Distributed sensors for damage detection and localization

Distributed fiber optic sensing technology based on Brillouin scattering effect has been proven as a mean to assess average strain and average temperature distributions in structures. However, detection of damage such as crack is very challenging, since only a short portion of sensor, much shorter than spatial resolution of the system, is exposed to very high concentrated strain. Beside this, the sensing fiber itself suffers from concentrated stresses and may be broken. In order to resolve above mentioned issues, first the detection algorithm was improved in order to make system sensitive to measurand changes occurring over length shorter than spatial resolution, and second a special manner of sensor installation is developed in order to make possible for optical fiber to survive high concentrated stresses. The system is applied on Götaälvbron (Gota Bridge), Gothenburg, Sweden, for the first time at a large scale. Number of reduced and full scale tests was performed in order to assess performance of the system. The system, its implementation method and results of the tests are presented in this paper.