Comparison between Capacitive and Microstructured Optical Fiber Soil Moisture Sensors

• Main Authors: Aitor Lopez Aldaba, Diego Lopez-Torres, Miguel A. Campo-Bescós, José Javier López, David Yerro, César Elosua, Francisco J. Arregui, Jean-Louis Auguste, Raphael Jamier, Philippe Roy, Manuel López-Amo
• Format: Article
• Language: English
• Published: MDPI AG 2018-09-01
• Series: Applied Sciences
• Subjects: photonic crystal fiber; microstructured optical fiber; fiber sensor; humidity sensing; soil moisture
• Online Access: http://www.mdpi.com/2076-3417/8/9/1499

Soil moisture content has always been an important parameter to control because it is a deterministic factor for site-specific irrigation, seeding, transplanting, and compaction detection. In this work, a discrete sensor that is based on a SnO2–FP (Fabry-Pérot) cavity is presented and characterized in real soil conditions. As far as authors know, it is the first time that a microstructured optical fiber is used for real soil moisture measurements. Its performance is compared with a commercial capacitive soil moisture sensor in two different soil scenarios for two weeks. The optical sensor shows a great agreement with capacitive sensor’s response and gravimetric measurements, as well as a fast and reversible response; moreover, the interrogation technique allows for several sensors to be potentially multiplexed, which offers the possibility of local measurements instead of volumetric: it constitutes a great tool for real soil moisture monitoring.