• Journal of Sensor Science and Technology
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• v.27 no.2
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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.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.105-110
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• 2007

A tunable band-pass filter of fiber Bragg gratings incorporating the Sagnac loop interferometer configuration is presented. The proposed band-pass filter with extinction ratio 20 dB has practical advantages in terms of price and performance in comparison with the conventional band-pass filter using a circulator.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.2
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• pp.44-50
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• 2012

When the fiber Bragg gratings are embedded in a fiber-optic Sagnac loop for measuring temperature or strain, it is difficult to separate the Bragg wavelengths. The transmitted light is mixed with the reflected Bragg wavelengths in the photo-detector, working as noises. To suppress the noises, we placed the FBG sensors and a fiber-optic attenuator at asymmetric positions in the loop. With the arrangement the reflected light became much bigger than the transmitted light, enabling the separation of the reflected Bragg wavelengths with almost the same signal-to-noise ratio of the FBG sensors outside the loop.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.10
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• pp.2461-2465
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• 2013

This paper investigates the influence of hydrogen loading process on the radiation sensitivity of fiber Bragg gratings (FBG). We made the FBG inscribed in the same commercial Ge-doped fiber with different hydrogen loading periods. We measured the Bragg wavelength shift (BWS) of the FBG exposed to gamma-radiation up to a dose of 18 kGy, and evaluated the change of full width at half maximum (FWHM) and the FBG temperature sensitivity coefficient after irradiation. Varying hydrogen loading parameter led to BWS differences up to nearly a factor of two.

• Current Optics and Photonics
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• v.2 no.3
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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.

• Korean Journal of Optics and Photonics
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• v.34 no.2
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• pp.72-75
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• 2023

In this paper, a fiber-optic current sensor for a bus bar conductor based on the fiber Bragg grating (FBG) is proposed and demonstrated experimentally. The metal bus bar and a magnet are connected to each other through an FBG and the Bragg wavelength of the FBG is changed by magnetic force between the two connected devices. The experimental results showed that the Bragg wavelength of an FBG shifted by 650 pm as the 500 A direct current was applied to the bus bar.

• Current Optics and Photonics
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• v.6 no.3
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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.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.104-109
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• 2009

In order to apply FBG(Fiber Bragg Grating) sensor as one of reliable sensors in the commercial railway structure, the reliability of FBG sensor in the mechanical strength viewpoint have to be confirmed and the maximum strain should surpass the fracture strain of the host structure to measure the measurands until the host structures fail. In this paper, several factors that influence the mechanical failure strength of fiber Bragg grating sensors were analyzed. A set-up for dynamic tensile testing of optical glass fibers with fiber Bragg gratings was made. To increase the FBG failure strength, techniques relying on the H2 loading treatment and stripping methods were established and testified as a result of the tensile strength test of optical fibers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.937-939
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• 2016

In this study, we studied the gamma-radiation effect of fiber Bragg gratings (FBGs) manufactured by array sensors. The array FBGs were fabricated in a different Bragg wavelength using the same commercial Ge-doped fiber and exposed to gamma-radiation up to a dose of about 100 kGy at the dose rate of 113 Gy/min. It was analyzed radiation effects by measuring the radiation-induced change in the temperature sensitivity coefficient and Bragg wavelength shift after irradiation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.350-356
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• 2012

The tension effect on fiber Bragg gratings was analyzed and the linearity of 1.24 nm/10kpsi was obtained when Bragg wavelength was varied within 3 nm by applied tension. Using tension control method, different center wavelength fiber Bragg grating(FBG) were fabricated by only single period phase mask. These serially connected four FBGs showed the transmission spectrum of 1.5 nm linewidth as a 3 dB bandwidth which was twice that of a conventional FBG.