Comparison between Capacitive and Microstructured Optical Fiber Soil Moisture Sensors

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

Experimental and Numerical Characterization of a Hybrid Fabry-Pérot Cavity for Temperature Sensing

A hybrid Fabry-Pérot cavity sensing head based on a four-bridge microstructured fiber is characterized for temperature sensing. The characterization of this cavity is performed numerically and experimentally in the L-band. The sensing head output signal presents a linear variation with temperature changes, showing a sensitivity of 12.5 pm/°C. Moreover, this Fabry-Pérot cavity exhibits good sensitivity to polarization changes and high stability over time

Simultaneous strain and temperature multipoint sensor based on microstructured optical fiber

International audienceIn this paper, a new sensor system for simultaneous and independent multipoint strain and temperature measurements is presented. The interrogation of the sensing heads has been carried out by monitoring their FFT phase variations. In particular, two of each microstructured optical fiber (MOF) cavity interference frequencies were used for the measures. This method is independent of the signal amplitude and also avoids the necessity of tracking the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency components with different sensitivities. The sensing heads present birefringent and multimodal properties and therefore both characteristics lead to their own interference with different properties and sensitivities. The multiplexing capability of the sensing heads and the interrogator method has also been tested and validated. Sensors were operated within a range of temperature 30°C-80°C and a deformation of ~450 was applied. Crosstalk between measurements can be corrected through simple math operations leading to independent and crosstalk-free multipoint and multiparameter sensors

Simultaneous Strain and Temperature Multipoint Sensor Based on Microstructured Optical Fiber

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Sensitivity Optimization of a Microstructured Optical Fiber Ammonia Gas Sensor by means of Tuning the Thickness of a Metal Oxide nano-Coating

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Comparison between Different Structures of Suspended-Core Microstructured Optical Fibers for Volatiles Sensing

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SnO2-MOF-Fabry-Pérot humidity optical sensor system based on fast Fourier transform technique

International audienceIn this paper, a new sensor system for relative humidity measurements based on a SnO2 sputtering deposition on a microstructure (MOF) low-finesse Fabry-Pérot sensing head is presented and characterized. The interrogation of the sensing head is carried out by monitoring the fast Fourier transform phase variations of the FP interference frequency. This method is independent of the signal amplitude and also avoids the necessity of tracking the wavelength evolution in the spectrum; moreover, it is applicable networks that require narrow band sensors, allowing high multiplexation rates. The sensor is operated within a wide humidity range (20%–90% relative humidity) with a maximum sensitivity achieved of 0.14rad/%. The system uses an optical interrogator as unique active element which presents a cost-effective feature

Characterization of a hybrid Fabry-Perot Cavity based on a four-bridge double-Y-shape-core microstructured fiber

International audienceIn this work, a hybrid Fabry-Perot interferometer based on a novel four-bridge microstructured fiber is presented and characterized. The characterization of this cavity is performed in the L-band using two different instruments: an optical spectrum analyzer and an optical backscatter reflectometer. The Fabry-Perot output signal presents linear variation with temperature changes (sensitivity 9.8-11.9 pm/ºC), variation with the polarization states of light and high stability

Study of Optical Fiber Sensors for Cryogenic Temperature Measurements

In this work, the performance of five different fiber optic sensors at cryogenic temperatures has been analyzed. A photonic crystal fiber Fabry-Pérot interferometer, two Sagnac interferometers, a commercial fiber Bragg grating (FBG), and a π-phase shifted fiber Bragg grating interrogated in a random distributed feedback fiber laser have been studied. Their sensitivities and resolutions as sensors for cryogenic temperatures have been compared regarding their advantages and disadvantages. Additionally, the results have been compared with the given by a commercial optical backscatter reflectometer that allowed for distributed temperature measurements of a single mode fiber