Tag: FBG strain sensors

Fiber Optic Sensors for the Structural Health Monitoring

Structural health monitoring or SHM is a crucial technique thanks to the development of architectural design. Its main goal is ensuring safety for the civil infrastructure. Due to the fiber optic sensors‘ benefits, a great number of the distributed sensing systems have found application in civil engineering as SHM systems. Fiber Optic Sensors for SHM systems

What is a Structural Health Monitoring System?

Structural health monitoring is a technique of evaluating and monitoring structural health. Thanks to its capability to respond to unfavorable changes, this method is widely used in many fields including aerospace, civil, and energy sectors, etc.

Why is SHM necessary?

All structures are vulnerable to various internal and external factors that can lead to wear or malfunction. There are various reasons that can cause it. For instance, deterioration, problems in construction process, an accident or environmental load, etc. That’s why it is important to implement a monitoring system.

Damage identification systems monitor all the changes in rates in real time 24/7. It gives an opportunity to detect deviations quickly and react properly in a short period of time before significant damage is caused. Therefore, timely maintenance and repair actions reduce the repair time and operating costs.

The structural health monitoring systems provide the following benefits:

Increased security;
Detecting of the damages at an early stage of difficulties;
Continuous tracking;
Saving of operating costs and time;
Development of rational management and maintenance strategies, etc.

Typical Fiber Optic Sensors

In accordance with the increase of the number of buildings’ and bridges’ under construction, the health monitoring of the concrete structures has become a topical issue.

1. Temperature Sensors

Most of all, the health of the concrete structure depends on the temperature influence. Its monitoring influences the general quality and thermal resistance of the entire structure.

At early stages, the temperature shifts affect structure’ cracks and thermal stresses that are usually caused by hydration. Besides, with the help of the two crucial parameters, the maximum temperature and the temperature trend, specialists predict the future structural health.

In addition to that, there is a special system called Distributed Temperature Sensing (DTS) that helps to monitor the cracks that may appear in the concrete structures. Its low cost and well-considered technology are believed to be important advantages in measurement. Other advantages of the FBG temperature sensors are their accurate measurements and fast response. Besides, temperature sensors are perfect for hard-to-reach places and massive sensing networks.

2. Strain Sensors

Another popular type of the fiber optic sensors is FBG strain sensors. To find out the deformation degree, the structure’s density information is used. In fact, the stability of the structure depends on its strength. It is safe when the structure strength is greater than the applied pressure.

After calibration, the unit acquires the features of a force transducer. The strain sensor transfers the component strain accurately. Characteristics such as light phase, frequency, amplitude, or polarization state, allow operators to monitor the health of the structure. All these features change under the influence of deformation.

Due to the common features of the strain sensors, like small size, they are universal sensors for force and load control. They are often used in large machines and steel constructions where there are high loads.

3. Displacement sensors

The other type of sensors are displacement sensors the main task of which is displacement measurement. It becomes possible by the constant measurement of the distance between the sensor and an object.

These FBG sensors are frequently used because they are greatly resistant to external impacts like corrosion and electromagnetic interference. Moreover, they are applied where long term reliability and safety are demanded.

If we compare them to the strain sensors and temperature sensors, FBG displacement sensors can’t measure quantity using only fiber optic sensors. They utilize FBG response to its equivalent Bragg wavelength.

Displacement sensors are perfect for monitoring of the civil engineering structures 24/7. They are suitable for monitoring aircraft, concrete structures and other industrial applications.

4. Pressure sensors

FBG pressure sensors use reflected wavelength analysis. This kind of sensors measure various parameters under severe conditions like high temperature or pressure rates.

The fiber pressure sensor’ operational principle is based on the fact that external factors affect the Bragg wavelengths by influencing the pressure sensor. In such a case, changes of the FBG’s physical or geometrical properties are implicitly measured.

FBG pressure sensors have the same characteristics as the other fiber optic sensors. They are small, portable and provide the highest accuracy and stability.

Usually, fiber pressure sensors measure the levels of liquids and gas in pipelines or tanks. They are used for the indirect flow control in tanks and pipes. FBG pressure sensors are crucially essential in various industrial fields like liquid level monitoring in oil storage tanks, gas turbine engines, etc.

In conclusion, we should say that any of these fiber optic sensors can perform measurements as a structural health monitoring. According to the existing situation and characteristics, the specialists choose the suitable variant, thus ensuring safety for any kind of civil construction.

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

Fiber optic sensors for deformation detection

Fiber optic sensors for deformation detection The development of stretchable fiber optic sensors promotes changing the operation of soft robots and smart systems. Recently, a team of scientists from the U.S. has developed a distributed fiber sensor that uses low-cost LEDs and dyes. The developed fiber optic sensors are stretchable and allow for finding different deformations (strain, pressure, bending).

To be more precise, these distributed sensors can be applied in soft robotic systems and augmented reality technology. The fiber optic sensors offer the opportunity to feel the same tactile sensations as animals use to navigate the natural world. The ability to determine deformations(for instance, strain, pressure, and bending) makes it possible to find exact locations.

The scientists claim that such a fiber optic technology will be useful for applications in sports medicine and physical therapy. The development of fiber sensors is based on previous technology, “in which light was sent through an optical waveguide, and a photodiode detected changes in the beam’s intensity to determine when the material was deformed.” Then numerous similar sensing systems have been created.

It should be noted that the operating principle is based on silica-based distributed fiber sensors. The distributed fiber optic sensors allow for recording the slightest wavelength shifts to determine, for example, changes in humidity, temperature, and strain. Nevertheless, silica optical fibers are not efficient with soft and stretchable devices.

Herewith, it is easy to deform soft materials in difficult-to-reach areas. Therefore, scientists develop a fiber sensor that can overcome these challenges. The new fiber optic system consists of a stretchable light guide for multimodal sensing. The two cores of optical fiber are made of polyurethane elastomeric. The first core is transparent, the second has dyed.

A pair of cores in distributed fiber optic sensors increase the number of outputs. They, in turn, help to find various deformations, their exact location, and magnitudes. Compared to standard distributed sensors, new sensing systems do not need high-resolution detection equipment.

Stretchable fiber optic sensors apply small optoelectronics with a lower resolution. Thus, they have a lower cost, simple manufacturing, and can be easily installed into small systems. Moreover, it is possible to wear this fiber optic technology. For example, scientists have installed these fiber sensors in a 3D-printed glove.

Finally, this fiber optic technology allows scientists to measure tactile interactions in real life. Additionally, the team finds the way how distributed fiber optic sensors can advances virtual and augmented reality experiences. The thing is that these systems’ operation is based on motion capture, and fiber sensors can add new experiences.

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Space fiber optic application: a short overview

FBG sensors in space New fiber optic solutions provide high-definition and fast fiber optic systems for sensing that become very promising in several space applications. Such advantages as composites in design and lightweight materials make fiber optic sensors highly important for the aerospace industry leading to a great requirement in non-destructive testing.

To be more precise, the development of advanced materials results in the fact that fiber optic sensors are considered to be essential in the design, production of aerospace vehicles, as well as their non-destructive testing. Fiber sensors are regarded as systems with flexible, low-profile optical fibers that do not need electrical sources.

It is possible to use fiber optic systems at sharply curved areas installed within devices or mounted directly to electrical components. Even though fiber optic sensors are compact and lightweight, they allow for distributed sensing directly stress, strain, acoustic, or temperature.

Compared to conventional strain gauges, fiber optic applications offer critical information with high density and low additional cost for various measurement points. A company-manufacturer of fiber optic systems from the U.S. has presented fiber sensors for aerospace industries.

Such fiber optic sensors perform more than 1,000 strain or temperature sensing per meter of a conventional compact, lightweight sensors. Additionally, “the high definition data can fully map the contour of strain or temperature for a structure under test or during manufacturing.”

These fiber sensors are suitable for dynamic applications or where lower sensor density is needed offering high-speed multipoint sensing, with tens or hundreds of fiber optic sensors on versatile optical fibers that cover long distances. Herewith, they provide the opportunity to perform several measurement types, for example, strain, temperature, vibration, or displacement by a single optical fiber.

Fiber optic applications include the aerospace industry and offer a more detailed design validation at every stage of the structural integrity building block process. It should be noted that composites provide a high level of strength-to-weight ratios. Nevertheless, new devices for validating the performance of fiber sensors are needed for their unique properties.

The compact size and distributed sensing of fiber optic sensors enable in-situ characterization for coupon testing, curing process validation, components/module testing as well as full-scale structural health monitoring of complex structures. It is possible to apply these fiber sensors in the predictive maintenance of smart elements.

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Fiber optic sensors in healthcare applications

FBG sensors in healthcare Fiber optic sensors of different physical quantities based on fiber Bragg gratings (FBGs) find its popularity and they are actively used in various fields of industry to solve a variety of engineering problems. The general operating principle of such fiber sensors is based on a change in the FBG wavelength under the action of external impacts.
It should be noted that nowadays the population presents specific requirements to the application of assistive technology and, in particular, towards novel healthcare tools and fiber optic sensors. For instance, novel fiber sensors offer such benefits he electromagnetic field immunity, high flexibility, high sensitivity for mechanical parameters higher elastic limits, and impact resistance.

To be more precise, such benefits of fiber optic technology comply ideally with the instrumentation requirements of numerous healthcare tools and in movement analysis. Additionally, fiber optic sensors are considered to be lightweight, compact, stable to chemical substances, and they have also multiplexing capabilities. Therefore, fiber sensors are regarded as safe technology suitable for industrial, medical, and structural health monitoring applications.

The thing is that fiber optic sensors allow measuring various parameters, for example, angle, refractive index, temperature, humidity, acceleration, pressure, breathing rate, oxygen saturation, etc. It is even possible to install optical fibers in textiles for sensing applications, as well as incorporate them in composite metals, concrete and etc.

The development of fiber sensors based on fiber optic technology leads to high demands for healthcare systems, especially because of the population aging. The appearance of new medical systems results in higher demands on the fiber sensors’ performance because reliable control strategies require a robust fiber optic sensing system.

The modern fiber optic sensor should be tiny, herewith, saving its flexibility and compactness as possible. Herewith, intrusive sensing systems have higher requirements – they also need for biocompatibility, this is the reason why fiber optic technology continues developing to overcome the current challenges and provide high performance of novel healthcare systems and tools.

The increasing demands on fiber optic sensors and the fast development of the technology result in the appearance of numerous sensing systems for healthcare and medical tools. The fiber sensors enable to examine bones decalcification and strain distribution, evaluation of intervertebral disks, dental splints, cardiac monitoring, and pathologies detection.

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Various fiber optic coatings for fbg strain sensors

FBG strain sensors' coatings Distributed fiber optic strain gauges are known for their crucial advantages compared with traditional measurement techniques, for instance, inductive displacement transducers, etc. To be more precise, fbg strain sensors are corrosion resistant, dielectric, and insensible to electromagnetic radiation.

It should be noted that any part of optical fibers is applied as the sensing element for the fiber optic strain sensors, herewith, the measurement is not limited by a specific section. Moreover, fbg strain sensors provide one more benefit that includes the opportunity of installing the optical fiber into the building material matrix.

Such a fiber optic sensing system allows detecting strain within concrete elements, which can include data about the curing and load behavior. The thing is that distributed fiber optic strain gauges play an important role in massive concrete structures, for example, foundations or concrete roads, therefore, these fbg strain sensors demonstrate the structural and loading conditions.

Herewith, such a fiber optic technology enables to combine the quality management of posttreatment and health monitoring. The operating principle of fbg strain sensors is based on the use of optical fibers, the core of which detects the strain. Also, it is necessary to pay careful attention to two techniques that influence the deformations of the fiber optic sensors: “slippage can occur between the fiber cladding (the so-called coating) and surrounding substrate; depending on the coating material, the cladding cannot wholly transfer the strain from the substrate to the fiber cladding and the core.”

Finally, optical fiber coatings are also important, therefore, different teams of scientists have analyzed their effect on strain transfer during matrix measurements. For instance, such a technique as Brillouin scattering shows that fiber optic cables have lower strain values in the matrix than the reference technique. Herewith, there are the strain transfer rates of embedded FBG sensors in mortar prisms.

The fiber optic technology has been already tested. The team installed the optical fiber into a reinforcing bar, which was later installed in the concrete. Herewith, a brass frame and optical fiber with a single-layer polyimide coating allow researchers to install the fiber in small concrete specimens and obtain similar values to the reference sensing measurements.

Additionally, distributed fiber optic sensors demonstrate higher values than the standard strain gauge measurements on the surface. The researchers claim that the concrete is required to be quite cured to provide the strain transfer in the fiber optic sensors. However, the acrylate coating has higher strain losses.

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Fiber Bragg gratings in bogie frame

FBGs for bogie frame The 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 that 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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Embedded fbg strain sensors for robotic applications

FBG strain sensors for robots Fiber optic technology continues to find new applications in various fields including medicine, biomechanics, space, oil industry, geophysics, etc. According to researchers from the U.S., fiber optic sensors are regarded as uniquely suited for utilizing in robotic hands. To be more precise, the researchers have developed a three-fingered soft robotic hand with multiple embedded fbg strain sensors resulting in emerging of a new type of stretchable fiber sensor.

The application of fiber optics allows installing 14 fbg strain sensors into each of the fingers in the robotic hand, therefore, it can “determine where its fingertips are in contact and to detect forces of less than a tenth of a newton”. Moreover, the researchers confirm that the new stretchable optical sensing material could find highly promising application in a soft robotic skin to offer even more feedback in the future.

Modern robotic hands include more strain sensors than is typical today, thus, they can operate autonomously and react safely to unexpected forces in everyday environments. It should be noted that human skin consists of thousands of tactile sensory units only at the fingertip, while a spider has about hundreds of mechanoreceptors on each leg, however, nowadays conventional humanoid includes only 42 fiber sensors in its hand and wrist.

Herewith, it is difficult to add traditional force or pressure sensors because of complex wiring, it is prone to breaking and susceptible to interference from different electromagnetic tools. Nevertheless, it is possible to embed several fbg strain sensors in a single optical fiber. The operating principle of such a robotic hand is based on several fiber sensors in each of the fingers that are connected with 4 optical fibers, through a single fiber can be used for this purpose.

Additionally, the embedded fbg strain sensors offer such an advantage as the immunity to electromagnetic interference. Other benefits of FBG sensors include:

Fiber sensors are passive and can be used in explosive environments.
Non-conductivity of fibers.
Opportunity to install more than 80 fiber sensors per optical fiber.
The fast response of FBG sensing systems.
Fbg strain sensors do not corrode and have a small diameter.

Robots used in the industry provide extremely accurate manipulation with only limited fiber sensors, herein, they operate in controlled environmental conditions where people do not risk to do it. Nevertheless, the development of soft robots, which will interact routinely and safely with people, require careful attention to tactile and force sensing. That is why fbg strain sensors are considered to be a perfect fiber optic solution.

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 fbg strain sensors. If you have any questions, please contact us at info@optromix.com

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FBG sensors in Biomechanics and Rehabilitation Application

FBG sensors in biomechanics Nowadays the technology of fiber Bragg gratings is considered to be quite attractive for sensing applications in biomechanics and rehabilitation engineering fields thanks to the proposed FBG benefits such as compact size, lightweight, biocompatibility, chemical inertness, multiplexing capability, and immunity to electromagnetic interference.

Additionally, FBG technology overcomes other traditional technologies for the measurement of a range of physical parameters or for the performance of high-sensitivity biochemical analysis because fiber Bragg gratings offer a high-performance alternative to conventional sensing devices.

It should be noted that the sensing application of FBG sensors includes such areas as aeronautics, automotive, civil engineering structure monitoring, and undersea oil exploration. Nevertheless, the use of FBG sensors in biomechanics and rehabilitation is quite novel and it still requires its practicality for full-scale implementation.

The potential application of FBG technology may include the following fields: strain detection in bones, “pressure mapping in orthopedic joints, stresses in intervertebral discs, chest wall deformation, pressure distribution in Human Machine Interfaces (HMIs), forces induced by tendons and ligaments, angles between body segments during gait, and many others in dental biomechanics”.

FBG sensors demonstrate great potential for biomechanics and rehabilitation engineering thanks to their benefits, thus, making FBG technology suitable for a human body. To be more precise, fiber sensors are able to adapt to the body, so it is possible to employ them for in vivo measurement and to left for long-term monitoring.

Moreover, fiber Bragg gratings can change traditional sensing technologies such as electrical strain gauge (ESG), piezoelectric, resistive, or another solid-state sensing, both for measuring physical characteristics or for carrying out high-sensitivity biochemical analysis. The development of FBG continues, and it is possible that very soon new FBG sensors with improved characteristics appear.

If you want to obtain a highly efficient 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. The company provides a wide range of sensors: temperature sensors, strain sensors, displacement sensors, tiltmeters, accelerometers. If you are interested in FBG sensors and want to learn more, please contact us at info@optromix.com

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FBG sensors: a comprehensive review

FBG sensors A fiber Bragg grating is an optical interferometer embedded in an optical fiber. At the same time, fiber optics combined with certain substances (usually germanium) can change its refractive factor when the fiber is exposed to ultraviolet light. If such a fiber is illuminated with ultraviolet light with a specific spatial periodic structure, the optical fiber becomes a kind of diffraction grating. In other words, this optical fiber will almost completely reflect the light of a certain, predetermined range of wavelengths, and transmit light of all other wavelengths.

Application of FBG sensors

The FGB application includes the following fields:

Point sensors (that is able to measure deformation, temperature, pressure, tilt, displacement), embedded in composite materials and others;
Laser systems and amplifiers (filters, mirrors);
Telecommunications (dispersion compensation modules, WDM technology);
Research and development.

Difference between electrical and fiber sensors

For decades, electrical sensors (tensor-resistive, string, potentiometric, etc.) have been the main method of measuring physical and mechanical phenomena. Despite their widespread use, electrical sensors have several disadvantages, such as loss during signal transmission, sensibility to electromagnetic interference, the need to organize a spark-resistant electrical circuit (if there is a danger of explosion). These mentioned above limitations make electrical sensors unsuitable or difficult to use for a number of applications.

The use of fiber optic sensors is an excellent solution to these problems. In fiber optic sensors, the signal is light in the optical fiber instead of electricity in the copper wire at traditional electrical sensors.

Over the past twenty years, a huge number of innovations in optoelectronics and in the field of fiber optic telecommunications has led to a significant reduction in prices for optical components and to a significant improvement in their quality. This factor allows fiber optic sensors to move from the category of experimental laboratory tools to the category of widely used devices in various areas.

Operating principle of Bragg gratings

A fiber Bragg grating or FBG acts as a sensitive element of point fiber optic sensors, which is capable to reflect certain wavelengths of light and transmit all others. This effect is achieved by periodically changing the refractive index in the core of the fiber optics.

When the laser light passes through an optical fiber, a part of it is reflected from the fiber grating at a certain wavelength. This peak of reflected light is registered by measuring equipment. As a result of the numerous parameters influence, the interval between the FBG bundles and the refractive index of the fiber optics change.

Consequently, the wavelength of the light reflected from the fiber Bragg grating changes. In addition, it is possible to determine the exact characteristics of the changes by changing the wavelength. In fiber optic sensors based on Bragg gratings, the measured value is converted to a Bragg wavelength offset. The recording system converts the wavelength offset into an electrical signal.

The sensing element of such FBG sensor does not contain electronic components and therefore it is completely passive, which means it can be used in the area of increased explosiveness, aggressiveness, strong electromagnetic interference. Numerous fiber Bragg gratings can be installed on a single fiber, each of which gives a response at its own wavelength. In this case, instead of a point sensor, we get a distributed sensing system with multiplexing along the wavelength.

The use of the light wavelength as an information parameter makes the FBG sensor insensitive to the long-term changes of the parameters of the source and radiation detector, as well as random attenuation of power in the optical fiber.

Common types of FBG sensors

The following types of fiber optic sensors based on FBG technology are used for automated monitoring:

FBG strain sensors;
FBG displacement sensors;
FBG temperature sensors;
FBG pressure sensors;
Fiber optic tilt sensors;
Fiber optic acceleration and vibration sensors;
Data recorders for fiber optic sensors;
Additional equipment for data recorders.

The principle of FGB sensor operation is based on the modulation of one or several properties of a propagating light wave (intensity, phase, polarization, frequency), which change occurs with a change in the measured physical quantity.

The basis of fiber-optic sensing technology is an optical fiber – a thin glass thread that transmits light through its core. The optical fiber consists of three main components: core, shell, and coating. The shell reflects the scattered light back into the core, allowing light to pass through the core with minimal loss.

It can be achieved by a higher refractive index in the core relative to the shell, resulting in a complete internal reflection of light. The outer coating protects the fiber optics from external influences and physical damage. It can consist of several layers depending on the required protection.

Benefits of fiber sensors based on Bragg gratings

The advantages of FBG sensors include:

Wide sensing range;
Possibility to integrate the FBG sensing system into the object structure;
Full fire and explosion safety;
Long-distance signal transmission;
Integration of several fiber optic sensors in one channel;
Insensitiveness to electromagnetic and radio frequency influences;
No need for recalibration (stable over time under constant external conditions).

Bridge, Australia, Bridge At the moment, most of the sensors used in the world are electrical sensors. As it was mentioned above, in optical sensors based on fiber Bragg gratings, the signal is light passing through an optical fiber (instead of an electric current passing through a copper wire). This fundamental difference allows FBG sensors to overcome many problems typical for electrical sensors.

Features of fiber optic sensors

Optical fibers and sensors are non-conductive, electrically passive, and immune to electromagnetic interference. Monitoring with a tunable high-power laser system allows sensing over long distances with virtually no signal loss. In addition, each optical channel is able to monitor a variety of FBG sensors unlike the electrical channel, which significantly reduces the size and complexity of such a sensing system.

Optical sensing systems are ideal for use in conditions where conventional electrical sensors (strain gauge, string, thermistor, etc.) can be difficult to use (long distances, EM fields, explosion safety, etc.). It is easy to switch to fiber optic solutions since the installation and operation of optical sensors are similar to traditional electrical sensors.

Understanding the principles of FBG operation and the benefits of Bragg grating sensor applications can greatly facilitate the solution of various problems in the field of sensing measurement (for example, monitoring of structures).

Nowadays FBG sensors are applied in various fields that require precise and fast measurements. Fiber Bragg sensing systems can be used in aeronautic, automotive, civil engineering structure monitoring, undersea oil exploration, in the mining industry, geotechnical engineering, structural engineering, tunnel construction engineering, etc.

Bragg sensors in medicine

The most promising application of FBG sensors is medicine. Now FBG technology is highly used for fiber-based biomedical sensing including biosensing, safety or security, and structural health monitoring. FBG sensors offer a new and effective way of real-time measurements. They can be applied in laser systems, medical tiny intra-aortic probes, and body sensors for biochemical analysis making.

For example, today fiber Bragg gratings apply optical-fiber sensing probes that are able to dissolve due to such ability as controlled solubility in a physiological environment. Thus, FBG technology enables safer diagnostic of sensitive human organs and there is no need for a surgical extraction. The development of FBG continues, and it is possible that very soon new FBG sensors with improved characteristics appear.

How to choose the right fiber optic product?

If you want to obtain a highly efficient 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. If you are interested in FBG sensors and want to learn more, please contact us at info@optromix.com

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Strain Measurement with Fiber Bragg Grating Sensors

Scientists and engineers can perform through the implementation of optical sensors measurements that were previously impractical or, in some cases, impossible with vibrating wire or foil gases. Many applications will require a hybrid approach using the benefits of both electrical and optical measurements together. Fiber Bragg gratings are often used in strain sensing especially in such places where the environment is harsh (for instance, high-EMI, high-temperature, or highly-corrosive). Strain measurement is imperative during prototype design and testing. Strain measurements ensure that materials perform as they should and that the equipment is safe and durable. Measuring strain is crucial for testing complex structures, like aircraft, turbines, etc.

Fiber Bragg grating strain sensors have been infrastructure monitoring of smart structures like bridges, dams, pipelines. By monitoring load, strain, temperature, vibration, and even liquid of gas flow, structural integrity can be assessed and tracked on a real-time basis. There various ways in which stress can be measured, but it is widely accepted that FBG sensors are the most efficient way of strain measurement.

There are two types of applications of the fiber Bragg grating strain sensors:

Long-term Static Strain Sensing. The main issue in the long-term static strain test is an interest in measuring the long-term static strain of the component in question. In order to carry out the above operation, it is necessary to set up the grating on the structure, find out what the initial wavelength is, and then within a set period of time to detect and record the changes that have occurred. Also, it is possible to return to the structure, reattach, and refer back to the initial wavelength. As a result, it becomes possible to obtain the determination of what this strain is from the initial condition at that time. The ability to disconnect your monitoring instrumentation and return for results after a large amount of time such as months or even years is a very great advantage of fiber Bragg grating sensors. For instance, in the case of bridges, it is common for engineers to visit the bridge and conduct the impact testing using an impact hammer on the different parts of the bridge. This is time-consuming and even hazardous because of the height of some bridge structures. The distribution of a number of FBG sensors throughout the bridge and the attachment of the instrumentation to this bridge on a periodic basis is a much more efficient solution. This is only one of the good examples to demonstrate the effectiveness of the fiber Bragg grating strain sensors. Besides bridges, other examples of using FBG for long-term static strain testing are buildings, piers, and structures in high earthquake-prone areas.
Dynamic Strain Sensing. The different structures may have very-low-frequency modes, and they may also have higher modes due to the effects of wind and tide. Most earthquakes and other earth tremors are low-frequency events. Fiber Bragg gratings can be attached to the structures and monitored for the vibrations during the earth’s tremors and earthquakes. The low-frequency dynamic strain testing can help in determining the reaction of high-rise buildings to the wind. In addition to this, FBG sensors create connections with peers and other shore structures to determine their vibrations during the ebb and flow of tides. Dynamic strain testing can also be performed on transportation vehicles like automobiles, trains, and airplanes. In addition to civil structures and vehicles, there are a number of other applications for dynamic strain testing and vibration stress testing using fiber Bragg gratings. FBG sensors can be attached to industrial machinery to determine the frequency and amplitude of the stress vibrations.

Optromix, Inc. is a U.S. manufacturer of innovative fiber optic products for the global market, based in Cambridge, MA. Our team always strives to provide the most technologically advanced fiber optic solutions for our clients. Our main goal is to deliver the best quality fiber optic products to our clients. We produce a wide range of fiber optic devices, including our cutting-edge customized fiber optic Bragg grating product line and fiber Bragg grating sensor systems.

If you would like to purchase Optromix FBG Strain Sensors, please contact us: info@optromix.com or +1 617 558 98 58

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