Ubiquitous optical fiber strain sensors against a background of large-scale urbanization

FBG strain sensors in urbanization processFiber 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. 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

 

Fiber-optic sensors in biomedical applications

FBG sensors in biomedical applicationsThe scientific experience of the last few decades was marked by major achievements in the field of fiber-optic sensors. Optical fiber sensors have certain advantages like immunity to electromagnetic interference and high sensitivity, small size and small weight, large bandwidth, and ease of use and distribution. Over the years, fiber-optic sensors have fastly grown in quality and functionality and have found widespread use in many areas such as defense, automotive, manufacturing, and among various other industries. A wide range of applications was defined for fiber sensors in general and in particular for medical and biomedical applications. Also, these technologies have become more commercially available.

The medical and biomedical industry provides many challenging requirements, for which optical fiber sensors can provide original and reliable solutions. In the coming years, scientists and engineers in the medical and biomedical areas will use fiber-optic sensor turnkey systems for sensing and measuring of any type of physical quantity. Such fiber-optic turnkey systems are a combination of four basic components: a light source, an optical fiber, a sensor element, and a light detector. In such systems, the fiber-optical sensor acts as a light modulator to change a property of light (phase, polarization, etc.).

Possible future applications of fiber-optic sensors in biomedical research include simultaneous collection and analysis of samples for drug safety evaluation for instance. Also, optical fiber sensors help in the identification of drug molecules and in the sensing of biomolecules, effluent monitoring, and overall pharmaceutical quality control of the product. In that context, it’s important to note that light-carrying fibers are potentially useful as physical sensors of temperature, pressure, and rapidation and as chemical sensors of pH, the partial pressure of blood, and glucose.

 

Optromix is a manufacturer of laser technologies, fiber-optic sensors, and optical monitoring systems. Optromix provides innovative world-class fiber-optic products to the global market. We provide optical fiber sensors using our own developments based on the research work and patents of an international R&D team. We try to understand and satisfy all the individual and specific needs of our clients in very advanced fields.

If you are interested in Optromix fiber-optic sensors, please contact us at info@optromix.com

Fiber Bragg grating sensors in smart cities

The infrastructure of modern cities is becoming increasingly more complex; it includes roads, pavements, railways, tunnels, and ducts. These structures are not only made of composite materials in which behavior under harsh environments can often be unpredictable, but they also interconnect. These systems are subjected to extreme environmental conditions, like severe winds, earthquakes, flooding, etc.; due to this, they are susceptible to catastrophic failure.

One of the main aspects of any smart city is safety. The transportation network needs to be assessed through gathering data on roadway conditions, like dangerous conditions due to roadway degradation, icing, and hydroplaning. Autonomous data gathering is vital for the safety and efficiency of the transportation network. The data gathered gives information on the inevitable roadway and infrastructure degradation over time, which enables informed decisions for life extension or timely replacement of these critical systems.

Computational tools are often not adequate for the task of condition assessment of complex infrastructure systems. These tools lack the capability to reliably predict response to extreme events. Therefore, a distributed sensor system is needed in order to ensure the safety and longevity of infrastructures in a smart city. The sensing system should also be capable of providing critical information to computational models to enable informed maintenance planning as opposed to the reactive maintenance schemes currently employed.

Fiber optic sensing systems provide the most efficient and economical solution. Fiber optic systems allow for the assessment of thousands of sensors in real-time on a single cable. FBG sensor systems are well-suited to the detection and recording

of critical structural response characteristics as well as environmental indicators that lead to degradation. FBG strain sensors are useful in the process of assessing the response to stressors, e.g. traffic, wind, earthquakes, blast events, support settlement, etc. Distributed acoustic sensing is ideal for the direct assessment of localized damage in steel and reinforced concrete that may occur due to seismic events, fatigue cracking, corrosion, etc. FBG sensors are also ideal for monitoring of weather conditions, as the presence of entrapped moisture in asphalt paving systems, as they are often the main cause of the rapid degradation.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) products line: FBG sensors, FBG interrogators, and multiplexers, Distributed Temperature Sensing (DTS) systems. We create and supply a broad variety of top-notch fiber optic solutions for the monitoring of various facilities all over the world. We provide a distributed acoustic sensing system that is much less expensive than other analogous systems present on the market.

If you are interested in Optromix distributed acoustic sensing system or Optromix FBG sensor systems, please contact us at info@optromix.com

Fundamentals of fiber Bragg grating interrogators

The fiber Bragg grating sensors work by sending the light into the fiber, where it is reflected back from the FBGs. The light that has been reflected travels back to the photodetectors of the instrument, where it is compared to wavelength reference artifacts. During this process the fiber Bragg grating interrogator evaluates the position of the center wavelength of the FBG; this information is later converted to engineering units. The gage factor supplied with the FBG sensor helps to determine and translate the data obtained during the measurements.

The described principle is true when one FBG sensor is present on a fiber. However, if the particular application requires multiple FBG sensors, like FBG sensor pipeline monitoring, fiber optic well monitoring, FBG temperature sensing, etc., the interrogators use one of the discriminating schemes in order to discriminate between one FBG sensor and the next. There are a couple of discrimination methods that are used in FBG interrogators. The first one is referred to as time division multiplexing utilizes the known speed of light in the fiber to discern which signal is reflected from which FBG along the fiber path. Around 100 FBG sensors can be interrogated with this method.

The second method, wavelength division multiplexing, is the most utilized one. As FBG sensors are at distinctly different nominal center wavelengths from their neighbors, the FBG interrogator uses the wavelengths of the sensors to track them along with the fiber. The range of this method is largely due to the developments in fiber optic technology.

Other approaches to FBG sensor interrogating, some of which include:

  1. Broadband source, Dispersive element, Diode Array;

This method is less reliable than the aforementioned ones due to limited resolution, which is a result of the inherent limitations of commercially available diodes.

  1. Broadband source, Optical Spectrum Analyzer/Multi-line wavelength meter;

The optical spectrum analyzers are large and expensive, which makes them less desirable in a laboratory setting. They are also not able to perform optimally under some temperatures.

  1. OTDR/TDM systems;

The system cannot handle a large number of sensors on the fiber as its data acquisition rates scale down with increasing sensor counts.

  1. External Cavity Tunable Laser, Power Meter, Wavelength Meter;

External cavity tunable lasers have low speed and do not have a wide operating temperature range. Moreover, they are expensive and do not have the required mechanical robustness.

Optromix interrogators can control up to 8 optical channels. The interrogator operates with the 20 maximum sensors per channel. The device is controlled by the PC with the specialized software for sensors monitoring. The system contains a broadband source of radiation and it can carry out spectrum analysis.

If you would like to purchase an FBG interrogator, please contact us: info@optromix.com or +1 617 558 9858

Fiber Bragg grating strain sensors for structural health monitoring

Fiber Bragg gratings stand out among other fiber optic sensors as the most developed and prominent technology for the measurement of strain, vibrations, temperature, and pressure. FBG sensors have attracted significant interest in structural health monitoring due to numerous advantageous properties:

  1.  immunity to electromagnetic interference;
  2. intrinsic fire safety;
  3. low invasiveness;
  4. minimum aesthetic impact;
  5. possibility to send the data remotely using the same sensing fiber.

There are multiple sensing advantages that FBG sensors provide. First of all, FBG sensors perform with an excellent balance between complexity and performance, which is one of the most attractive qualities of fiber Bragg grating sensors for structural health monitoring. Secondly, FBG sensors are able to work in low signal-to-noise ratios better than other optic sensors. Moreover, fiber Bragg grating sensors are predictable and less dependent on the temperature of the surrounding environment, as well as are well-suited for multiplexed optical sensor networks.

Over the past decade, structural health monitoring has attracted a lot of attention as modern technology develops, and new materials and compounds are used in the construction of buildings and structures. Structural health monitoring involves the collection and analysis of information obtained through measurements of the structure. The results of data analysis are used to assess the damage and evaluate the performance of the structure under harsh conditions.

FBG sensor structural health monitoring has become an important tool for assessing the performance of different structures and measurements of temperature, strain, pressure, displacement, etc.

Fiber optic strain gauge is welded directly to the surface of the metal structure (pipes, beams, etc.), and it has a protective silicone cover. Fiber optic strain sensors are durable and stable, widely used for civil engineering constructions, particularly they reinforce concrete structures exceptionally well.

Fiber Bragg Grating strain sensors demonstrate lots of advantages compared to the regular electrical strain gauges. Namely, they are immune to electromagnetic interference and power shortages. Compact size devices provide the most accurate measurements. FBGs are, literally, the best strain sensors right now.

If you would like to purchase Optromix FBG Strain Sensors, please contact us: info@optromix.com or +1 617 558 9858

Fast fiber Bragg grating sensors

Numerous advantages of fiber Bragg grating sensors, like compact size, passive nature, immunity to electromagnetic interference, the capability to directly measuring physical parameters such as temperature and strain, have inspired researchers to develop FBG sensor systems for applications outside laboratories. FBG sensors are now used in mainstream sensing technology applications. One of the recent developments in fiber Bragg grating technology is FBG sensors based on femtosecond lasers. These sensors are promising for use in extreme environments, such as high temperatures, high pressures, and ionizing radiation. Multiple industries might benefit from fast FBG sensors, like energy production applications.

Fiber Bragg grating temperature sensors that are inscribed with femtosecond lasers are stable up to the fiberglass transition temperature.

FBG sensors that are thermally stable can be used in a variety of applications. For example, stable FBG temperature sensors are optimal for sensing in extreme conditions that are often present within power plants, combustion systems, turbines, and in the aerospace sector. Regular FBG sensors do not perform optimally under extreme temperatures as they are hampered by optical losses that are a result of ingress of high-temperature hydrogen gas. However, FBG sensing arrays are difficult to produce in pure silica core fiber. The use of pure silica prevents the detrimental effects that hydrogen gas has on the fiber.

Fast FBG-based sensors have already been tested at a power generation plant. Many energy production processes require accurate temperature measurements that are difficult to realize with standard sensor technology, like electronic thermocouples. The advantages of FBG temperature sensors deployment are ease of installation, high density of sensing points, more rapid response to thermal changes, etc. Overall, fast FBG temperature sensors are an optimal solution for extreme environments, including high temperatures and high pressures. They are easy to install, maintain, are cost-effective, and accurate.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) products line: fiber Bragg grating sensors, FBG interrogators, and multiplexers, Distributed Temperature Sensing (DTS) systems. We create and supply a broad variety of top-notch fiber optic solutions for the monitoring of various facilities all over the world.

If you are interested in Optromix fiber Bragg grating temperature sensors, please contact us at info@optromix.com

Crack monitoring of wind turbine foundations using FBG strain sensors

FBG strain sensors for crack monitoringThe increased demand for energy due to the growing population has forced the industry to develop new sustainable ways to produce energy. Among new and developing energy technologies are wind turbines. They are widely used to produce energy in many parts of the world. However, there are multiple concerns that are yet to be solved, one of them has been the lack of effective monitoring devices and techniques. Structural health monitoring of wind turbines is needed to ensure that the infrastructure around wind power remains reliable. It is crucial to monitor the operation of wind turbines to ensure effective wind power generation and avoid costly downtimes.

Besides monitoring of wind turbine temperatures, which can be effectively performed with the use of FBG temperature sensors, the monitoring of wind turbine foundations can prevent premature decay of the foundations and prolong the operational time of the turbines. Often the access to the underground part of the foundations is limited, therefore the degradation of onshore, reinforced-concrete wind turbine foundations is assessed via above-ground inspections, or through excavations that suspend energy generation. Sustained measurements of crack behavior could be used to quantify the risk of water ingress and reinforcement corrosion. However, the cracks that occur during turbine operation are not monitored. A solution to this issue is the use of fiber Bragg grating sensors.

Subterranean fiber Bragg grating strain sensors can be used to monitor the opening and lateral displacements of foundation cracks during wind turbine operation. Cracks that occur in the foundation of the turbines are often caused by the vibrations that are produced by turbines themselves. Therefore crack displacement results that are obtained via FBG strain sensors installed on the foundations are correlated with the strains measured by the second series of FBG sensors affixed to the turbine tower and verified against wind speed and turbine data from the operator.

The use of FBG strain sensors can be used to better assess the risks of water ingress and subsequent corrosion of the foundation’s steel reinforcement. The data obtained by fiber Bragg grating sensors may help engineers to more accurately determine the current asset lifetime and the design and construction of foundations in the future.

Fiber Bragg grating strain sensors demonstrate lots of advantages compared to the regular electrical strain gauges. Namely, they are immune to electromagnetic interference and power shortages. Compact size devices provide the most accurate measurements. FBGs are, literally, the best strain sensors right now.

If you would like to purchase Optromix FBG Strain Sensors, please contact us: info@optromix.com or +1 617 558 9858

Fiber Bragg grating (FBG) temperature sensors and FBG interrogators in power line monitoring and temperature surveillance

FBG interrogators for power line monitoringElectricity is the backbone of modern civilization; it holds the development of both economy and technology. It is established that it is no longer an option to rely on existing infrastructure as there is a need to constantly evolve and adapt to the growing demand of the populace. The state of current infrastructure is weakened by its age of installation or by the growing demand of the population. The breakdown is imminent as it cannot bear the burden of previous years.

As the demand for energy increases, the need to monitor the efficiency of the assets arises. Despite the increased number of new power assets, it still cannot cater to the demand of the entire nations.

The development of fiber optic sensing technology became prominent for the monitoring of the power line temperature. Fiber optic sensors, including FBG temperature sensors, have proven to be valuable for the industry. It is immune to electromagnetic interference, mechanical vibrations, and electric noise. FBG sensors are more reliable and perform best under harsh conditions.

FBG temperature sensors are introduced into a fiber where they are evenly placed. The light that travels through the fiber will experience a wavelength shift if any strain is applied to the sensors. This, in turn, causes a magnitude change of the reflections that allow for accurate measurements to be performed. FBG that is used inside the sensors is highly sensitive to not only mechanical deformation but also temperature changes. To obtain and process signals emitted by FBG sensors, FBG interrogators are used. These devices can carry out spectrum analysis.

FBG temperature sensors can capture ultra-fast events in real-time, providing useful data for power line integrity monitoring and localization of stress areas. An accumulation of the data on the temperature profile of the power lines can be useful for the improvement of the intensity of the electrical current, the maintenance of power lines, and determine a threshold of the power cables. The data obtained will allow for a surplus of energy to meet modern energy needs while sustaining existing power assets.

Nowadays FBG sensors are used in a variety of different fields that require accurate and fast measurements. Depending on the nature of the application, FBG temperature sensors, FBG strain sensors, FBG pressure sensors, FBG displacement sensors may be utilized. The sensors are often accompanied by FBG interrogators to interpret the signals, and FBG multiplexers to create large monitoring systems with a big number of FBG sensors. The more complex the sensor system, the more intricate data can be obtained.

Optromix offers a wide range of FBG sensors, including FBG temperature sensors, as well as FBG multiplexers, and FBG interrogators. If you would like to purchase fiber Bragg grating sensors, please contact us: info@optromix.com or +1 617 558 9858

FBG strain sensors in structural health monitoring

Fiber Bragg grating sensors are used over conventional sensors in structural health monitoring based on a number of advantages they provide:

  • FBG sensors are more stable;
  • fiber Bragg grating sensors are more durable, namely, they don’t rust;
  • FBG sensors can be highly multiplexed;
  • the sensors can be used in highly explosive atmospheres, like natural gas or oil.

These features are desirable for the health monitoring of complex structures. FBG structural health monitoring systems are essential in the design of smart buildings. The FBG sensor systems help to ensure building safety and performance. The systems are of particular use for buildings situated in earthquake-prone zones.

The mechanism behind FBG sensors allows to monitor complex structures based on the measurements of the wavelength of the reflected light; its wavelength changes under the influence of pressure, building incline, etc. Due to the fact that a single FBG sensor reflects a narrow region of the light, it is possible to multiplex them, which provides higher data accuracy. However, the number of FBG elements should be carefully designed and spaced in accordance with the range and bandwidth of the input light source.

The FBG strain sensors are fragile on their own, therefore they need to be placed on a base of some kind to protect them from outside physical influence. Usually, the sensors have a metal protective cover that prevents damage to the sensors from environmental factors. The sensors are then welded or glued to a structural member. FBG strain sensors, or FBG deformation strain sensors, can be used in both steel and concrete structures; they offer high accuracy and resolution. The measurements received from the sensors are often used to detect the behavior of structural materials under different environmental influences. The detection of segments that are stressed is essential for proper maintenance of the building and its structural parts and prevents premature aging and failure of these structures.

FBG strain sensors may also be used in the monitoring of tunnel ribs, pipelines, ship hulls, etc. Their high accuracy, easy installation, and compact nature provide a wide area of applications.

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

Fiber Bragg Grating Sensors in biomedical science

Biomechanical engineering experiences rapid development as a result of FBG sensor application to strain and deformation measurements. The use of fiber Bragg grating sensors in biomedicine is a promising new method of enhancing biomechanical studies.

Fiber Bragg gratings were proposed for use in medical applications at the end of the 20th century. Some of the applications were monitoring ultrasound fields, monitoring the temperature inside nMRI devices, foot pressure monitoring in diabetic patients, etc.

One of the first uses of FBG sensors in biomedicine was an electrically assisted ventilation device triggered by an FBG sensor. A deformable strap was placed on the patient’s chest; the strap had FBG sensors embedded into it that were measuring chest deformations that were caused by air inspiration. A threshold level was set to produce a trigger signal to stimulate the phrenic nerve. Nowadays FBG sensors are used in medical-grade textiles for healthcare monitoring.

Fiber Bragg grating sensors provide several advantages over traditional methods of measuring ligament and tendon deformation and strain, namely an opportunity to record the deformations under several postures. For example, a foot pressure sensing system with embedded FBG was presented; it contains several carefully calibrated FBG sensors in an optical fiber strand. The distribution of transversal pressure and its analysis help to indicate abnormal standing gait in diabetic patients.

The research suggests that FBG sensors are superior to traditionally used strain gauges in soft tissue strain measurement. FBGS easily adhere to a bone or a curved surface; their dimensions are more compatible with bone size than those of the strain gauges; they are easily implantable, highly accurate, and less invasive.

The use of fiber Bragg grating sensors in intervertebral disc pressure measurements is very promising as it is significantly more sensitive than other measuring methods. Moreover, the FBG sensors are more compact which allows them to be inserted through a needle, and to be used for small discs, e.g. cervical or biodegenerated.

Fiber Bragg sensors proved to be useful in a femoral prosthesis. The multiplexing ability of FB sensors allows us to place several sensors on a prosthesis surface and connect them using a single optical link to interrogate all of them. The sensors aid in locating potential failure areas in the prosthesis under normal strain conditions.

Optromix is a fiber Bragg grating sensor vendor; we manufacture innovative fiber optic products for the global market. We are dedicated to delivering the best products and supports to all our customers, our engineers have extensive experience and strong technical expertise in creating fiber Bragg grating products. If you would like to buy FBG strain sensors, please contact us at info@optromix.com.