Abstract
We have constructed an optical setup which can measure strain at a sampling rate up to an order of megahertz. The system consists of broadband light source, fiber Bragg grating (FBG) sensor, dielectric multilayered optical filter and photodetector. The Bragg wavelength of FBG varies with strain applied to the FBG. The Bragg wavelength is converted to light intensity with an optical filter. Intensity of light transmitted through and reflected from the optical filter was measured using photodetectors. Strain can be evaluated from the ratio of the difference to the sum of the two photodetector outputs. Strain of a thin stainless-steel cantilever beam during free vibration was measured with an FBG sensor and a resistive strain gauge. Experimental results demonstrate that the FBG-based optical system is capable of strain measurement with a higher S/N ratio compared to conventional strain gauges.
