Recent Applications of Fiber Bragg Grating Sensors in Humidity and Water Content Detection in Agriculture: A Comprehensive Review of Development, Challenges, and Future Trends

There has been a growing interest in using Fiber Bragg Grating (FBG) sensors for the detection of humidity and water content due to their high sensitivity, ease of installation, multiplexing capability, reliability, and resistance to electromagnetic interference. Although, several studies and papers have been published on FBG sensors and their applications in various fields such as construction, geophysical, there is a lack of a consolidated review that specifically focuses on recent developments in agriculture with particular reference soil humidity and water content. Therefore, a comprehensive and up-to-date analysis of the advances, detection mechanisms, challenges, and potential future directions in this field is needed. This paper provides an in-depth analysis and summarizes the fundamental principles, advancements, methodologies, and recent research findings, highlighting the potential application in agriculture, development, challenges, and prospects for FBG-based humidity and water content detection. By utilizing the changes in FBG wavelength or amplitude caused by the presence of humidity, they provide an effective means for real-time monitoring and control of water content. However, challenges remain to be addressed, such as the need for accurate calibration and the potential for drift over time. In this review, we further discuss the strategies and techniques proposed to overcome the highlighted challenges, such as sensor packaging, signal processing algorithms, and calibration procedures, and suggest that further studies could be done to investigates the novel materials with enhanced sensitivity and selectivity, development of miniaturized and wireless FBG sensor system, as well as investigating multiplexing techniques for simultaneous measurement of multiple parameters.