scholarly journals Review of the Strain Modulation Methods Used in Fiber Bragg Grating Sensors

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Kuo Li
Keyword(s):  
Fiber Bragg Grating ◽  
Transverse Force ◽  
Bragg Grating ◽  
Fiber Bragg Grating Sensors ◽  
Displacement Sensors ◽  
Strain Change ◽  
Fbg Sensors ◽  
Strain Modulation ◽  
Modulation Methods ◽  
Reduced Temperature

Fiber Bragg grating (FBG) is inherently sensitive to temperature and strain. By modulating FBG’s strain, various FBG sensors have been developed, such as sensors with enhanced or reduced temperature sensitivity, strain/displacement sensors, inclinometers, accelerometers, pressure meters, and magnetic field meters. This paper reviews the strain modulation methods used in these FBG sensors and categorizes them according to whether the strain of an FBG is changed evenly. Then, those even-strain-change methods are subcategorized into (1) attaching/embedding an FBG throughout to a base and (2) fixing the two ends of an FBG and (2.1) changing the distance between the two ends or (2.2) bending the FBG by applying a transverse force at the middle of the FBG. This review shows that the methods of “fixing the two ends” are prominent because of the advantages of large tunability and frequency modulation.

Measurement of the Thermal Expansion for Space Structures Using Fiber Bragg Grating Sensors and Displacement Measuring Interferometers

2008 ◽  
Author(s):  
Hong-Il Kim ◽  
Lae-Hyong Kang ◽  
Jae-Hung Han
Keyword(s):  
Fiber Bragg Grating ◽  
Real Time ◽  
Deformation Monitoring ◽  
Space Environment ◽  
Space Structures ◽  
Bragg Grating ◽  
Environment Change ◽  
Time Deformation ◽  
Fiber Bragg Grating Sensors ◽  
Fbg Sensors

Dimensional stability of the space structures, such as large telescope mirrors or metering substructures, is very important because even extremely small deformations of these structures might degrade the optical performances. Therefore, precise deformation data of the space structures according to environment change are required to design these structures correctly. Also, real-time deformation monitoring of these structures in space environment is demanded to verify whether these structures are properly designed or manufactured. FBG (fiber Bragg grating) sensors are applicable to real time monitoring of the space structure because they can be embedded onto the structures with minimal weight penalty. In this research, therefore, thermal deformation measurement system for the space structures, composed of FBG sensors for real time strain measurement and DMI (displacement measuring interferometers) for accurate specimen expansion data acquisition, is developed. Thermal strains measured by distributed FBG sensors are evaluated by the comparison with the strains obtained by highly accurate DMI.

Metrological Performances of Fiber Bragg Grating Sensors and Comparison with Electrical Strain Gauges

2011 ◽  
Vol 495 ◽  
pp. 53-57
Author(s):  
Marco Borotto ◽  
Enrico De Cais ◽  
Marco Belloli ◽  
Andrea Bernasconi ◽  
Stefano Manzoni
Keyword(s):  
Fiber Bragg Grating ◽  
Thermal Effects ◽  
Measurement Accuracy ◽  
Signal To Noise Ratio ◽  
Bragg Grating ◽  
Light Spectrum ◽  
Static Tests ◽  
Measurement Systems ◽  
Fiber Bragg Grating Sensors ◽  
Fbg Sensors

The fiber Bragg grating sensors (FBGs) have been recently introduced: they present a photorecord grating on the fiber itself, which allows the reflection of a certain wavelength of the input light spectrum. The applied strain is estimated relying on changes of the reflected wavelength. One of the possible applications that has prompted us to study this type of sensors is the possibility to create smart dynamometric structures based on carbon fiber by embedding FBGs. Many papers are available in literature about some applications with smart structures but there is not yet an appropriate metrological characterization about these FBG sensors, their strengths and weaknesses: for these reasons it was deemed useful making several tests on FBG sensors in terms of measurement accuracy, signal to noise ratio, ability to compensate for thermal effects and their behavior for dynamic applications. All these results have been compared to electrical strain gauge ones, which represent the actual reference strain measurement systems. The various solutions to compensate for thermal effects have offered several information for further analyses and the basis for a future use of these sensors for static or semi-static tests. Being fully aware of FBGs characteristics allows to draw down guidelines about their integration in composite materials for the most different applications, understanding in a better way the sensor response.

STRAIN MEASUREMENT AT CANTILEVER BEAM WITH FIBER BRAGG GRATING SENSORS AND COLLIMATORS AND ITS CORRECTION METHOD

2012 ◽  
Vol 06 ◽  
pp. 576-582
Author(s):  
Seung Min Tak ◽  
Min Kyu Kang ◽  
Dong Jin Park ◽  
Seok Soon Lee
Keyword(s):  
Optical Fiber ◽  
Fiber Bragg Grating ◽  
Cantilever Beam ◽  
Strain Measurement ◽  
Wave Length ◽  
Correction Method ◽  
The Other ◽  
Bragg Grating ◽  
Fiber Bragg Grating Sensors ◽  
Fbg Sensors

Recently, Fiber Bragg Grating(FBG) sensors are being used in various fields. However, it has difficulty to measure at the place where it is not possible to connect fibers each other physically. In this study, using FBG a collimator, we have measured strains with a single optical fiber with many FBG sensors where FBG sensors on one optical fiber line is installed on the beam and the other optical fiber line is connected with an optical interrogator installed at stationary side. The optical fiber lines between an optical fiber line with FBG sensors on the beam and the other optical fiber line on the stationary part are connected by the collimator which makes the use of light's unique characteristic - light travels through space. The experiment showed that the wave length of the light were changed to be linear as strains increased, and the accurate strains were measured by applying the collimator collection factor, which was proposed in this paper.

The Curing Residual Strain Monitored by Fiber Bragg Grating Sensors

2012 ◽  
Vol 605-607 ◽  
pp. 1007-1011 ◽  
Author(s):  
Heng Tian ◽  
Chun Sheng Ye ◽  
Xiu Ting Bao
Keyword(s):  
Residual Stress ◽  
Glass Transition ◽  
Fiber Bragg Grating ◽  
Bragg Grating ◽  
Gel Point ◽  
Strain Sensitivity ◽  
Curing Process ◽  
Central Wavelength ◽  
Fiber Bragg Grating Sensors ◽  
Fbg Sensors

The origin and damage of curing residual stress were firstly investigated briefly in this paper.And then Fiber Bragg Grating (FBG) sensors with different central wavelength were used to test the temperature sensitivity and the strain sensitivity. At last, the naked and encapsulated FBG sensors were layed parallelling into prepreg to monitor the whole curing process, and the results clearly showed the situation change of strain, the appearance of gel point and glass transition temperature.

scholarly journals SIMULTANEOUS STRAIN AND TEMPERATURE MEASUREMENT USING COMBINED FIBER AND FIBER BRAGG GRATING SENSORS

2021 ◽  
Vol 7 (3) ◽  
pp. 6-10
Author(s):  
Hedi Bellil ◽  
◽  
Mustafa A.G. Abushagur ◽  
Keyword(s):  
Temperature Measurement ◽  
Fiber Bragg Grating ◽  
Dynamic Range ◽  
Detection System ◽  
Processing System ◽  
Bragg Grating ◽  
Fiber Bragg Grating Sensors ◽  
Strain Change ◽  
A New Technique ◽  
Interferometric Detection

We propose here a new technique for simultaneous strain and temperature measurement using a Fiber Bragg Grating sensors. This technique employs an interferometric detection using two Fiber Bragg Gratings. A fiber Bragg grating is used as a reference while another fiber Bragg grating and a length of a bare fiber are used as the two sensing elements. As the temperature and strain change, the length of the sensing elements, (Fiber and Fiber Bragg Grating) change. These changes result in a phase and wavelength shifts. To measure these effects we use a Folded Mach Zhender interferometer, and a detection system made out of two photodiodes and data processing system. The sensitivity and dynamic range are analyzed and presented.

scholarly journals Strain Monitoring of a Composite Drag Strut in Aircraft Landing Gear by Fiber Bragg Grating Sensors

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2239 ◽  
Author(s):  
Agostino Iadicicco ◽  
Daniele Natale ◽  
Pasquale Di Palma ◽  
Francesco Spinaci ◽  
Antonio Apicella ◽  
...  
Keyword(s):  
Fiber Bragg Grating ◽  
Load Condition ◽  
Early Warning Systems ◽  
Landing Gear ◽  
Bragg Grating ◽  
Mechanical Resistance ◽  
Fiber Bragg Grating Sensors ◽  
Aircraft Landing ◽  
Aircraft Landing Gear ◽  
Fbg Sensors

This work reports on the use of Fiber Bragg Grating (FBG) sensors integrated with innovative composite items of aircraft landing gear for strain/stress monitoring. Recently, the introduction of innovative structures in aeronautical applications is appealing with two main goals: (i) to decrease the weight and cost of current items; and (ii) to increase the mechanical resistance, if possible. However, the introduction of novel structures in the aeronautical field demands experimentation and certification regarding their mechanical resistance. In this work, we successfully investigate the possibility to use Fiber Bragg Grating sensors for the structural health monitoring of innovative composite items for the landing gear. Several FBG strain sensors have been integrated in different locations of the composite item including region with high bending radius. To optimize the localization of the FBG sensors, load condition was studied by Finite Element Method (FEM) numerical analysis. Several experimental tests have been done in range 0–70 kN by means of a hydraulic press. Obtained results are in very good agreement with the numerical ones and demonstrate the great potentialities of FBG sensor technology to be employed for remote and real-time load measurements on aircraft landing gears and to act as early warning systems.

scholarly journals Fiber Bragg grating strain modulation based on nonlinear string transverse-force amplifier

2013 ◽  
Vol 38 (3) ◽  
pp. 311 ◽  
Author(s):  
Kuo Li ◽  
Man Hong Yau ◽  
Tommy H. T. Chan ◽  
David Thambiratnam ◽  
Hwa Yaw Tam
Keyword(s):  
Fiber Bragg Grating ◽  
Transverse Force ◽  
Bragg Grating ◽  
Strain Modulation ◽  
Nonlinear String

Tower Deflection Monitoring of a Wind Turbine Using an Array of Fiber Bragg Grating Sensors

2011 ◽  
Author(s):  
Hyung-Joon Bang ◽  
Hong-Il Kim ◽  
Moonseok Jang ◽  
Jae-Hung Han
Keyword(s):  
Wind Turbine ◽  
Fiber Bragg Grating ◽  
Field Tests ◽  
Element Model ◽  
Dynamic Strain ◽  
Bragg Grating ◽  
Shape Estimation ◽  
Fiber Bragg Grating Sensors ◽  
Wind Turbine Tower ◽  
Fbg Sensors

This paper introduces a fiber Bragg grating (FBG)-based sensing system for the multi-MW scale wind turbine health monitoring, and describes the results of field tests of dynamic strain monitoring and the deformed shape estimation of the wind turbine tower structure. An FBG interrogator was developed with a spectrometer-type demodulator based on a linear photo detector. Real-time shape estimation of the wind turbine tower was accomplished using strain data gathered by surface mounted fiber Bragg grating sensors. The finite element model of the wind turbine tower was created and the displacement-strain transformation (DST) on the basis of the modal approach was obtained. The time histories of the strain were gathered for the cases of blade stop and start using the FBG sensors located at the upwind side of the tower. Finally, the full deflection shapes of the tower were successfully estimated using arrayed FBG sensors.

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