Fiber-Bragg-Grating-Based Displacement Sensors: Review of Recent Advances

With the development of fiber optical technologies, fiber Bragg grating (FBG) sensors are frequently utilized in structural health monitoring due to their considerable advantages, including fast response, electrical passivity, corrosion resistance, multi-point sensing capability and low-cost production, as well as high accuracy and resolution over a long period. These characteristics allow FBG to be a proper alternative sensing element for displacement measurements. In this article, the recent sensing advances and principles of detection of FBG-based displacement sensors are illustrated. Specifically, the latest FBG-based displacement technologies are examined from three principles of detection, i.e., wavelength, intensity and phase signal demodulation. Regarding wavelength detection methods, the problem related to the cross-sensitivity can significantly be reduced depending on the new type of cantilever-FBG-based sensing developed. Vice versa, only the packaging method of FBG prestressed between two fixed ends can still avoid the chirp phenomenon in the reflection spectrum. Moreover, to attenuate the influence of temperature variations on the accuracy of FBG displacement sensors, specific temperature self-compensation structures were successfully designed according to the concepts of phase signal demodulation. In future investigations, different elastic structures and gratings manufactured through special fibers and new methodologies for temperature compensation will still highly refine the efficiency of FBG-based displacement sensors.

Automated summary

With the development of fiber optical technologies, fiber Bragg grating (FBG) sensors are increasingly used in structural health monitoring. This article provides an overview of the recent advancements and principles of FBG-based displacement sensors, focusing on wavelength, intensity, and phase signal demodulation. Future research will aim to improve the efficiency of FBG-based displacement sensors through the use of different elastic structures, gratings manufactured through special fibers, and new temperature compensation methodologies.