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

Fiber optic sensing solutions for extreme conditions

on August 3, 2020

jennifer-latuperisa-andresen-U1y2ye6nPks-unsplashElectrical sensing systems (strain sensors, string-based, potentiometric, etc.) have been the main method of measuring physical and mechanical phenomena for decades. Despite their widespread application, electric sensing systems have a number of disadvantages, such as loss of signal transmission, susceptibility to electromagnetic interference, the need to organize an intrinsically safe electrical circuit (if there is a danger of explosion). 

These inherent limitations make electrical sensors unsuitable or difficult to use for a number of tasks. The application of fiber optic sensing solutions is an excellent way to overcome these problems. The signal in fiber optic sensors is light in the optical fiber used instead of electricity in the copper wire of standard electrical sensors.

Over the past twenty years, a huge number of innovations in optoelectronics and in the field of fiber optic telecommunications have led to a significant reduction in the price of fiber sensor components and to a significant improvement in the quality of fiber optic systems. These improvements allow fiber optic sensors to move from the category of experimental laboratory devices to the category of widely used devices in such areas as monitoring of buildings and structures, etc.

One of the most commonly used fiber optic sensors is considered to be fiber Bragg grating sensors (FBG). The fiber Bragg gratings in these sensors reflect a light signal whose spectral characteristic (wavelength) shifts along with changes in the measured parameter (temperature and/or deformation). During the manufacture of gratings, a region with a periodic change in the refractive index is created inside the optical fiber core, herewith, this region is directly called the FBG.

Optical fibers and fiber sensors are non-conductive, electrically passive, and immune to EM interference. The interrogation using a tunable high-power laser allows measurements to be made over long distances with virtually no signal loss. Additionally, in contrast to the electrical sensing system, each optical fiber channel can interrogate a variety of FBG sensors, which significantly reduces the size and complexity of such a fiber optic system.

Fiber optic sensing solutions are ideal for applications where conventional electrical sensors (strain gauges, strings, thermoresistors, etc.) have proved difficult to use due to extreme conditions (long distances, EM fields, explosion protection, etc.). Since the installation and operation of fiber sensors are similar to conventional electrical sensors, it is easy to switch to fiber optic solutions. Understanding how such fiber optic systems work and the benefits of using them can greatly facilitate various measurement tasks (for example, structural health monitoring).

In short, the main advantages of FBG sensors include:

  • high sensitivity and performance;
  • relatively large range of measured deformations;
  • the best weight and overall dimensions, small size;
  • high noise immunity, insensitivity to electromagnetic interference, such as microwave field, spark discharge, magnetic fields, electromagnetic pulses of various nature and any intensity;
  • absolute electrical safety due to the absence of electrical circuits between the fiber optic sensor and the recording module;
  • full electrical, explosion and fire safety, high chemical resistance of sensor elements.

The conditions of the environment and controlled conditions in which one or more external factors — radiation, temperature, electromagnetic field, aggressiveness, humidity, pressure, and deformation — have the maximum possible constant values are regarded as extreme. 

In such conditions, primary converters of control systems for dangerous technological processes (oil production, transportation, and processing of oil and gas, nuclear power generation, storage of radioactive waste), monitoring and diagnostics systems for complex construction and engineering structures (dams, bridges, mines, etc.), and military and emergency management systems operate.

Currently, fiber optic technologies are widely used in various fields of science and technology. One of the main applications of fiber optics is the creation of portable high-sensitivity sensors. Pressure, strain, vibration, tilt, linear motion, and temperature sensors are widely applied in the industries of structural health monitoring pipelines, heating lines, power cables, mines, etc.

ajay-pal-singh-atwal-gRdTreyRops-unsplashRadiation

Compared to fiber sensors, the lack of power supply at the location of electrical sensing systems does not prevent continuous remote monitoring of dangerous objects, such as nuclear power plants, in an emergency beyond design situations. For instance, the well-known events at the Japanese nuclear power plant “Fukushima-1” in 2011 were characterized by the fact that during the two weeks when the nuclear power plant was completely de-energized, there was no information from electronic sensors, which was extremely important for monitoring the technical condition of the emergency station.

Temperature

Problems of standard sensing systems control of tightness of tanks with liquid hydrogen, which is the fuel of modern rocket engines, has a temperature of -253 °C and very high fluidity, due to the fact that at such temperatures, most materials become very fragile, and the sensitivity of palladium sensors quickly decreases. 

It is problematic to measure the pressure and dryness of superheated steam in gas generators and superheated gas in jet engine nozzles at temperatures up to + 600 °C since piezoelectric sensors quickly degrade at temperatures above + 300 °C. Modern FBG sensors of physical quantities are heat-resistant (up to +2300 °C) and cold-resistant (up to -270 °C). This provides reliable and long-term monitoring of the technical condition of high-temperature and cryogenic objects.

Electromagnetic interference

Measurements of physical quantities using electrical sensing systems in conditions of high-power electromagnetic interference, including guidance on coaxial electrical cables and sensors from lightning discharges, in conditions of monitoring the patient’s pulse in a medical nuclear magnetic resonance facility, as well as measurements of high voltages and high currents in electrical engineering, are highly problematic.

Fiber Bragg grating sensors are completely immune to electromagnetic interference and are stable insulators. This makes it possible to measure high voltages up to 800 kV and high currents up to 200 kA with high accuracy (class 02s) by fiber optic sensing technology.

Aggressive environment

Measurements of physical quantities of chemically aggressive media, long — term measurements of deformation of dynamically loaded objects and structures, as well as multi-sensor measurements-with the number of control points in several hundred and thousands, are also problematic for electrical sensing systems since the volume of measuring electrical cables is unacceptably increasing.

Distributed fiber optic sensors are multi-sensors: up to 10 thousand consecutive intra-fiber sensors can be used in one optical fiber (fiber optic cable) to measure physical quantities (temperature, strain, seismoacoustics, pressure, radiation, etc.). Multimode fiber optic cables allow performing remote measurements with high accuracy using borehole video cameras, and temperature fields — using pyrometers and thermal imagers.

Metrological calibration

A serious problem of electrical sensing systems embedded in objects (in the concrete of hydraulic dams and bridges, in the pylons and walls of high-rise buildings, etc.) presents the practical difficulty of their periodic calibration (metrological verification).

Modern fiber sensors have the function of metrological self-monitoring (FMSM) due to the multimodality of the optical signal, which allows for self-calibration of fiber optic sensors in real-time without stopping the controlled processes and without verification standards.

In the last decade, there were implemented many similar applications of modern fiber sensors and systems in extreme environments of nuclear, oil and gas and aerospace industries, shipbuilding, hydraulic engineering, energy, construction, military, and natural emergencies.

robin-sommer-wnOJ83k8r4w-unsplashMoreover, the durability of FBG sensors in these extreme conditions creates an obvious advantage of their use in the energy, oil and gas, aerospace, construction, and transport industries in comparison with non-optical types of measuring systems.

Thus, the extreme operating conditions of fiber Bragg grating sensors, for example in wells (extreme parameters, flammable, aggressive and abrasive environments) or power plants (ultra-high currents and discharges, voltages and fields, significant ionizing radiation), actually belong to the usual operating conditions of fiber optic sensors.

If you are looking for reliable fiber optic sensing solutions for structural health monitoring, you should choose the Optromix company. Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com 

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editorFiber optic sensing solutions for extreme conditions

Fiber Bragg grating sensors perform structural health monitoring

on July 27, 2020

space-shuttle-774_640Nowadays fiber Bragg gratings are actively applied in the aerospace industry. The thing is that fiber optic multiplexing abilities of sensors based on FBG technology allow performing structural health monitoring of airborne vehicles resulting in an increase of their lifetime. Thus, fiber Bragg grating sensors play a crucial role in the spacecraft industry where mistakes and damage can lead to death.

It should be noted that fiber Bragg gratings are considered to be a thin optical fiber device that includes a physical “grating” area at its core. Herewith, the FBG core is not homogeneous, and the fiber optic sensor has a periodic variation in the refractive index of the material. Also, there is a dependency between the wavelength of light (reflected vs transmitted) and the periodic spacing of the grating.

FBG sensors can block specific wavelengths and transmit others like in laser cavities during the mode choice. Additionally, such factors as pressure and strain also influence the qualities of FBGs and the wavelengths resulting in stretching or compressing the grating period while temperature leads to thermo-optic effects. These and some other effects (for instance, vibration and displacement)  promote the application of fiber Bragg grating sensors to monitor various physical effects.

FBG sensors enable to determine ultrasonic and acoustic wave signals that are important in structural health monitoring of aerospace vehicles. For instance, acoustic-ultrasonic determination provided FBG technology helps to find out damage when the spacecraft is not mobile.

The detection offered by fiber optic sensors is regarded as highly accurate and quantitative because it is possible to monitor both the form function of the waves and the repetition of measurements. Nevertheless, the resolution and the bandwidth limitation of conventional tools employed with fiber Bragg gratings (for example, optical spectrum analyzers) do not enable accuracy in high-frequency determination.

The fact is that accurate determination of ultrasonic waves requires a demodulation method to interpret the detected signals. Four demodulation methods are distinguished in FBG technology both in practice and in laboratory testing: “a broadband light source (power detection), laser light source (edge-filter detection), Erbium-Doped Fiber Laser (EDFL), and modulated lasers.” Moreover, it is necessary to pay careful attention to the installation technique of the FBGs.

Finally, specialists apply several various techniques to employ fiber Bragg grating sensors into a vehicle or craft. The fiber optic sensors have been already tested at their installation into composite materials (inside of a fiber honeycomb sandwiches.) However, the technique can cause signal distortion, that is why an ideal way for spacecraft is gluing fiber Bragg gratings on with some adhesive.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com

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editorFiber Bragg grating sensors perform structural health monitoring

Fiber Bragg grating sensors measure physical factors

on July 6, 2020

tablet-2471184_640Fiber Bragg grating (FBG) has quickly become popular in fiber optics, and now it is impossible to imagine the absence of fiber optic sensing systems based on FBG technology. Researchers prefer to use fiber Bragg grating (FBG)-based sensing because of its benefits, for instance, compact size, fast response, distributed sensing, and immunity to the electromagnetic field. 

To be more precise, FBG technology finds its wide application in measurements of different physical factors (pressure, temperature, and strain for civil engineering, industrial engineering, military, maritime, and aerospace applications). Herewith, structural health monitoring of engineering and civil structures plays a crucial role now that can be easily carried out with fiber Bragg grating sensors.

It should be noted that the grating types of FBG include uniform, long, chirped, tilted, or phase-shifted (that has periodic perturbation of refractive index inside the core of the optical fiber). The development of fiber optic systems has greatly changed almost all areas of communication technology. Nowadays fiber optic sensors are widely used in the measurement of strain, refractive index, the vibration of structures and machines, electric current, voltage, impedance, temperature, pressure, humidity, etc.

Despite the crucial advancement in fiber optics,  integration of optical mirrors, partial reflector, and wavelength filters provide numerous difficulties because of the complexity and high cost of fiber optic systems. Nonetheless, FBG technology allows overcoming all these challenges because fiber Bragg grating can offer the function of reflection, dispersion, and filtering required for sensing applications.

Ever since its development, fiber Bragg grating sensors have obtained much attention because they offer numerous benefits, for example, pretty low cost, compact size, real-time response, high precision, high sensitivity, and independence to electromagnetic interference. Moreover, FBG sensors are considered to be very promising in measuring physical parameters.

Modern applications of fiber Bragg grating sensors include such areas as “high-temperature sensors, health and biomedical devices, structural engineering, industries, biochemical applications, radioactive environment, aerospace, maritime and civil engineering, and many other fields.” Additionally, FBG sensors rapidly moved from research laboratories to actual installation in fiber optic systems.

Finally, it is very difficult to think of fiber optic sensors without employing fiber Bragg gratings due to its attractive parameters, which make them a highly advanced technology in the sensing field. The combination of FBG technology with other systems, in turn, will lead to the overall enhancement of sensor design in terms of sensitivity, performance, cost, and size.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com

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editorFiber Bragg grating sensors measure physical factors

Fiber optic sensors began to be widely used in space

on June 29, 2020

nasa-yZygONrUBe8-unsplashMembers of NASA claim that they plan to test an enhanced fiber optic sensing system that allows performing thousands of measurements along the optical fiber about the thickness of a human hair for application in space. Herewith, such a promising fiber optic technology can control spacecraft systems during missions to the Moon and landings on Mars.

To be more precise, the system based on fiber optic sensors has been designed at NASA’s Armstrong Flight Research Center in California to obtain strain and other measurement data for aircraft. The researchers adapted the fiber optic system for application in space, where its potential uses contain temperature and strain information essential for space flight safety.

It should be noted that four fiber optic sensing systems are planned to test in space during five months, herewith, such tests carried out will demonstrate whether space fiber optic sensors can pass the hard conditions of a rocket launch. The thing is that rockets and spacecraft are considered to be highly complex systems and they have a myriad of various factors to be measured that is why NASA plans to keep the first applications of space fiber optic systems simple.

The new fiber optic technology based on space-rated sensors enables us to measure distributed temperatures on the Low-Earth Orbit Flight Test. The aim of aeroshell of the fiber optic system is to slow down and protect heavy payloads from the intense heat of atmospheric re-entry. Additionally, the fiber optic sensors monitor temperatures on the backside of the inflatable decelerator, therefore, the researchers “are working on space optical fiber experiment that will travel as a self-contained experiment on a Blue Origin New Shepard rocket through NASA’s Flight Opportunities program.”

The opportunities provided by fiber optic technology also include the decrease of the heat produced by the unit’s electronics and by way of conduction, or moving the heat away from the unit, because of a lack of air in space. The fiber optic system is regarded as self-contained and essentially ready for plug and play application. The thing is that the operating principle of the system is based on fiber optic sensors that can endure severe conditions to measure distributed temperatures in a cryogenic environment that play a crucial role.

NASA is also developing a compact, economically, and hardly fiber optic sensing system version. Thus, the new fiber optic technology based on a temperature-tuned laser is used to overcome the challenges. The researchers continue improving the production techniques of fiber optic sensors and discussing performing a potential test of the sensors at NASA’s Ames Research Center in California to support the study of the new fiber optic technology.

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com

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editorFiber optic sensors began to be widely used in space

Dynamic gratings produce new fiber optic sensors

on June 22, 2020

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

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

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

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

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

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

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

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com

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editorDynamic gratings produce new fiber optic sensors

What you should know about fiber Bragg gratings

on June 15, 2020

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

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

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

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

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

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

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

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

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com

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editorWhat you should know about fiber Bragg gratings

Multi-addressed fiber Bragg gratings for microwave sensors

on June 8, 2020

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

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

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

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

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

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

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com

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editorMulti-addressed fiber Bragg gratings for microwave sensors

Distributed fiber optic sensors and their prospects

on June 1, 2020

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

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

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

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

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

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

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in structural health monitoring systems and want to learn more, please contact us at info@optromix.com

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editorDistributed fiber optic sensors and their prospects

Why DTS systems are beneficial to pipelines

on May 25, 2020

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

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

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

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

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

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

Optromix is a fast-growing vendor of fiber Bragg grating (FBG) product line such as fiber Bragg grating sensors, FBG interrogators and multiplexers, Distributed Acoustic Sensing (DAS) systems, Distributed Temperature Sensing (DTS) systems. The company creates and supplies a broad variety of fiber optic solutions for monitoring worldwide. If you are interested in temperature measurement systems and want to learn more, please contact us at info@optromix.com

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editorWhy DTS systems are beneficial to pipelines

FBG sensors that dissolve inside the body have been developed

on May 18, 2020

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

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

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

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

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

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

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

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editorFBG sensors that dissolve inside the body have been developed