Strain Measurement in Construction Steel Bar Using a FBG Sensor Coated by a Thin Metal Tube

The fiber Bragg gratings(FBG) are coated with thin metal tube for protection and adhered to two different constructional bars.Pulling the bars and the Bragg wavelengths of the FBG are shifted.The experimental result indicates that the shifts of Bragg wavelengths are in good linear relationship with the pulling force:the lineanties are 0.995 6 and 0.999 5 for two kinds of steel bars respectively.The experimental result agrees with theory well.