NON DESTRUCTIVE MONITORING OF CULTURAL HERITAGE USING FIBER OPTIC SENSORS

Fiber optic sensors have several advantages over the conventional ones. In fact they are: electrically and chemically passive (they are made of glass fibers) and immune to electromagnetic interference. They are also very small and almost transparent. Particular interest have the Fiber Bragg Grating (FBG) sensors because they can be multiplexed on one single fiber thus strongly reducing the amount of wiring on the object to be monitored. When a broad band signal is sent into the fiber a specific wavelength is reflected and measured accurately. Any strain in the fiber will cause a wavelength shift that will allow the measurement of strain with accuracies of 1 μstrain or less. Our research group is working with fiber optic sensors in several areas ranging from aerospace to civil structural element and cultural heritage. As far as cultural heritage is concerned we are considering the possibility of monitoring old buildings. One example, made in collaboration and with the sponsorship of Schult’z s.a of the Republic of San Marino, will be shown. Several FBG sensors have been installed into the “San Giacomo dell’Orio” Church and in the “Scuola Grande di San Rocco” which has in display paintings of Tintoretto. Both structures are in Venice Italy. Another application under study is the monitoring of humidity absorption and temperature of tufitic rocks. The same technique can be applied on marble artifacts. Finally we are evaluating the technique also on bronze statues for monitoring cracks and corrosion onset. Furthermore these sensors can provide a continuous monitoring of stress induced to structures by the wind and other accidental loads.