Articles

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

Embedded fbg strain sensors for robotic applications

on December 9, 2019

hand-3308188_640Fiber optic technology continues finding 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, though 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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editorEmbedded fbg strain sensors for robotic applications

Distributed temperature sensors of high precision for Raman-based sensing

on December 2, 2019

pipeline-58142_640A new distributed temperature sensor (DTS) system has been developed to perform optimization of the temperature precision with the enhanced temperature sensitivity of backscattered spontaneous Raman scattering. The DTS system is based on the difference in sensitive-temperature compensation. 

Distributed temperature sensors apply the dual-demodulation, self-demodulation and double-end configuration principles. The DTS system has been already tested and demonstrates great results: the temperature precision is considered to be 12.54 °C, 8.53 °C and 15.00 °C along the 10.8 km under the traditional R-DTS systems, respectively.

It is possible to use the sensing system with difference sensitive-temperature compensation for the dual-demodulation, self-demodulation, and double-end configuration R-DTS, herewith, this fiber optic sensing technology enables to make the temperature precision better than 1 °C for these three demodulation systems.

The operating principle of Raman Distributed Temperature Sensor is based on “specific optical effects along the sensing optical fiber to obtain a spatially distributed temperature profile”. Compared to traditional discrete sensing techniques, R-DTS systems provide unique attributes and capabilities.

It should be noted that spontaneous Raman scattering of distributed temperature sensors uses the energy exchange in the optical fiber, therefore, when the pulsed light quantum and fiber optic material molecule leads to an inelastic collision in optical fiber, this will create an anti-Stokes light.

The thing is that the anti-Stokes light is regarded to be very sensitive to the surrounding temperature, and it allows modulating the environmental temperature using the principle of Raman scattering. Nowadays, such DTS systems find their application in the temperature safety monitoring thanks to the benefits of distributed measurement, long-distance, and high spatial resolution, as well as in transport infrastructure, smart grid and gas pipeline, etc.

It is necessary to pay on the following parameters when you choose distributed temperature sensors with high-performance: temperature precision, temperature resolution, and spatial resolution. DTS systems can be used as an industrial temperature measurement system, for instance, the carrier density in the power cable can be measured by employing a specific temperature. Additionally, distributed temperature sensors allow locating the position of pipeline leakage.

Tests demonstrate that the temperature demodulation system based on distributed temperature sensing offers higher temperature precision and resolution of the self-demodulation than the dual-demodulation system due to the signal-to-noise ratio. Moreover, the double-ended configuration for DTS systems allows avoiding the measurement error based on the change of local external attenuation.

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

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editorDistributed temperature sensors of high precision for Raman-based sensing

Compact FBG sensors control traffic density

on November 25, 2019

A new compact sensing system based on fiber Bragg grating technology has been designed to control urban traffic density up to 80 kph. road-4598095_640The sensing technology includes a 2.5-m-long and a 2-cm-high fiber optic sensor made from a combination of silicone addition rubber and fiber Bragg grating put inside a carbon tube.

The design of the compact FBG sensors allows monitoring and detecting the traffic density and car crossing in a single lane. It should be noted that such a sensing system has been already tested in real traffic and demonstrated quite a high detection rate of 98.946% based on the control of 1518 vehicles of various types and sizes.

To be more precise, traffic sensing systems are considered to be special devices that determine input data and information for other transport infrastructure systems. It is possible to install traffic sensors next to, above, into or onto a road’s surface. The fiber optic sensors control “the presence of a vehicle, vehicle speed, vehicle classification, wheelbase and number of axles, total vehicle weight, road axle load, and occupancy, all of which indicate the traffic flow quality”.

The thing is that sensing systems based on optical fibers provide the following benefits: robustness, precision, high sensitivity, electromagnetic and chemical resistance, electrical passivity and a broad temperature operating range. Additionally, it is possible to use fiber optic sensors in hybrid systems. The operating principle of fiber sensors is based on transmitting and receiving a laser or infrared beam from an emitter to a receiver.

Another type of fiber optic sensor is distinguished that is a micro-motion one. Such a fiber sensor operates using the increasing of optical fiber attenuation. Herewith, these optical fibers have special protective coatings and they are installed into a roadway. Nevertheless, their application is experimental, and these fiber sensors are not employed in general practice.

Also, the DAS technology (Distributed Acoustic Sensor) can be used for the same purposes. For instance, DAS systems apply a single optical fiber to control multiple traffic parameters, such as detecting a car, its direction, its speed, etc. However, FBG sensors require proper protection in order to avoid damage to the sensors. The use of composite fiber protection to the FBG sensors enables to successfully solve the current problem.

The high sensitivity of portable FBG sensors and success rates in determination vehicles are regarded as a good supposition for expanding research and future developments for monitoring automotive traffic. Nowadays researchers plan to improve the design of fiber sensors to provide a more stable sensitivity, as well as to expand the determination capabilities of the sensing system, and to produce the sensor for year-round application.

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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editorCompact FBG sensors control traffic density

A new application of FBG sensors

on November 18, 2019

FBG sensorA team of researchers offers a new application of fiber Bragg grating sensors (FBG sensors) in the construction and characterization of Micro Pattern Gaseous Detector. Such a FBG sensing system includes 144 gas electron multiplier chambers of about 0.5 m2 active area each. It should be noted that FBG technology has been applied in high energy physics only for high precision positioning and re-positioning fiber sensors due to their benefits (low cost, easy installation, low space consumption). Nowadays the most common application of fiber Bragg gratings remains the use for very accurate strain measurements in material studies.

Now FBG technology is used as flatness and mechanical tensioning sensors employed to the wide GEM foils of the GE1/1 chambers. FBG sensor array allows detecting the optimal mechanical tension applied and characterizing the mechanical tension that should be applied to the foils. A new application of FBG sensors has been already tested and demonstrated great results that can determine a standard assembly procedure and possible future developments.

Fiber Bragg gratings are considered to be a type of distributed Bragg reflector, developed by a short segment of optical fiber that enables one to reflect certain wavelengths of light and transmit all others. The operating principle of FBG sensors is based on “the creation of a periodic variation in the refractive index of the fiber core, which generates a wavelength-specific dielectric mirror”. Thus, the FBG sensing system can be applied as a strain measurement device because changes in fiber Bragg gratings lead to various light frequency responses.

One more application of FBG sensors in GEM chamber construction includes the opportunity to be applied as a load gauge for accurate measurement of the tensile load employed to the foils, of the various layers, at the same moment. The thing is that this FBG application plays a crucial role in the case of the GE1/1 chambers because the foils are stretched through screwing nuts with a dynamometric screwdriver during their assembly procedure, therefore, it is necessary to know accurately how much to strain the foils to escape to stretch them too much.

The testing of fiber Bragg grating sensors consist of proper stretching of the GE1/1 GEM stack, then the researchers removed a single stretching screw from the chamber and replaced it with an eyelet screw with installed stainless steel wire applied to set various weights. Additionally, it was necessary to add weights in different steps until they applied load achieves in the fiber Bragg gratings facing the eyelet the same response as when stretching of the GEMs occurs by the traditional screw.

Finally, the technology of FBG sensors is regarded as a highly reliable glue-less technique that offers the correct tensioning of the three GEM foils. The correct tension across the GEM stack leads to uniform gaps resulting in the required performance of the detector. Moreover, FBG sensors operate successfully as load gauges for accurate detection of the used stretching force to GEM foils.

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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editorA new application of FBG sensors

Fiber optic sensors based on the vapor deposited conducting polymer

on November 11, 2019

fibre-1562702_640A team of researchers from Australia has developed a mathematical model, which is based on energy deposition and the laser-induced damage threshold (LIDT) for low-intensity light radiation resulting in the appearance of conducting polymers in novel fiber optic sensing applications.

It should be noted that nowadays polymer features are regarded as one of the most potential and studied CP’s, herewith, the material may find numerous applications such as light-emitting diodes (OLED), optical displays, photovoltaic devices, and fiber optic sensors.

The thing is that the poly(3,4-ethylenedioxythiophene) is almost visibly transparent in its doped state, while it converts into an opaque material (dark blue) in the dedoped state, thus, making the polymer ideal for optical applications, for instance, in electrochromic devices and optical fiber sensors.

The interaction between light and the sensing material plays a crucial role in fiber optic sensing. To be more precise, there is a reaction between the sensing material and an external stimulus, therefore, it becomes possible to interrogate and measure the change, linking the optical fiber measurement to the external stimuli. 

Optical fibers are considered to be an ideal example of a way to send light to a volume or point of interest for fiber optic sensing. Usually, “optical material is coated on the side or at the tip of the fiber, which are typically inorganic material”. Numerous recent sensing applications (temperature sensors, hydrogen sensors and polymer functionalization of exposed-core microstructured optical fibers) include fiber tip fabrication and side coating.

Thus, the researchers present a new fiber optic sensing architecture based on coating the tip of an optical fiber with the vapor-deposited conducting polymer. They confirm that such fiber optic sensors enable us to study the unique electrochemical properties of PEDOT:Tos at the sub-micron length scale. Additionally, the polymer material can be integrated with optical waveguides (optical fibers as well) resulting in a range of electro-optical devices.

Optical fibers provide such benefits as immunity to electromagnetic fields, the possibility for in-vivo and distributed measurements with the electrochemical properties of poly((3,4-ethylenedioxythiophene). Also, the researchers prepare a technique to gradually deposit PEDOT:Tos layers with desired thicknesses on the tip of optical fibers to produce such a fiber optic sensor.

Finally, the fiber optic technology was tested, and the polymer material was deposited at the tip of cleaned and cleaved SMF-28 optical fiber. Moreover, the deposition technique is based on 4 steps: “ 1. Oxidant solution preparation, 2. Oxidant coating and splitting at the tip of the fiber, 3. VPP process and 4. Washing of unbound and unreacted monomers”.

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

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editorFiber optic sensors based on the vapor deposited conducting polymer

Distributed acoustic sensing for railway structural health monitoring

on October 28, 2019

The principle of distributed acoustic sensing (DAS) operation is based on the processes occurring in fiber optic cables. To be more precise, sound waves falling at the fiber cable change the reflection of laser beam pulses inside it. Thus, these changes are possible to be detected. 

1railway-track-2049394_640Specially developed algorithms allow converting a measurable backscatter signal trace (signature) into valuable information, for example, about moving rolling stock, about people moving along or near tracks, or other actions, such as earthmoving operations.

The application of DAS-based systems becomes widespread, for instance, in the oil and gas industry, as well as in the border protection due to these technical capabilities.

Any single-mode fiber can be quickly and easily converted into a series of “virtual microphones” by distributed acoustic sensing. This requires only minimal exposure to the ends of the optical fibers

Since the majority of railway tracks already have fiber optic cables, the above-mentioned possibilities of DAS application in the railway infrastructure can be performed to a large extent using existing resources.

If an existing fiber optic cable already laid close to the railway infrastructure is used, it is possible to monitor trains, auxiliary rolling stock, track crews, strangers near tracks or natural influences on the infrastructure. 

Accordingly, DAS technology can find application in tracking systems for the movement of trains, monitoring the track and rolling stock, as well as in the protection of railway infrastructure.

Only one set of DAS systems enables to monitor processes and components on and off track for 40 km. It is possible to combine many such units into a common sensing system to cover extensive networks of railway tracks. At the same time, the DAS system operates with an accuracy of 10 m and provides information about the location of the recorded event on the site and GPS coordinates.

Several acoustic sensing sets can be combined into a single system to control longer tracks. The possibilities of the co-use of distributed acoustic sensing and wheel hole registration systems were already studied to meet the requirements of the railroads, taking into account the considered limitations.

The application of advanced axis counters is caused by the need to detect individual axes and the train location on a particular track in compliance with safety conditions.

Unlike track circuits, directly establishing the free or occupation part of the track, the axis counting system operates indirectly. If the track part was free in the initial period, and then the number of wheelsets entering and leaving coincided, the part is registered as free from railroad rolling stock. If this condition is not fulfilled, the part is considered occupied.

The data combination from both sensing systems creates a whole variety of new possibilities by using the generated information from fiber optic acoustic sensors. This technical solution of acoustic sensing makes it possible to detect a train to a concrete track precisely. 

Also, DAS technology provides an even more accurate determination of the train length. Moreover, this combination of sensing systems offers the opportunity to localize events, for example, you can determine which axis has a slider. In this combination, DAS can also be used on sections of railway tracks with complex track development, where several parallel tracks are connected by operations.

The user interface system of distributed acoustic sensing displays in a convenient form both data received directly from the DAS system and information generated using combined technical solutions, including additional axis counters and a system for registering the wheel hole of railroad rolling stock.

Conditions detected by the DAS system and a combined technical solution are carefully classified and all received information is provided in a visual form. This serves as the basis for the planning and implementation of activities arising from the detection results.

Besides, the data collected by distributed acoustic sensing can be redirected directly to mobile end-use devices. Nevertheless, they can also be transmitted, for example, to unmanned aerial vehicles, which are sent to the appropriate location using available GPS data. Thus, the DAS system allows you to quickly respond to a variety of events.

The interference of both signals will make it possible to more accurately correlate information about the state of train components with a specific location in the future, for example, it will be easy to establish which axis has the slider on it. New possibilities are opened up for using DAS technology in complex railway tracks, where several parallel tracks are connected by operations. 

1000px-Distributed_Acoustic_SensingThe system of distributed acoustic sensing allows both monitoring of rolling stock and state track components: the DAS system completely controls the railways and the area around them. Even unforeseen events that are difficult to detect are recognized reliably.

This also applies to fractures of rails, which represent one of the main risks on the railway. This sensing system also detects electrical discharges on air-track lines due to overload, floods, stone falling, falling of trees, and mudflows. Fiber optic acoustic sensors can significantly reduce the number of costly violations of the usual operation in railway transport.

With an increase in the accuracy of event localization, conditions are created for the application of DAS technology in areas with complex track development.

The signals (signatures) recorded during the movement of trains by the axis counters and the acoustic sensors are brought together to determine the exact location.

The possibilities of using acoustic sensing technology in railways open up broad prospects for increasing the effectiveness of monitoring infrastructure and rolling stock. Thus, the DAS system provides structural health monitoring information about:

– location of the train;

– direction of the traffic;

– speed;

– time of train arrival;

– the distance between trains;

– rail break;

– slide;

– falling of stones;

– spark discharge in the contact network;

– unauthorized access;

– cable theft;

– vandalism, etc.

Axis counters provide information about:

– the state of free/occupation of a track particular section;

– number of axes on the track section;

– speed;

– direction of the traffic;

– diagnostics.

An important aspect of railway operation is safety. Security has many indications and affects numerous different areas. DAS provides a comprehensive solution to cope with several tasks – from labor protections to the protection against vandalism.

Distributed acoustic sensing offers railway operators a single solution for the protection of infrastructure and the safety of railway workers, with an extended range and high efficiency.

DAS converts measured signals (signatures) into valuable information, for example, about moving vehicles and individuals. Based on this information, messages are generated about the presence of objects or people, which can be more accurately classified due to the high sensitivity of the sensing system. It also allows for directly recognizing certain actions, for example, earthmoving on the way, and displaying the corresponding alarm messages.

Finally, distributed acoustic sensing systems will change the way that trains are monitored and infrastructure is operated soon. An integrated railway structural health monitoring system is becoming available, which opens up previously unimaginable DAS applications and allows for the implementation of the most challenging ideas in the field of train and operation control.

The use of a distributed acoustic sensing systems for the railway industry opens up wide applications for monitoring the movement of trains, monitoring the condition of equipment, protecting infrastructure and ensuring the safety of people in real-time.

Moreover, recent advances in DAS make the sensing systems cost-effective, highly precise, herewith, these acoustic sensors do not require accurate alignment resulting in tuning vibration measurement to a particular point in the optical fiber. Thus, new DAS systems promote the speed of measurement beyond the previously established theoretical limit set by the sensing distance. The technology of new fiber optic acoustic sensors is based on the application of “colored” probe pulses or linear frequency multiplexing.

It should be noted that DAS is a highly reliable technology because it continues its operation even after it has been cut. DAS has the biggest influence in the signaling area, for example,  distributed sensing helps to manage trains by control of their accurate position and motion in real-time. The technology enables to reduce journey times while increasing rail capacity and improving safety.

Of course, the distributed acoustic sensing system continues improving and the improvement will provide quantitative measurement with improved sensitivity and higher spatial resolution on longer lengths of the sensing fiber in the future.

3das_1Optromix is a DAS system manufacturer that provides top of the line distributed acoustic sensing systems suitable for monitoring of commerce networks. If you have any questions or would like to buy a DAS system, please contact us at info@optromix.com

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editorDistributed acoustic sensing for railway structural health monitoring

Recent developments in Distributed Acoustic Sensing

on October 21, 2019

ear-2972890_640The operational principle of distributed acoustic sensing or fiber optic DAS is based on coherent Rayleigh backscattering in an optical fiber. Today the technology of acoustic sensing is regarded as a common technique for structural health monitoring of various dynamic actions in real-time. DAS applications in safety, security, and integrity monitoring systems promote a steadily growth of the fiber optic DAS market.

Fiber optic acoustic sensors offer the opportunity to measure various changes in environmental parameters provoked by numerous events over long distances. The applications of DAS technology include transportation, oil and gas, and process control systems, herewith, they continue increasing. Additionally, distributed acoustic sensing allows performing measurements of both slowly changing (for instance, temperature or static strain) and fast-changing parameters (dynamic strain or vibration) providing fast and precise monitoring in real-time.

Therefore, DAS systems for the mentioned measurements are required to pay careful attention. Despite numerous developments that have been made in distributed acoustic sensing to increase the measurement speed over short distances with high spatial resolution, measurements at long distances remain considerably slow. Nevertheless, fiber optic acoustic sensors provide interesting alternatives for fast distributed measurements over long distances.

Such developments in distributed acoustic sensing  as “use of high ER pulses to reduce coherence noise, fast denoising in the optical domain using optical pulse coding technique, generation of high ER pulses using nonlinear Kerr effect, and the identification of pulse shapes robust against modulation instability” enable to enhance the performance of fiber optic acoustic sensors.

Moreover, recent advances in DAS make the sensing systems cost-effective, highly precise, herewith, these acoustic sensors do not require accurate alignment resulting in tuning vibration measurement to a particular point in the optical fiber. Thus, new DAS systems promote the speed of measurement beyond the previously established theoretical limit set by the sensing distance. The technology of new fiber optic acoustic sensors is based on the application of “colored” probe pulses or linear frequency multiplexing.

Finally, the improved distributed acoustic sensors have higher spatial resolution due to the use of tweaking of the conventional set up to make the optical noise lower, and more accurate quantitative measurement of an external impact thanks to frequency shift measurements and direct phase demodulation techniques.

Optromix is a DAS system manufacturer that provides top of the line distributed acoustic sensing systems suitable for monitoring of commerce networks. If you have any questions or would like to buy a DAS system, please contact us at info@optromix.com

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editorRecent developments in Distributed Acoustic Sensing

Distributed acoustic sensing for phase-sensitive OTDR technology

on October 14, 2019

1000px-Distributed_Acoustic_SensingThe sensing system is a fundamental device that presents data information about the features of the surrounding environmental conditions to electronic tools. The information obtained through distributed fiber sensing is used for analytical purposes or processed and employed to take specific actions. Herewith, today distributed sensors find widespread application since they are applied in most of the human daily used items.

For instance, distributed optical fiber sensors apply light to probe a kilometer-length optical fiber employed as the sensing system. Thus, distributed sensors allow for the detection of strain or temperature variations along the fiber length. The principle of distributed optical fiber sensor operation is based on “scattering processes happening along the optical fiber, either Rayleigh stimulated Brillouin or Raman scattering”.

The characteristics of various scattering processes offer different applications to distributed sensors. For example, distributed optical fiber sensors based on Raman technology are regarded as highly efficient temperature sensing devices. Recent developments in sensing technology enable to reach a better resolution, higher bandwidth or longer-range operation.

Nowadays new sensing technique to interrogate an optical fiber applying Rayleigh backscattering process is considered to be very advanced. Such distributed sensors are based on phase-sensitive optical time-domain reflectometry (OTDR) technology, herein, they use a train of linearly-chirped optical pulses resulting in a quite simple conventionally used methodology. Additionally, distributed acoustic sensing for phase-sensitive OTDR technology provides amazing robustness against laser phase noise and a record measured sensitivity.

The technology of distributed acoustic sensing for phase-sensitive OTDR has been experimentally demonstrated a couple of years ago, based on the application of a chirped-pulse as a probe, in an otherwise direct-detection-based standard setup: chirped-pulse (CP-)ΦOTDR. The benefits of DAS systems include intrinsic immunity to fading points and use of direct detection, therefore, distributed acoustic sensing offers reliable high sensitivity measurements.

Finally, DAS technology for OTDR finds its use in diverse applications that include seismology or civil engineering (monitoring of pipelines, train rails, etc.), and new applications based on distributed acoustic or temperature sensing appear everyday. Such a distributed optical fiber sensor can operate in up to 100 km with a low cost-setup, showing performances close to the attainable limits for a given set of signal parameters.

Optromix is a DAS system manufacturer that provides top of the line distributed acoustic sensing systems suitable for monitoring of commerce networks. If you have any questions or would like to buy a DAS system, please contact us at info@optromix.com

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editorDistributed acoustic sensing for phase-sensitive OTDR technology

FBG sensors for measuring human body temperature

on October 7, 2019

thermometer-1539191_640The opportunity to measure body temperature plays a crucial role in both physiological studies and clinical investigations. New wearable sensors based on fiber Bragg grating or FBG technology offer such an opportunity in intelligent clothing for human body temperature measurement.

The main purpose of the development is the integration of FBG sensors into functional textiles to enhance the abilities of wearable fiber optic solutions for body temperature monitoring. Thus, the FBG sensing system provides the temperature sensitivity of 150 pm/°C, which is almost 15 times higher than that of a bare fiber Bragg grating.

It should be noted that fiber Bragg grating is regarded as a type of distributed FBG reflector installed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all the others. The FBG technology is used here as an inline optical filter to block specific wavelengths, or as a wavelength-specific reflector.

Additionally,  FBG sensors offer great benefit over electronic sensing systems for the use in intelligent structures, civil engineering, harsh environmental conditions, built structural health monitoring system and other. Distributed temperature sensors based on fiber Bragg gratings measure human body temperature at fiver places: left chest, right chest, left armpit, right armpit, and at the center of the upper back. Herewith, the data information provided by these FBG sensors at five places is not the same because different parts of the human body have different temperatures.

The application of distributed temperature sensors based on FBG technology allows developing a sample of intelligent clothing and testing the heat transmission mechanism from numerous aspects. New mathematical model of heat transmission for the human skin, the air and clothing has been created. Therefore, FBG sensors provide the theoretical basis of human temperature measurement applying intelligent clothing with distributed temperature sensors and demonstrate the implementation of optical fiber grating into the clothing. 

Finally, the temperature measured by DTS systems can be useful to represent human body temperature in clinics. Nonetheless, it is planned to enlarge “research in intelligent clothing to cover the measuring and recording of real-time physiological information, such as human respiration, heartbeat, blood pressure, and other physiological signals.”

The biomedical application of wearable FBG sensors, which are non-intrusive, non-invasive, and continuously being monitored, is considered to become a highly potential monitoring and diagnostic devices. Thus, these distributed temperature sensors can determine and process physiological signals, extract signal characterization, transmit data, and have other basic options.

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 for measuring human body temperature

Spacecraft structural health monitoring by fiber Bragg grating sensors

on September 30, 2019

space-shuttle-992_640Fiber Bragg gratings or FBGs are considered to offer a markworthy application in fastly growing aerospace industry. The FBG benefits such as phenomenal optical multiplexing make them possible to use as smart fiber optic sensors that allow them to perform structural health monitoring of airborne vehicles and maintain and lengthen their lifetime. Thus, FBG technology plays a crucial role in the spacecraft industry where tiny errors and damage can lead to death for the crew aboard.

To be more precise, fiber Bragg grating is regarded as a thin, tubular optical fiber device that includes a physical “grating” area at its core. Herewith, the core of fiber Bragg gratings is not homogeneous, it has a periodic variation in the refractive material index. The principle of FBG technology operation is based on the change in the core refractive index because of which “some light will be reflected and some will be transmitted through the tube.” Additionally, the periodic spacing of the grating influences the reflected vs transmitted wavelength of light.

FBGs demonstrate efficient operation as narrow bandwidth light filters. The FBG application includes a block of specific wavelengths and transmission of others that is similar to the mode selection that appears in laser cavities. Nevertheless, such features as pressure and strain as well as vibration and displacement also influence at the wavelengths of fiber Bragg gratings, while the temperature may lead to thermo-optic effects in the silica material that conventional FBG sensors are made from. Therefore, the mentioned FBG properties allow using them as fiber optic sensors to measure various physical effects at the same time.

FBG technology opens an opportunity to use FBG sensors to determine ultrasonic and acoustic wave signals, with a unique application in structural health monitoring of aerospace vehicles. The thing is that acousto-ultrasonic detection by fiber Bragg grating sensors is highly effective in damage detection if the spacecraft is not mobile (on the ground). Herewith, an ultrasonic actuator is required to produce the ultrasonic signals. It should be noted that the damage detection by FBG sensors is very accurate and quantitative because it allows controlling both the waveform function and the repetition of measurements.

Nevertheless, the limitations in resolution and bandwidth of conventional tools applied with fiber Bragg grating sensors, for example, optical spectrum analyzers, do not provide accuracy in high-frequency detection. It is necessary to use a demodulation method to interpret the detected signals for accurate detection of ultrasonic waves. Herewith, the installation technique of the fiber Bragg gratings is also important in ultrasonic detection. The installation of the fiber Bragg grating sensors into an aerospace vehicle or craft require the use of various techniques. For example, it is possible to place FBGs into composite materials, however, it may cause signal distortion. This is the reason why a better way is gluing FBG sensors on with some adhesive, such as epoxy. 

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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editorSpacecraft structural health monitoring by fiber Bragg grating sensors