All-Optical Self-Heated Sensing Platform for Water Content Monitoring in Soil

Abstract

In this contribution, we propose the use of an advanced all-optical self-heated sensing platform for highly sensitive monitoring of the volumetric water content (VWC) in the soil. The sensor is realized by properly integrating, inside a standard metallic needle, a fiber optic heating device based on core offset light coupling method and a Fiber Bragg Grating (FBG) acting as thermal monitor. The performance of the proposed device was validated through a series of measurements in the range [9 - 36] %VWC in the soil temperature range between 5 and 40 °C. Collected results have demonstrated that the presented platform is able to perform highly stable, fast and robust measurements, with time response lower than 10 seconds. The possibility of tuning the value of the injected power according to the application makes the proposed sensing solution extremely flexible and versatile for its exploitation in large areas and/or long-distance.