Fibre bragg grating system for strain monitoring

Fiber Bragg grating sensors currently represent one of the most exciting and strongest growth areas in optical sensing. In this study, a new technique for the strain measurements round a hollow cylinder has been demonstrated. The fiber Bragg grating system, consisting of Excimer Laser, Mask Aligner, Optical Spectrum Analyzer and Tunable Laser Source was utilized to fabricate the fiber gratings. The sensing principle is based on tracking Bragg wavelength shifts caused by varying the load conditions. The fiber grating was screwed on a material (hollow cylinder) on either sides of grating and Optical Spectrum Analyzer was utilized to Measure the wavelength shift. The longitudinal strain corresponding to each load conditions is calculated. The experimental results of this study are being discussed in detail. Considering the bare FBG fibers used in this experiment, its strain sensitivity can be expressed as lambda(B) approximate to 1.2x10(-3) epsilon(Z) + lambda(0) in the range of 1550 nm. Where epsilon(Z)is the applied axial strain in mu epsilon (microstrain), lambda(B)is the shifted grating wavelength in nm (nanometer). Therefore one can anticipate approximately 1.2pm grating wavelength increases as a result of axially strain applying 1 mu epsilon, to bare FBG fiber. The correlation of theoretical calculations and experimental results are showing the capability of the proposed system to perform strain measurements. It was inferred that the use of fiber Bragg grating technology for the monitoring of smart structures is very promising, and the future is sure to bring further advancements and improvements.