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 b eam 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 compe nsation has been taken into account for the strain measurement due to sunli ght radiation. The compressive strain has been measured, without needing pr etension on the fiber with a Brillouin scattering-based distributed sensor system, when the fiber is glued to the steel beam at every point. The dynam ic range in the strain measurement has been increased due to the eliminatio n of the pretension requirement. The spatial resolution of the strain measu rement is 0.5 m. The strain measurement accuracy is +/- 10 mue (mum/m) in t he laboratory environment with nonuniform-distributed strain. With uniform strain distribution, the strain accuracy for this system can be similar to +/-5 mue. These results were achieved with the introductions of a computer- controlled polarization controller, a fast digitizer-signal averager, a pul se duration control, and the electrical optical modulator bias setting in t he software.