Abstract
A comparative investigation on fiber Bragg grating (FBG) sensor and electrical strain gauge for strain measurements is carried out. The fiber Bragg grating system, consist of Excimer Laser, Mask Aligner, Optical Spectrum Analyzer and Tunable Laser Source was utilized to fabricate the fiber gratings. The experiment was performed on a specimen made of steel having dimension 400 x 100 x 2 mm(3). The fiber Bragg grating sensor was a piece of 1000 mm bare optical fiber with 100 mm stripped section in the middle, in which 10 mm was written with Bragg gratings. The type of electrical strain gauge was FLA-6-11. The data logger wires were soldered to the lead wires of electrical strain gauge through connecting terminals. The steel plate with the FBG sensor and strain gauge bonded was welded on one end, and the other end was depressed by a micrometer with equal increment of 2mm. Based on the results, the FBG sensor data correlates better with the theoretical calculation than the electrical strain cantilever gauge values. The fiber grating sensor did perform quite consistently over the two trails than the electrical strain gauge. There is a consistency in the results of electrical strain gauge but the electrical strain gauge gave low values of strain. The test results discussed in this research show a reasonable correlation between the strain values obtained from the fiber grating sensors and those obtained from conventional foil gauges, from a maximum difference of 13%. The findings provide an essential and useful basis for developing a fiber Bragg grating sensor system for real time and long term monitoring of mechanical and steel structures.