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about Fiber Bragg Gratings (FBG), FBG Sensors and Monitoring Systems

Dynamic gratings produce new fiber optic sensors

on June 22, 2020

science-in-hd-7mAYDCamwrQ-unsplashResearchers have presented dynamic gratings used instead of depending on fixed-position fiber Bragg gratings, and now core-launched laser beam light can unite to the cladding modes of conventional optical fiber resulting in distributed fiber sensing of the external environment.

The thing is that fiber optic sensors allow distinguishing between chemicals and liquids external to the optical fiber, herewith, they are usually based on refractive-index changes in the cladding modes of the fiber. Moreover, fixed-position fiber Bragg gratings (FBGs) are applied to excite these cladding modes and unite laser beam light from the core mode.

Nevertheless, FBG sensors need specific equipment to create the gratings at the optical fiber, also they only work as point sensors at specific, predetermined locations. A team of researchers from Israel tries to overcome these challenges by developing dynamic gratings at reconfigurable short sections along with the optical fiber.

Thus, the new gratings are independent of any permanent change in the fiber structure. It is possible to switch them on and off at will, and fiber optic sensors based on dynamic gratings allow scanning along with the optical fiber. According to researchers, after the installation of a grating, its effect is not restricted only to light in the core mode.

Similar to conventional FBGs, the dynamic gratings also unite laser beam light between core and cladding modes. Herewith, in analogy to fiber Bragg gratings, such connection will occur for the light at very specific frequencies. “An optical probe wave of tunable frequency is launched at the dynamic grating, and the exact frequency in which coupling takes place is carefully noted.”

Compared to FBGs, dynamic gratings enable the researchers to carry out tests in any chosen position. It should be noted that the developed fiber optic sensors have been already tested over 2 m of traditional optical fiber. To be more precise, fiber sensors consisted of  8 cm length dynamic gratings perform scanning along with the optical fiber resulting in the combination of spectra between core and cladding modes in each position.

Measurements accurately detect the parts of optical fiber that were immersed in ethanol and water, herewith, the fiber sensors can distinguish between the two with an 8 cm resolution. At the same time, the refractive index outside the fiber is possible to estimate precisely with fourth-decimal-point accuracy (0.0004).

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating 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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editorDynamic gratings produce new fiber optic sensors

What you should know about fiber Bragg gratings

on June 15, 2020

yingchih-cJLVf49Ri7k-unsplashFiber Bragg gratings are currently widely used in optical fibers and light guides for compaction of channels along the wavelength, optical filtering of signals, as resonator mirrors in fiber and semiconductor laser systems, as smoothing filters in optical amplifiers, to compensate for dispersion in the main communication channels.

Another field of application of FBG technology includes its use in various measuring systems that control environmental parameters, such as temperature, humidity, pressure, deformation, and chemical content. Bragg gratings distributed along the length of the light guides allow for creating distributed acoustic systems that differ favorably from traditional complexes of the same purpose in cost and technology of production.

FBG technology for recording Bragg gratings distributed in a light guide is a key element in creating a new generation of measurement systems. Hydroacoustic antennas developed on the basis of such optical fibers, as well as systems for the protection of extended objects and systems for monitoring the condition of main pipelines, are increasingly being used abroad. 

A distinctive feature of these fiber optic systems is the large extent of controlled zones, speed, and unique information capabilities. When fiber Bragg gratings are written at a standard optical fiber, a problem arises because of the fact that such a fiber has weak photosensitivity and a low saturation threshold, which is not sufficient for effective recording of gratings. 

The main solution method of FBGs is to increase the concentration of germanium dioxide in the core. Other methods consist of alloying the pieces for the creating of optical fibers with such chemical elements as boron, tin, nitrogen, phosphorus, antimony together with germanium, which leads to an increase in the photorefractive power of the light guides.

Writing of fiber Bragg gratings can be classified by the type of laser system used for production, the wavelength of beam emission, the recording technique, the irradiated material, and the type of Bragg grating. Lasers used for FBG writing can be either continuous or pulsed, with a wavelength of emission from the infrared (IR) to the ultraviolet (UV) range of the spectrum. 

These differences determine the spatial and temporal coherence of the optical emission sources used for writing, which, in turn, determines the choice of the appropriate method for recording fiber Bragg gratings. The main methods for FBG writing include the step-by-step method, the phase mask method, and the interferometric method.

The need to increase the speed of information transmission, associated with the development of telecommunications, increasing information flows, the growth of global information systems and databases, the expansion of the number of users, led to the fact that fiber optic system communication lines were developed using spectral multiplexing of optical channels.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating 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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editorWhat you should know about fiber Bragg gratings

Multi-addressed fiber Bragg gratings for microwave sensors

on June 8, 2020

luminescence-3069828_640Nowadays fiber Bragg gratings (FBG)  face several challenges in fiber optic sensor systems because of their complex installation and the high cost of interrogators provided by interrogation methods and FBG multiplexing. The thing is that such features as wavelength, time, frequency, polarizing, and spatial division multiplexing necessary for most applications also need complex tools, for instance, spectrum analyzers, spectrometers with tunable interferometers, Bragg gratings, etc.

It should be noted that one more challenge for FBG sensors include “the fact that these sensors are not addressable per se, and therefore, any spectrum overlapping leads to interrogation errors.” The possible way to overcome the problem is to use the addressed fiber Bragg gratings combined with the microwave photonics interrogation technique. The addressed FBG is considered to be a specific type of fiber Bragg gratings with two narrow notches in the reflection spectrum.

The operating principle is based on the light that passes through the FBG that has two narrow optical frequencies, herein, the difference between them is less than an optical frequency and installed in the microwave range. Such an addressed frequency does not depend on stress or temperature fields, it is also independent of fiber Bragg grating’s central frequency shifting.

The addressed FBG sensors act both as a two-frequency source and as a fiber optic sensor of the measurement system simultaneously. Thus, it is possible to develop a microwave-photonic fiber optic sensor system based on arrays of the addressed fiber Bragg gratings, if the set of address frequencies in the array is regarded as orthogonal. The addressed FBGs, in their turn, allow designing multi-addressed fiber Bragg grating structures.

The thing is that multi-addressed FBGs apply three (or more) frequency carriers, while their beatings on a photodetector create three (or more) address frequencies. The combination of address frequencies enables increasing the fiber optic sensor capacity of the measurement system as well as increasing the precision of central wavelength determination. Therefore, the multi-addressed FBGs are regarded as a specific type of fiber Bragg gratings with three (or more) narrow notches in the reflection spectrum.

The operating principle of the multi-addressed FBGs is based ion the light with three (or more) narrow optical frequencies, and the difference between them is less than an optical frequency and is placed in the microwave range. Additionally, the address frequencies set in FBG sensors does not depend on strain or temperature fields, central frequency shifting as well. Finally, the multi-addressed fiber Bragg gratings are both a multi-frequency source and a fiber optic sensor of the measurement system at the same time leading to the appearance of new applications.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating 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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editorMulti-addressed fiber Bragg gratings for microwave sensors

Distributed fiber optic sensors and their prospects

on June 1, 2020

pump-jack-848300_640Modern industrial systems are subject to increasingly strict requirements. Structural health monitoring must always work reliably regardless of environmental conditions. Observability and manageability become an important parameter. The operator must be able to detect a problem, including a potential one, determine the location of its occurrence, and respond in a timely manner, taking the necessary measures to reduce time and material costs in emergency situations.

Current fiber optic sensing technologies make it possible to continuously, accurately and in real-time detect small changes in temperature, acoustic background, and deformations in any place of an industrial facility. Fiber optic cables, which are traditionally used in the telecom industry for transmitting information, come to the rescue to perform this. Depending on the type of devices connected to the optical cable, it is possible to detect various environmental events at a long distance (up to several tens of kilometers) performing structural health monitoring. The sensitive medium is the optical fiber and a huge number of “virtual” sensors inside it.

DAS (Distributed Acoustic Sensing) are “virtual” microphones installed along with the optical fiber. Standard single-mode optical fiber and Rayleigh scattering are used when acoustic vibrations cause small changes in the refractive index that are detected using this scattering. The fiber literally “hears” events occurring in the environment. The number of DAS is a combination of spatial resolution, distance, and pulse duration. Modern distributed fiber optic sensors can operate at distances of up to 80 km. Combining several devices into a single network allows creating thousands of kilometers of structural health monitoring lines.

DTS (Distributed Temperature Sensing) is “virtual” thermometers along with the optical fiber. The distance range for a conventional single-mode fiber is up to 100 km with a spatial resolution of 1 to 5 meters and a measurement accuracy of less than 1 degree Celsius, with a measurement time of 2 to 30 minutes. These parameters are interdependent. For example, the longer the measurement time is, the better the spatial resolution and accuracy of the measurement are, and vice versa. 

Herewith, analytics show that the market for such distributed fiber optic sensors will grow by at least 10% per year in the foreseeable future. These fiber optic systems are most in-demand in North America. In terms of application, the oil and gas industry has the greatest potential. Temperature control prevails by type of monitoring.

Over the past 10 years, fiber optic sensing technology has been used to monitor thousands of kilometers of pipelines, thousands of oil and gas wells, and more. There are numerous fiber optic solutions that allow accelerating the introduction of promising technology in the industry, devices, and fiber optic cables are constantly being improved and become more accurate and affordable.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating 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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editorDistributed fiber optic sensors and their prospects

Why DTS systems are beneficial to pipelines

on May 25, 2020

jj-ying-4XvAZN8_WHo-unsplashAlmost all pipelines suffer from numerous leaks during their operation, therefore, they require systems for fiber optic pipeline leak detection. Despite the fact that there are various techniques for leak detection, distributed temperature sensing systems (DTS) are considered to be an ideal option for the purpose.

Distributed temperature sensing is a technique that has been applied for more than two decades. DTS systems are regarded as the best option when a leak leads to a temperature differential between the ambient air and the escaping liquid or gas. The thing is that “temperature differentials generally occur when the pipeline product is at high pressure, high temperature or low temperature, all relative to ambient, which is characteristic of numerous pipelines.”

The operating principle of DTS is based on fiber optic sensing systems that operate as a sensor and measure temperatures along the entire length of optical fibers. Herewith, the optical fiber is put along the outside of the pipeline within the protective coating. It should be noted that the accurate installation location depends on the relative area(s) of the anticipated temperature differential caused by a leak, and on other reasons such as available mounting space.

To be more precise, DTS systems allow fastly identifying and precisely locating slow leaks at weld points, pipeline fittings, and herewith, sudden leaks. Fiber optic pipeline leak detection system enables detecting the precise location of leaks, often overcoming other distributed sensing technology. The fact is that even a tiny leak leads to a crucial temperature change, one that can be recorded by the DTS system.  Most DTS measures temperatures with a precision of a few degrees, more than sufficient for leak detection.

For instance, a modern leading distributed temperature sensing technology allows measuring temperatures at a distance of 6 km, totaling 6000 points of measurement. The fiber optic sensing system’s transceiver measures “temperatures for 6 km both upstream and downstream of its installation point, for a total coverage of 12 km per each transceiver.” It is possible to employ several transceivers with accompanying fiber optic cables to offer coverage for long pipelines, totaling hundreds or thousands of kilometers in distance.

DTS technology acts as a semi-automatic leak detection system, obtaining data information to enable operators to take action before automation and/or safety system activation. It should be mentioned that a semi-automatic system means that the leak detection occurs automatically, resulting in an alarm signal in a continuously staffed control room. 

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating 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 temperature measurement systems and want to learn more, please contact us at info@optromix.com

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editorWhy DTS systems are beneficial to pipelines

FBG sensors that dissolve inside the body have been developed

on May 18, 2020

umberto-xbrMwBgYUHY-unsplashResearchers have been firstly created a fiber optic sensing system, known as a fiber Bragg grating (FBG), inside bio-soluble optical fibers. According to Science Daily, fiber optic technology can be used to monitor the condition of fractures and safely study sensitive organs, such as the brain.

Fiber Bragg gratings that reflect the light of a particular wave are often applied in optical fibers used as distributed sensors. For example, such fibers are employed to monitor bridges in real-time or to track the integrity of aircraft wings. However, they have not yet been used in medicine. The new fiber technology will overcome these limitations by using optical fibers that break down in the body.

Firstly, researchers from Greece and Italy have created biodegradable glass for FBGs. They used phosphorus oxide in combination with oxides of calcium, magnesium, sodium, and silicon to perform this. The resulting optical glass combines excellent optical properties with water solubility and compatibility with living organisms, and its properties can be changed by adjusting the chemical composition.

Then the fiber Bragg gratings made from biodegradable glass were placed in conditions that are similar to the human body. As the experiment demonstrated, the created structures dissolve without a trace in such an environment, which opens the way for their medical application. Such FBG sensors are considered to be safe for the body and will not need to be removed after their use.

Possible examples of using optical fiber with FBGs include creating fiber optic sensors to assess joint pressure and monitor the heart and other sensitive organs. This optical fiber can also improve laser techniques for removing tumors by simultaneously conducting a laser beam and measuring temperature, necessary for the laser ablation process. Nevertheless, its safety and effectiveness will be tested on laboratory animals before developing medical applications of FBG technology.

Thus, a group of engineers from the University of Connecticut has created a biocompatible pressure sensor that will help doctors monitor chronic lung diseases, brain tumors, and other medical conditions, and then dissolve into the human body without a trace. Such a FBG sensor should replace existing implanted pressure sensors that are made up of potentially toxic substances and require removal after use.

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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editorFBG sensors that dissolve inside the body have been developed

FBG multicore fibers are used as medical tools

on April 27, 2020

vivid-3079201_640It is highly essential to have accurate spatial information of a medical device inside the patient for proper manipulation of the instrument. The thing is that a wide range of clinical applications requires spatial information. Nevertheless, each technique has its disadvantages, the promising solution is the application of fiber optic sensors in the catheter for its spatial information.

Fiber sensors are applied in various medical devices such as endoscopes and catheters. Such features as compact size, flexibility, lightweight, immunity to electromagnetic interference and compatibility with medical imaging modalities make fiber optic sensors ideal for the medical environment. Therefore, FBG sensors are used in different studies to offer feedback from medical tools, they allow monitoring muscle fatigue, cardiac activities, and body temperature.

Moreover, the application of fiber optic sensors also includes cardiovascular diagnosis, artery pressure detection, artery detection, intra-aortic balloon pumping, prostatic implants, and urology. For instance, FBG sensors are employed as force sensors to determine the interface between various tissues in order to help in precisely installing a catheter in the epidural space. 

Additionally, sensors based on FBG multicore fibers are used in numerous different shape sensing applications. “They have been used for 3D shape recognition of solid objects, shape recognition of flexible morphine wing, and curvature detection of a continuum manipulator.” Nowadays the studies describe the application of FBG sensors in single-core optical fiber but there are also FBG multicore fibers.

To be more precise, FBG multicore fibers can work as a curvature sensor and 3D shape sensors. Although their cost is higher than in single-core optical fibers, the cross-sectional area of the shape sensor with FBG multicore fibers is smaller than the shape sensor with single-core fibers. Herewith, certain devices require the use of FBG multicore fibers because of the limited space. Also, the cores of multicore optical fibers are mechanically coupled, and the relative distance between the cores remains constant, while they experience identical temperature. Such features of FBG multicore fibers make them more beneficial than single-core optical fibers.

Finally, fiber Bragg grating sensors (FBG) written on multicore optical fibers are applied as shape sensors for flexible devices. Several FBG multicore fibers have been uniquely tested as a shape sensor for a catheter. More particularly, 4 multicore optical fibers are applied despite a single multicore fiber with 3 or more cores that have FBG sensors is enough for reconstructing the shape of a flexible device. Several multicore optical fibers expand the reliability of the sensing system against individual FBG sensor failure.

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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editorFBG multicore fibers are used as medical tools

DTS performs dam monitoring

on April 13, 2020

dam-929406_640Dams applied for hydropower, irrigation or mining play a crucial role in human life, herewith, they evoke significant human, economic, and environmental consequences when they fail. Nevertheless, distributed fiber optic sensing increases dam safety by offering early alerts of potential problems.

To be more precise, modern distributed sensing systems are considered to have high accuracy for monitoring promoting a continuous understanding of dam conditions, taking dam safety to a higher level. For instance,  distributed temperature sensing (DTS technology) uses high spatial resolution temperature data from distributed temperature sensors to record tiny seepage flow changes and to estimate seepage rates in a dam structure. 

It should be noted that seepage happens in most embankment and earth dams as the impounded water looks for the path of least resistance through the dam and its foundations. Therefore, excessive seepage presents a threat while high-tech sensing systems enable to detect and analyze subsurface processes and prevent erosion. Distributed fiber optic sensing is a promising technology that can be employed to control critical geophysical parameters, for instance, temperature and strain with a sub-meter resolution over several km. 

Additionally, distributed sensing systems provide the benefits of cost-effective high spatial monitoring coverage. The thing is that optical fiber acts as the sensing system along the full length of the fiber optic cable allowing operators to obtain detailed data information along the entire dam. Distributed temperature sensors can catch tiny, localized changes in the seepage flow rates that would otherwise remain unnoticed. “They deliver temperature readings with the accuracy of point sensors with the indisputable benefit of fiber optics: the highest possible spatial coverage. ”

Moreover, the distributed temperature sensing does not need specialized optical fibers resulting in relatively low-cost installation. The thing is that measurements based on DTS systems provide data along the entire dam with high spatial resolution and high-temperature precision. Herewith, distributed temperature sensors have already been used in tailings dams. One of the main elements of the increasing number of permanent tools is the ever-increasing performance of the DTS systems. Modern fiber optic sensing systems achieve the world’s most accurate measurements, with sampling resolutions of 12cm (over 5km) and with temperature resolution as low as 0.01 C.  

Finally, seepage detection used distributed temperature sensing is regarded as a crucial technology and has prominently improved the monitoring capabilities of dam operators. The application of optical fiber networks provides additional benefits like the ability of distributed sensing systems develops further.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating 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 temperature measurement systems and want to learn more, please contact us at info@optromix.com

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editorDTS performs dam monitoring

Fiber Bragg gratings in bogie frame

on April 6, 2020

wheelThe application of fiber optic technology as temperature and strain gauges is quite surprising in bogie frames. To be more precise, these fiber optic sensors are applied for examining the carbon fiber bogie, in addition to standard surface-mounted electrical-resistance fiber optic strain gauges.

Optical fibers of 125 micrometers in diameter or 250 micrometers with a coating layer are perfect for this aim. The thing is that the optical fiber is improved to produce fiber Bragg gratings (FBG) in the fiber, efficiently producing a number of semi-reflective mirrors over short but equal intervals.

The operating principle of the FBG system is based on the reflection of the signal (a small amount of the signal at each semi-reflective mirror) when the light is transmitted through a fiber Bragg grating. Herewith, “the originally reflected wavelengths (without the influence of strain) from each Bragg grating are compared to the reflected wavelengths when the structure is loaded.”

It should be noted that in the case of FBG deformation by strain, the spacing between the semi-reflective mirrors is either enlarged (tension) or decreased (compression). Therefore, the change combined with the efficient refractive index and the period of the fiber Bragg gratings leads to a shift in the reflected central Bragg wavelength.

The thing is that the wavelength size demonstrates the strain magnitude. Nevertheless, there is the same effect happened with temperature change, while the temperature effect is over 10 times the strain effect that is why the fiber optic technology needs to correct for temperature.

The researchers present the techniques applied to compensate for temperature where the fiber Bragg grating is placed close to the end-face of a cleaved optical fiber. The fact is the optical fiber with FBG is put in a capillary tube where one end is fused to the fiber, well away from the grating, and the opposite end is sealed. Finally, the FBG system responds only to temperature.

Nonetheless, it is not enough only to install several strain gauges into the bogie and link them to the instrumentation either. Ir is required to choose the proper fiber, for instance, bend-insensitive optical fibers are suitable. These are optical fibers where the diameter of the core includes 9.5-micrometer fibers with 4.5 mm long fiber Bragg gratings.

Additionally, it is necessary to properly install FBG systems to the bogie so as to act as a homogeneous part of the structure. Fiber Bragg gratings provide such benefits as efficient strain gauge transfer, capable to accommodate localized variations in the surface topology of the composite.

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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editorFiber Bragg gratings in bogie frame

Distributed temperature sensors promote warning systems

on March 30, 2020

smart-3871774_1280Temperature is a key safety indicator in any industry. The technology of distributed temperature sensors using optical fiber allows measuring the temperature at any point in the fiber, with an interval of 1 meter, resulting in the detailed temperature dependence of all required areas. The data obtained by this technique makes it possible to develop intelligent warning systems based on it, therefore, replacing outdated point-based monitoring systems.

The optical fiber itself acts like a fiber optic sensor, and the distributed nature of the DTS technology enables us to determine the temperature change at an arbitrary point, spreading many kilometers from it. Moreover, the measurement quality is not affected by electromagnetic radiation, thus, the distributed temperature technology is free from false alarms.

To be more precise, distributed temperature sensors (DTS) allow measuring the characteristics of an object along a fiber optic cable, while the fiber cable is a linear sensor, which is a continuously distributed sensing element throughout its entire length.

The operating principle is based on the reflectivity of stimulated Raman scattering of light (Raman effect). A semiconductor laser is also used to determine the location of temperature changes in a fiber optic cable. The fact is that the structure of the optical fiber changes when the temperature changes. 

When laser beam light from the laser system enters the area of temperature change, it interacts with the changed structure of the optical fiber and in addition to direct light scattering, reflected light appears.

The main advantages of fiber optic sensors in comparison with classical analogs are the following:

  • Compact size;
  • Very fast response to parameter changes in the environment;
  • Low weight;
  • Multiple parameters can be registered simultaneously by a single distributed sensor;
  • Reliability;
  • Very wide operating temperature range of DTS;
  • Small price per unit length of the sensing system;
  • High sensitivity;
  • Long operating time;
  • The high spatial resolution of temperature sensors;
  • Resistance to chemicals and aggressive environments;
  • DTS is not affected by electromagnetic disturbances;
  • The sensitive part of the fiber sensor does not require connection to power lines.

The processing unit measures the propagation speed and power of both direct and reflected light and determines where the temperature changes. For instance, at a wavelength of 1550 nm, a pulsed generation mode is used with a laser power limit of 10 mW.

There are several types of optical fibers, each of which meets certain requirements for its properties, depending on the application due to the fact that the properties of the optical fiber can be varied over a wide range. 

Physical effects on the optical fiber, such as pressure, deformation, temperature change, affect the properties of the fiber at the point of exposure and it is possible to measure the environmental parameters by measuring the change in the properties of the fiber at a given point.

In general, a fiber optic sensor consists of two concentric layers: fiber core and optical coating. The fiber optic light guide part can be protected by a layer of acrylate, plastic, reinforced sheath, etc., depending on the application of this fiber cable.

Thus, distributed fiber optic sensors are perfect for industries related to combustible and explosive materials, such as coal, oil and gas production, etc. for use in fire alarm systems of various structures.

alarm-3410065_640Application of distributed temperature sensors includes:

  • fire alarm systems in the road, rail or service tunnels;
  • thermal monitoring of power cables and overhead transmission lines to optimize production processes;
  • improving the efficiency of oil and gas wells;
  • ensuring the safe working condition of industrial induction melting furnaces;
  • monitoring the tightness of containers with liquefied natural gas on ships in unloading terminals;
  • detection of leaks in dams;
  • temperature control in chemical processes;
  • leak detection in pipelines.

In addition, DTS systems combined with other tools open completely new areas of application. For example, it is possible to design a specialized device – a fire detector based on a distributed fiber optic temperature sensor.

Detecting a fire in an industrial environment is not an easy task because of the large number of disturbing factors, many of which can be considered by detectors as carriers of fire signs. In addition, dust deposited on the DTS‘ sensitive elements makes it difficult to operate and it can disable them.

It is also necessary to take into account the possible smoldering of the deposited dust, which can also lead to false alarms. The presence of fumes and aerosols makes it impossible to operate smoke optical-electronic fire detectors. The presence of carbon monoxide will trigger gas fire detectors.

Industrial facilities and production are characterized by large volumes of premises, high ceilings, the presence of long tunnels, collectors, mines, inaccessible areas and premises with a complex configuration and geometry. And in these conditions, it is certainly possible to protect using traditional fire alarm systems, but this involves the use of a large number of detectors, and therefore they have high costs, including installation and maintenance of alarm systems and automation.

It is difficult to select detectors for explosive zones, especially for use in underground operations and mines. Aggressive media are often present in chemical industries. There are also objects of sea and river transport, characterized by the aggressive salt fog.

The use of non-electric sensing devices, the use of fiber optic cable allows the DTS to be applied in enterprises of the oil and gas complex, mines, underground operations, chemical industries (including those with aggressive environments), and metallurgy and energy enterprises.

As for oil companies, the active development of high-viscosity oil fields, which imposes strict requirements on the production equipment, and the severe depletion of most oil and gas fields require mining organizations to conduct prospecting and exploration operations, change production technologies and control the technical condition of wells.

The main task for mining companies to increase the well’s production capacity in real-time is to track information about the processes occurring in wells and fields. Solutions based on standard temperature sensors suggest well logging using point measuring instruments, which leads to the inaccuracy of the data obtained. 

The disadvantages of such sensing devices include the inability to fix the distribution of one of the most important parameters of the well – the temperature profile in real-time, as well as the need for power supply, the impact on the measurement results of external electromagnetic fields, labor and time costs required for the departure of the team and performing various operations, including the immersion of the fiber sensor element and its movement along the well, data processing, etc.

The fiber optic sensing system consists of distributed temperature sensors designed to measure temperature along the borehole, and point-to-point fiber pressure sensor. Optical fibers of a distributed temperature sensing system and pressure sensors can be structurally installed in a single fiber cable.

The fiber optic cable is resistant to mechanical damage. Additional fiber optic cable protection is not required during descent and lifting operations, but the protection of the fiber cable from mechanical damage during descent and lifting operations can be provided by the use of protective coatings.

If you want to obtain a highly efficient distributed temperature sensing system, you should choose the Optromix company. Optromix is a manufacturer of innovative fiber optic products for the global market. The company provides the most technologically advanced fiber optic solutions for monitoring worldwide. Optromix is a fast-growing vendor of fiber Bragg grating (FBG) products line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, distributed acoustic sensing (DAS) systems, distributed temperature sensing (DTS) systems. 

Distributed temperature system provides continuous underground power lines monitoring of temperatures, detecting hot spots, delivering operational status, condition assessment, and power circuit rating data. This helps operators to optimize the transmission and distribution networks, and reduce the cost of operation and capital.

Usually, the DTS systems can detect the temperature to a spatial resolution of 1 m with precision to within ±1°C at a resolution of 0.01°C. Measurement distances of greater than 30 km can be monitored and some specialized systems can provide even tighter spatial resolutions.
The advantages of working with Optromix:

  • Our DTS system has the superior quality, however, its price is one of the lowest in the market;
  • Optromix is ready to develop DTS systems based on customer’s specifications.

If you are interested in DTS systems and want to learn more, please contact us at info@optromix.com

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editorDistributed temperature sensors promote warning systems