Tag: fiber optic technology

FBGs for Monitoring in Hydrogen and Radiation Environment

Fiber Bragg gratings (FBGs) are commonly applied in different fiber optic devices, for instance, in fiber lasers, sensors, etc. However, because of the harsh environmental conditions, where FBGs are operating, there are several important factors that should be taken into consideration.

According to the experiments and field results, FBGs’ characteristics can change with time. Negative environmental effects such as radiation and hydrogen effects can not only influence the parameters but also shorten the operation time of the fiber Bragg gratings. It is especially important to understand the radiation effects and other factors on essential dimensions of fiber optic systems during fiber optic technology manufacturing.

What are the Fiber Bragg Gratings (FBGs)?

Fiber Bragg grating is an optical fiber that has the refraction index changing along the fiber length. Due to its modulation, FBG acts as a mirror that reflects certain wavelengths and transmits the others.

FBGs have become significant tools of the fiber optic technology from the very first day of their creation. Specialists have drawn much attention to the fiber optic sensing because of its properties, for example, compact sizes, immunity to the electromagnetic interference, etc.

What are the applications of the FBGs?

Specialists have already applied fiber optic solutions in various industrial sectors: industrial and civil constructions, aerospace, etc. Fiber optic sensors are applied for measurement of different physical parameters including temperature, strain, pressure, etc. Nowadays, these abilities are effectively applied in such structures as a structural health monitoring device by fiber Bragg grating sensors.

However, implementing such a powerful instrument in difficult environmental conditions, where most tools can not be used at all, brings some troubles. Scientists have learned to deal with it and have improved fiber Bragg gratings greatly.

So, nowadays FBGs are capable of operating in high radiation conditions, as an example, for nuclear installations and space applications.

Fiber Bragg gratings (FBGs) for space

The most up-to-date fiber optic sensors can be used not only for spacecraft systems, but also for astronauts’ security and health. In space, the radiation level is very high, taking into consideration the periodic solar flares.

There is a need for an accurate system that is able to operate in radiation environments. Especially, considering the fact that it brings some troubles even to replace some equipment onboard not to tell about when a satellite is put into orbit.

That’s why fiber optic systems are highly suitable for applying in this industry and providing data about temperature, strain and radiation. Moreover, based on the received information, it can foresee possible malfunctions. They are able to operate in extreme conditions and survive during the entire mission.

These factors make all the difference in future space exploration and its colonization.

FBGs for the nuclear industry

Fiber Bragg grating sensors can be also implemented for the development of nuclear applications. It is well-known that the radiation affects the surrounding materials and consequently their features. It is about photonic and electronic components that are the most susceptible to nuclear radiation exposure.

Usually, in the nuclear industry there is no possibility to replace components or make any repairs of the already operating systems. That’s why it is required to monitor the systems’ maintenance in the radiation conditions.

There are two types of radiation that are always taken into consideration: gamma-rays and neutrons. Gamma-rays are radiated by the surrounding structures, and neutrons are relevant to the inner reactor core during its operation. FBGs can be implemented in different sensing operations. For example, monitoring of the temperature in the reactor core and observation of the underground nuclear waste storage facilities, mechanical stress measurements, etc.

FBGs in radiation environments

There are several types of FBGs that can be divided according to their diverse inscription processes, thermal and radiation resistances. In reality, fiber optic sensors can malfunction under the long-term exposure of radiation that leads to the future measurement errors. These malfunctions depend on the structure of distributed fiber optic sensors and the radiation environment.

Scientists have conducted a range of special studies to watch how fiber Bragg gratings are operating in radiation conditions. Space, high energy physics and nuclear facilities are able to apply fiber optic technology to their advantage.

Fiber optic sensors’ sensitivity to the radiation depends on their way of manufacturing and concentration. However, ionization is able to break the bonds. Moreover, there is a possibility of structural changes such as densification that causes further defects. These factors lead to the degradation of optical characteristics that are invisible to the eye.

The main effect applied in this technology is radiation-induced attenuation. It depends on various parameters including:

Harsh environments;
Qualities of the optical fibers like manufacturer process, etc;
Testing environment.

Due to the composition of the optical fibers, they will react in radiation environments differently. That’s why except for the accurate calculations, specialists take tests on the fiber radiation response in conjunction with temperature. They watch fiber optic sensors’ possible reactions before applications in the real-world environment.

Fiber Bragg gratings have many capabilities and can be applied for prevention of disasters and accidents. With a proper coating and method of inscription, FBGs are able to detect any changes and, due to it, define the concentration of the hydrogen, etc. The quick and accurate location of the resulting leakage can prevent crucial damages, unexpected expenses, and danger to human life.

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

Multicore Fiber Optic Sensors for 3D Shape Sensing

Multicore fiber optic sensors have found a range of applications in different fields. One of them is 3D shape sensing which has greatly risen in recent decades. Nowadays, 3D shape sensing can be produced for industrial necessities or for the area of research depending on the purposes of applications. Multicore fiber optic sensors have proved to be the most effective instruments for this technology in comparison with other methods. They are used particularly in the cases when there is a need for the most precise measurements and minimal invasive procedures.

What is 3D Shape Sensing?

Fiber optic 3D shape sensing is a fiber optic technology that applies a fiber optic cable for permanent monitoring of the objects’ 3D shape and position in real-time.

Shape sensing has a capability of finding and detecting all the deformation processes that take place at one or more locations along the fiber optic cable. This fiber optic technology can detect just one kind of deformations with certain types of fiber optic sensors or a range of deformations with the types of several distributed measurements.

Multicore optic fibers themselves have an ability to transmit the data at high speed. They also can be applied as fiber optic sensors, when they have fiber Bragg gratings (FBGs) in the cores. FBGs are reflective gratings that can filter specific wavelengths. Any changes of the form or position cause the wavelength changes.

As for the 3D shape sensing, there is a special way of fiber Bragg gratings’ inscription into multicore fibers. Firstly, they are spun while stretching. Then fiber Bragg gratings are written along the cores’ length. This technique makes it possible to identify the fiber’s rotation as well as three-dimensional changes.

The Most Common Advantages of the 3D Shape Sensing

Fiber optic sensors are proved to be effective in different technologies. They are especially suitable when there is a need for a complex measurement system. It usually involves the whole system with a number of fiber optic sensors and can provide the measurements of several characteristics simultaneously.

Moreover, FBG sensors have a range of other benefits in comparison with other traditional sensors. So, fiber optic sensors are:

highly sensitive to temperature and strain modifications that lead to the high levels of accuracy;
immune to external electromagnetic interference;
lightweight and small sized;
easy to attach and reliable;
corrosion resistance;
resistant to the harsh environmental conditions such as humidity, high temperatures, etc.

Due to their compact size, fiber optic sensors can be embedded in small devices and objects. Moreover, they can be implemented into distributed sensing systems so the FBG interrogator units can be installed at some other place and send all the data remotely without any wiring.

Fiber Optic Sensors Applications in 3D Shape Sensing

3D shape sensing technology has recommended itself as an effective and even preferable instrument.

This technology has a significant use in the structural health monitoring of different constructions such as buildings, bridges, etc. Besides, fiber optic sensors are produced for aircraft monitoring. Fiber optic solutions are also utilized for damage detection, deformation monitoring and structural fatigue life evaluation. Moreover, intelligent material deformation and intelligent robot posture monitoring are of the applications where fiber optic technology is used.

3D Shape Sensing in Medicine

As for the medicine and biomedical fields, fiber Bragg gratings (FBGs) as well as 3D shape sensing have got a special place. This technique has significantly decreased the healing and rehabilitation time and resulted in minimum functional and cosmetic damage to the body. Here are some examples where fiber optic sensors have proved to be an effective option:

FBG sensors have found a wide range of applications connected to cardiac activities and cardiovascular diseases. They are applied in artery pressure detection, intra-aortic balloon pumping, etc.
In surgery, they are applied as surgical instruments that, among all other options, help in visualization. If we are talking about laparoscopic or robotic surgery, the process of visualization has become more simple due to the fiber endoscopes.
Endourology is another field that uses shape sensing technology’s advantages. One of the endourological procedures is cystoscopy that means the treatment of bladder and tumors. Sensing technology makes the device navigation and localization process better. As a result, specialists can carry out operations faster and safer, therefore, conducting the procedures more effectively.
3D shape sensing was able to improve another medical field called colonoscopy. A common colonoscope coupled with the fiber optic technology makes the navigation better and allows preventing most challenges that specialists usually face. Due to the benefits of the fiber optic solutions, including shape reconstruction over the whole device, specialists can get the data about the procedure in real time. As a result, medical procedures become safer and more comfortable.
Epidural anesthesia is getting popular in difficult operations where pain management methods are required. The insertion procedure is conducted with a thin needle that makes it impossible to use most of the sensors due to their size. However, fiber optic sensors based on the distributed sensing principle are able to solve this problem. Specialists have conducted accurate calculations to provide a navigation system that is able to make the correct penetration into the tissue easier. So, it also helps the operators in determination whether the epidural space has been reached.

All in all, 3D shape sensing is a fiber optic technology that has found many applications and become an indispensable tool in medicine, for example, as needles and catheters. Fiber optic sensors, being cost-effective tools, are especially irresistible when there is a requirement in detecting small deformations.

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Dual Lasers in DTS Systems for Oil and Gas Wells

DTS systems provide the oil and gas and other industries with the new cutting-edge fiber optic solutions such as a groundbreaking dual laser technology which offers the most robust and the simplest distributed temperature sensing systems accessible to the industry. This technology also includes the ability of the automatic correction for dynamic changes to the sensing fiber.

What is Distributed Temperature Sensing?

Distributed temperature sensing, also known as DTS, is a technology that measures the temperature along the whole fiber optic cable in a continuous fashion. The fiber optic line can be any required length up to 30 km. The system includes the recording instrumentation at one or both ends of the cable. It can work permanently or from time to time for each use, depending on the requirements.

Most Common DTS Applications

Distributed sensing systems have established themselves as an effective part of fiber optic technology. High temperatures are related to the severe environmental conditions which make operational processes difficult. However, fiber optic sensors can operate in such conditions greatly, especially, if we compare them with the electrical-based temperature sensors. That’s why fiber optic systems have found many applications, such as fire detection, healthcare, railways, etc.

DTS systems are installed on the electric power lines to monitor temperature changes. The temperature may indicate the electrical overload or other deviations from the norm in time. DTS technology allows power companies to exploit the assets more effectively.

With the help of constant monitoring, it is easy to react immediately to the temperature rising. When this rising is above a predefined threshold, the alarm sets off. The early detection and warning lead to reduction of the damage that failures may cause.

DTS Applications in the Oil and Gas Industry

Fiber optic technology has been used in the oil and gas industry for over the last 25 years. Fiber optic systems were installed in various types of oil wells starting from land wells and ending with offshore wells. Fiber optic technology allows watching down hole casing deformation or changes in sand screen completions.

Thanks to its operational principles, distributed temperature sensing offers critical asset monitoring solutions that can be applied for oil and gas companies. DTS systems immediately provide the actual and accurate information about temperature with high resolution and high speed. Fiber optic cable provides specialists with the numerous measurement readings along the whole optical fiber. This feature helps companies in detecting leaks along the pipelines, whether along its length or anywhere on the cross-section. The faster the leaks are found, the less damage can be. It means considerable cost savings for companies. Moreover, DTS technology helps in identifying under-performing zones, optimizing gas lift operations, etc.

Distributed temperature sensing has been applied safely to follow up pressure or reactor vessels. Depending on the required set-ups, the temperature measurements can be held as frequently as every 30 seconds. Any changes in temperature may point out some problems that have occurred. So the increasing temperature of the vessel wall usually predicts the system or the process failure.

Dual Lasers in DTS Systems

Each year, specialists implement DTS systems more often to make the efficiency of production better. The integration of the dual lasers into such systems is a new technology, aiming at the life extension of optical fibers and solving the most appearing concerns. The most common issues that optical fibers face are fiber darkening or their damage.

The fiber darkening can misrepresent the statements and lead to the failure of the DTS system. It occurs where there are high pressure and high temperature environments that are usual for oil wells. The darkening happens unevenly and is progressive over time that makes the manual calibration techniques ineffective. Moreover, different connectors on the fiber can result in various degrees of optical loss. Two lasers operate at different wavelengths, so there is an automated adjusting system for any changes in optical loss in the fiber. They immediately react and correct these effects which allows the further use without re-installation of the whole system from the very beginning.

Such fiber optic systems help in cost-reducing by avoiding the re-deployment of the equipment. Despite the other systems, they don’t need the manual calibration techniques, but operate automatically all over the length. The manual calibration usually requires repeated recalibration efforts.

Newly developed DTS systems with dual lasers offer great advantages especially where there is no or limited access to the optical fiber. They help to extend the lifetime of the fiber and ease fiber optic systems’ deployment.

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 Bragg Grating Sensors for Railways

Fiber Bragg grating (FBG) sensors have already been applied in various applications and still arouse great production interest. They are commonly used in structural health monitoring for aerospace, civil engineering, oil & gas, etc.

As for the railway industry, fiber optic technology has made a substantial contribution to its development. It is anticipated that within a few years the number of goods that will be transported by railways will be increased, as well as the number of passengers. This, in turn, will lead to the growth of the axle load and trains’ faster speeds operating.

That’s why there is a great need for a full understanding of the rails’ structural and operating conditions as well as for providing safe and reliable operating conditions. So modern innovative technologies are required.

Fiber Optic Solutions for Monitoring Systems in the Railway Industry

In railways, common monitoring systems use strain gauge sensors. The sensors constantly measure resistance caused by the stress transmitted by the rail when the train runs through it. This fiber optic technology is already prominent due to its effectiveness. However, it still has several shortcomings. For example, it is expensive, huge and has difficulties in usage, in comparison with modern FBG sensors. Moreover, the most important disadvantage is that they can be affected by electromagnetic interference. FBG sensors are immune to the external interference such as electromagnetic interference, lightning and many other external disturbances.

Because of this, fiber Bragg grating sensors are getting more and more applications in high-speed railway networks. Applications are train weight estimation, measurement of train speed for real time, wheel imbalance detection, etc. It is clear from experiments that FBG sensors are more appropriate as railway monitoring systems compared to electrical ones.

Fiber Bragg Grating Sensors Characteristics

FBG sensors provide many crucial features for unique operational conditions in railways. In comparison with usual electrical sensors, fiber Bragg grating sensors have EMI/RFI immunity, multiplexing capability and can offer interrogation for long distances. In FBGs the data is wavelength-encoded, which makes the signals less susceptible to intensity fluctuations. Moreover, the fiber optic cable can be interrogated from either end, offering redundancy to FBG sensing networks. Plus, FBGs have a self-calibration capability. The strain and temperature measured findings is an absolute parameter. So there is no dependency on the measurement value and losses between the interrogation unit and the FBGs. To fabricate FBG sensors, FBGs are packaged and transformed into different types of transducers. That makes it possible to install them on the rail track fasteners, clips, bogie, train body, chassis, and axle boxes of a train to provide ongoing inspection for health checking.

In addition to that, FBG sensors can be interrogated at very high-speeds.

Providing reliable operational conditions, fiber optic designs can measure a wide range of other parameters such as inclination and acceleration through the modulation of light in reaction to the environment. Therefore, one FBG interrogator can work with a lot of FBG sensors to measure many options at the same time at different locations over the vast territory. The sensing signals can be read at distances more than 100 km away.

These features are especially useful for the railway industry because they allow simplifying the installations a lot and reducing costs.

Fiber Bragg Grating Sensors in Field Projects

Over the past few years, specialists have safely held a number of field trial railway projects involving FBG sensors. For example, in 2007, about fifty FBG-based vibration sensors were installed along the East Rail Link that connects Hong Kong and Mainland China. Then fiber optic solutions were applied in metro lines of Hong Kong, part of the Beijing-Shanghai High-speed Rail Link, and in Delhi Airport Metro Express Line.

In Hong Kong this fiber optic technology was applied on a passenger rail system as a structural health monitoring system. The FBG sensors were attached to the bottom of the carriages. The goal was temperature and strain measurement. The fiber optic system supplied all the necessary data including rail tracks’ and carriages’ deformation. The acquired information helped to assess the rates of the corrosion and bearing wear.

According to the results, due to FBG sensors, costs of maintenance were greatly reduced. Moreover, it helped to avoid or prevent problems at early stages due to the early detection of excessive vibrations. All these works showed that FBG sensors are superior in comparison with conventional sensors in many essential aspects.

Nowadays, fiber optic solutions are regarded as one the most cost-effective technology that helps in monitoring the condition and structural health of the carriages, tracks, and under frame equipment in railway systems. There are still some parameters that need to be improved, like the lack of proprietary and custom specifications. However, in the future major railway operators can apply modern FBG sensors, gaining more field experience.

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Fiber Optic Sensing for the Steam Assisted Gravity Drainage

Fiber optic sensing technology has proved to be an effective method in well and reservoir management. Fiber optic sensors constantly track temperature changes along the wells at specified intervals and collect all the data.
This technique is also compliant with the other technologies such as Steam Assisted Gravity Drainage (SAGD).

What is Steam Assisted Gravity Drainage?

Steam Assisted Gravity Drainage (or SAGD) is an enhanced oil recovery drilling technique that helps in extracting heavy crude oil or bitumen from oil sands deposits. Mostly, the accustomed approaches in such cases are economically inefficient. Specialists may use it in particular cases when the production is difficult. With the help of the fiber optic technology this approach becomes more cost-effective.

How does Steam Assisted Gravity Drainage work?

In short, the SAGD system’s principle is heating the heavy oil or bitumen by the steam for further extraction. For that two horizontal wells are drilled at an angle of 90 degrees to a vertical bore well. In the wells, there are two pipes, one above the other for around 4-5 meters.

At the very beginning, the cold heavy oil is essentially immobile because of the high viscosity, and it needs to be warmed up to extract it. To do so, the steam is applied. It travels through the upper well into the reservoir and expends the heat in all directions of the formation, making a steam chamber. The heat warms the bitumen and reduces its viscosity. Then the bitumen flows downward into the production well and is pumped to the surface. Both processes are going at the same time.

Current Applications of the Steam Assisted Gravity Drainage

Due to the growing level of oil consumption, the level of its development needs to be increased. Not the last role is played by the SAGD and fiber optic systems such as fiber optic sensors and fiber Bragg gratings.

Like any exploration, heavy oil production needs accurate analysis and planning, especially if there are other factors that make the production difficult. Such aspects as great depth, high temperature conditions, etc. are essential. All of these issues need to be considered. The low mobility and high viscosity make the oil producing complicated and lead to low recovery indexes. However, due to the SAGD and fiber optic technology, there is an opportunity to maximize the recovery indexes.

For SAGD technology, FBG sensors are usually applied in wells to track the steam as it moves along the wellbore. Due to the fiber optic sensors, there is an opportunity to see the data in real time. According to the achieved data, the velocity of the steam can be identified. Besides, temperature sensors can also define the speed of the heating. The accurate settings of the temperature, pressure and steam-injection rates can lead to the operational savings. All the information can be used to plan the further work of the production operations.

Fiber Optic Sensors in Downhole Monitoring

Fiber optic sensors have proved to be effective for various parameters’ monitoring in downhole applications. Most of all, distributed temperature sensing (DTS) is applied for these purposes. Distributed sensing has demonstrated good results. It has high recommendations in the oil industry. DTS can monitor well temperature all over the fiber optic cable.

Due to the modernly developed fiber optic designs and improvement of fiber optic sensing technology, a range of issues related to downhole production have been solved. However, the harsh environmental conditions in the downhole can still bring some problems to the fiber optic sensors.

The sensors still need to cope with hydrogen in the severe environmental conditions. It has a great impact on the optical fibers. Firstly, it can cause pressure and temperature errors. The appearing errors are connected to the hydrogen diffusion into the microstructure and to the changes of the refractive index when hydrogen penetrates into micro holes and fiberglass. So the hydrogen leads to the additional Bragg wavelength shift.

With this in mind, specialists are constantly developing fiber optic monitoring systems based on fiber Bragg grating technology.

Advantages and disadvantages of the SAGD

SAGD has played a crucial role in the rapid development of the oil resources. However, as everything, this method has some pros and cons that should be taken into account.

Most Common Disadvantages for SAGD technology

Firstly, as any other technology, SAGD has its restrictions. It is not well-suited for every production area with heavy oil. It has several aspects to be fulfilled, like homogeneous and relatively thick reservoirs.
Secondly, high water and fuel consumption. To work effectively, SAGD needs a large amount of water and natural gas. Both of them are used in the process of steam production. That’s why the energy consumption is high but worth it. When all these conditions are satisfied, SAGD technology can be used. Moreover, the specialists advise using deep water sources that are not appropriate for consumption or agricultural uses. In fact, the majority of deployments’ developers follow this recommendation for environmental protection.
Thirdly, some think that SAGD technology is an expensive tool for oil production. However, specialists consider this technology as a superior alternative to reduce the high expenses and at the same time increase productivity. The reason for the cost reduction is that less horizontal wells are required to be drilled.
Fourthly, concerns about an environmental effect of the steam assisted gravity drainage (SAGD) are still a topic of discussion. However, according to the statistics, over the last 20 years the environmental analysis is getting better. It is obvious that the production of the crude bitumen and oil cause environmental consequences, but due to the development of modern cleaner extraction technologies, the situation is improving.

The Main Advantages of the SAGD technology

The main benefit of the whole SAGD technology is the improved steam-oil ratio and high ultimate recovery. Besides, the DTS systems help in optimization of the oil and bitumen production.

The other SAGD advantage is the constant evolution. Every next project makes a great contribution and brings new ideas and experiences. Meanwhile, the diversity of newly developed methods leads to new approaches to different types of oil fields.

So there are other modified types of SAGD technique:

Shaft and Tunnel Access (SATAC);
Single Well SAGD (SW-SAGD);
Multi-drain SAGD;
Fast-SAGD;
Enhanced Steam Assisted Gravity Drainage (ESAGD).

The SAGD was firstly implemented in Canada, where there are the largest reservoirs of crude bitumen. This allowed to advance the recovery factors in excess of 50%.

SAGD (steam assisted gravity drainage) well temperature monitoring provide:

Temperature profile control of injection and production wells;
Determination of inflow (injection) intervals of the fluid;
Determination of the fluid level in the well and perforation intervals;
Identification of issues in the well.

Plus, as any fiber optic technology, distributed temperature sensing for SAGD offers:

Maximum protection of the cable against chemical and physical effects;
Longer service life;
Convenience and speed of the installation;
Operations in the well without the extraction of the cable sensor.

The SAGD wells have implemented all the advantages of fiber optic sensing. FBG sensors offer real-time, precise temperature measurements along the fiber optic cable in the wellbore. Fiber optic solutions allowed us to monitor the objects that were unapproachable before. For example, fiber optic sensors with extended temperature range were applied in the oil wells for temperature control during oil production using SAGD technology.

Steam assisted gravity drainage is commonly believed to be applied for complex deployments. It aims to make the process simpler. And the fiber optic technology is good at helping it. However, the specialists should discuss and decide how fiber optic technology can fit into the development at the planning stage. Fiber optic solutions may simplify the production process.

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Distributed Temperature Sensing at shallow depths

Distributed temperature sensing (DTS) is a state-of-the-art tool that possess an ability to monitor temperature rates over large territory and across wide temporal scales. This fiber optic technology has proved to be effective in different spheres and industries. However, despite the long field experience story, it still has its limitations and challenges apart from all the advantages. For example, when we talk about its application at shallow or deep depths.

The main difficulties in Distributed Temperature Sensing application

Despite all the progress that was achieved during this decade, distributed temperature sensing still meets some challenges. For example, when applied to the ocean, since dynamic oceanographic processes have a wide range of parameters, ranging from various types of turbulence to different climates, all data obtained from DTS systems fully help in understanding the dynamics of a complex ocean. However, different constraints can make modifications in time scales creating restrictions. Furthermore, there is a need for many additional advanced equipment for broad spatial resolution. That’s why it’s still complicated to use DTS in oceanography. However, now there are cases when distributed temperature sensing (DTS) is applied, for instance, in the Atlantic.

Recently, the scientists announced the first experiments on the seafloor of the Arctic sea ice with the help of the distributed acoustic sensing (DAS) system. This research has shown that fiber optic technology is effective, despite all the difficulties the scientists have faced due to the harsh environment. The system recorded a range of events that commonly applied equipment couldn’t even detect. Moreover, the DAS technology has detected the icequakes, various climate signals, and marine life.

From the other side, DTS systems can be applied in measuring surface water temperature spatial variability in lakes and rivers. The received data helps in the assessment of different factors such as estimating fish habitat and thermal inertia, the interaction between surface water and groundwater, etc. Usually, distributed temperature sensing is successfully applied in rivers and lakes with sensitive and high-resolution temperature monitoring under the wide temporal and spatial scales. Nevertheless, difficulties may arise in streams with cobbly or bedrock-lined streambeds. To avoid all the challenges, more expensive additional technologies are needed.

There are other factors that should be ensured like sensitive equipment needs protection and continuous power to work. Besides, optical fibers are delicate, they shouldn’t be bent or crimped.

How the Distributed sensing system works

Distributed sensing systems are appealing because they are able to continuously sample preserving while maintaining relatively high temporal and spatial resolution. Moreover, the accuracy indicators stay the same over a vast territory.

Distributed temperature sensors measurement allows to constantly observe temperature changes along the fiber optic cable. In this fiber optic technology the whole cable plays the role of the sensing element that measures temperature. It differs this method from the usual electrical temperature measurement. Moreover, the distributed temperature sensing is regarded as the most cost-effective and efficient system among the modern temperature measurement technologies.

The main operation principles of measurement are built on detecting the back-scattering of light:

1. 1. 1. The first type is an optical fiber that uses Raman scattering. This approach was invented in the United Kingdom. Optical fibers are usually made from doped quartz glass. When the light falls on the excited molecular oscillations, the electrons of the molecule and the electrons of the molecule start interaction. This process is called Raman scattering and results in scattered light.
    2. The second method is the Brillouin scattering-based approach. It was mostly developed in the 1990s. It refers to the scattering of a light wave by an acoustic wave because of the interaction with the acoustic phonons. Thanks to the ability of the Brillouin scattering of making both frequency down- and up-shifted light, this method can be applied whether for distributed temperature or strain sensing. It can contain both, but they can’t work at the same time.
    3. The third technique is named Rayleigh back-scattering. This is the latest development. As well as for the previously developed distributed sensors, a usual optical fiber can be used as the sensor. It allows the entire cable to be used as a single sensor, without purchasing expensive individual sensors. Scientists applied this technique, for example, for measuring distributed temperature in a nuclear reactor.

If we compare all these three techniques, each of them has its pros and cons. According to the scientists, the Rayleigh scattering demonstrates the highest rates in comparison with other types. However, it has limits in a range of fiber length. This factor is crucial for long lengths of cables’ monitoring. For this characteristic, the Brillouin scattering shows the best results. Besides, it has temperature sensitivity and good measurement time. Moreover, Brillouin scattering allows to detect distributed strain, unlike the other two methods. But usually it is applied either for distributed temperature measurement or strain. According to the data, Brillouin scattering is more often used as a substitute for Raman scattering.

DTS systems in field experiments

In accordance with the final field experiments, despite all the challenges, temperature measurements with the help of the DTS systems have been performed successfully in various environments including rivers, lakes, seas, etc. The fiber Bragg grating sensors have been applied both in fresh and sea water and demonstrated good results. Furthermore, it refers to simultaneous measurement of temperature and depth which has been impossible for previous fiber sensors.

Modern fiber optic sensors provide the parallel measurements of temperature and pressure at the same place. Besides, in comparison with other methods, fiber optic technology provides much lower power consumption. It allows the DTS systems to work longer and makes longer experiments and observation possible.

The developed fiber optic technology can be used for measurements and monitoring of the physical parameters. Moreover, it is well-placed for many cases and can be applied to various applications, such as wave and tide gauges, tsunami warning systems, etc.

All in all, we can say that distributed temperature sensing (DTS) can be successfully applied in various cases at shallow depths due to their diversity. The system can be designed and installed in accordance with the existing conditions and parameters in every single case.

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

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Fiber Bragg Grating (FBG) Sensors for Industrial Sensing

Recently, researchers have presented a new generation of fiber Bragg grating (FBG) sensors that are covered with aluminum and copper. These FBG sensors are compact and hermetically sealed. Depending on the applied coating, they are resistant to high or low temperatures and can be applied in harsh environmental conditions. As well as gold-coated fiber Bragg grating sensors, they are representatives of a modern generation of humidity-proof different sensors, for example, temperature sensors, strain sensors, pressure sensors, etc.

Main Fiber Bragg Grating Sensors advantages

It’s a well-known fact that FBG sensors are widely applied in various fields and spheres thanks to their advantages. A lot of measurements in harsh environmental conditions would become possible by the usage of fiber optic technology.

Here are the most common advantages of fiber Bragg grating sensors:

absolute temperature and other measurements in comparison with usual electric sensors;
rapid linear response in strain, pressure, or temperature measurements;
the compact size of the construction reduces the weight and allows to use of many sensing points on a single fiber strand;
measurements over long distances;
acceptable price, etc.

The new type of FBG Sensors

However, a usual FBG sensor with the glass fiber coating can have several limitations because of the high humidity, high temperatures, corrosion, etc. The new type of Fiber Bragg Gratings are embedded into optical fibers coated with aluminum, copper, or gold have much more applications.

Scientists have offered processes that allow providing two lays of metal coatings. It gives an opportunity to create different lengths of window stripping and make the second layer with the needed thickness and length.

In conclusion, we must say that scientists from all over the world keep finding new fiber optic solutions to solve the modern problems we face in real life. That means that fiber optic technology will be better and more effective every day.

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FBG Interrogators with a size of a memory stick

Fiber optic sensors are a modern technology that helps in shape and temperature measurements in various spheres and industries, for example, civil structures, aircraft, medicine, etc. Scientists from all over the world aim to create the most compact and cost-effective device according to the market demand. So the specialists from Europe have produced the new memory stick-sized FBG Interrogators.

Fiber optic sensors’ nature

Fiber optic sensors have many characteristics that make them very effective for a multitude of applications. They are small, inert to chemical substances, immune to electromagnetic interference, and capable of withstanding high temperatures. There is no doubt that they have a lot of applications thanks to their unique characteristics. Fiber optic sensors are applied in structural health monitoring. In medicine, they are also used in catheters, endoscopes, etc.

Over the last years, scientists have developed fiber Bragg grating (FBG) sensors that can measure strain and temperature. For example, fiber optic sensors are successfully applied in the new generation of planes. The whole principle of the fiber optic sensors is based on the reflected light. The light is sent through a fiber optic cable and partially reflected by a microstructure inscribed into the fiber core. Researchers can observe different changes in strain or temperature thanks to the shifts in the wavelength of the reflected light.

Modern sensor devices such as FBG interrogators are based on free-space spectrometry. Spectrometers measure the properties of light in a specific part of the electromagnetic spectrum. However, this approach still has several limitations including measurement resolution, power consumption, etc. That is why scientists aim to develop fiber optic technology further.

The new generation of FBG interrogators

As fiber optic technology develops, scientists create new ways of device dimensions, power, and cost consumption to serve the increasing applications and clients’ requirements. There are many types of FBG interrogators that can include multiple photonic functions in one device. These devices represent the second generation on the market responding to the clients’ demands.

Nowadays, scientists even work on the third generation of fiber optic systems that have the size of a memory stick. With the size optimization, they also make the cost-effectiveness better. The new fiber optic technology includes a photonic submodule that consists of two light sources and a spectrometer section. Scientists have added three thermistors to measure the temperature of those three parts. The small box that has a size of a memory stick detects the reflected light that’s coming in on the fiber. The light is produced by one of the two light sources inside the model, injected into the fiber. The photodiodes record the reflections and the electronics amplify them.

Despite all the advantages of these new fiber optic systems, the future market adoption needs a more compact and lower-cost solution, including the costs of the consumables in medical and fiber optic battery monitoring systems.

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Fiber Optic Solutions for 3D visualization in agriculture

Scientists have developed a new technology based on the distributed sensing system. They have found a fiber optic solution for 3D visualization in real-time that demonstrates crop root growth. Moreover, the newly developed distributed sensing system serves as radar and can be applied to measure temperature, acoustic, strain, etc.

In fact, in the 21st-century farmers agree that soil fiber optic sensors play a crucial role in agricultural development. Thanks to the data received from fiber optic sensors and other advanced technologies, they can easily develop more precise uses of water and other inputs.

Modern fiber optic technology in agriculture

According to recent studies, the plant root directly influences crop resilience and productivity rates. For instance, deep root architecture suits better for drought resistance. Thanks to it, it is possible to keep high crop yields even in the absence of rainfalls. In contrast, shallow root structures are better for paddy fields where there is a deficiency in oxygen. To speed the crops’ adaptation to such anticipated environmental conditions, scientists had an aim to create a system that would quickly provide data in real-time on root architecture. That is why they applied modern fiber optic technology.

The whole procedure of plant roots’ visualization seems to be difficult because it requires digging. Moreover, there is still a lack of convenient and high-resolution underground imaging systems that could help in studying plant root structures.

Fiber optic sensors for root growth monitoring

With the help of fiber optic technology, scientists prototype the newest imaging device which monitors root growth underground by using distributed fiber optic sensors. During the experiments, the fiber optic sensor was attached to a soft film and transformed into a spiral. Then a distributed sensing system was put into a pot filled with soil. As a result of the tests, scientists demonstrated that the distributed sensing system is able to detect small movements within solids even when a fiber optic sensor is placed into a film structure. This fiber optic solution provides a new approach to imaging movements in the field.

Each year researchers aim to turn farming technologies into a more automated sphere. The fiber optic sensors can help in it by providing more feedback on the soil conditions, temperature, etc. This modern device based on a distributed sensing system is an important addition to the next-generation agriculture instruments. It can be applied for data-driven automation.

According to scientists, this novel method with the usage of fiber optic sensors can also have other different applications. It can suit any small-scale perturbation occurring in solids, for instance, for monitoring worms’ movements through sediments or the propagation of mushrooms in loam.

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FBG sensors application in VR technology

It is not a secret that fiber optic technology already has a wide range of different applications starting with medicine and ending with road monitoring. However, scientists still have a lot of spheres for FBG sensors implementation. And the VR ecosystem is one of them.

So one Korean company has developed motion capture suits based on fiber optic solutions. This company is a developer of virtual reality technologies that aims to create a fully integrated VR ecosystem with the usage of fiber Bragg grating sensors.

VR entertainment is becoming more popular and capturing the minds of consumers. Nowadays, VR equipment can be installed at homes and other VR-based devices. Its applications are very diverse and can be applied in many industries, including education and even defense.

The FBG suits based on fiber optic technology are considered to be the fourth generation VR technologies. This generation intends to make VR more exciting and easily accessible. The previously created motion capture devices were much more expensive and required experience to work with. However, the company has solved both these problems with the help of fiber optic technology.

The company found out that there were some aspects that prevent VR adoption, for example, high installation costs and a long list of limitations. However, with the application of fiber optic sensors, the maintenance costs can be greatly reduced which will lead to greater adoption.

A lot of VR systems working on the principle of inertial sensor technology have a great number of cameras to detect a person’s movements. On the one hand, this method provides more accurate results. However, it also provides too much information that is needed to be handled. This factor makes it difficult to participate simultaneously for many users. Moreover, inertial sensor technology can be influenced by electromagnetic fields and cause an error.

The alternative design was developed with the usage of FBG sensors. This fiber optic technology is based on recognizing a person’s position through the refraction of light in the fiber optic cable. Fiber optic sensors precisely measure joint movement. Moreover, it can be used for a long perspective, providing no errors. According to scientists, this is a new implementation of FBG sensors into the existing products.

Now the company plans to deliver suites based on FBG sensors for VR applications in various fields and for different producers. And scientists hope to work in this direction further.

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