High strain and high strain gradients measured with fiber Bragg gratings in structural engineering applications

We report on the monitoring of high strain and high strain gradients with narrow spaced fiber optical Bragg gratings placed inside structural important components. The fiber optical measurements are based on an interferometric, tunable laser set-up that allows distributed strain sensing over many Bragg gratings of identical wavelengths along several meters of the sensing fiber. Estimated strain resolution for the discussed application is 20 /spl mu/m/m. Strain and strain gradients of 27 mm/m and 2000 mm/m per meter were measured, respectively.