• Title, Summary, Keyword: FBG

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Temperature Compensation Technique for Steel Sleeve Packaged FBG Strain Sensor and Its Application in Structural Monitoring

  • Yun, Ying-Wei;Jang, Il-Young
    • Journal of the Korean Society of Hazard Mitigation
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    • v.8 no.6
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    • pp.1-5
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    • 2008
  • As bare Fiber Bragg Grating (FBG) sensors are very fragile, bare FBG without encapsulation is not properly applied in practical infrastructures directly due to the harsh environment in practical engineering. Steel sleeve packaged FBG strain sensor is widely used in civil engineering. Since FBG senses both strain and temperature simultaneously, for accurate measurement of strain, temperature compensation for FBG strain sensors is indispensable. In this paper, based on the FBG's strain and temperature sensing principles, the temperature compensation techniques for steel sleeve packaged FBG sensors are brought forward. And the experiment of concrete early-age shrinkage monitoring by dual FBG sensors is carried out to test the feasibility of the temperature compensation technique.

Reflection Signal Analysis for Time Division Multiplexing of Fiber Optic FBG Sensors (광섬유 FBG 센서의 시간 분할 다중화를 위한 반사 신호의 분석)

  • Kim, Geun-Jin;Kwon, Il-Bum;Yoon, Dong-Jin;Hwang, Du-Sun;Chung, Young-Joo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.1
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    • pp.6-12
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    • 2010
  • Fiber optic sensor using fiber Bragg grating(FBG) probes is used for monitoring strain and temperature distributed on the wide surfaces of large structures. In this paper, in order to use many FBG probes in one optical fiber line, we propose a complex multiplexing technology which is composed of two techniques, one is time division multiplexing and another is wavelength division multiplexing. However, we only investigate the characteristics of time division multiplexing because FBG sensors basically can be operated by wavelength division multiplexing. We calculate the optimal reflectivities and the lengthwise location of five FBG probes in serial connection in order to obtain the unique reflected intensities from the FBG probes. We fabricate five FBG probes with the reflectivities of 13%, 16%, 25%, 40% and 80%, which are determined by the theoretical calculation, and observe the signal reflected from each FBG in the time domain from the experiment. There are differences between experimental and theoretical results caused by the signal noise and the differences of reflectivities of FBG probes. But the experimental results shows the reflected signals of five FBG probes which prove the availability of complex multiplexing.

Temperature Compensation Technique for Steel Sleeve Packaged FBG Strain Sensor in Structural Monitoring (Steel Sleeve Packaged FBG 변형률센서를 이용한 구조물 모니터링에서의 온도보정 기술)

  • Jang, Il-Young;Yun, Ying-Wei;Ryu, Jeong-Su;Park, Jin-Young
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.805-808
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    • 2008
  • Due to the fact that bare FBG sensors are very fragile, bare FBG sensor is not properly applied in practical infrastructures as it is not suitable to the rudeness of construction. Therefore packaged FBG sensors are developed for construction application. Since FBG senses strain and temperature simultaneously, temperature compensation for FBG strain sensors is indispensable. In this paper, temperature compensation techniques for steel sleeve packaged FBG sensors are brought forward. And its application on monitoring concrete beam was carried to test the feasibility of the temperature compensation technique. Temperature compensation technique used in this paper is feasible to be extended to structure health monitoring in civil engineering especially in large infrastructures etc.

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Measurement of Residual and Internal Strain of 3-D Braided Hybrid Composite using Embedded FBG Sensor (FBG 센서를 삽입한 3차원 브레이드 하이브리드 복합재료의 잔류변형률 및 내부변형률 측정)

  • Jung, Kyung-Ho;Kim, Don-Gun;Kang, Tae-Jin
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.21-24
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    • 2005
  • Three dimensional circular braided Glass/Aramid hybrid fabric/epoxy resin composite was fabricated. FBG sensor was embedded along the braid yam in order to monitor the internal dimensional changes of the 3-D braid composite. The amount of cure and thermal shrinkage of epoxy resin was also determined using FBG sensor system. FBG sensors with different grating length were embedded and their response were compared. The thermo-optic coefficient of FBG sensor was measured by several preliminary experiments. The internal strain that measured by FBG sensor and electric strain gauge was compared during compressive test. The released residual strain of the fabricated tubular composite was estimated using cutting method. The internal strain of the composite was estimated using FBG sensor system, and the result was compared with the value from electric strain gauge. It was found that FBG sensor system is a very useful technique to investigate inside region of complicated structure.

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A Study on the High-Temperature Characteristics of a Tunable All-Optical Filter Using Fiber Bragg Grating (FBG를 이용한 파장가변 형 전광 필터의 고온 특성에 관한 연구)

  • Son, Yong-Hwan;Yang, Se-Hoon;Kim, Hyun-Seung;Han, Sang-Kook
    • Journal of IKEEE
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    • v.14 no.4
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    • pp.263-269
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    • 2010
  • In this paper, we present high temperature characteristics of a tunable all-optical filter using fiber Bragg grating(FBG) filter in Ge doped and Ge & B co-doped fiber, including peak reflectivity, bandwidth and various normalized refractive index change with temperature variation. The reflection spectrum of a FBG filter with refractive index change is affected by its thermal stability. Consequently Ge doped FBG tunable filter has a better thermal stability than Ge & B co-doped FBG tunable filter. Also, both FBG tunable filters show good thermal stability up to about $500^{\circ}C$.

Implementation of FBG Sensor Network System for Monitoring Structure Deformation (구조물 변형 모니터링을 위한 FBG센서 네트워크 시스템 구현)

  • Park, Jang-Sik;Park, Keun-Soo
    • The Journal of the Korea institute of electronic communication sciences
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    • v.9 no.8
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    • pp.841-846
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    • 2014
  • FBG sensors are mainly used to measure deformation of structures such as tunnels, bridges and ships. In this paper, an interrogator of FBG sensors is developed and implemented to measure the status of structures. A developed interrogator includes CAN wired and Zigbee wireless communication for remote monitoring. Strain of structure is measured using shift of wavelength of reflected light from FBG sensor. A digital signal controller is used to process signals of a FBG sensor and transmit data for remote monitoring. As a result of experiment, developed interrogator is effective to measure deformation of structures.

FBG Optical Fiber Sensors Embedded in Fiber Reinforced Polymer Composite Reinforcing Bars (철근대용 FRP 복합재에 삽입된 FBG 센서의 변형률에 관한 연구)

  • Kim, Myong-Se;Cho, Hyung-Sik;Cho, Sung-Kyu;Yoon, Jae-Jun;Baek, Hyun-Deok;Kim, Ki-Soo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.2
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    • pp.124-133
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    • 2007
  • In our research, we focused on the FBG sensor system which is one of the fiber optic sensor system. The FBG sensor system is used for structural measurements. The problem of FBG sensor is very thin and weak. The methods that can protect FBG optical fiber sensor front outside forces such as the impacts are investigated. The FBG sensor embedded in the fiber reinforced composites which can replace the reinforcing steel bars in concretes can be applied to the concrete structures by embedding to the composite materials. The progresses in tensile strength of FBG sensor embedded in the reinforcing FRP bars in the concrete structures compare to plain FBGs were observed and the good long term durability is expected.

Development of Wireless Measurement System for Bridge Using PDA and Fiber Optical Sensor (PDA와 광섬유 센서를 이용한 교량의 무선계측 시스템 개발)

  • Kwak, Kae-Hwan;Hwang, Hae-Sung;Jang, Hwa-Sup;Kim, Woo-Jong;Kim, Hoi-OK
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.13 no.1
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    • pp.88-96
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    • 2009
  • This study proposes a wireless measurement system that is a new safety management system by using an FBG sensor and a PDA. The sensor part has many advantages of implementing a wireless measurement system, and the study emploies an FBG-LVDT sensor, FBG-STRAIN sensor, FBG-TEMP sensor, and FBG-ACC sensor, using FBG sensors. Also, the study show a configuration of a signal process system for operating a wireless transmission system of FBG sensors applied to the signal process system, and engrafted the cutting edge information technology industry in order to display from a remote distance using a PDA. In order to verify the applicability of the developed FBG sensors and wireless measurement monitoring system to the field, their accuracy, and usability, the study has conducted a static and dynamic test to a bridge in the field. The study made an assessment of service for the vibration of the bridge by applying dynamic data measured by an FBG-LVDT sensor and FBG-ACC sensor to Meister's curve and prepared methods for assessing the vibration of the bridge by proposing a standard of vibration limitation given the service of vibration of the bridge. As a follow up for this study, it would be necessary to set up an overall model for the standard of service assessment established in this study.

Development of A FBG Sensor Interrogator for Detecting Strain and Performance Comparison of Peak Detection Algorithms (변형 검출을 위한 FBG 센서 인테로게이터 개발과 피크검출 알고리즘 성능 비교)

  • Park, Keun-Soo;Park, Jang-Sik
    • The Journal of the Korea institute of electronic communication sciences
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    • v.8 no.8
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    • pp.1137-1142
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    • 2013
  • FBG sensors are mainly used to measure strain and temperature of structures. In this paper, an interrogator of FBG sensors is developed and implemented to measure the crack of structures using FPGA and DSP. Developed interrogator consists of an optical source, an optical circulator, an optical grating and a CCD sensor and controller. The spectrum of the reflected light from the FBG sensor is analyzed and peak wavelength is detected. Next, strain of structure can be measured using shift of peak wavelength. Centroid algorithm and Gaussian fitting which are mainly applied to detect peak wavelength of the interrogator are compared in this paper. As a result of experiment, Gaussian fitting is suitable for a developed interrogator.

Effects of Cyclic Thermal Load on the Signal Characteristics of FBG Sensors Packaged with Epoxy Adhesives (주기적인 반복 열하중이 패키징된 FBG 센서 신호 특성에 미치는 영향)

  • Kim, Heonyoung;Kang, Donghoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.4
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    • pp.313-319
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    • 2017
  • Fiber optics sensors that have been mainly applied to aerospace areas are now finding applicability in other areas, such as transportation, including railways. Among the sensors, the fiber Bragg grating (FBG) sensors have led to a steep increase due to their properties of absolute measurement and multiplexing capability. Generally, the FBG sensors adhere to structures and sensing modules using adhesives such as an epoxy. However, the measurement errors that occurred when the FBG sensors were used in a long-term application, where they were exposed to environmental thermal load, required calibration. For this reason, the thermal curing of adhesives needs to be investigated to enhance the reliability of the FBG sensor system. This can be done at room temperature through cyclic thermal load tests using four types of specimens. From the test results, it is confirmed that residual compressive strain occurs to the FBG sensors due to an initial cyclic thermal load. In conclusion, signals of the FBG sensors need to be stabilized for applying them to a long-term SHM.