Theory and experiments on optical fiber strain sensors embedded in concrete

This thesis reports on theory and experiments on optical fibers embedded in concrete structures for the development of a polarimetric strain sensor. The objective is to study the feasibility of such a sensor and to identify the important issues in the design of the sensor system as well as its limitations. The two most important contributions of the theoretical analysis are the description of the micromechanics involved in measuring ambient strain from within a body using an embedded fiber sensor and the strain effects on the anisotropic birefringent properties of the optical fiber. The transmitted optical signal of the sensory system is theoretically studied, tested with different specimens and correlated with experimental work with good agreement. Throughout the experimental work much experience was gained on how to embed fibers in concrete and set up the system. This thesis provides guidelines and recommendations on the design of embedded fiber sensors in concrete structures. The detection of stress waves within concrete with the embedded polarimetric fiber sensing system is also demonstrated.