Performance Analysis and Experimental Verification for FBG Sensors Applied for Smart Structure
Among a variety of fiber sensors, the fiber Bragg grating (FBG) sensor has numerous advantages over other optical fiber sensors. One of the major advantages of this type of sensors is attributed to wavelength-encoded information given by the Bragg grating. Since the wavelength is an absolute parameter, signal from FBG may be processed such that its information remains immune to power fluctuations along the optical path. This inherent characteristic makes the FBG sensors very attractive for application in smart material structure, health monitoring field et al. But FBG sensors are sensitive to temperature and strain simultaneously; it is necessary to analyze the characteristics of temperature and strain of FBG applied for smart structure. Short overview of the FBG sensing principle as well as theoretical analyses is presented at first; then the paper proposes a simple, convenient, and low cost experimental method to verify the performance of FBGs. The improved high-accuracy experimental instrument of thermal deformation, which consists of an accurate temperature controlling and measuring subsystem, supporting and adjusting subsystem, collimating and positioning subsystem and fine motion and measuring sub-system, is simply introduced. The proposed experimental method involves bonding one uniform FBG to the center of the pole, which is about 89.5mm long; another FBG temperature sensor is free in the temperature-control box. The temperature in the box is -20°C-+50°C is adjusted according to experimental schedule. The characteristics of the FBG are analyzed by actual datum, which are simultaneously collected by a PC through a FBG interrogator. Comparing the data of FBG bonded to the pole with another FBG temperature sensor in the free state, the characteristics of the temperature and the thermal strain of the FBG can be obtained. The experimental result shows the FBGs used to the smart material have good agreement characteristics with theoretical calculation of the FBGs.
Wei Pan and Jianghong Gong
X. Y. Chen, L. Fang, "Performance Analysis and Experimental Verification for FBG Sensors Applied for Smart Structure", Key Engineering Materials, Vols. 336-338, pp. 1357-1360, 2007