POF Sensors for Structural Health Monitoring
This chapter provides a comprehensive overview on current plastic optical fiber – based sensing principles and Structural Health Monitoring (SHM) technologies, highlighting their diverse applications in civil engineering structures. In the application-related context, close attention is paid to the development of smart sensor-based geotextiles and geogrids. Distributed measurement techniques provide the advantage of complete spatial acquisition of measurands along the whole sensor fiber. The Rayleigh-based Optical Time Domain Reflectometry (OTDR) is a common testing technique widespread in telecommunication industry for in-depth fiber characterization and fault analysis and has been recently utilized for SHM applications. The frequency domain techniques basically use a Fourier pulse decomposition given by a progressive amplitude modulation of a continuous-wave light source at different modulation frequencies using an electro-optic modulator. The Incoherent Optical Frequency Domain Reflectometry approach provides the possibility of fully distributed strain measurement based on the measurement of local increase of backscattered signal which can be converted into strain analogically to the OTDR method.