• 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.

• 한국철도학회논문집
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• 제12권1호
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• pp.104-109
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• 2009

광섬유 센서 중 대표적인 FBG센서를 철도 구조물에 실제 적용하기 위해서는, 센서 자체의 기계적 강도에 대한 내구성이 확증되어야 하고, 철도 구조물의 파손 시까지 FBG 센서가 측정치를 측정할 수 있도록 충분한 변형률 한도를 가져야만 한다. 본 논문에서는 FBG센서의 기계적 강도에 영향을 미치는 변수들에 대한 연구를 수행하였다. 기계적 인장 강도 시험을 위한 시험 셋업을 구성하였고, 광섬유의 광민감성을 증진하기 위해 사용된 수소함침법과 코팅층을 제거하기 위한 피복 제거기법을 사용한 FBG 센서의 인장 강도 변화를 시험 및 통계 처리를 이용하여 측정하였고, 강도저하가 거의 없음을 보여 주었다.

• Current Optics and Photonics
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• 제4권6호
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• pp.477-482
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• 2020

Recently, one of the authors has been reported an optically tunable fiber Bragg grating (FBG) with a photomechanical polymer. It was based on a typical FBG with a downsized diameter of 60 ㎛, coated with azobenzene-containing polymer material. Azobenzene is a well-known reversibly photomechanical stretchable material under ultraviolet (UV) light. The small part of the functional-coating region on the FBG absorbed UV light, which pulled the UV-exposed part of the grating. It was selectable as tunable FBG or tunable chirped FBG, by adjusting the position of UV exposure on the grating. As proof of concept for the tunable FBG device, the characteristics just including UV-induced center-wavelength shift and spectral-width changes of the device were reported. In this paper, we report for the first time that the microactuator makes it possible to control the spectral shape of the FBG reflection, according to the specifications (shape and intensity) of the UV beam that reaches the FBG coated with the azobenzene polymer. In addition, we provide the group-delay profiles for the chirped FBG, so that the sign of its dispersion (normal or anomalous) can be tailored by simply selecting the moving direction of the UV light's displacement in the experiment.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3039-3045
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• 2023

Fiber-reinforced polymer (FRP) composites are considered suitable candidates for structural materials of spacecrafts due to their excellent properties of high strength, light weight, and corrosion resistance. An online health monitoring method for FRP composites must be applied to space structures. However, the application of existing health monitoring methods to space structures is limited due to the harsh space environment. Here, carbon fiber-reinforced polymer (CFRP) composites embedded with fiber Bragg grating (FBG) sensors were prepared to explore the feasibility of strain monitoring using embedded FBG sensors in γ-radiation environment. The analysis of the influence of radiation on the strain monitoring demonstrated that the embedded FBG can be successfully applied to the health monitoring of FRP composites in radiation environment.

• 센서학회지
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• 제9권4호
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• pp.281-287
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• 2000

FBG (Fiber Bragg Grating)를 이용한 광섬유 수중 음향센서의 주파수 특성을 개선하기 위하여, 새롭게 고안된 음향- 광변환기(acoustic-optic converter)에 진동판과 FBG의 일체형을 개발하므로써, 1.4 KHz대 까지의 주파수와 음파 지향성 검출이 가능하였다.

• Composites Research
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• 제17권4호
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• pp.32-39
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• 2004

여러 광섬유 센서 중에서, FBG 센서는 다중화의 큰 장점으로 인해 다른 광섬유 센서에 비해 더 활발히 연구가 진행되고 있다. 최근, FBG 센서의 적용 연구는 부착보다는 복합재료 내부에 삽입 적용되는 경우가 많아지고 있다. 하지만, FBG 센서의 삽입 시 복합재료의 강화섬유와 평행하지 않게 삽입할 경우 발생하는 센서의 복굴절 현상으로 인해 삽입에 많은 제한이 있었다. 본 연구에서는 제작이 간편하고 다중화에 영향을 받지 않으며 복합재료 내부에 삽입 시 복굴절의 영향으로부터 보다 안정한 다양한 격자 길이의 FBG 센서 제작 기법에 대해 연구하였다. 그리고, 2 가지 종류의 복합재료에 대한 성형 모니터링을 통해 제작된 센서의 신호 특성에 대해 고찰하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.416-420
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• 2002

This Paper describes a matched-filter type strain sensor system using optical fiber Bragg grating (FBG) sensor. Matched-filter type uses another wavelength-matched FBG filter to track wavelength shift in the FBG sensor. Filter FBG is attached on a fiber stretcher and stretched by PZT actuator. To overcome the nonlinearity and hysteresis of the PZT actuator that degrades system accuracy, a string resonator which can measure an absolute strain is employed. And the effect of vibration modes on string resonator is investigated particularly regarding its sensitivity and stability.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.25-28
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• 2005

The optical fiber is known for the proper sensor which can accomplish the structural health monitoring, Fiber Bragg Grating sensors are being studied more than any other fiber optic sensors due to good multiplexing capabilities. But because the signal stability of FBG sensors can be influenced by the strain gradient, it needs to analyze signal of FBG sensors. Particularly acoording to strain gradient induced by structural geometry or cracks, the spectrum peak of the FBG sensor signal can be split easily. In this paper, the spectrum analysis of the FBG sensor signal was performed and the region of embedment of FBG sensors was determined in $H_2$ pressure vessel by numerical method.

• 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.

• 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.