• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.330-331
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• 2003

분포형 광섬유 센서시스템은 일정한 길이의 연속적인 광섬유 및 광케이블을 매질로 하여 길이 방향에서 생기는 투과율 또는 산란 특성의 변화를 통해 물리량의 변화와 그 위치를 감지하는 시스템을 말한다. 그 중에서 광섬유 내부의 브릴루앙 산란효과를 이용하여 광케이블 주위에 진동, 압력등에 매우 민감한 분포형 광섬유센서를 구성하고 외부로부터의 침입 유무와 위치를 파악함과 동시에 주요시설물의 감시 및 진단이 가능하도록 한다. (중략)

• 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.

• Optical Science and Technology
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• v.17 no.1
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• pp.7-17
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• 2013

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.218-219
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• 2001

본 실험에서는 RF 소자들과 650 nm InGaAIP FP LD를 사용하고 이득스위칭에 의하여 선폭이 35psec 되는 극초단 광펄스를 생성하였다. 또한 이렇게 생성된 극초단 광펄스를 이용하여 언덕형 굴절률 분포를 가지는 다중모드 광섬유의 대역폭을 빠른 푸리에 변환(Fast Fourier Transform)으로 계산하였다 따라서 본 실험에서 이용된 언덕형 굴절률 분포를 갖는 다중모드 광섬유의 대역폭은 670 MHz.km로 측정되었다.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.127-135
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• 2006

We implement numerical simulations for the distributed optical fiber sensor system that uses the spatially-selective Brillouin scattering, by treating the superposition of the optical-frequency-modulated pump/probe waves in the time domain. We obtain temporal and spatial distributions of Brillouin gain for various cases. Simulations are applied to the case of concatenated optical fibers of different kinds and the case of distributed temperature along the fiber, which give reasonable results for the distributed sensor. The result of using a triangular wave instead of a sinusoidal one as a modulation waveform shows that the triangular wave modulation has an advantage in spatial resolution.

• Composites Research
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• v.31 no.6
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• pp.429-434
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• 2018

We investigate strain transmissions of a surface bonded distributed optical fiber sensor considering strain variation according to positions. We first derive a strain transmission ratio depending on a wavelength of a strain distribution of the host structure from an analysis model. The strain transmission ratio is compared with numerical results obtained from the finite element method using ABAQUS. We find that the analytical results agree well with the numerical results. The strain transmission ratio is a function of a wavelength, i.e. the strain transmission ratio decreases (increases) as the wavelength of the host strain decreases (increases). Therefore, if an arbitrary strain distribution containing various wavelengths is given to a host structure, a distorted strain distribution will be observed in the distributed optical fiber sensor compare to that of the host structure, because each wavelength shows different strain transmission ratio. The strain transmission ratio derived in this study will be useful for accurately identifying the host strain distribution based on the signal of a distributed optical fiber sensor.

• 전기산업
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• v.6 no.1
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• pp.60-65
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• 1995

• Tunnel and Underground Space
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• v.21 no.1
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• pp.1-10
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• 2011

In these days, the development of optical fiber sensor technology is so remarkable that it can measure various physical and chemical quantities ranging from a few millimeters to over several kilometers. In addition, it is attempted to assess the structural integrity of the state of the advanced technologies and existing structures such as ships, aircrafts, and bridges. This paper introduced the case histories of the measuring technology of optical fiber applied on structures such as roads and tunnels. The case history using OTDR (Optical Time Domain Reflectometery) was also introduced in this paper. Measurement of the pre-convergence of a tunnel is essential to assess the safety of a tunnel and understand the geological conditions ahead of an advancing tunnel. Therefore, the pre-convergence measuring technology using OTDR is expected to substitute conventional measuring techniques.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.223-230
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• 2006

We demonstrate a distributed fiber sensor system based on spatially-selective Brillouin scattering, using a single laser diode as a light source whose optical frequency is directly modulated by the injection current. The pump and the counter-propagating probe lights, which are sinusoidally frequency-modulated, are superposed in the fiber so that stimulated Brillouin scattering takes places only at a specific location along the fiber. Brillouin gain peak position is controlled by varying the modulation frequency. Distributions of Brillouin shift frequency are measured for the case of concatenated optical fibers of two different kinds and also for the case of temperature distribution. The temperature coefficient of the Brillouin shift frequency is measured to be $1.33MHz/^{\circ}C$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.8
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• pp.816-822
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• 1992

In this paper, propagation characteristics of trapezoidal-shaped segmented core single mode fibers is investigated theoretically as a function of relative Index difference ratio( =p) under the condition of zero dispersion at i=1.,isrm, and bending loss of trape zoidalshaped segmented core single mode fiber is greatly decreased less than that of conventional single mode fibers ( triangular Index, dual shape core). And mode field distribution In core Is confined 2H% stronger than that of a tapezoidal Index fiber In addition, the advantages of trapezoldal-shaped segmented core fibers are compared with t hose of conventional triangular -shaped segmented core fibers.