Structural health and behavior monitoring has always been both a common concern and need in civil engineering. Several classic approaches have been given to this problem including the widely used strain gauges as well as the topographic measurements. These two techniques are almost always used to monitor the behavior of the structures whereas the health monitoring is accomplished by a simple periodic visual inspection. These approaches present serious problems that limit their practical use in real structures such as: lack of friability, long-term drift (strain gauges), impossibility of full-time measurements (topographic measurements), or lack of thoroughness (visual inspection). Centering the discussion in the strain gauges, for being the most representative of the classical civil engineering monitoring methods, it must be said that due to their electric nature they are expose to both electromagnetic interference and corrosion. The latter greatly reduce their operating life time pushing it typically to less than one year after installation. That is why new ways of monitoring civil structures were looked for, and that is how photonic fiber sensing came up. Characteristics shared by all fiber sensors are their electromagnetic immunity for being manufactured using a dielectric material (silica glass), low weight, small size, and compatibility with construction materials [1,2]. As can be seen these inherent characteristics make them very suitable for their use in civil engineering structures. An example of a quasi-distributed transducer is presented in this communication. First the theoretical fundaments of the transducer and its behavior is explained, and an in-field experiment consisting on monitoring a bridge is described and its results reported.
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