Low-cost FBG interrogator for dynamic measurements

FBG interrogator for dynamic measurementsFiber Bragg grating technology (FBG technology) offers fiber optic sensors that allow carrying out the measurement of such parameters like temperature and/or mechanical strain. However, the high cost of fiber sensing systems is considered to be a major disadvantage for commercial applications.

It should be noted that the popularity and fast growth of fiber optic technology for sensing applications promote numerous research in various areas, for example, industry, medicine, aerospace, civil applications where such physical and chemicals factors as acceleration, level, temperature, strain, pressure, deformation, refractive index play a very important role.

Optical fiber sensors are perfect for use in the mentioned measurements. Fiber optic technology offers numerous benefits that include “intrinsic safety, resistance to chemical corrosion, immunity to electromagnetic interference, electric isolation, compact size, lightweight sensing heads, high resolution, easy multiplexing, and capability for extremely remote monitoring without the need of electrical power at the measuring point”.

Moreover, fiber Bragg gratings are the most used technology for the measurement of temperature and/or mechanical strain parameters among other optical fiber sensors. To be more precise, the term “fiber Bragg gratings defines as nanometer periodical refractive index changes engraved in an optical fiber core.” 

The principle of FBG technology operation is based on the injection of a broadband light spectrum in the optical fiber. Herewith, there is a concentration of the reflected spectrum at the fiber Bragg grating wavelength, herewith, it is possible to see a suppression in the transmitted signal at the same wavelength.

Additionally, the same operation principle of the FBG technology is used in new and more complex structures, for example, planar FBG sensors. Thus, the FBGs offer very precise measurements due to the wavelength that is considered to be a permanent feature of the signal along the optical fibers

Nevertheless, the FBG interrogators have some challenges in large commercial applications because of their high cost. That is why the development of new, low-cost alternatives to the current FBG interrogators is highly required. Therefore, there are several solutions to the present problem.

One of the solutions is the use of frequency-to-amplitude conversion (a fast and low-cost FBG interrogation technology), in which the spectral variations of fiber Bragg gratings are straightforwardly transmitted into optical power variations. Herewith, the presented FBG technology is based on the twist between both the FBG sensors and the edge filter spectra.                            

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

Fiber Bragg gratings make semiconductor lasers more stable

FBGs for lasersResearchers from the Czech Republic demonstrate a new technique that allows improving wavelength stability and tunability of semiconductor laser diodes in fiber laser interferometers due to fiber Bragg gratings (FBGs) technology. This simulation technique makes the calculation of arbitrary fiber Bragg grating (apodized, chirp, etc.) with a high level of accuracy by a combination of techniques based on layered dielectric media (LDM) and transfer matrix technology.

Thus, based on the simulations and measurements made by the commercially available FBG technology, it has succeeded in the development of a special 100 mm long fiber Bragg grating with apodization. Herewith, the researchers confirm that the new FBG technology of improved linewidth and mode-hop free tuning range of semiconductor laser systems at the wavelength 760 nm enables to increase the resolution of a laser interferometer. Therefore, the absolute fiber laser interferometer with Vertical Cavity Surface Emitting Laser (VCSEL) to easily apply the FBG system to make the wavelength parameter more stable and monitor the tuning range was produced.

Typically, two types of fiber Bragg gratings are distinguished in the used technology: FBG with a period of ~0.5 µm, and Long-Period Fiber Bragg Gratings (LPFGs) with a period from 100 to 500 µm. Additionally, it should be mentioned that their production requires different methods. Thus, the creation of fiber Bragg gratings is performing by interference patterns, while long-period FBGs are produced by side irradiation of the fiber optic components through an amplitude mask or using the fiber translating technique.

Therefore, the application of FBGs offers high thermal stability, retaining optical properties up to 500 °C. Moreover, the production technique has a dependence on such parameters as the length, the type, and the other factors of the FBG technologyIt is possible to determine the necessary parameters on the basis of the FBG spectral profile.

Finally, the simulation technique based on the application of fiber Bragg gratings was developed and tested several types of FBGs. For example, chirped and apodized fiber Bragg gratings (FBGs with modulation of the amplitude and with modulation of the spacing). Herewith, this new FBG system provides numerous benefits in comparison to other types of FBGs.

The main benefit is suppressing the side lobes in the fiber Bragg grating spectral properties. The developed FBG system is a compact reliable one that ensures the operation in an industrial environment where the majority of optical components would be fiber-optic.

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

FBG sensors in Biomechanics and Rehabilitation Application

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

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

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

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

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

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

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

Distributed temperature sensing for the fog detection

DTS for the fog detectionTraditional in situ observations of meteorological variables are limited by surface levels, herein, it is possible to carry out the lowest observation around just 1-m height. Therefore, observation results of both shallow fog, and the initial growth stage of thicker fog layers can be missed in this case. Nevertheless, the use of distributed temperature sensing or DTS technology allows measuring temperature and humidity parameters at centimeter resolution in the lowest 7 m.

It should be noted that it is very important to obtain high-resolution observation for radiation fog, and DTS sensors solve the problem. Two techniques are applied to make tests in the near-surface layer at a higher resolution than the traditional sensing devices.

Distributed temperature sensing is ideal for the measurement temperature and relative humidity parameters. DTS technology offers a high spatial and temporal resolution. DTS application includes detection of surface temperature and soil heat fluxes, the radioactive skin effect at the surface of water bodies, the Bowen ratio, near-surface turbulent fluxes under varying stability, and wind speed.

The combination of distributed temperature sensing with unmanned aerial vehicle provides the observation of the morning boundary-layer transition from stable to unstable conditions. Compared to traditional sensing techniques, DTS technology has a great advantage for studies of the stable boundary layer that is the resolution of steep gradients.

DTS sensors are able to detect shallow cold pools at high resolution that is the mark of radiation fog formation. The thing is that the fog presence causes elevated DTS temperatures of up to 0.7 ℃ when compared to traditional temperature parameters. However, the technology of distributed temperature sensing is required to be further tested to provide its reliability under stable, foggy conditions.

DTS devices enable to measure temperature characteristic along with optical fiber cables that are based on the backscattered signal of a laser pulse. The DTS sensors were tested, herewith, the optical fiber includes two multi-mode cores, while a simple single-ended (non-duplexed) configuration is applied for the measurements.

Finally, even in the conditions of fog formation absence, compared to DTS technology traditional sensing devices are not able to measure the strong temperature inversions in the lowest 1 m of air. Distributed temperature sensing provides an efficient solution to the problem.

The application of DTS systems is not limited by fog detection, but the broader near-surface (stable) boundary layer. Additionally, DTS sensors offer a better physical understanding of such processes as the collapse of turbulence at the onset of the stable boundary layer, intermittent turbulence within the stable boundary layer, and the transition between different boundary-layer regimes due to the ability of distributed temperature sensing to catch steep gradients in both temperature and relative humidity parameters.

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