Distributed Temperature Sensing (DTS) measures moisture

DTS for moisture estimationPassive distributed temperature sensing (DTS) helps to improve the measurement of moisture content and temperature increase. The DTS technology has been already tested in China to prove the opportunities provided by this technique. Therefore, distributed temperature sensors are very promising for agriculture.

Several land conditions include bare soil, plastic mulch, plastic mulch covered with potatoes, and plastic much covered with maize. Land moisture plays a crucial role in influencing grain yield. Nevertheless, distributed temperature sensing is not suitable for the last type of land.

The thing is that several techniques allow for determining soil moisture content. Distributed sensing systems include point, ground, and regional types. Herewith, point fiber optic sensors consist of “oven-drying, neutron scattering, electrical impedance, time-domain reflectometry (TDR), frequency domain reflectometry (FDR), tensiometer, and thermal probe techniques.”

Conventional fiber sensors offer benefits of high precision and reliability but most of them are limited to a specific area. This is the main reason why it is difficult to determine accurately the overall ground moisture condition, especially in places where soil moisture distribution is discontinuous.

Thus, scientists have suggested applying distributed temperature sensing (DTS). DTS technology allows for estimating agricultural soil moisture, herewith, the distance of measurement can achieve several tens of kilometers. The operating principle of distributed temperature sensors is based on the heating of optical cables. When the temperature increases, the soil moisture can be estimated.

The DTS technology is not new and it quickly found the application in moisture measurement. According to this technique, it is possible to measure in situ soil moisture by employing analytical or semi-empirical models. Nevertheless, firstly it is necessary to calculate the thermal conductivity of the soil.

Compared to traditional techniques that have limitations, distributed temperature sensing allows for overcoming them. DTS estimates the temperature response of soil, therefore, measures soil moisture based on the data obtained by fiber optic sensors. Nonetheless, the proposed technique has several disadvantages.

Various weather conditions can influence the heat transfer way in the soil and the data obtained by distributed temperature sensors will be inaccurate. Additionally, boundary conditions and even time change periods also influence the precision. Finally, the standard algorithm is very difficult for application in practice.

Optromix is a DTS system manufacturer that provides top of the line distributed temperature sensing systems suitable for monitoring commerce networks. If you have any questions or would like to buy a DTS system, please contact us at info@optromix.com

Distributed fiber optic sensors: common applications

FBG sensors and common applicationsCommon communication channels apply fibers in fiber optic sensors where laser beam light passes along haul distances. These fiber sensors allow for determining, controlling, and measuring external parameters in a distributed format. Herewith, the optical fiber in a fiber optic system operates both as a distributed transducer and optical channel.

To be more precise, the fiber optic sensors measure various changes on specific parameters along with the transducer. Such factors as the dynamic range and the spatial resolution play a crucial role in distributed sensing but still have to be improved. The operating principle of fiber optic systems is based on “the incident light wave that produces acoustic waves through the electrostriction effect. It induces a periodic modulation of the refractive index of material that evokes a light-backscattering like a fiber Bragg grating of FBGs.”

It should be noted that a fiber sensor or sensing system is a tool that determines, measures physical or chemical parameters. Herewith, in the case of light use in such systems, this is a photonic or optical sensor. The fiber optic sensors, in turn, consist of optical fibers and the fiber optic technology around them.

Distributed fiber optic sensors detect and measure physical factors by Brillouin scattering of light in optical fibers. Brillouin scattering advances the development of precise distributed fiber optic systems. Additionally, these fiber sensors enable to measure specific variables.

Distributed sensing systems are very promising for structural health monitoring. The following parameters can be detected: strain and temperature, acoustic waves, and others. Moreover, these fiber optic sensors maintain severe environments and offer noise electromagnetic immunity, durability, and reliability.

The most common application of fiber sensors based on the Brillouin sensing technique includes laboratory implementation. Nevertheless, their applications are not limited to labs only. Distributed fiber optic sensors are widely used in such fields as:

  • The civil infrastructure where distributed sensing systems detects variables in bridges, railways, and land monitoring;
  •  Bridges and monitoring where compact fiber sensors promote accurate diagnostic load test;
  • Geotechnical structures monitoring for measuring and controlling of the stress distribution;
  • Pipelines monitoring by distributed fiber optic sensors in real-time for early warning of liquid and gas pipes;
  • Monitoring of some materials and structures, for instance, competition yachts or experimental vehicles.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, for example, fbg strain sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com

FBG sensors for temperature and pressure measurement

FBG sensors for temperature and pressureNowadays fiber optic solutions play a crucial role in information technology. Fiber optic technology promotes the development of advanced fiber optic sensors. These fiber sensors offer numerous benefits that make them very attractive. The benefits include “durability, flexibility, biocompatibility, high sensitivity, and electromagnetic interference immunity.”

The applications of fiber optic sensors consist of numerous fields. They are widely used in medicine, environmental protection, industrial production, and structural health monitoring. Herewith, different types of fiber sensors allow for measuring various physical and chemical parameters. For instance, they sense temperature, acoustic, pressure, humidity, and others.

The production of distributed sensing systems requires different types of fibers. The following types are the most popular: photonic crystal, polarization-maintaining, double-core, sapphire optical fibers, etc. It should be noted that various fiber optic sensors use various measurement principles. Additionally, fiber Bragg gratings (FBGs) – the most popular measurement principle.

FBG sensors can also perform multi-parameter measurements to meet the practical demands of scientists. Thus, a team of researchers has demonstrated a cascaded multi-mode FBG sensor that performs the dual-parameter measurement. They apply optical fiber with several modes to create a distributed sensing system. Moreover, the FBG sensors measure the Brillouin frequency shift for temperature and strain sensing.

To be more precise, these FBG sensors have a hybrid structure (FBGs and FPI) with a nano-silica diaphragm on the tip. Besides, the total length of the fiber sensor is less than a human hair. These FBG sensors determine both environmental temperature and pressure. Therefore, such a fiber optic solution is highly promising in specific applications in severe environments.

Finally, the hybrid fiber optic sensor has been already produced and even tested. The distributed sensing system includes an FPI with a silica diaphragm. Also, fiber optic technology applies the femtosecond laser inscription technique and arc discharge methods. These FBG sensors demonstrate a high level of pressure and temperature sensitivity.

Additionally, the fiber optic sensor has an ultra-low level of cross sensitivities. “The temperature-induced error of the pressure measurement was –1.4286 kPa/ and ℃ pressure-induced error of the temperature measurement was ~0℃/MPa.” The mentioned-above benefits of FBG sensors make them perfect for numerous fields of applications.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, for example, fbg strain sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com