• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.157-163
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• 2006

Vibration and deformation sensing control of lightweight structures using optical fiber sensor technology is introduced in this presentation. This paper shows several examples of vibration control and deformation estimation for structures using these optical fiber sensor systems. Among various optical fiber sensors, in this paper, two types of optical fiber sensors, Fabry-Perot Interferometer(EFPI) and Fiber Bragg Grating(FBG) sensors, are mainly dealt with. Fiber optic sensors show many advantages over conventional strain gages for the measurement of vibration and deformation of lightweight structures.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.1
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• pp.1-5
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• 2010

Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect or monitor preexisting defects and leaks in the vessel structures. A Bragg grating based acoustic emission sensor system is developed. Various type of fiber Bragg grating sensor including the variable length of sensing part was fabricated and prototype sensor system was tested by using PZT pulser and pencil lead break sources. Two types of sensor attachment were used. First, the fiber Bragg grating sensor was attached fully to the surface using bonding agent. Second one is that one part of fiber was attached to the surface partly by bonding and the other part of fiber will be act as a cantilever. That is, the resonant frequency of the fiber Bragg grating sensor will depend on the length of sensing part. The final goal of the sensor system is to provide on-line monitoring of cracks or leaks in reactor vessel head penetration of nuclear power plants.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1936-1938
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• 2002

A tunable fiber laser and the Quadrature Sampling technique are used to construct highly sensitive fiber-optic distributive Bragg grating strain sensor system. By using a wavelength-modulated fiber laser, the variations of strain-dependent Bragg wavelengths are transformed into the variations of time-domain reflection profiles. The locations of profile peaks that correspond to the applied strains are demodulated using a precise wavelength encoder that uses a fiber-optic Mach-Zehnder interferometer and Quadrature Sampling technique. With the extremely high sensitive optical encoder, we could obtain not only high sensitivity, but also very linear responses that was impossible with the conventional techniques. This paper is attempted to report the theoretical and experimental results.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.201-208
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• 2000

Axial load distribution in model piles was measured by fiber Bragg Grating(FBG) sensor to investigate a possibility of analyzing the load transfer mechanism by Fiber Optic sensor system. Since FBGs of different wave lengths can be multiplexed in an optical fiber, the installation of sensor system and the measurement of strains are relatively simple, compared with consisting strain gages. In this study, FBG sensors and electric strain gages were embedded in the same piles and the distributions of load transfer by two sensor systems were measured. It was observed from the test results that the variations of axial load by both systems showed insignificant difference and that the measurements by FBG were smoother than those by strain gage. Under the environments of laboratory testing, survival rate of embedded FBG system was higher than that of strain gage. Therefore, it was concluded that the use of FBG sensor has a great potential for the measurement of load transfer for pile foundation.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.215-218
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• 2005

In this research, design scheme of fiber Bragg grating(FBG) sensor system for aircraft application is suggested from the results and the know-how from the fon11er researches on structural health monitoring techniques using fiber optic sensors. Design factors to be taken into consideration were derived for both sensor parts including connection and system parts. For the stability of FBG sensor system, design requirements of temperature, vibration, humidity, electromagnetic interference were presented from U. S. military standards. The direction of software programming which increases stability and perfon11ance of the aircraft with the FBG sensor system was also examined.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.1 s.94
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• pp.3-11
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• 2005

For monitoring of the civil and building structure, optical fiber sensors are very convenient. The fiber sensors are very small and do not disturb the structural properties. They also have several merits such as electro-magnetic immunity, long signal transmission, good accuracy and multiplexibility in one sensor line. Strain measurement technologies with fiber optic sensors have been investigated as a part of smart structure. In this paper, we investigated the possibilities of fiber optic sensor application to the monitoring of beam-column joints of structures. We expect that the fiber optic sensors replace electrical strain gauges. The commercial electric strain gauges show good stability and dominate the strain measurement market. However, they lack durability and long term stability for continuous monitoring of the structures. In order to apply the strain gauges, we only have to attach them to the surfaces of the structures. In this paper, we investigate the possibility of using fiber optic Bragg grating sensors to joint structure. The sensors show nice response to the structural behavior of the joint.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.595-601
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• 2003

For monitoring of the civil and building structure, optical fiber sensors are very convenient. The fiber sensors are very small and do not disturb the structural properties. They also have several merits such as electro-magnetic immunity, long signal transmission, good accuracy and multiplicity of one sensor line. Strain measurement technologies with fiber optic sensors have been investigated as a part of smart structure. In this paper, we investigated the possibilities of fiber optic sensor application to the monitoring of beam-column joints of structures. We expect that the fiber optic sensors replace electrical strain gauges. The commercial electric strain gauges show good stability und dominate tile strain measurement market. However, they lack durability and long term stability for continuous monitoring of the structures. In order to apply the strain gauges, we only have to attach them to the surfaces of the structures. In this paper, we investigate the possibility of using fiber optic Bragg grating sensors to joint structure. The sensors show nice response to the structural behavior of the joint.

• Korean Journal of Optics and Photonics
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• v.34 no.2
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• pp.72-75
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• 2023

In this paper, a fiber-optic current sensor for a bus bar conductor based on the fiber Bragg grating (FBG) is proposed and demonstrated experimentally. The metal bus bar and a magnet are connected to each other through an FBG and the Bragg wavelength of the FBG is changed by magnetic force between the two connected devices. The experimental results showed that the Bragg wavelength of an FBG shifted by 650 pm as the 500 A direct current was applied to the bus bar.

• International Journal of Aeronautical and Space Sciences
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• v.2 no.2
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• pp.56-64
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• 2001

An optical temperature sensor based on the etched planar waveguide Bragg grating is developed and its performance is explored using theoretical and experimental methods. The planar waveguide is designed and fabricated using optical lithography and wet chemical etching. An efficient butt coupled optical fiber is used to examine the spectral characteristics of the grating sensor, and to investigate the grating parameters. The typical bandwidth and reflectivity of the surface etched grating has been ~0.2 nm and ~7%, respectively, at a wavelength of ~1,552 nm. The temperature-induced wavelength change of the optical sensor is found to be slightly non-linear over ${\sim}200^{\circ}C$ temperature range. Theoretical models for the grating response of the sensor based on waveguide and classical laminated plate deformation theories agree with experiments to within acceptable tolerance.

• Journal of IKEEE
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• v.8 no.1 s.14
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• pp.117-120
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• 2004

We demonstrate a fiber-optic sensor scheme, capable of the simultaneous measurement of strain and temperature using a single fiber Bragg grating written in an erbium: ytterbium-doped fiber. This novel and compact fiber grating based sensor scheme can be used for synchronous measurement of strain and temperature over ranges of $1100\;{\mu}{\varepsilon}$ and $50-180\;^{\circ}C$ with rms errors of $55.8\;{\mu}{\varepsilon}$ and $3^{\circ}C$, respectively. The simple and low-cost sensor approach has a considerable potential, particularly for wide-range strain sensing applications in which high resolution is not required.