• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.150-153
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• 2003

Longitudinal strains({$varepsilon}_x$) of the core and skin layers in glass fiber reinforced plastic(GFRP) cross-ply composite laminates have been studied using the embedded optical fiber sensor of totally-reflected extrinsic Fabry-Perot interferometer(TR-EFPI). Foil-type strain gauges bonded on both the upper and lower surfaces were used for the measurement of the surface strains. Both TR-EFPI sensor and strain gauge bonded on the specimen surface showed excellent agreement within -0.0086 ~ +0.0302% strain. It was shown that values of {$varepsilon}_x$ in the interior of the surface layer and the core layer measured by embedded TR-EFPI sensor was significantly higher than that of the specimen surface measured by strain gauges. The experimental results were ascertained with finite element analysis. Embedded TR-EFPI optical fiber sensor could measure accurately the internal strains which were different from the surface.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.111-114
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• 2004

Using the embedded optical fiber sensor of totally-reflected extrinsic Fabry-Perot interferometer(TR-EFPI), longitudinal strains(Ex) of the core and skin layers in glass fiber reinforced plastic(GFRP) cross-ply composite laminates have been measured. Transmission optical microscopy was employed to study the damage formation around the TR-EFPI sensor. It was observed that values of ex in the interior of the skin layer and the core layer measured by embedded TR-EFPI sensor was significantly higher than that of the specimen surface measured by strain gauges. The experimental results agreed well with those from finite element analysis on the basis of uniform stress model. Large strains in the core layer led to the occurrence of transverse cracks which drastically reduced the strain at failure of optical fiber sensor embedded in the core layer.

• 한국광학회지
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• 제6권4호
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• pp.365-372
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• 1995

취상변조기나 3*3 광결합기와 같은 특수 광부품을 사용하지 않고도 간섭형 센서의 고감도를 유지할 수 있고, 주변환경의 변화에도 영향을 받지 않는 간섭형 광섬유 센서를 위한 신호처리 기술을 소개하였다. 이 기법은 간섭형 센서의 넓은 다이나믹 레인지와 고감도를 유지한 신호처리를 위해 레이저 다이오드의 주파수 처핑을 이용하며 주변환경의 변화에 의한 측정에러를 보상하기 위해 별도의 간섭계를 기준 간섭계로 사용하였다. 새로운 신호처리 기법을 거울 내장형 Fabry-Perot(FT) 간섭계 온도센서에 적용한 결과 1cm 광섬유 FP 간섭계 센서소자로 부터 $4\times10^{-3\circ}C$(광위상 4.5mrad)의 분해능을 얻었으며 광위상 변화량의 크기가 $\pi$ 이내로 제한되지 않으므로 다이나믹 레인지가 넓은 온도센서의 구현이 가능하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.459-464
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• 2001

Vibration control of a plate using an optical fiber sensor and a PZT actuator is considered in this study. An aluminum plate with attached Extrinsic Fabry-Perot Interferometer (EFPI) and PZT actuator is prepared for experimental investigation. Vibration level of EFPI that can represent the mechanical strain without severe distortion is validated by forced vibration experiment. A numerical model of the plate is constructed based on the experimentally obtained frequency responses, and an optimal controller is designed for the multi-modal vibration suppression. It is found that the vibration level of the first three modes can be greatly reduced. The effect of low-pass filtering used to eliminate high frequency noise on the stability and control performance is also considered.

• 센서학회지
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• 제14권5호
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• pp.302-307
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• 2005

Precision displacement of less than a few nm resolution was measured in real-time using fiber optic EFPI sensor. The novel method for real-time processing of analyzing EFPI output signal was developed and verified. Linearity in the mean values of interferometric light intensity among adjacent fringes was shown and verified the sinusoidal approximation algorithm that estimates past and coming fringe values. Real-time signal processing program was developed and the intensity signal of the EFPI sensor was transformed to the phase shift with this program. The resolution below $0.36{\sim}8.6$ nm in the displacement range of $0{\sim}300{\mu}m$ was obtained. The nano-positioner with a piezoelectric actuator and the EFPI sensor system was designed and tested. The positioner successfully reached to the desired destination within 1 nm accuracy.

• 한국광학회지
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• 제16권4호
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• pp.319-325
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• 2005

고속으로 간섭피크의 위치를 찾기 위해 일련의 아날로그 신호처리를 수행하는 백색광간섭(WLI)센서용 신호처리 방식을 고안하고, 이를 WLI 온도센서 시스템에 적용하였다. 새로운 신호처리방식을 적용한 결과 잡음은 $0.019^{\circ}C/\sqrt{Hz}$로 측정되었으며, 선형성도 우수하였다. 그러나 보상용 간섭계에서의 온도변화가 센서출력의 드리프트로 나타났으며, 현재의 구성에서 드리프트의 온도 의존성은 $1.42{\mu}m/^{\circ}C$인 것으로 계산되었다. 또한 간섭피크간 간격이 광원의 가간섭길이에 비해 충분히 넓지 않은 경우 간섭무늬 피크의 간격과 신호처리기가 측정한 피크 간격과의 관계가 비선형적으로 나타날 수 있음도 확인하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.135-138
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• 2002

Experimental studies on vibration control of a composite beam with a piezoelectric actuator and an extrinsic Fabry-Perot interferometer (EFPI) have been performed using a neural network controller and an LQG controller. Vibration control performance was investigated in the nonlinear sensing range according to the vibration amplitudes. Using a neuro-controller, adaptive vibration control experiment has been performed for the structure with frequency variations, and its performance is compared with that of an LQG controller. The vibration control results show that the neuro-controller has good performance and robustness with respect to the system parameter variations.

• Current Optics and Photonics
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• 제5권6호
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• pp.721-729
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• 2021

We demonstrate a Pr³⁺:YLF 639.7-nm laser with single-frequency output based on the Q-switched pre-lase technology, pumped by a fiber-coupled GaN blue laser diode. The pre-lase technology is realized by the step-type loss of the acousto-optical Q-switched device. The conclusions of the theoretical research are verified experimentally. The mode-suppression ratio was 44 dB at the single-frequency laser output. Detection by interferometer verified the realization of the stable single-frequency laser. In addition, the emission spectrum had a linewidth of 139.9 MHz, measured by Fabry-Perot interferometer. The single-frequency laser's single-peak power was over 19.7 W with 98.8-ns pulse duration, obtained under an absorption power of 1.74 W.

• 한국소음진동공학회논문집
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• 제12권4호
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• pp.294-301
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• 2002

Vibration control of a plate using an optical fiber sensor and a piezoelectric actuator is considered in the present study, An aluminum plate with attached Extrinsic Fabry-Perot Interferometer (EFPI) and piezoelectric actuator is prepared for experimental investigation. Vibration level of EFPI that can represent the mechanical strain without severe distortion Is validated by forced nitration experiment. A linear time invariant system model is constructed based on the experimentally obtained frequency responses, and an optimal controller is designed for the multi-modal vibration suppression. Control performance is presented in frequency and time domains. It is found that the nitration level of the first three modes can be greatly reduced. The effect of low-pass filtering used to eliminate high frequency noise on the stability and control performance is also considered.

• Composites Research
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• 제17권5호
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• pp.15-24
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• 2004

유리 섬유 강화 플라스틱 직교적층판의 내부층과 표피층의 길이방향 변형률을 삽입된 절대변형 외부 페브리 페로 간섭 센서를 이용하여 측정하였다. 투과식 광학현미경을 이용하여 삽입된 A-EFPI 센서 주위의 파손거동을 관찰하였다. 시험편 표면부의 변형률 측정을 위해 포일 형식의 스트레인 게이지를 시험편 아래 위 표면부에 부착하였다. 또한 삽입된 A-EFPI 센서로 측정한 내부층과 표피층의 길이방향 변형률 값은 스트레인 게이지로 측정한 시험편 표면의 변형률 값 보다 다소 크게 나타났다. 균일 응력 모델을 기초로 한 3차원 유한요소해석을 통해 실험 결과의 타당성을 확인하였으며 내부층의 큰 변형률은 많은 횡단형 균열의 발생을 야기시켰는데 이로 인해 내부층에 삽입된 광섬유센서의 고장시 변형률이 급격히 낮아졌다.