Temperature-insensitive Strain Sensor based on the Measurement of Reflected Bandwidth from Tapered Fiber Grating by a Scanning FBG

摘要

One of the most significant limitations of FBG sensors is their dual sensitivity to temperature and strain. Many methods have reported to avoid this problem by using a tapered fiber grating for the strain measurement free from temperature influence. But all of them are based on the measurement of the reflected power from the tapered fiber grating (TFG). In fact, they have abandoned the major advantage that the measured information is encoded in light wavelength instead of light intensity of FBG sensors, and the revolution of these sensors is begin to depend on the light power fluctuation, connection loss and many other elements. All of these would enlarge the cost of the sensing system. On the basis of the theory calculation and experiment, we demonstrate the feasibility to make a temperature-independent strain sensor by measuring the bandwidth of the reflected light from the tapered fiber grating. In this paper, we also present a novel demodulating method based on a scanning FBG In the experiment, a PZT is used to make the reflected wavelength of FBG scanned from short wavelength to long wavelength to measure the bandwidth of the reflected light from TFG. From the experimental results, it could be seen that the influences of the light power fluctuation and connection loss are eliminated thoroughly. This simple and low-cost sensor approach has a considerable potential, particularly application for strain sensing in the smart structures.