Fiber Bragg grating sensors perform structural health monitoring

FBG sensors for sctructural health monitoringNowadays 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

Fiber Bragg grating sensors measure physical factors

FBG sensors for physical factorsFiber 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