• Title/Summary/Keyword: FBG

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Fabrication of a Temperature-Compensating FBB Sensor for Measurement of Mechanical Strain (온도 보상형 Double FBG센서의 제작과 기계적 변형률 측정시험)

  • Jung, Dal-Woo;Kwon, Il-Bum;Choi, Nak-Sam
    • Journal of the Korean Society for Nondestructive Testing
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    • v.25 no.5
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    • pp.356-361
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    • 2005
  • A temperature-compensating double fiber Bragg grating(FBG) sensor having two different FBGs in one fiber line was proposed for real time measurement of mechanical normal strain in structures. Measurement of mechanical strains of the aluminum beam surface by the double FBG sensor was performed under various thermal conditions, and the results were compared with those of electrical resistance strain gage. The FBG sensor fabricated in this study was able to measure accurately the mechanical strains without containing any thermal strain component.

Spectral-shape-controllable Chirped Fiber Bragg Grating with a Photomechanical Microactuator: Simulation and Experiment

  • Moon, Jong-Ju;Ko, Youngmin;Park, Su-Jeong;Ahn, Tae-Jung
    • Current Optics and Photonics
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    • v.4 no.6
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    • pp.477-482
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    • 2020
  • Recently, one of the authors has been reported an optically tunable fiber Bragg grating (FBG) with a photomechanical polymer. It was based on a typical FBG with a downsized diameter of 60 ㎛, coated with azobenzene-containing polymer material. Azobenzene is a well-known reversibly photomechanical stretchable material under ultraviolet (UV) light. The small part of the functional-coating region on the FBG absorbed UV light, which pulled the UV-exposed part of the grating. It was selectable as tunable FBG or tunable chirped FBG, by adjusting the position of UV exposure on the grating. As proof of concept for the tunable FBG device, the characteristics just including UV-induced center-wavelength shift and spectral-width changes of the device were reported. In this paper, we report for the first time that the microactuator makes it possible to control the spectral shape of the FBG reflection, according to the specifications (shape and intensity) of the UV beam that reaches the FBG coated with the azobenzene polymer. In addition, we provide the group-delay profiles for the chirped FBG, so that the sign of its dispersion (normal or anomalous) can be tailored by simply selecting the moving direction of the UV light's displacement in the experiment.

Static Behavior of Hollow Cantilever Beam Using Multiplexed FBG Sensors (다중화된 FBG센서를 이용한 중공 내민보의 정적 거동 분석)

  • Lee, Tae-Hee;Kang, Dong-Hoon;Chung, Won-Seok;Mok, Young-Jin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.4
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    • pp.316-322
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    • 2009
  • This paper presents a preliminary study to monitor the lateral behavior of pile foundation using multiplexed fiber Bragg grating(FBG) sensors. In the Preliminary study, an 1.7 meter long cantilever beam with the shape of square hollow box was fabricated and tested under the static loading. Four FBG sensors were multiplexed in a single optical fiber and installed into the top and bottom of the cantilever beam. The strains are directly measured from FBG sensors followed by curvature calculations based on the plane section assumption. Vertical deflections are then estimated using the regression analyses based on the geometric relationships. It has been found that excellent correlation with conventional sensing system was observed. The success of the test encourages the use of the FBG sensing system as a monitoring system for pile foundations. However, further consideration should be given in the case of the sensor malfunction for the practical purpose.

Structural health monitoring of a newly built high-piled wharf in a harbor with fiber Bragg grating sensor technology: design and deployment

  • Liu, Hong-biao;Zhang, Qiang;Zhang, Bao-hua
    • Smart Structures and Systems
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    • v.20 no.2
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    • pp.163-173
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    • 2017
  • Structural health monitoring (SHM) of civil infrastructure using fiber Bragg grating sensor networks (FBGSNs) has received significant public attention in recent years. However, there is currently little research on the health-monitoring technology of high-piled wharfs in coastal ports using the fiber Bragg grating (FBG) sensor technique. The benefits of FBG sensors are their small size, light weight, lack of conductivity, resistance corrosion, multiplexing ability and immunity to electromagnetic interference. Based on the properties of high-piled wharfs in coastal ports and servicing seawater environment and the benefits of FBG sensors, the SHM system for a high-piled wharf in the Tianjin Port of China is devised and deployed partly using the FBG sensor technique. In addition, the health-monitoring parameters are proposed. The system can monitor the structural mechanical properties and durability, which provides a state-of-the-art mean to monitor the health conditions of the wharf and display the monitored data with the BIM technique. In total, 289 FBG stain sensors, 87 FBG temperature sensors, 20 FBG obliquity sensors, 16 FBG pressure sensors, 8 FBG acceleration sensors and 4 anode ladders are installed in the components of the back platform and front platform. After the installation of some components in the wharf construction site, the good signal that each sensor measures demonstrates the suitability of the sensor setup methods, and it is proper for the full-scale, continuous, autonomous SHM deployment for the high-piled wharf in the costal port. The South 27# Wharf SHM system constitutes the largest deployment of FBG sensors for wharf structures in costal ports to date. This deployment demonstrates the strong potential of FBGSNs to monitor the health of large-scale coastal wharf structures. This study can provide a reference to the long-term health-monitoring system deployment for high-piled wharf structures in coastal ports.

Reliability Evaluation of Fiber Optic Sensors Exposed to Cyclic Thermal Load (주기적인 반복 열하중에 노출된 광섬유 센서의 신뢰성 평가)

  • Kim, Heon-Young;Kang, Donghoon;Kim, Dae-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.36 no.3
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    • pp.225-230
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    • 2016
  • Fiber Bragg grating (FBG) sensors are currently the most prevalent sensors because of their unique advantages such as ease of multiplexing and capability of performing absolute measurements. They are applied to various structures for structural health monitoring (SHM). The signal characteristics of FBG sensors under thermal loading should be investigated to enhance the reliability of these sensors, because they are exposed to certain cyclic thermal loads due to temperature changes resulting from change of seasons, when they are applied to structures for SHM. In this study, tests on specimens are conducted in a thermal chamber with temperature changes from -$20^{\circ}C$ to $60^{\circ}C$ for 300 cycles. For the specimens, two types of base materials and adhesives that are normally used in the manufacture of packaged FBG sensors are selected. From the test results, it is confirmed that the FBG sensors undergo some degree of compressive strain under cyclic thermal load; this can lead to measurement errors. Hence, a pre-calibration is necessary before applying these sensors to structures for long-term SHM.

Feasibility Study of Embedded FBG Sensors for the Smart Monitoring of High Pressure Composite Vessel (복합재 고압용기의 스마트 모니터링을 위한 FBG 센서의 삽입 적용성에 관한 연구)

  • Park, Sang-Wuk;Park, Sang-Oh;Kim, Chun-Gon
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.04a
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    • pp.33-36
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    • 2005
  • In this research, for the smart health monitoring of the hydrogen storage high pressure composite vessel, the feasibility study of an embedded fiber Bragg grating(FBG) sensor is carried out. To verify strain measurement in various temperature environment which is needed for the hydrogen pressure vessel, tensile test of a composite specimen with both an embedded FBG sensor and a strain gauge is made in low temperature. Before we try a real-size hydrogen storage pressure vessel, a small & cheap composite pressure vessel having the same structure is fabricated with embedded FBG sensors and tested. In the case of an aluminum liner inside the vessel, survivability of FBG sensors at the interface is lower than the other areas.

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Monitoring of Temperature and Strain Variation with FBG Sensors (FBG 센서를 활용한 온도와 스트레인 변화 모니터링)

  • Ko, Ki-Han;Park, Young;Cho, Yong-Hyeon;Jung, Ho-Sung;Cho, Yong-Suk;Choi, Won-Seok
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.3
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    • pp.218-221
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    • 2009
  • This paper reports on measurement method for the fiber optic strain monitoring of overhead contact line systems of trains, We used FBG (Fiber Bragg Grating) sensors to measure the strain variation of overhead contact line. FBG sensors can sensitively measure the variation of strain and! or temperature by the shift wavelength of reflected wave according to the lattice variation during the measurement. FBG sensor were attached on the contact line and connected to the monitoring system with optical fibers. The monitering system with FBG sensors showed very good sensitivity to measuring strain variation and this system could be applied to the overhead contact line of KTX (Korea Train eXpress).

이중파장 광섬유 브래그 격자센서(FBG)를 이용한 고해상도 광대역 측정

  • Ali, Mumtaz;Sin, Seo-Yong;Jeong, Tae-Gyeong;Lee, Sang-Hyeon;Kim, Eun;Ju, Gwan-Sik
    • Proceedings of the Optical Society of Korea Conference
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    • 2009.02a
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    • pp.221-222
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    • 2009
  • 이 논문에서는 기존의 FBG 광센서와는 달리 이중파장 구조를 갖는 FBG 센서를 제안하여 기 존의 FBG 센서가 측정할 수 있는 범위를 획기적 으로 증대시킴을 보이고자 한다. 고해상도의 광범 위한 지역 측정은 두 가지의 광대역 광원을 이용 하는 매트릭스 구조의 FBG를 이용해 구성하였으며, 두 광원을 사용하는 통합시스템은 도파로 열격자(AWG)로 구성되어 있다.

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A Study on the develoment of FBG hydrophone (FBG(Fiber Bragg Grating)Hydrophone 개발에 관한 연구.)

  • Kim kyung-Bok;Kim Sung-Soon;Jung Jae-Myung;Kwack Kae-Dal;Lee Sang-Bae;Choi Sang-Sam
    • Proceedings of the Acoustical Society of Korea Conference
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    • spring
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    • pp.407-410
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    • 2000
  • In the using of FBG developed in home land, We designed and manufactured three types of FBG sound transducers the first in Korea. Analysizing special character's on FBG transducers manufactured, we made an experiment on respective frequency peculiarities in the water and we made an experiment on multi-point signal detection and direction about optional acoustic underwater. As the experimental result, we made it possible acoustic detection on frequency peculiarities to maximum 18k0z and made certain the system arrary possibilities, from now on we prepared the practical use study possibilities.

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Internal Strain Monitoring of Filament Wound Pressure Tanks using Embedded Fiber Bragg Grating Sensors (삽입된 광섬유 브래그 격자 센서를 이용한 필라멘트 와인딩된 복합재료 압력탱크의 내부 변형률 모니터링)

  • Kim, C.U.;Park, S.W.;Park, S.O.;Kim, C.G.;Kang, D.H.
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.04a
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    • pp.17-20
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    • 2005
  • In-situ structural health monitoring of filament wound pressure tanks were conducted during water-pressurizing test using embedded fiber Bragg grating (FBG) sensors. We need to monitor inner strains during working in order to verify the health condition of pressure tanks more accurately because finite element analyses on filament wound pressure tanks usually show large differences between inner and outer strains. Fiber optic sensors, especially FBG sensors can be easily embedded into the composite structures contrary to conventional electric strain gages (ESGs). In addition, many FBG sensors can be multiplexed in single optical fiber using wavelength division multiplexing (WDM) techniques. We fabricated a standard testing and evaluation bottle (STEB) with embedded FBG sensors and performed a water-pressurizing test. In order to increase the survivability of embedded FBG sensors, we suggested a revised fabrication process for embedding FBG sensors into a filament wound pressure tank, which includes a new protecting technique of sensor heads, the grating parts. From the experimental results, it was demonstrated that FBG sensors can be successfully adapted to filament wound pressure tanks for their structural health monitoring by embedding.

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