Fiber Bragg grating(FBG) sensor, one of the fiber optic sensors (FOS), based on the wavelength division multiplexing(WDM) technology offers lots of advantages for structural health monitoring due to multiplexing capability. Also, fiber optic sensors are proper to sensing of the structural vibration with no mass concentration effect. In this paper, we constructed a signal processing board with an electric circuit for an accurate measurement of wavelength shifts of FBG sensors This circuit board supplies tremendously the enhancement of real-time signal processing program using Labview software for data storage and visualizing of sensor strains. To improve its multiplexing capability for large numbers of sensor signals, multi-channel sensor arrays with a wavelength-swept fiber laser (WSFL) are also constructed.
This powerful sensor system showed a good resolution of dynamic strain (〈 10με) and proved to be effective for real-time strain monitoring of large structure. To demonstrate the sensor system performance, real-time dynamic strain sensing of multi-points located on a composite beam was executed. Based on the acquired strains of multi-points, natural frequencies and the strain mode shape of the composite beam are calculated. The experimental results of natural frequencies and mode shapes showed a good agreement with numerical results by ABAQUS.
