State-of-strain evaluation with fiber Bragg grating rosettes: application to discrimination between strain and temperature effects in fiber sensors.

An optical rosette that incorporates fiber Bragg gratings as strain gauges has been designed, fabricated, and tested. We investigated it by measuring the state of strain of a thin plate as the test structure submitted to an increasing load in a four-point bending configuration and for various angular orientations. This device has also been successfully investigated as a self-temperature-compensated in situ uniaxial strain sensor without any angular dependence and with high accuracy in recovery analysis, leading us to expect many industrial applications. Printed circuit processes or integrated optics on polymers would provide a means for accuracy, reproducibility, and integration in a mass-produced process.