How Reliably do Fiber Bragg Grating Patches Perform as Strain Sensors?

In Germany, the first guideline for the use of fiber Bragg grating strain sensors, “Optical Strain Sensor based on Fiber Bragg Grating” (Berlin, Germany: Beuth-Verlag, 2010), has been developed by the GESA guideline group of VDI, “The Association of German Engineers” and published by Beuth-Verlag. This guideline provides the basic specifications of this sensor type and the sensor characteristics, which have to be known for a reliable sensor performance. In conformity to this guideline, experimental investigations on the strain transfer characteristics of fiber Bragg grating patches have been carried out. A comparison between patches and resistance strain gauges during tensile tests and combined temperature and tensile loading was carried out. The evaluated strain gauge factor and the temperature sensitivity of the strain gauge factor have been compared to the manufacturer´s data. The overall performance of the patches has been evaluated. The experimental investigations showed that there are considerable disagreements between the manufacturer´s specifications and the observed characteristics.