Tensile and compressive strain measurement in the lab and field with the distributed Brillouin scattering sensor

The structural strain measurement of tension and compression in the steel beam was demonstrated with a distributed fiber-optic sensor system based on Brillouin scattering. The experiments were conducted both in the laboratory and outdoors. When it is in the outdoor environment, the temperature compensation has been taken into account for the strain measurement due to sunlight radiation. The compressive strain has been measured, without needing pretension on the fiber with a Brillouin scattering-based distributed sensor system, when the fiber is glued to the steel beam at every point. The dynamic range in the strain measurement has been increased, due to the elimination of the pretension requirement. The spatial resolution of the strain measurement is 0.5 m. The strain measurement accuracy is /spl plusmn/10 /spl mu//spl epsi/(/spl mu/m/m) in the laboratory environment with nonuniform-distributed strain. With uniform strain distribution, the strain accuracy for this system can be. /spl sim//spl plusmn/5 /spl mu//spl epsi/. These results were achieved with the introductions of a computer-controlled polarization controller, a fast digitizer-signal averager, a pulse duration control, and the electrical optical modulator bias setting in the software.