Multiple Fiber Loop Strain Rosettes in a Single Fiber Using High Resolution Distributed Sensing

Simple, circular loops in a single optical fiber bonded to a metal test sample are used to form multiple strain gauge rosettes. Strain measurements are made using an optical backscatter reflectometer to detect changes in the phase of the Rayleigh Scatter of the fiber with 160-μm spatial resolution along the length of the fiber. Applied strain levels, as well as the axis along which the loads are applied, are measured. Thermal gradients are also detected. The high spatial resolution and strain sensitivity of this technique enable highly functional fiber rosettes formed of small diameter loops of unaltered low-bend-loss optical fiber. Using this technique, multiple rosettes can be formed in a single fiber to created distributed measurements of principal strains.