• Title/Summary/Keyword: fiber Bragg grating

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A Fiber Laser Spectrometer Demodulation of Fiber Bragg Grating Sensors for Measurement Linearity Enhancement

  • Kim, Hyunjin;Song, Minho
    • Journal of the Optical Society of Korea
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    • v.17 no.4
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    • pp.312-316
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    • 2013
  • A novel fiber-optic sensor system is suggested in which fiber Bragg grating sensors are demodulated by a wavelength-sweeping fiber laser source and a spectrometer. The spectrometer consists of a diffraction grating and a 512-pixel photo-diode array. The reflected Bragg wavelength information is transformed into spatial intensity distribution on the photo-diode array. The peak locations linearly correspond to the Bragg wavelengths, regardless of the nonlinearities in the wavelength tuning mechanism of the fiber laser. The high power density of the fiber laser enables obtaining high signal-to-noise ratio outputs. The improved demodulation characteristics were experimentally demonstrated with a fiber Bragg grating sensor array with 5 gratings. The sensor outputs were in much more linear fashion compared with the conventional tunable band-pass filter demodulation. Also it showed advantages in signal processing, due to the high level of photo-diode array signals, over the broadband light source system, especially in measurement of fast varying dynamic physical quantities.

Strain Sensitivity of Fiber Optic Bragg Grating Sensor (광섬유 브래그 격자 센서의 변형률 감지도)

  • Kwon, Il-Bum;Choi, Man-Yong;Kim, Min-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.3 no.3
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    • pp.237-243
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    • 1999
  • Recently, there has been considerable interest in the development of fiber-optic sensors based on fiber Bragg gratings (FBGs), which can be made into Ge-doped fiber's core by UV phase mask or holographic methods. A good sensitivity and small size of this sensor make it an ideal candidate for distributed sensing in smart structures or other structural monitoring applications. In this study, fiber optic Bragg grating sensor, which could be applied to measure the absolute strains, was constructed and the strain sensitivity of this sensor was investigated in order to apply to the structural health monitoring. Fiber Fabry-Perot (FFP) filter has been used to detect the optical signals instead of optical spectrum analyzer. It has been convenient to determine the structural strains from the output signal of FBGs. The fiber optic Bragg grating sensor was attached on the aluminum beam near the electrical strain gage to measure the same strain. The relationship between strain and fiber signal was linearly fitted. The strain sensitivity of the fiber optic Bragg grating sensor was determined as $l.57{\mu}{\varepsilon}/{\mu}sec$ from the aluminum beam test.

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Development of Flexible Force Sensor Using Fiber Bragg Grating for Tactile Sensor and Its Evaluation (광섬유 브래그 격자를 이용한 촉각 센서용 유연 단축 힘 센서의 개발 및 평가)

  • Heo, Jin-Seok;Lee, Jung-Ju
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.2 s.179
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    • pp.51-56
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    • 2006
  • This paper shows the development of flexible force sensor using the fiber Bragg grating. This force sensor consists of a Bragg grating fiber and flexible silicone rubber (DC184, Dow corning co. Ltd). This sensor does not have special structure to maximize the deflection or elongation, but have good sensitivity and very flexible characteristics. In addition, this sensor has the immunity to the electro magnetic field and can be multiplexed easily, which is inherited from the characteristics of fiber Bragg grating sensor. In the future, this sensor can be utilized the tactile sensor system minimizing the sensor size and developing the fabrication method.

Hydrogen Sensor Based on Palladium-Attached Fiber Bragg Grating

  • Lee, Sang-Mae;Sirkis, Jim-S.
    • Journal of the Optical Society of Korea
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    • v.3 no.2
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    • pp.69-73
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    • 1999
  • This paper demonstrated the performance of a palladium wire hydrogen sensor based on a fiber Bragg grating as a means of developing a quasi-distributed hydrogen sensor network capable of operating at cryogenic temperatures. The new approach employing a fiber Bragg grating based palladium hydrogen sensor described in this study is advantageous over other traditional hydrogen sensors because of the multiplexing capability of fiber Bragg gratings. The sensitivity of the hydrogen sensor at room temperature is approximately 2.5 times that of the hydrogen sensor at cryogenic temperatures.

Simultaneous Measurement of Temperature and Refractive Index of a Medium Using by a Side-Polished Fiber Containing a Fiber Bragg Grating (광섬유 브래그 격자가 포함된 측면 연마된 광섬유를 이용한 매질의 온도와 굴절률 동시 측정)

  • Kim, Kwang Taek
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.8
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    • pp.513-517
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    • 2015
  • We proposed and demonstrated a simultaneous measurement method to detect the refractive index and temperature of a medium using a side-polished fiber involving FBG (fiber Bragg grating). The temperature of a medium was obtained by using the Bragg wavelength shift of FBG, while the refractive index of medium were calculated by using the transmission loss. The Bragg wavelength is independent on the refractive index of the covering medium placed on surface of side-polished fiber, while the transmission loss at off-Bragg wavelength highly depends on the environmental temperature because of thermo-optic effect of the medium.

Humidity Sensor Using Polyimide Film Coated Fiber Bragg Grating (폴리이미드가 코팅된 광섬유 브래그 격자를 이용한 습도센서)

  • Jae Chang Yang;Gun Pyo Kim;Kwang Taek Kim
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.36 no.6
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    • pp.594-597
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    • 2023
  • We have proposed and demonstrated a fiber optic RH (relative humidity) sensor based on fiber Bragg grating covered with a polyimide film. As the polyimide film absolves the moisture in the air, its volume expands. As a result, the grating period of the FBG (fiber Bragg grating) covered with a polyimide film becomes wide and the Bragg wavelength is shifted. The sensor is implemented by fixing a 30 ㎛ thickness polyimide film on the surface of an optical fiber grating using an adhesive, and the characteristics of the device according to humidity are analyzed. The fabricated FBG RH sensor showed a high sensitivity of 0.0186 nm/RH% and a wide measurement range from 30% to 90%. The influence of environmental temperature on the characteristics of the RH sensor was also measured and analyzed. The feasibility of commercialization is presented.

Uniform-fiber-Bragg-grating-based Fabry-Perot Cavity for Passive-optical-network Fault Monitoring

  • Xuan, Zhang;Ning, Ning;Tianfeng, Yang
    • Current Optics and Photonics
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    • v.7 no.1
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    • pp.47-53
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    • 2023
  • We propose a centralized passive-optical-network monitoring scheme using the resonance-spectrum properties of a Fabry-Perot cavity based on fiber Bragg gratings. Each cavity consists of two identical uniform fiber Bragg gratings and a varying cavity length or grating length, which can produce a unique single-mode resonance spectrum for the drop-fiber link. The output spectral properties of each cavity can be easily adjusted by the cavity length or the grating length. The resonance spectrum for each cavity is calculated by the transfer-matrix method. To obtain the peak wavelength of the resonance spectrum more accurately, the effective cavity length is introduced. Each drop fiber with a specific resonance spectrum distinguishes between the peak wavelength or linewidth. We also investigate parameters such as reflectivity and bandwidth, which determine the basic performance of the fiber Bragg grating used, and thus the output-spectrum properties of the Fabry-Perot cavity. The feasibility of the proposed scheme is verified using the Optisystem software for a simplified 1 × 8 passive optical network. The proposed scheme provides a simple, effective solution for passive-optical-network monitoring, especially for a high-density network with small end-user distance difference.

Fabrication optimization of Fiber Bragg gratings (광섬유 브래그 격자(Fiber Bragg grating) 제작과 제작 조건에 따른 특성 향상)

  • Choi, Bo-Hun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.14 no.7
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    • pp.1680-1686
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    • 2010
  • Optical fiber Bragg grating to have the lowest transmitivity at 1549.9nm wavelength was fabricated using a Gaussian distributed KrF Eximer laser of 248nm lasing wavelength and a phase mask of 1.072um period. The proper alignment of an optic setup to fabricate fiber gratings was investigated and the reproductivity of the grating fabrication was examined using the obtained optimum fabrication condition in this experiment.

Deformation Measuring of Tensegrity Structure by Optical Fiber Bragg Grating Sensor (광섬유 브래그 격자 센서를 이용한 텐서그리티 구조물의 변형 계측)

  • Lee, Seung-Jae
    • Journal of Korean Association for Spatial Structures
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    • v.8 no.6
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    • pp.95-100
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    • 2008
  • The object of this paper is to verify possible to monitor the deformation of cable in the tensegrity structure. Also, always monitoring system of tensegrity structure using Fiber Bragg Grating Sensor is described. We carry out experiments with measuring deformation of cable in the tensegrity structure based on loading conditions. In the result of experiment, the Fiber Bragg Grating Sensors shows accurate response to the loading conditions. Therefore, we can make sure the possibility of Fiber Bragg Grating Sensor in health monitoring of the cable structure like tensegrity structure.

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External Cavity Laser with a Tunable Chirped Fiber Bragg Grating for Adjusting the Number of Longitudinal Laser Mode (외부 공진기 레이저의 발진 모드 수 조절에 관한 연구)

  • Yook, Tae-Kyung;Lee, Kyung-Shik;Park, Manh-Yong;Kim, Byoung-Whi
    • Korean Journal of Optics and Photonics
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    • v.16 no.5
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    • pp.406-410
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    • 2005
  • we propose an external cavity laser which can adjust the number of longitudinal laser mode by using a tunable chirped fiber. Bragg grating. By inducing a tunable temperature gradient in a uniform fiber Bragg grating, the bandwidth of the unform fiber Bragg grating can be tuned. With the chirped fiber Bragg grating as an external reflector of the external cavity laser, the number of longitudinal laser mode was able to be tuned from one to two or three modes.