• 한국광학회지
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• 제8권5호
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• pp.415-419
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• 1997

광섬유 격자는 외부의 가해진 물리량에 대해 선형적인 응답을 하며, 광섬유 격자의 파장 인코딩 특성으로 인해 S/N비가 높은 신호 처리를 할 수 있는 장점이 있다. 본 논문에서는 편광 유지 광섬유 격자를 이용한 압력 센서에 관한 실험을 수행하였다. 편광 유지 광섬유 격자는 위상 마스크를 이용하여 Bow-Tie형 광섬유에 형성시켰는데, 편광 유지 광섬유는 두 개의 고유 편광 축을 가지므로 두 개의 브래그 peak을 가진다. 종방향 스트레인과 온도 변화에 따른 두 개의 브래그 파장 변화를 측정한 결과 각각 1.2 pm/.mu..epsilon.의 종방향 스트레인에 대한 파장 민감도와 11.4 pm/.deg. C의 온도에 대한 파장 민감도가 관측되어, 단일 모드 광섬유 격자의 보고된 값과 거의 일치하였다. 반면에 편광 유지 광섬유 격자에 횡방향 스트레스를 가하면 두 브래그 파장사이의 간격이 변화함을 관측하였고, 두 브래그 파장 간격에 대하여는 14.6 pm/N의 횡방향 스트레스에 대한 파장 민감도를 얻었다. 편광 유지 광섬유 격자 센서는 온도의 변화에 무관한 횡방향 스트레스 즉, 압력센서로 이용할 수 있음을 보였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.157-163
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• 2006

Vibration and deformation sensing control of lightweight structures using optical fiber sensor technology is introduced in this presentation. This paper shows several examples of vibration control and deformation estimation for structures using these optical fiber sensor systems. Among various optical fiber sensors, in this paper, two types of optical fiber sensors, Fabry-Perot Interferometer(EFPI) and Fiber Bragg Grating(FBG) sensors, are mainly dealt with. Fiber optic sensors show many advantages over conventional strain gages for the measurement of vibration and deformation of lightweight structures.

• 센서학회지
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• 제27권2호
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• pp.82-85
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• 2018

This paper proposes a new temperature-compensative displacement sensor with a pair of fiber Bragg gratings (FBG) attached to the inner and outer surfaces of an elastic metal band. The sensor can be also used as a temperature sensor with high sensitivity. The FBG pair shifted Bragg wavelengths in the same direction according to changes in the temperature. However, because the pressure of the metal band shifted a pair of Bragg wavelengths in the opposite direction, the displacement sensor could compensate for the effect of the temperature change in the proposed FBG pair. Results of the experiments showed that the two FBG displacement sensors responded linearly and symmetrically with respect to the displacement, and the displacement could be obtained using the difference between the two Bragg wavelengths.

• 한국소음진동공학회논문집
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• 제16권11호
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• pp.1172-1178
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• 2006

Measurement of blade strain with sensors directly installed on the blade has one critical issue, how to send the sensor signal to the ground. Strain-gauges have been dominantly used to directly measure stress of a blade and either a slip ring or a telemetry system has to be used to send measured signal to the ground. However, both systems have many inherent problems and sometimes very severe limitations to be practically used. In this paper, new on-line strain monitoring method using. FBG(Fiber Bragg Grating) sensors and a beam coupler is introduced. Measurement of rotor stress using FBG sensors is nothing new, but unlike other system which installs all necessary instruments on the rotor and use telemetry system to send data to the ground, this system makes use of light's unique characteristic - light travels through space. In this new approach, single optical fiber with many FBG sensors is installed on the blade and all other necessary instruments can be installed at ground thereby giving tremendous advantages over slip ring or telemetry system. A reference sensor is also introduced to compensate the beam coupler's transmission loss change due to rotation. The suggested system's good performance is demonstrated with experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1936-1938
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• 2002

A tunable fiber laser and the Quadrature Sampling technique are used to construct highly sensitive fiber-optic distributive Bragg grating strain sensor system. By using a wavelength-modulated fiber laser, the variations of strain-dependent Bragg wavelengths are transformed into the variations of time-domain reflection profiles. The locations of profile peaks that correspond to the applied strains are demodulated using a precise wavelength encoder that uses a fiber-optic Mach-Zehnder interferometer and Quadrature Sampling technique. With the extremely high sensitive optical encoder, we could obtain not only high sensitivity, but also very linear responses that was impossible with the conventional techniques. This paper is attempted to report the theoretical and experimental results.

• 센서학회지
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• 제9권4호
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• pp.307-315
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• 2000

FBG (Fiber Bragg Grating) hydrophone sensor의 arrays system을 구축하고, 수중에서 넓은 영역에 대한 다중점 신호 검출을 구현하기 위하여, WDM(Wavelength Division Multiplexing) 방법과 passive band-pass filter system을 이용하여, 설계 및 제작된 2개의 FBG transducers의 수중 음향파 신호 검출을 실행하였다. 실험 결과 수중에서 주파수 1.3 KHz대까지 다중점에 대하여, 주파수 신호가 각각 다른신호의 검출이 가능하였다. 따라서, 제작된 FBG transducers을 이용한 hydrophone sensor arrays의 시스템 설계가 가능함을 확인하였다.

• 한국정밀공학회지
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• 제29권10호
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• pp.1101-1109
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• 2012

Accelerometers play a key role in the structural assessment. However, the current electric type accelerometers have certain limitations to apply some structures such as heavy cabling labor, installed sea structure and sensitivity to electromagnetic fields. An optical Fiber Bragg Grating (FBG) accelerometer has many advantages over conventional electrical sensors since their immunity to electromagnetic interference and their capability to transmit signals over long distance without any additional amplifiers, and there is no corrosion from sea water. In this paper, we have developed a new FBG-based accelerometer. The accelerometer consists of two cantilevered type beams and a mass and two rollers. A bragg grating element is not directly glued to a cantilever to avoid possible non-uniform strain in the element. Instead, the bragg grating element will be attached to rotation part that rolled inducing vertical movement of the mass and support cantilever beams so that the bragg grating element is uniformly tensioned to achieve a constant strain distribution. After manufacturing, we will prove the performance and the natural frequency of the accelerometer through the experiment with a vibration shaker. The FBG-based accelerometer is developed for measuring the vibration not exceeding 50 Hz for the marine and civil structures.

• 센서학회지
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• 제17권4호
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• pp.261-266
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• 2008

In this paper, we present thermal characteristics of high-temperature measurement sensor using fiber Bragg grating(FBG), including peak reflectivity, FWHM bandwidth and various normalized refractive index change along temperature variation. The temperature stability of FBG temperature sensor can be changed by varying the refractive index change and grating length. The proposed FBG temperature sensor can measure up to about $600^{\circ}C$ and 1000 hours of heating time.

• Current Optics and Photonics
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• 제6권3호
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• pp.297-303
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• 2022

Multiple fiber Bragg gratings (FBGs) have been proposed and demonstrated for gas-flow measurements in a flow channel, using the temperature-difference method. This sensor consists of two FBG temperature sensors and two coil heaters. Coil heaters are used to heat the FBGs. The flow rate of the gas can be obtained by monitoring the difference in the Bragg-wavelength shifts of the two FBGs, which has features that exclude the effect of temperature fluctuations. In this study, experiments are conducted to measure the wavelength shift based on the flow rate, and to evaluate the gas-flow rate in a gas tube. Experimental results show that the sensor has a linear characteristic over a flow-rate range from 0 to 25 ℓ/min. The measured sensitivity of the sensor is 3.2 pm/(ℓ/min) at a coil current of 120 mA.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.215-218
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• 2005

In this research, design scheme of fiber Bragg grating(FBG) sensor system for aircraft application is suggested from the results and the know-how from the fon11er researches on structural health monitoring techniques using fiber optic sensors. Design factors to be taken into consideration were derived for both sensor parts including connection and system parts. For the stability of FBG sensor system, design requirements of temperature, vibration, humidity, electromagnetic interference were presented from U. S. military standards. The direction of software programming which increases stability and perfon11ance of the aircraft with the FBG sensor system was also examined.