• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.237-243
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• 2011

Thermal characteristics, such as diffusivity and temperature induced change in the fiber mode index of rotation sensing fiber coil are critical factors which determine the time varying, thermo-optically induced bias drift of interferometric fiber-optic gyroscopes (IFOGs). In this study, temperature dependence of the transient effect is analyzed in terms of the thermal characteristics of the fiber coil at three different temperatures. By applying an analytic model to the measured bias in the experiments, comprehensive thermal factors of the fiber coil could be extracted effectively. The validity of the model was confirmed by the fact that the extracted values are reasonable results in comparison with well known properties of the materials of the fiber coil. Temperature induced changes in the critical factors were confirmed to be essential in compensating the transient effect over a wide temperature range.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.74-77
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• 2008

We improved an efficiency of fiber-optic current transformer by using a metal-coated sensor coil. To reduce the linear birefringence, we used a length of spun fiber as sensor coil, and then used a flint glass fiber coil for comparison. To make the sensor coil in the reflection type, we used different reflection mirrors at the end of the sensor coil, such as a Faraday rotator mirror, a simple mirror, a metal-coated fiber end and a simple fiber end. From the experimental results, the linear error of current measurements were less than ${\sim}$ 0.2 % regardless of the mirror types. The metal-coated sensor was the most cost-effective considering the fabrication cost and the simple structure.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.1
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• pp.153-158
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• 2009

Stable and tunable dual-wavelength erbium-doped fiber ring laser(EDFL) using a single fiber Bragg grating(FBG) and two coil heaters is proposed and demonstrated. Installing two identical coils into a single FBG, the FBG is symmetrically divided into two different portions. While a current supply to the coil, the refractive index of the FBG under the coil is changed. The FBG can operate as a joint of two different FBGs. Due to the thermo-optic effect of a fiber, the resonance wavelength split into two peaks. The spacing between two adjacent channels was changed as much as the difference of heating power. It was tuned up to 3 nm of wavelength under the electrical power with a 1000 mW. Moreover, the lasing wavelength can be individually tuned without influencing to the adjacent channel.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.135-141
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• 2004

We developed a polarimetric fiber-optic current sensor system for protective relaying usage. A fiber sensing coil that consisted of a length of twisted fiber and a FRM (Faraday rotator mirror) was used in order to suppress the linear birefringence effect. From the experiments with various sensing coil configurations and environmental conditions, the proposed current sensor system showed feasibility of suppressing environmental noises, and the obtained measurement stability was less than $\pm$3％ at rated primary current.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.2
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• pp.222-227
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• 2009

The bias characteristics due to the changes of temperature and temperature gradient of fiber coil are investigated in fiber-optic gyroscope. The bias performance is degraded with the changes of temperature and temperature gradient of fiber coil. The temperature compensation using both the temperature-dependent bias measurement and the temperature-induced error model of fiber-optic gyroscope improves the bias stability about 3 times as much as the uncompensated original case, which leads to very stable bias performance over the temperature range from $-35^{\circ}C$ to $+77^{\circ}C$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.28-33
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• 2004

We developed a fiber-optic CT for large current monitoring in power systems. We used a FRG fiber sensor coil to suppress CT output degradation caused by linear birefringence, and different optical sources were used to compare their noise characteristics. From the experiments, we obtained output variation less than $\pm$0.4(%) when the sensor coil suffered mechanical perturbations, and the ASE source showed -23(㏈) less noise in the output than singlemode laser diode.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.1
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• pp.73-78
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• 2008

A polarimetric fiber-optic CT has been developed by using a sensing coil made of a length of sun fiber. A Faraday rotator mirror is attached to the end of the sensor coil to double the sensitivity and to suppress the residual linear birefringence effect. From the current measurements, the linear error no more than ${\pm}2[%]$ was obtained. The output of spun fiber sensor coil was compared with those of the twisted- and the flint glass fiber's, and it fumed out to almost 50 times, 2 times more sensitive, respectively.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.53-57
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• 2004

The stabilization of fiber-optic current sensor has been achieved by using a broadband light source and a Faraday Rotator Glass fiber sensor coil. The very low Photo-elastic constant of the fiber suppressed output variations within ${\pm}0.4[%]$ when mechanical disturbance was applied to the sensor coil. Noise characteristics, with different light sources, have also been analyzed, which experimentally proved that the wider bandwidth source showed the better noise performance.

• Journal of Navigation and Port Research
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• v.32 no.9
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• pp.717-722
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• 2008

We have proposed and demonstrated an gas-flow sensor using optical fiber bragg grating(FEG). The flow sensor has no electronics and no mechanical parts in its sensing part and the structure is th11s simple and immune to electromagnetic interference(EMI). The FEG sensor was consisted qf the sensing element and a coil heater. The metal coil was used to supply the current to the FEG. While some currents supply to the coil, the refractive index of the FEG under the coil is changed and thus the wavelength shift of fiber optic sensor was induced In this work, the wavelength shift according to flow-rate was experimentally studied and was used to evaluate the gas flow-rate in a gas tube. As a result, it was possible to measure the flow-rate in a linear range from 5 to $20{\ell}/min$ with a resolution of approximately $1{\ell}/min$ at the applied currents of 100 mA and 120 mA. The measured sensitivities were $15.3\;pm/\ell/min$ for 100 mA and $20.2\;pm/\ell/min$ for 120 mA.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.1
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• pp.77-83
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• 2013

This paper presents the feasibility on the application of composite coil spring, which has great interest in the automobile industry. In order to obtain much lighter weight of the composite spring, it will be necessary to optimize the design variables such as fiber angles and diameter of coil, etc. First of all, mechanical properties were measured to consider the effects of FVR and ply angles for carbon fiber composite material. And the shear modulus with respect to ply angles were derived based on twisting angles calculated by torsional beam model. Next we determined the design parameters of composite coil spring, which has equivalent spring rate to the steel coil spring. In order to assess the proposed method, finite element model of the composite spring was developed and analysed to obtain the spring constant. The results showed that static spring rate of the composite spring was in a good agreement with that of steel spring.