Tag: fiber optic sensing

Distributed Temperature Sensing Systems for Coal Mines

Distributed temperature sensing systems as well as fiber Bragg optic sensors are focused on the continuous monitoring of the constructions’ health condition and prevention of potential damages. The DTS system consists of a fiber optic cable, typically several kilometers long, that works as a temperature sensor. As a result, specialists can watch all dynamic temperature changes in a continuous temperature profile.

DTS Systems as a Fire Detection Technology

In the mining industry, the risk of fires still remains very high. Conventional fire and heat alarm systems require constant and expensive maintenance and are not as effective as fiber optic monitoring systems. Thanks to modern DTS technology, both of these problems are now solved.

There are many forces in mines that can cause a fire. The possibility of fire is especially high in certain locations due to the complicating factors such as:

geological settings;
presence of the vehicles, heat-generating and mobile equipment;
conveyor failures;
lighting faults, etc.

Distributed temperature sensing systems have been proven to outperform standard fire detection systems in a range of aspects including efficiency and high level of safety.

The DTS system includes a single fiber optic cable and a DTS unit. The traditional system includes many components and devices. The distinction of DTS results in lower installation and maintenance costs due to less equipment, and in improved system reliability. Therefore, there is no need in its regular service that can be complicated because of the difficulty of access and huge size of the mine. Moreover, the conducted field projects have demonstrated that fiber optic sensors inform the operators about the heat significantly earlier than a fire starts.

All these advantages have made DTS technology one of the main methods for the detection of potential fires or other abnormal conditions.

Fiber Optic Sensors for Detection of Faulty Conveyor Belt Rollers

The conveyor belts are cost-effective instruments for continuous transporting of dry bulk materials over various distances. Due to the latest technologies, the accidents related to the problems with conveyor belts are relatively rare in modern underground coal mines. However, to this day there is a possibility of causing damage related to the conveyor belt accidents that can result in the interruption of the production process.

The reliability of the whole conveyor belt depends on the robustness of its separate components. Distributed temperature sensing (DTS) system helps to monitor the thermal conditions of each idler and detect the malfunctions. DTS systems use the latest advancements of fiber optic technology. They have proven to be a safe method of application in underground mines.

There are some aspects to consider when choosing the suitable monitoring system. Firstly, it is not easy to obtain data from a vast area. It requires the setting up of thousands of sensor elements. Secondly, the data transmission can be challenging due to the underground mine environment. Therefore, some types of equipment are prohibited for usage, such as electrical cables. Fiber optic monitoring systems have been able to solve a number of such issues that engineers usually face during underground mining.

The DTS system consists of a DTS unit and a fiber optic cable. The system measures temperature along the entire length of the cable and transmits the data to the operators who can detect any mechanical failures of the rolling components at an early stage. The specialists see real-time data of the conveyor structure and the surrounding area.

The specialists conducted a range of experiments to find the most effective placement of the fiber optic monitoring system. The problem is that fiber optic sensors can’t be located over the idlers because they will interrupt the operation. So they are attached to the frame of the idler, as close to the bearing as possible. This affects the results because fiber optic sensors take longer to capture the heat. However, they still have better results compared to the traditional methods.

Fiber Optic Sensing for Monitoring of Roof Activity

According to statistics, there are many causes that can lead to mine accidents including dust explosions, mine support deterioration, etc. However, the most common cause of the accidents that take place in underground coal mines is mine collapse.

Design and functioning of the underground mines creates a number of complicated factors for operation. The dynamism of mining operations and increasing depth can lead to the associated risks and jeopardize an acceptable level of safety. At the same time, there are always natural risks to the mine structures, such as seismic shocks which can also lead to roof stratum displacements.

Roof activity monitoring can be used for a variety of purposes, including structural health construction monitoring of the underground openings and design optimization. For the majority of projects, fiber optic monitoring systems are applied due to their ease of use in harsh environments compared to other conventional methods.

Fiber optic sensing monitoring is able to help in reduction of the mine roof displacement and thus avoid severe consequences. There are different types of fiber Bragg grating sensors that are used to monitor displacement, temperature or strain in underground openings or nearby them depending on the purposes. FBG sensors have proved to be reliable and accurate monitoring equipment of roof activities in underground coal mining. Modern fiber optic monitoring systems have made it possible to display all changes of the required parameters on the screen almost instantly and prevent any accidents in underground mines.

The conducted projects on the mining sites have demonstrated the benefits of fiber optic sensors. The fiber optic monitoring systems can detect the slight roof displacement during the progressive face advance. The received data is usually used for roadway support and design of the mine.

In conclusion, thanks to the latest state-of-the-art technologies nowadays there is an opportunity to monitor structural health constantly. That is why distributed temperature sensing systems are widely applied for structural health monitoring of different constructions including mines. The fiber optic sensing has found many spheres of applications due to the qualities it has.

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

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.

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.

distributed temperature sensors FBG sensors FBG temperature sensors Fiber Bragg grating temperature sensors fiber optic sensing fiber optic sensors

Fiber Optic Sensors for Underground Coal Mines

Thanks to the fiber optic sensors, a number of fields and industries have found new approaches in safety and production processes. As a part of fiber optic technology, fiber Bragg grating sensors have proved to be an effective technique of monitoring and security insurance.

Fiber Optic Sensing Applications in Underground Mining

Underground extraction of the minerals continues to be a high-risk industry. This industry has become highly dangerous because of the permanent presence of difficult challenges. Such factors as dynamic changes, hidden defaults and seismic tremors can lead to disastrous consequences.

Due to the advancement of fiber optic technology, there is an opportunity of constant monitoring with the help of fiber optic sensing systems. Fiber Bragg grating (FBG) sensing has already demonstrated its abilities in other directions like for monitoring of the dams and bridges. For mining, the deployment of FBG sensors has become possible because of the properties they have such as high and long-term sustainability and high resistance to electromagnetic events.

This article presents the most common applications of the fiber Bragg grating (FBG) sensing in the coal industry.

Fiber Optic Sensors for Structural Safety of the Mines

Distributed sensing can be called a crucial component in the structural health monitoring of the underground mines. Previously, devices for the structural health construction monitoring couldn’t allow watching the data 24/7, and thus, respond quickly in such environmental conditions. However, today’s fiber optic monitoring systems make all this possible.

Due to the fiber Bragg grating sensors’ qualities, like reliability, they are able to constantly track the extractive activities. Moreover, thanks to their high level of sensitivity, there is a possibility to detect the slight modifications in equipment functioning and prevent severe damages at an early stage. So, fiber optic sensors are fit for mine structural monitoring as a proactive damage detection system and as one of the accident prevention strategies.

Therefore, fiber Bragg grating (FBG) sensing is able to ensure the necessary level of safety in mines. It provides the estimation of the mines’ present environment when FBG sensors collect and transmit the data remotely.

Fiber Optic Sensing for Coal Dressing Chamber Bottom Plate

Apart from safety monitoring of the roof activity, there is an opportunity to monitor changes in the coal dressing chamber bottom plate with the fiber optic monitoring systems. However such monitoring has a range of aspects that should be taken into account.

Firstly, huge equipment occupies most of part of the chamber. During the coal production it produces vibrations that may influence the stability of the mine country rock. This fact should be considered while installing fiber optic technology.
Secondly, monitoring systems should be immune to electronic interference. That is a great benefit of the fiber optic sensing, especially for the chamber, where electromagnetic interference phenomenon is strong.
Thirdly, the system shouldn’t interfere with the operation of the equipment.
Fourthly, due to the constant production around the coal separation chamber it is complicated to get accurate information.

Nowadays, fiber Bragg grating sensors can not always be applied for monitoring of the coal dressing chamber bottom plate. Still, there are some challenges that specialists can face. The lack of space, chances of inaccurate data and other difficulties can make fiber optic sensors’ setup harder or even impossible. As well as wet environments, FBG sensors are often applied in heavy environmental conditions, and specialists got used to developing such projects.

Microseismic Monitoring System as Part of the Fiber Optic Technology

Microseismic monitoring technology is an important instrument designed to prevent any dangerous accidents with the help of seismic assessment and alert about any changes.

Fiber optic sensing has also been successfully applied as a microseismic monitoring system for coal mines. The sensors were suggested to use because of their significant advantages such as large dynamic range, high sensitivity, etc.

Due to the conducted experiments, fiber Bragg grating sensors were installed in the tunnels. During the field projects they have proved to be effective by providing all the data about dynamic activities in the mine accurately. Such level of accuracy is possible due to the fact that the microseismic data are tracked over the full length of the installed fiber optic cable. The interrogation system collects the data, provides the seismic interrogation and transfers the received data. It allows improving the dynamic range and installing more fiber optic sensors. Both these factors increase the positioning accuracy of seismic events.

All in all, monitoring with fiber optic sensors in combination with the automatic processing of data can bring major benefits to identification of any changes, malfunction of mine operation and damage prevention.

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

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Fiber optic sensors for biological liquids

A team of scientists from Israel and Russia has developed a novel, straightforward, and low-cost fiber optic technology. It allows for the testing of liquid biological samples. Herewith, the developed fiber optic system is very promising in clinical settings, containing real-time testing during surgery.

To be more precise, fiber optic sensors are widely applied in the healthcare system for real-time diagnostic testing for biological samples. The fiber sensors offer a high level of sensitivity, however, usually “that sensitivity comes at a cost in terms of time and resources.”

Therefore, scientists tend to create simple, inexpensive fiber optic sensors as a more efficient alternative. It should be noted that they pay careful attention to the optical dispersion of the refractive index of a sample. The thing is that this process of the fiber optic system operates as a fingerprint of sorts that controls the changes in its composition.

Thus, the team has presented the concept of multispectral fiber optic sensing for liquid biological samples in both static and real-time modes. Herewith, fiber optic technology is accurate, robust, and highly sensitive to impurities in the sample. These fiber optic sensors will be helpful for diagnostic applications and real-time simulations of different biological processes.

The fiber sensors include hollow-core microstructured optical fibers. It is a specific type of optical fiber that keeps light inside a hollow core of the fiber optic system surrounded by microstructured cladding. Liquid passes through champers of fiber sensors, and the team registers spectral shifts of maxima and minima in the transmission spectrum.

These signals show the chemical composition of the sample. Additionally, the fiber optic sensors do not require an external cavity or interferometer. This is the main reason why fiber optic sensing is straightforward and virtually cheap to create. Such fiber optic technology has been already tested by scientists.

The fiber sensors test the concentration of bovine serum albumin, generally applied in such experiments, dissolved in water and phosphate-buffered saline solution. The fiber optic system demonstrated a resolution similar to the accuracy of standard albumin tests and complied with clinical requirements.

The potential application of these fiber optic sensors includes the analysis of biomarkers of various types. It is necessary to test the fiber sensors on other bioanalytics and then modify them to enhance specificity. The fiber optic technology opens new opportunities ina fast, inexpensive and robust analysis of blood and other bodily liquids in real-time.

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Distributed fiber optic sensing applies an entangled quantum network

Quantum-enhanced metrology is regarded as a popular area of research for years because of its promising applications, varying from atomic clocks to biological imaging. According to the researches, a non-standard distributed sensing system offers significant advantages compared to traditional fiber optic systems.

These researches help a team of scientists from Denmark to carry out an experiment on distributed fiber optic sensing and the benefits of employing an entangled quantum network to detect an averaged phase shift among numerous distributed sensing nodes. The fiber optic sensing technology uses several methods that enable collecting more accurate measurements in different areas.

The purpose of the new study is based on squeezed light and homodyne detection that is now established distributed fiber optic sensing techniques. The team aims at “measurement of a global property of numerous spatially separated objects and investigate whether probing these objects simultaneously with entangled light led to more accurate results than probing them individually”.

Thus, the application of a quantum network to probe the objects simultaneously allows distributed sensing systems with far higher accuracy than that attainable when examining probes individually. To be more precise, the team measures the phase shifts (set with wave plates to a known value) by the fiber optic system that sends a weak laser beam through and detects the change in the light’s phase quadrature with homodyne detectors.

The benefit of applying distributed fiber optic sensing plays a really important role when it is necessary to measure the property of numerous objects connected in an optical network. Nevertheless, the losses in the network and detectors are required to be kept low in order to successfully raise the accuracy, alternatively, the quantum benefit of distributed sensing disappears.

The researchers succeeded in the experimental demonstration of the benefits connected with employing multi-mode entanglement for distributed fiber optic sensing. The thing is that the benefits have been previously predicted, however, only highly idealized scenarios and experimentally very difficult probe states or detection methods were taken into consideration. The developed fiber optic system demonstrates that these benefits are available even with current noisy sensing technology.

The fiber optic system finds potential applications in various areas of research and technology development. For instance, they provide a high sensitivity of molecular tracking devices, atomic clocks, and optical magnetometry methods. Moreover, the distributed fiber optic sensing gives valuable information about how quantum-enhanced metrology can be reached utilizing readily accessible technologies, for example, squeezed light generation and homodyne detection.

Optromix is a manufacturer of innovative fiber optic products for the global market. The company provides the most technologically advanced fiber optic solutions for the clients. Optromix produces a wide range of fiber optic devices, including cutting-edge customized fiber optic Bragg grating product line and fiber Bragg grating sensor systems. Moreover, Optromix is a top choice among the manufacturers of fiber Bragg grating monitoring systems. If you have any questions, please contact us at info@optromix.com

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Fiber optic sensors make cities “smarter”

Companies from the U.S. and Japan have developed for the first time a new fiber optic sensing technology that allows delivering traffic-related data to smart cities without tearing up streets. To be more precise, in smart cities connected intersections and traffic fiber optic sensors play a crucial role in the whole infrastructure.

Thus, the combination of intersections with fiber sensors may greatly affect improving traffic flows resulting in congestion and pollution reduction, finally, improving life quality, resident safety, and raising economic activity and productivity. Additionally, these fiber optic sensors may promote pedestrian safety and save lives in different cities.

It should be noted that data information on traffic patterns and road congestions required to make the best application of such fiber sensing systems. Fiber optic technology makes it possible to get the data without physical inspections, putting in new infrastructure, or tearing up streets.

The concept has been already tested and demonstrated the opportunity to apply network infrastructure with existing fiber optic cables already installed in the ground as distributed optical sensors to compile data on city traffic patterns, road conditions, road capacity, and vehicle classification information.

Nowadays it is planned to enlarge tests of the fiber optic sensing technology and to decide how it can be employed in smart cities. The main purpose of technology is regarded as to enable “existing optical fiber providers to deliver smart city traffic-related data without tearing up roads or sidewalks”

The manufacturers apply new fiber optic technology and combine fiber sensors with artificial intelligence-based software to provide “intelligent traffic monitoring including the sensing of vehicle density, direction, speed, acceleration, deceleration and more”. The thing is that until recently it was required to install purpose-built optical fiber in very shallow spaces in the ground with fiber Bragg grating at predetermined intervals to collect and analyze this type of data information.

Today the proposed fiber optic solution suggests utilizing optical fibers already in the ground. The representatives of the companies confirm that these fiber optic sensors may lead or improve various public functions, for example, they allow first responders to identify and respond to gunshots as well as increasing municipalities’ capability to more quickly and efficiently detect earlier deterioration of bridges, tunnels, and other infrastructure.

Application of a single FBG interrogator in the distributed multi-parameter fiber optic sensor system estimated different characteristics of back-scattering light, which can be utilized to determine the static strain, dynamic strain, acoustics, vibrations, and temperatures for each optical fiber segment.

FBG interrogator fiber optic sensing fiber optic sensors

Chirped Fiber Bragg Gratings (CFBG) for high-speed fiber optic communications systems

A chirp is a linear variation in the grating period, that can be added to the refractive index profile of the grating. The reflected wavelength fluctuates with the grating period, broadening the reflected spectrum. A grating possessing a chirp has the ability to add dispersion—especially, different wavelengths reflected from the grating will be subject to different delays.

A non-uniform resonance wavelength along the length of the grating in a CFBG can be accomplished by varying the period or by varying the average effective refractive index. The average refractive index can be changed using different methods, for example, changing the amplitude of the reflective index modulation profile or variation the fiber in the region of the grating length. The chirped FBG was manufactured with the usage of a chirped phase mask to generate a variation in the period of the refractive index.

Chirped fiber Bragg gratings have been widely used for dispersion compensations in high-speed fiber optic communications systems because they are able to retard pulsed light depending on its wavelength. Experience has proven that ideas in one field find applications in another. Actually, this type of optical device has been attracting significant attention in the fiber optic sensing community, in high sensitivity sensors or wavelength discriminators in interrogation systems.

There are two prevailing fields of application of chirped FBG: measurement of curvature based on chirped fiber Bragg gratings and new interrogation system, written in an Erbium-doped fiber. The increasing demand for measurement of curvatures has stimulated the appearance of few sensing systems that depend on the intrinsic characteristics of fiber Bragg gratings. A curvature measurement technique using a smart composite consists of two chirped fiber Bragg gratings. The two gratings are embedded on the opposite sides of the composite laminate and serve as curvature sensors and as wavelength discriminators enabling a temperature-independent intensity-based scheme for the measurement of the radius of curvature.

FBG interrogation relies on the usage of the edge filtering concept applied to a chirped fiber Bragg grating written in an erbium-doped fiber as the processing element. Through the combination of the photon amplification of the erbium-doped fiber and of the distributed wavelength reflection characteristics of the chirped FBG, it becomes possible to reach different reading sensitivities and amplification of the remote sensing signal. The ability of chirped FBG has also been employed successfully in the development of interrogation techniques. One of these techniques uses the group-delay in a Sagnac loop interferometer and another the spectra response of broadband chirped gratings.

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