Optical fiber as a sensor
Extremely thin, light, flexible, immune to electromagnetic interferences, corrosion or alteration due to chemical agents: the excellent properties of optical fibers have contributed to a strong impetus to the development of applications in which they are used as sensors, in different fields of application.
In particular, through the Brillouin Scattering Technology both strain and temperature can be measured at very high spatial resolution.
Through a single fiber installed on the structure to monitor (a pipeline or an earth dam, a beam or a geosynthetic, an anchor or a train rail and so on), any strain induced by mechanical or thermal processes and/or any temperature change caused by environmental or any other type of phenomena can be easily monitored.
In fact, if properly connected to the monitored element, a single fibre can capture strains or temperature changes every 10 centimetres all over the instrumented length, up to a distance of some tens of kilometres.
By separating these functions, two parallel fibers can record both strain and temperature of the same element.
The main advantage of distributed monitoring lies in the ability to record the subject strain or temperature in every point of the element to monitor, provided a fiber is connected to it, and this up to distances of some tens of kilometres with an acquisition frequency as high as some times per second.
This enables to avoid a priori selecting the part, considered critical, to monitor as in the more traditional approach.