High-Temperature Measurements with FBG Temperature Sensors

Fiber optic sensors, in particular FBG temperature sensors, are relatively new technical applications in optoelectronics, fiber and integrated optics. The reason for their popularity is the optical signal itself. It simultaneously provides information about the change in phase, amplitude, wavelength and polarization in space and time.

Fiber Bragg grating temperature sensors are better suited for solving many issues than conventional sensors and measurement systems. For example, fiber optic sensors are applied for preventive diagnostics and forecasting of emergency situations. FBG sensors can be built into critical structures such as bridges, dams, ships, aircraft, power plants and other structures. By continuously monitoring the structural integrity of objects, fiber optic solutions prevent possible catastrophic failures and accidents.High-Temperature Measurements with FBG Temperature Sensors

FBG Temperature Sensors in Measurements of High Temperatures

The measurements of high temperatures, especially over 1000 °C, were always difficult to conduct in harsh environments. However, high temperatures are essential in a number of processes and widely applied in such fields as metallurgical industry, aerospace, and nuclear energy production. Due to the FBG temperature sensors, the problems with high pressures, temperatures and strong electromagnetic radiation that conventional temperature sensors used to have, were solved.

Here are some examples of fiber optic technology applications:

  • Distributed fiber optic sensors are proved to be effective for pipeline protection and safe operation of the deep underground wells;
  • In metallurgy, fiber Bragg grating temperature sensors measure the internal temperature of high-temperature boilers for monitoring of the combustion efficiency and enhancement the safety;
  • FBG temperature sensors monitor the combustion chambers and turbines of an aircraft. For example, scientists are working on the implementation of fiber optic sensors into an aircraft gas turbine engine. Its monitoring helps in the extension of durability and is difficult because the temperature and pressure rates are constantly changing. So to prevent all the emergency and undesirable situations, there is a need for a large amount of control and measuring equipment. Moreover, fiber optic sensors have to operate at temperatures of 400-1800 °C and provide data in real time.

Advantages of the FBG Sensors

Fiber Bragg grating temperature sensors have got close attention because of their inherent benefits in comparison with usual electronic sensors. Due to specialists’ continuous scientific work, sensors have built a reputation based on successful field projects.

Fiber optic sensors are capable of stable operation for a considerable period of time in harsh conditions. High temperatures and pressures, poisonous or corrosive environments negatively affect the measurement results. However, all these factors have little effect on the FBG sensors, especially in comparison with electrical sensors. Moreover, it is easier and cheaper to replace fiber optic sensors if necessary.

Considering all the above, FBG temperature sensors are able to provide the most accurate data despite bad environmental conditions.

Types of the High-Temperature Measurement Systems

There are different types of high-temperature measurement systems due to their installation and detection techniques. There are contact and non-contact measuring systems:

  • Contact temperature measurement systems include thermocouple sensors. Despite simplicity of use, they have a number of disadvantages such as poor corrosion resistance and exposure to electromagnetic interference. Moreover, high temperatures greatly shorten their service life. They are getting damaged and, as a result, provide inaccurate measurement rates.
  • Infrared thermography (IRT) as a non-contact temperature measurement excludes the direct contact between the equipment and high-temperature sections. However, it works only for the surface temperature measurements, so the internal structure can’t be measured.

The most common fiber optic sensors are fiber Bragg grating (FBG) sensors and distributed temperature sensors. Due to the material of the fiber and laser inscription technique, the maximum temperature can be increased.

  • Fiber Bragg gratings are units that have found different applications, especially as they are effective in distributed sensing devices. FBG sensors are proved to be useful as fiber optic sensing instruments. They are able to provide high stability, multiplexing and other features that are widely produced in a number of industrial and scientific applications.
  • Distributed temperature sensors as a part of DTS systems measure temperature along the whole fiber optic cable. Their main goal is providing the most accurate temperature data in space and over a long distance. As a result, specialists get a distributed profile of the temperature conditions along the whole fiber optic cable.

All in all, the latest developments in fiber optic sensing have gotten a great amount of attention due to their capability of operating in environments with high temperatures. FBG temperature sensors can make up a continuous optic line that provides accurate and reliable data in real time that can be stored and compared with the previous data in the future.

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

Fiber Optic Technology in earthquake monitoring

The improvement of life quality is the main factor in the development of every new technology including fiber optic technology. Scientists from all over the world have always looked for new solutions for the prevention of seismic events, which is one of the most essential points in life quality improvement.

Seismic data of the previous years, electric sensors, fiber Bragg grating sensors, and modern distributed acoustic sensing have an aim to predict all catastrophes connected to earthquakes in the future. Especially, it concerns areas with high rates of population. More accurate monitoring gives an opportunity to reduce the risks resulting from most common natural events like earthquakes, landslides, eruptions, etc.

Fiber Optic Technology in earthquake monitoring


FBG sensors in the prediction of seismic events

In the past, the only approach to all the natural phenomena was the information about the cases. Then electric sensors were applied. However, usual electric sensors are hard to comply with the monitoring requirements of high sensitivity and long lifetime. That is why scientists have tried to use different FBG sensors. In fact, fiber Bragg grating temperature sensors were produced for better monitoring and observation of seismic activity. Except for fiber Bragg grating temperature sensors, there are FBG strain sensors that can be also applied for collecting data as geothermal monitoring.

In comparison with the usual electric sensors, FBG sensors can offer ease in signal transmission and immunity to electromagnetic interference that plays an important role. In fact, temperature monitoring with the help of the FBG is considered to be one of the most popular applications. Moreover, modern sensors can be sensitive to both strain and temperature.

Distributed Acoustic Sensing in earthquake prediction

If we speak of seismic activity and the prediction of seismic events, we should definitely mention another fiber optic technology that helps in geothermal monitoring called distributed acoustic sensing. DAS systems are widely applied in various spheres, including vibroacoustic monitoring of the oil wells.

Scientists have already held a number of experiments with the help of the distributed acoustic sensing studying seismic activity in different areas such as metropolitan, oceans, etc. The results prove that DAS systems are able to accurately detect vibrations even in conditions of a highly noisy environment and far away from the epicenter. That’s why this fiber optic technology draws the attention of many researchers and is popular where there is a need for precise and robust information. The DAS’s improved performance has shown its potential to be a powerful instrument in geophysics studies thanks to its bandwidth, waveform fidelity, cost-effectiveness, and simplicity.

Despite all the achievements in fiber optic technology, scientists still consider that DAS technology for seismic monitoring is still in its infancy. However, they are sure that such promising opportunities will play a crucial role in the next seismic networks.

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