Abstract: In this work we proposed a relative humidity (RH) sensor based on a Bragg grating written in an optical fiber, associated with a coating of organo-silica hybrid material prepared by the sol-gel method. The organo-silica-based coating has a strong adhesion to the optical fiber and its expansion is reversibly affected by the change in the RH values (15.0–95.0%) of the surrounding environment, allowing an increased sensitivity (22.2 pm/%RH) and durability due to the presence of a siliceous-based inorganic component. The developed sensor was tested in a real structure health monitoring essay, in which the RH inside two concrete blocks with different porosity values was measured over 1 year. The results demonstrated the potential of the proposed optical sensor in the monitoring of civil engineering structures.
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Correia, S.F.H.; Antunes, P.; Pecoraro, E.; Lima, P.P.; Varum, H.; Carlos, L.D.; Ferreira, R.A.S.; André, P.S. Optical Fiber Relative Humidity Sensor Based on a FBG with a Di-Ureasil Coating. Sensors 2012, 12, 8847-8860.
Correia SFH, Antunes P, Pecoraro E, Lima PP, Varum H, Carlos LD, Ferreira RAS, André PS. Optical Fiber Relative Humidity Sensor Based on a FBG with a Di-Ureasil Coating. Sensors. 2012; 12(7):8847-8860.
Correia, Sandra F. H.; Antunes, Paulo; Pecoraro, Edison; Lima, Patrícia P.; Varum, Humberto; Carlos, Luis D.; Ferreira, Rute A. S.; André, Paulo S. 2012. "Optical Fiber Relative Humidity Sensor Based on a FBG with a Di-Ureasil Coating." Sensors 12, no. 7: 8847-8860.