedded highly birefringent optical fiber strain gauge with zero thermal-apparent strain</title>

“…Combining the interferogram Ij with its numerical Hubert transform [6] to give an analytic signal of the form Ii = 'Oj exp[iqj} (3) From which the extraction of is trivial. By fringe-unwrapping qj , we obtain the instantaneous scan delay -cb )HeNe ri-2-c () We then have a calibrated value of delay rj for each sample.…”

“…Optical fibre strain gauges [1] have many characteristics that are well-suited to this application: they can be embedded between the layers in the material [2], can be multiplexed in series and in parallel [3], and have a high tolerance to EMI. Fibre strain gauges that measure strain and temperature independently have been developed [4,5] which allows thermal-apparent strain to be calibrated out in signal processing, using knowledge of the host thermal expansion coefficient.…”