• Title/Summary/Keyword: distributed optical fiber

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Light Coupling and Propagation Between a Fiber and a Dielectric Slab with a Conductor Cladding (측면 연마된 광섬유와 완전도체면 아래의 유전체 사이에서의 결합과 전파특성의 해석)

  • Kwon, Kwang-Hee;Yoon, Ki-Hong;Kim, Jeong-Hoon;Song, Jae-Won;Park, Euy-Dong;Son, Seok-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.2A
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    • pp.70-79
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    • 2003
  • A theoretical presentation of evanescent coupling is offered with respect to the refractive indexes between a side polished optical fiber and an infinitely planar waveguide with a conductor cladding(PWGCC). The PWG is suspended at a constant distance from an unclad fiber core and attached with the perfect conductor(PEC) on one side. The behavior of the distributed coupler is examined using a coupled mode model, which takes account of the two dimensions of the waveguide configuration. The coupling and propagation of light were found to depend on both the relationship between the refractive index values of each structure and the configuration of the side polished fiber used in the PWGCC. The spreading of light in the unconfined direction of the PWGCC is described in terms of a simple geometrical interpretation of the synchromization condition that is in agreement with a previous investigation of the problem based on the coupled-mode theory(CMT). The power of the light propagation in the fiber decreased exponentially along the fiber axis as it was transferred to the PWGCC.

Monitoring the Structural Behavior of Reinforced RC Slabs Using Optical Fiber-embedded CFRP Sheets (광섬유 매립 CFRP 시트를 활용한 RC 슬래브의 구조적 거동 모니터링 기술 개발)

  • Kim, Jaehwan;Jung, Kyu-San;Kim, Byeong-Cheol;Kim, Kun-Soo;Park, Ki-Tae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.42 no.3
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    • pp.311-322
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    • 2022
  • This study performed 4-point flexural tests of reinforced concrete to which was attached a distributed optical fiber sheet and carbon fiber reinforced polymer (CFRP) sheets in order to assess the effect of the CFRP sheets and the applicability of a BOTDR sensor simultaneously. To evaluate the reinforcing effect, various degrees of CFRP sheet attachment were manufactured, and to evaluate the sensing ability, strains obtained from a BOTDR sensor were compared with strains measured from electric resistance strain gauges that were attached to the concrete surface. From the results, the reinforcing effects were evidently different according to the attachment type of the CFRP sheets, and it was confirmed that the main influencing factor on the reinforcing effect was the type of attachment rather than the attachment area. The reinforced concrete structural behavior was visualized with strains measured from the BOTDR sensor as load increased, and it was identified that load was concentrated in the CFRP reinforced area. Strains from the BOTDR sensor were similar to those from the electric resistance strain gauge; thereby a BOTDR sensor can be effective in the analysis of structural behaviorsof massive infrastructure. Finally, the strain from a BOTDR sensor was high where CFRP sheet fall-off occurs, and it would therefore be efficient to track local damage locations of CFRP sheets by utilizing a BOTDR sensor.

Species Concentration Measurement Using Diode Laser Absorption Spectroscopy (I) (다이오드 레이저를 이용한 광흡수 농도 계측 기법 (I))

  • Ahn, Jae-Hyun;Kim, Yong-Mo;Kim, Se-Won
    • Journal of the Korean Society of Combustion
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    • v.9 no.3
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    • pp.27-35
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    • 2004
  • Diode laser absorption sensors are advantageous because they may provide fast, sensitive, absolute, and selective measurements of species concentration. These systems are very attractive for practical applications owing to its compactness, resonable cost, robustness, and ease of use. In addition, diode lasers are fiber-optic compatible and thus enable simultaneous measurements of multiple species along a line-of-sight. Recent advances of room-temperature, near-IR and visible diode laser sources for telecommunication, optical data storage applications make it possible to be applied for combustion diagnostics based on diode laser absorption spectroscopy. Therefore, combined with fiber-optics and high sensitive detection strategies, compact and portable sensor systems are now appearing for variety of applications. The objectives of this research are to develope a new gas sensing system and to verify feasibility of this system. Wavelength and power characteristics as a function of injection current and temperature are experimentally found out. Direct absorption spectroscopy has been demonstrated in these experiments and has a bright prospect to this diode laser system.

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Reinforcing effect of CFRP bar on concrete splitting behavior of headed stud shear connectors

  • Huawen Ye;Wenchao Wang;Ao Huang;Zhengyuan Wang
    • Steel and Composite Structures
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    • v.48 no.2
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    • pp.131-143
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    • 2023
  • The CFRP bar was used to achieve more ductile and durable headed-stud shear connectors in composite components. Three series of push-out tests were firstly conducted, including specimens reinforced with pure steel fibers, steel and CFRP bars. The distributed stress was measured by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) optical fiber sensor with high spatial resolution. A series of numerical analyses using non-linear FE models were also made to study the shear force transfer mechanism and crack response based on the test results. Test results show that the CFRP bar increases the shear strength and stiffness of the large diameter headed-stud shear connection, and it has equivalent reinforcing effects on the stud shear capacity as the commonly used steel bar. The embedded CFRP bar can also largely improve the shear force transfer mechanism and decrease the tensile stress in the transverse direction. The parametric study shows that low content steel fibers could delay the crack initiation of slab around the large diameter stud, and the CFRP bar with normal elastic modulus and the standard reinforcement ratio has good resistance to splitting crack growth in headed stud shear connectors.

Measurement of Exhaust Gas Concentration using Wavelength Modulation Spectroscopy (파장 변조 기법을 이용한 연소배기 가스의 계측)

  • Kim, Dong-Hyuck;Kim, Se-Won;Shin, Myung-Chul;Kim, Yong-Mo
    • 한국연소학회:학술대회논문집
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    • 2006.10a
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    • pp.97-103
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    • 2006
  • This work forcus on the development of gas sensor that measure the concentrations of exhaust gas using diode laser. Each diode laser for exhaust gas measurement is set to work at near-IR using both DA and WMS methods. Also use of fiber-coupled optical elements makes such a sensor rugged and easy to align. On-line data acquisition and processing can be performed with a PC running LabVIEW software, and absorption signals are measured simultaneously by multiplexing method. Finally, It were experimentally compared WMS (Wavelength Modulation Spectroscopy) with DA (Direct Absorption) for the accuracy.

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Diode-Laser Absorption Sensors for measurement of combustion Gas (연소배기 가스의 계측을 위한 다이오드 레이저 센서)

  • Shin, Myung-Chul;Kim, Se-Won;Kim, Dong-Hyuck
    • Journal of the Korean Society of Combustion
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    • v.11 no.3
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    • pp.26-35
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    • 2006
  • This work forcus on the development of gas sensor that measure the concentrations of exhaust gas using diode laser, Each diode laser for exhaust gas measurement is set to work at near-IR using both DA and WMS methods. Also use of fiber-coupled optical elements makes such a sensor rugged and easy to align. The results showed that gas concentrations of $O_2$, CO, $CO_2$, NO are accurately measured within ${\pm}2%$ error. The application of WMS method increased the beam intensity 2-3 times higher than DA method. It were experimentally compared WMS (Wavelength Modulation Spectroscopy) with DA (Direct Absorption) for the accuracy.

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Growth and upconversion properties of erbium doped $LiNbO_3$ single crystal fibers ($Er^{3+}$ 첨가 $LiNbO_3$ fiber 단결정의 성장 및 upconversion 특성)

  • Yang, Woo-Seok;Suh, Su-Jeong;Lee, Jong-Ho;Tsuguo Fukuda;Yoon, Dae-Ho
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • 1999.06a
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    • pp.321-335
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    • 1999
  • Erbium(Er) doped LiNbO3(Er:LiNbO3) single crystal gibers were grown free of cracks along the c-axis by micro-pulling down method. the Er3+ concentration was distributed homogeneously along the growth axis. The samples for optical characterization were cut from as-grown single crystal fibers and polished. When the 980 nm light was incident on the sample, upconversion phenomena were observed at the green range of wavelength 510~570 nm. In addition, the intensity of upconversion was remarkably increased by increasing the concentration of Er2O3 dopant in as-grown Er:LiNbO3 crystals.

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A study on the temperature characteristic in OPGW link due to meteorological effects (기상조건에 따른 OPGW회선온도특성 연구)

  • Yoon, Il-Hwan;Lee, Jae-Jo;Huh, Young;Yoo, Jae-Tack
    • Proceedings of the KIEE Conference
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    • 1997.11a
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    • pp.581-583
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    • 1997
  • In this paper, we present a temperature characteristic in OPGW link due to meteological effects. we measured a temperature on a 2km OPGW using a distributed optical fiber temperature sensing system. The measurement showed that OPGW temperature was several degrees lower to ambient atmospheric temperature in the nighttime and several degrees higher than that in the daytime due to sunshine. It'll be used for a reference data of the transmission delay variations in OPGW link due to meteorological effects.

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Application of Supervisory System in Extra High Voltage Cable (초고압 케이블의 송전 감시 시스템 소개 및 기술동향)

  • Kwon, Byung-Il;Nam, Jeong-Se;Kang, Deok-Hwan
    • Proceedings of the KIEE Conference
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    • 1997.07e
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    • pp.1791-1793
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    • 1997
  • Since Korea was initiated a industrialization, many transmission lines have been installed to meet the increasing demand for the electric power. In large city, underground transmission lines were widely installed because of the environmental issue. But there have been appeared many failures on the lines, such as the external scar of cable, a fire in the culvert, overheating of cable, and so on. There have been many studies to monitor them and improve the reliability of the power supply. As a method monitoring the lines, a DTS(Distributed Temperature Sensor) system is developed and applied. This system monitors the lines and predicts the failures, using a optical fiber sensor. This paper describes this DTS system and its application for the underground transmission lines.

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Monitoring System of Rock Mass Displacement and Temperature Variation for KURT using Optical Sensor Cable (광섬유센서케이블을 이용한 지하연구시설의 지반변위 및 온도변화 감시시스템 구축)

  • Kim, Kyung-Su;Bae, Dae-Seok;Koh, Yong-Kwon;Kim, Jung-Yul
    • The Journal of Engineering Geology
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    • v.19 no.1
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    • pp.63-70
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    • 2009
  • The optical fiber cable acting as a sensor was embedded in the underground research tunnel and portal area in order to monitor their stability and the spatial temperature variation. This system includes two types of sensing function to monitor the distributed strain and temperature along the line, where sensor cable is installed, not a point sensing. According to the results of one year monitoring around the KURT, there is no significant displacement or movement at the tunnel wall and portal slope. However, it would be able to aware of some phenomena as an advance notice at the tunnel wall which indicates the fracturing in rockmass and shotcrete fragmentation before rock falls accidently as well as movement of earth slope. The measurement resolution for rock mass displacement is 1 mm per 1 m and it covers 30 km length with every 1m interval in minimum. In temperature, the cable measures the range of $-160{\sim}600^{\circ}C$ with $0.01^{\circ}C$ resolution according to the cable types. This means that it would be applicable to monitoring system for the safe operation of various kinds of facilities having static and/or dynamic characteristics, such as chemical plant, pipeline, rail, huge building, long and slim structures, bridge, subway and marine vessel. etc.