Multiplexed fibre Bragg grating sensor system for bridge monitoring applications: Fid-Bau Portal

Multiplexed fibre Bragg grating sensor system for bridge monitoring applications

Gebremichael, Y.M. / Boyle, W.J.O. / Leighton, J. / Grattan, K.T.V. / Meggitt, B.T.

An advanced high bandwidth, multiplexed FBG interrogation system has been developed and evaluated as a field trial prototype. The multiplexed optical system is much more versatile and vastly superior to a system based upon the same number of discrete and individually connected conventional sensors, an advantage that is of increasing value, as the number of sensor points is also increased. It has been extensively evaluated in the laboratory environment to analyse its performance. The capability to measure multipoint data using the multiplexed system successfully developed for potential use in strain mapping across a large structure has been demonstrated with higher resolution of +/-2 my epsilon and bandwidth of 100 Hz. Comparative measurements with resistive strain gauges showed close correlation highlighting the performance of the system. No degradation of the sensor or the bonding mechanisms that have been employed for attaching the FBG sensors to the structure was evident during repeated cyclic tests in the lab. Tensile test results on post embedded array of Bragg grating sensors into carbon fibre structures, in an attempt to create a smart sensing strips or strengthening rods, have shown good results correlating with surface attached electrical strain gauges. The objective of this exercise is to embed Fibre Bragg grating sensors into carbon composite structures of various thicknesses during the composite pultrusion stage. Such robust sensor packaging will result in preassembled sensors that could routinely be used in harsh environments, large concrete or masonry structures with ease.