• Title, Summary, Keyword: Optical Fiber Sensors

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A study on the mechanical behavior of the optical fiber sensors embedded in the composite laminate (복합재료 적층판에 삽입된 광섬유 센서의 기계적 특성에 관한 연구)

  • Shin, Kum-Cheol;Lee, Jung-Ju;Kwon, Il-Bum
    • Journal of Sensor Science and Technology
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    • v.8 no.6
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    • pp.440-447
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    • 1999
  • Tensile stress loaded on smart composite structures and thermal stress occurred during the during process of the smart composite materials with embedded optical fiber sensors affect directly the mechanical behavior of the embedded optical fiber sensors within the smart composite structures. Stress distribution within the optical fiber sensors varies with respect to the stacking sequence of the composite laminate and the coating conditions of the optical fibers. The cracks occurred within the composite laminate affect not only the fracture of the composite laminate but also the fracture of the optical fiber sensors embedded within the composite laminate. In this study, firstly, stress distribution of the optical fiber sensors embedded within the composite laminate which is subjected to the tensile and thermal stresses was analyzed using Finite Element Method. And, secondly, the effect of the stacking sequence of the composite laminate and the coating conditions of the optical fiber sensors on the stress distribution of the optical fiber sensors was investigated. Finally, the effect of the crack occurred within the smart composite laminate on the fracture behavior of the optical fiber sensors was also observed through the tensile test.

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Fabrication of Optical Fiber Gas Sensor with Polyaniline Clad

  • Lee, Yun-Su;Song, Kap-Duk;Joo, Byung-Su;Lee, Sang-Mun;Choi, Nak-Jin;Lee, Duk-Dong;Huh, Jeung-Soo
    • Journal of Sensor Science and Technology
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    • v.13 no.2
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    • pp.96-100
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    • 2004
  • Optical fiber sensors have been used to detect small amounts of chemical species. In this work, a new thin polymer-clad fiber sensor is developed. Polyaniline is chemically synthesized and thin clad layers of the polymer are easily deposited on optical fiber by dip-coating technique. The optical property of polyaniline as a sensing material is analyzed by UV-Vis-NIR. The light source is stabilized He-Ne laser at 635 nm wavelength with 1 mW power. The light power transmitted through the optical fiber is measured with a spectrophotometer. By selecting a fixed incident angle, variation of transmitted light intensity through the optical fiber can be detected as gas molecules absorbed in the polyaniline clad layer. Among the various gases, the fabricated optical fiber sensor shows good sensitivity to $NH_{3}$ gas. The optical fiber sensors was shown more improved properties than polymer based sensors which measure conductivity changes.

Fiber optic sensor technology for sensing/controlling vibration and deformation of lightweight structures (경량 구조물의 진통 및 변형 감지/제어를 위한 광섬유 센서 기술)

  • Han, Jae-Hung;Kang, Lae-Hyong;Mueller, Uwe C.;Rapp, Stephan;Baier, Horst
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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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.

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FEM Analysis of Distributed Optical Fiber Sensors for the Strain Transfer (표면부착된 분포형 광섬유 센서의 유한요소해석)

  • Kim, Sang-Hoon;Lee, Jung-Ju;Kwon, Il-Bum;Huh, Jeung-Soo
    • Journal of Sensor Science and Technology
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    • v.10 no.1
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    • pp.16-23
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    • 2001
  • Comparing with general optical fiber sensors performing localized measurement, distributed optical fiber sensors can measure along an optical fiber, and they have large measuring range. The surface-mounting method with epoxy adhesive is general in attaching optical fiber sensors to structures, This is also appliable to the structural integrity monitoring with Brillouin-scattering distributed optical fiber sensors. In this paper, Brillouin-scattering distributed optical fiber sensors, which are attached to the surface of a structure with epoxy adhesive, was verified with the finite element method. From the analysis results of strain transfer through the structure, optical fiber coating, cladding and core, the strain transfer rates were calculated. And the influence of the epoxy free-end was also studied.

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Protection Method for Diameter-downsized Fiber Bragg Gratings for Highly Sensitive Ultraviolet Light Sensors

  • Seo, Gyeong-Seo;Ahn, Tae-Jung
    • Current Optics and Photonics
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    • v.2 no.3
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    • pp.221-225
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    • 2018
  • We suggested the use of miniature hollow glass tubes having high ultraviolet (UV) transmission characteristics for the protection of optical-fiber-type UV sensors. We have recently proposed a highly sensitive optical sensor in the UV spectral range, using a fiber Bragg grating (FBG) coated with an azobenzene polymer as the photoresponsive material. In this study, we used UV-transparent miniature glass tubes to protect the etched FBG with the azobenzene polymer coating. This technique will be very useful for protecting various fiber-based UV sensors.

Monitoring of Fatigue Damage of Composite Laminates Using Embedded Intensity-Based Optical Fiber Sensors (광강도형 광섬유 센서를 이용한 복합재 적충판의 피로손상 감시)

  • 이동춘;이정주;서대철
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.124-127
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    • 2000
  • In this study, a technique for monitoring of fatigue damage of composite laminates by measuring the stiffness change using embedded intensity-based optical fiber sensors was investigated. Firstly, the underlying measurement principle and structure of intensity-based sensors and then a simple stiffness conversion process was explained. The monitoring technique was evaluated by fatigue tests of composite laminates with an embedded intensity-based sensor. From the test results, the response of the intensity-based sensor showed good correlation with that of surface mounted extensometer. Therefore, it can be concluded that the intensity-based sensors have good potential for the monitoring of fatigue damage of composite structures under fatigue loading. In addition, it could be confirmed that the intensity-based sensors have higher resistance to fatigue than the commercial electrical strain gauge.

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Interferometric Optical Fiber Sensors for Health Monitoring Systems of Structures (구조물 유지관리용 간섭형 광섬유 센서)

  • 김기수
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.355-359
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    • 1995
  • In this paper, the possibility of interferometric shows very good linearity to the strain. Fiber optic sensors have various merits for health monitoring systems. They are very small in diamerter. So, they don't give any disturbance in strength to the structures, Optical fiber sensors are innert to the electro-magnetic field. Therefore, fiber optic sensors give us a good solution to the electro-magnetic field. Therefore, fiber optic sensors give us a good solution to the maintainance systems of the structures, which are exposed to the electric fields, such as bridges, dams and buildings.

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Measurement of Pile Load Transfer using Optical Fiber Sensors (광섬유 센서에 의한 말뚝 하중전이 측정)

  • 오정호;이원제;이우진
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.397-404
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    • 1999
  • It is essential to measure load transfer mechanism of pile to check the appropriateness of assumptions made for design purpose and to continuously monitor the behavior of pile foundation. Through many attempts to monitor the behavior of super-structure in civil engineering area using several optical fiber sensors have been made, application of optical fiber sensor technology on pile foundation has not been tried up to now. Load transfer of model piles during compression loading was measured by optical fiber sensors and compared with the measurement by strain gauges. Fiber Bragg Grating(FBG) sensor system was used since it has many advantages, such as easy multiplexing, high sensitivity, and simple fabrication. Besides the model pile tests, uniaxial tension test of steel bar and compression tests of mortar specimen were carried out to evaluate the performance of FBG sensors in embedded environments. The shift of refilming wavelength due to the strain in FBG sensor is converted to the strain at sensor location and the dependence between them is 1.28 pm/${\mu}$ strain. FBG sensors embedded in model pile showed a better survivability than strain gauges. Measured results of load transfer by both FBG sensors and strain gauges were similar, but FBG sensors showed a smoother trend than those by strain gauge. Based on the results of model pile test, it was concluded that the use of FBG sensor for strain measurement in pile has a great potential for the analysis of pile load transfer.

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Begavuir if Embedded intrinsic Fabry-Perot Optical Fiber Sensors in the Cement Concrete Structure (콘크리트에 매설된 구조물 유지관리용 Fabry-Perot 광섬유 센서의 거동)

  • Kim, Ki-Soo;Yoo, Jae-Wook;Lee, Seung-jae;Choi, Long;Lee, Woong-Jong;Kim, Jong-Woo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.295-299
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    • 1996
  • Intrinsic Fabry-Perot Optical fiber sensors were embedded to tensile side of the 20cm$\times$20cm$\times$150cm cement concrete structures. The sensors were attached to the reinforcing steels and then, the cement concretes were applied. It took 30 days for curing the specimens. After that, the specimens were tested with 4-point bending method by universal testing machine. Strains were measured and recorded by the strain gauges embedded near optical fiber sensors. Output data of fiber sensor showed good linearity to the strain data from the strain gauges up 2000microstrain. The optical fiber sensors showed good response after yielding of structure while embedded metal film strain gauges did not show any response. We also specimens were broken down. In conclusion, the optical fiber sensors can be used as elements of health monitoring systems for cement concrete infra-structures.

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Development of optical dual-sensors for submersion monitoring using zigbee-based wireless sensor networks (지그비 기반 센서 네트워크를 이용한 침수감지용 광 이중센서 개발)

  • Key, Kwang-Hyun;Kim, Hyung-Pyo;Sohn, Kyung-Rak
    • Journal of Sensor Science and Technology
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    • v.19 no.3
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    • pp.184-190
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    • 2010
  • In this paper, a remote submersion warning system based on multi-mode optical fiber(MMF) sensors and a wireless sensor network(WSN) are proposed. To improve the reliability and stability of the sensors, the dual optical fiber sensors combined to the optical coupler are demonstrated. A slave zigbee as a wireless sensor module was used as a platform to monitor and record the signal from the MMF sensors and then transmits these information to a master zigbee wirelessly. The monitoring system running the $LabVIEW^{(R)}$ software was connected to the internet to support the short message service(SMS) through extensible markup language(XML) web service. No matter where the managers are, they can always receive the real-time remote-monitoring data for safety check.