Optimal positioning of continuous optical fiber sensors for the modal analysis of turbine blades with optical backscatter reflectometer technology

There are many methods described in the literature for the modal analysis of turbine blades, using well established technologies. The aim of this paper is the introduction of a new method, based on continuous optical fiber sensors and on optical backscatter reflectometer (OBR) technique. Contrary to other methods, the sensor is not invasive and all the measuring points are aligned in sequence on the same wire (i.e. the same optical fiber) characterized by a limited length. In the literature, many optimal positioning methods for the sensors have been proposed, but none of them considers sensors arranged sequentially along the same wire, limiting to independent sensors, such as strain gauges or accelerometers. On the contrary, in this paper, an optimal method is proposed and illustrated in detail to arrange the optical fiber along the blade to perform the modal analysis. Finally, some numerical and experimental tests performed on a blade will be presented.