• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 하계학술발표회 논문집
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• pp.399-400
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• 2006

Etched fiber Bragg grating, Sensitivity of fiber-Bragg-grating sensors to index of surrounding, Hybridization of DNA

• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.925-931
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• 2009

This paper reports a preliminary experimental investigation and characterization of an optical fiber-based submersion sensor system for applications in water flooding and leakage. The sensor system comprises a multi-mode fiber spliced with fiber Bragg grating and an intensity-based interrogator. Submersion tests were conducted in water-air and Glycerin-air environments. By the refractive index of the fiber-probe surrounding materials, the reflectance and the detecting power level is determined. When the probe is dipped into the water, the optical output power dramatically decreases from -7.5dBm to -17.5dBm. But, the center of Bragg wavelength is not affected in spite of external material changes. Temporal response characteristics of the sensor system is investigated to verify the real-time reaction. When the probe is immersed into the liquid, there is no transition time.

• Current Optics and Photonics
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• 제2권3호
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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.

• 센서학회지
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• 제27권6호
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• pp.403-406
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• 2018

We have investigated a fiber-optic sensor for detecting the hydrogen gas dissolved in insulation oil based on a palladium (Pd)-coated fiber Bragg grating (FBG). As the palladium absorbs the hydrogen gas dissolved in the insulation oil, its volume expands and the Bragg wavelength shifts to a longer wavelength. The experimental results showed that the Bragg wavelength of FBG increased to 70 nm when the concentration of hydrogen dissolved in the insulation oil was 409 ppm.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.423-428
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• 2001

Fiber Bragg Grating sensors currently attract a great deal of attentions, mainly due to their potentials in health monitoring for civil structures and composite materials. In this experimental study, the strains of reinforced concrete beams were measured to failure In order to verify the applicability of FBG(Fiber Bragg Grating) sensors. The FBG sensors were directly buried in concrete and attached to re-bars at the time of fabrication. In this experiment, the changes of strains in concrete and re-bars were successfully measured as the movement in wavelength of light signals. The FBG sensors may be a very effective tool to investigate the behavior inside of reinforced concrete structures.

• Journal of the Optical Society of Korea
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• 제9권3호
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• pp.123-128
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• 2005

An electrically controllable fiber Bragg grating inscribed in a hydrogen-loaded standard single-mode fiber with liquid-crystal cladding is presented. Control of the optic axis of liquid crystals by means of external electric fields results in the change of reflectivity and Bragg wavelength of the grating. The increase of surrounding refractive index of a fiber makes effective refractive index of a propagation mode higher, which results in high field confinement and longer Bragg wavelength. The reduction of the fiber diameter by chemical etching process improves the long-range ordering of liquid-crystal molecules and reduces controlling voltage. The tunable ranges of reflectivity and Bragg wavelength of the liquid crystal-cladding fiber Bragg grating were $\~4.6dB\;and\;\~0.3nm$, respectively.

• 대한전자공학회논문지SD
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• 제41권3호
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• pp.39-44
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• 2004

광섬유 브래그 격자 센서는 광섬유의 코어의 굴절률 변조에 의해서 제작되며, 이 센서는 외부의 스트레인에 따라 브래그 파장이 변화하게 된다. 본 논문에서는 광섬유 브래그 격자 센서를 파장 영역에서 신호처리 할 수 있는 방법에 대하여 연구하였다. SLD와 F-P 필터로 구성된 sweep 반도체 광원과 F P 필터내의 PZT의 히스테리시스 특성을 보상하기 위한 에탈론 필터와 장기 계측을 위해 절대 파장 기준으로 온도 안정된 광섬유 브래그 격자를 사용하였다. 콘크리트 흄관에서 FBG 센서의 스트레인 응답 특성을 전기저항 센서와 비교하였다. 그리고 광섬유 격자 센서를 이용하여 장거리 변위의 측정 가능성을 확인하였다.

• 비파괴검사학회지
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• 제21권2호
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• pp.147-151
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• 2001

광섬유 센서는 구조물에 대한 비파괴적인 측정이 가능하고, 전자파에 의한 간섭이 발생하지 않으므로, 전자파 장애의 영향을 무시할 수 있는 장점이 있다. 또한 구조물 건조시 콘크리트 같은 대상체에 광섬유를 내장시킬 경우에는 검사시 대상체를 파괴시키지 않고서도 대상체의 손상여부와 역학적 거동을 측적 및 해석할 수 있는 비파괴 검사기술이다. 특히 광섬유 브래그 격자 센서는 그러한 대상체에 대한 비파괴 검사를 수행하는데 가장 적합한 센서이다. 광섬유 브래그 격자는 특정파장의 빛을 반사 또는 제거시키는 특성을 지니고 있으며, 스트레인 같은 물리량이 광섬유 브래그 격자에 가해지면, 반사되는 빛의 중심파장이 이동하여 이를 통해 물리량을 측정할 수 있다. 정 동적 스트레인을 측정할 수 있는 광섬유 브래그 격자 센서는 건축물이나 토목구조물 등의 안전 진단(health monitoring)을 위해 사용되고 있으며, 최근에는 도로나 교량과 같은 토목 구조물로의 응용에 있어서 필수적인 동적 스트레인의 측정에 대해 그 관심이 집중퇴고 있다. 본 연구에서는 패브리-페로(Fabry-Perot) 필터를 이용하여 다중점에서 동적 스트레인을 측정할 수 있는 센서 시스템을 제작하였으며, 제작된 센서 시스템을 모의 구조물(외팔보)에 적응하여 모의 구조물에 가해지는 정적, 동적 스트레인을 측정하였다. 측정 결과는 기존의 전기적 센서와 유사하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.153-158
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• 2009

Stable and tunable dual-wavelength erbium-doped fiber ring laser(EDFL) using a single fiber Bragg grating(FBG) and two coil heaters is proposed and demonstrated. Installing two identical coils into a single FBG, the FBG is symmetrically divided into two different portions. While a current supply to the coil, the refractive index of the FBG under the coil is changed. The FBG can operate as a joint of two different FBGs. Due to the thermo-optic effect of a fiber, the resonance wavelength split into two peaks. The spacing between two adjacent channels was changed as much as the difference of heating power. It was tuned up to 3 nm of wavelength under the electrical power with a 1000 mW. Moreover, the lasing wavelength can be individually tuned without influencing to the adjacent channel.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.329-334
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• 2011

We proposed a poly-dimethylsiloxane (PDMS)-coated fiber Bragg grating (FBG) temperature sensor for enhancing temperature sensitivity. By embedding the bare FBG in a temperature-sensitive elastomeric polymer, the temperature sensitivity of the proposed structure could be effectively improved by 4.2 times higher than those of the conventional bare-type FBG sensors due to the high thermal expansion coefficient of the PDMS. We analyzed the temperature-sensitivity enhancement effect with the increased Bragg wavelength shift in our structure and dependence on the temperature sensitivity with respect to the cross-section area of the PDMS.