• 한국광학회지
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• 제34권2호
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• pp.72-75
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• 2023

본 논문에서는 500 A용 bus bar에 적용할 수 있는 광섬유 브래그 격자를 이용한 전류 센서를 제안하여 실험으로 구현하였다. Bus bar와 영구자석을 광섬유 격자로 연결하여 전류 인가 시, 연결된 두 소자 사이에서 발생하는 자기력에 의해 광섬유 브래그 격자의 브래그 파장이 변하게 된다. 실험 결과 500 A 직류 전류를 인가 시 브래그 파장은 650 pm의 변화를 보였다.

• 센서학회지
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• 제30권6호
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• pp.420-428
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• 2021

In this study, linearized sweeping of a wavelength sweeping laser was realized. This technique was used to measure the strain on a fiber Bragg grating(FBG) sensor. For linear sweeping, PID control over the wavelength difference between linear and nonlinear sweeping was employed. The performance test showed that linear sweeping with a 46 nm range and a 1 kHz frequency held up well with a 99.5 % decrement in nonlinearity after the 120th feedback. When attached to a strain gage, the FBG sensor registered strain that matched the data sheet within a difference of 4.5[με]. Altogether, linear sweeping can play a leading role in monitoring a safety of large SOC structures as well as in other wavelength sweeping laser related fields.

• 한국지반공학회논문집
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• 제16권4호
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• pp.201-208
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• 2000

본 연구에서는 광섬유 센서의 일종인 격자소자(Fiber Bragg Grating sensor)를 모형말뚝에 설치하고 말뚝의 하중전이 측정을 시도하였다. 말뚝의 축방향 하중 및 주면 마찰력의 분포를 측정/분석시 사용되고 있는 스트레인 게이지에 의한 방법에 비해 광섬유 격자소자는 한 라인에 여러 개의 센서를 설치함으로써 여러 지점을 동시에 측정할 수 있다는 것과 센서의 설치가 용이하다는 장점을 가지고 있다. 본 연구에서 광섬유 격자소자와 스트레인 게이지를 모형말뚝에 함께 매설하고 재하시험중 하중전이를 측정한 결과, 두 측정치가 상당히 유사한 경향을 보였으며, 센서의 생존정도와 설치의 용이성에 있어서는 광섬유센서가 우수한 결과를 보였다. 따라서, 광섬유 격자소자의 말뚝 하중전이 측정에 대한 적용 가능성이 충분한 것으로 결론지었다.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1257-1262
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• 2008

A long-distance remote sensing of temperature and current based on a fiber Bragg grating (FBG) is proposed and demonstrated. The thermal expanding effect of the epoxy and the Er-doped fiber ring laser (EFRL) are applied to the sensor system to enhance the temperature and current sensitivity. An EFRL with a 5 km-single-mode fiber and a FBG shows a high extinction ratio of more than 60 dB and a low power fluctuation of less than 1 dB. The metal wires are used to supply the current to the sensors. When the NOA65 puts on the FBG as a thermal expanding material, the temperature and current sensitivity of the lasing wavelength shift are about $30\;pm/^{\circ}C$ and 3pm/mA, respectively. The proposed sensing scheme is useful for measurement of current or temperature at a distant object of more than several km.

• International Journal of Aeronautical and Space Sciences
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• 제2권2호
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• pp.56-64
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• 2001

An optical temperature sensor based on the etched planar waveguide Bragg grating is developed and its performance is explored using theoretical and experimental methods. The planar waveguide is designed and fabricated using optical lithography and wet chemical etching. An efficient butt coupled optical fiber is used to examine the spectral characteristics of the grating sensor, and to investigate the grating parameters. The typical bandwidth and reflectivity of the surface etched grating has been ~0.2 nm and ~7%, respectively, at a wavelength of ~1,552 nm. The temperature-induced wavelength change of the optical sensor is found to be slightly non-linear over ${\sim}200^{\circ}C$ temperature range. Theoretical models for the grating response of the sensor based on waveguide and classical laminated plate deformation theories agree with experiments to within acceptable tolerance.

• 한국항공우주학회지
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• 제32권7호
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• pp.43-50
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• 2004

변형률과 파손선호를 동시에 계측하기 위하여 이중복조기를 갖는 광섬유 브래그 격자 센서시스템을 제안하였다. 이중복조기는 가변 패브리-페로 필터를 사용하여 변형률과 같이 변화가 큰 저주파신호를 측정하는 복조기와 수동 마흐 -젠더 간섭계를 사용하여 충격이나 파손신호와 같이 미세한 크기의 고주파 신호를 측정하는 복조기로 구성된다. 제안된 광섬유 브래그 격자 센서시스템을 이용하여 인장하중을 받는 직교적층 복합재 구조물의 변형률과 파손신호를 동시에 계측할 수 있었다. 하나의 광섬유 브래그 격자 센서로 측정한 변형률과 파손신호를 분석한 결과, 복합재 시편의 90도 층에서 기지 균열이 발생할 때 급격한 변형률 변이가 유발되고, 최대 수백 킬로헤르츠에 이르는 주파수 성분을 가진 진동신 호가 발생함을 알 수 있었다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.155-160
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• 2002

A new fabrication method of FBG sensor with gage length shorter than 10 mm is introduced using the reflection prism with special coating on the surface. It is verified that the bandwidth of FBG sensor increases exponentially as the gage length of it decreases. The transverse stress and strain gradient induced by local stress concentration which occurs during curing has an influence on the FBG sensor with gage length of 2 mm less than that of 10 mm.

• 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.

• Journal of the Optical Society of Korea
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• 제3권2호
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• pp.64-68
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• 1999

The performance of a fiber Bragg grating strain sensor constructed with 3$\times$3 coupler is investigated. A 3$\times$3 coupler Mach-Zehnder (M/Z) interferometer is used as wavelength discriminator, interrogating strain-induced Bragg wavelength shifts. Two quadrature-phase-shifted intensities are synthesized from the as-coupled interferometer outputs, and digital arctangent demodulation and phase unwrapping algorithm are applied to extract the phase information proportional to strain. Due to the linear relation between the input strain and the output of quadrature signal processing, signal-fading problems eliminated. In the experiment, a fiber grating that was surface adhered on an aluminum beam was strained in different ways, and the photodetector signals were transferred and processed in a computer-controlled processing unit. A phase recovery fo 7.8$\pi$ pk-pk excursion, which corresponds to ~650$\mu$strain pk-pk of applied strain, was demonstrated. The sensor system was stable over the environmental intensi쇼 perturbations because of the self-referencing effect in the demodulation process.

• 대한기계학회논문집A
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• 제32권1호
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• pp.77-82
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• 2008

Strain-gauges have been dominantly used to measure strain at various points on a rotor, however, either a slip ring or telemetry has to be used to send sensor signals to data acquisition instruments at stationary side. Both slip ring and telemetry have numerous inherent problems which force severe limitations in real applications. This paper introduces a new rotor condition monitoring system using FBG(Fiber Bragg Grating) sensors and a rotary optical coupler. A single optical fiber with many FBG sensors is installed on the rotor and an optical dynamic interrogator is installed at stationary side. The sensor signal connection between rotating part and stationary part is made by the rotary optical coupling method which makes use of light's unique characteristic-light travels through space. Broad band light source from the interrogator travels to the optical fiber on the rotor and reflected FBG sensor signals travel back to the optical fiber on stationary side and are connected to the interrogator. Rotary optical coupler's insertion loss change due to rotation is compensated by using a reference sensor installed at the center of the rotor. The proposed system's performance has been successfully demonstrated by accurately measuring strains at 5 points on a blade rotating at high speed.