• Composites Research
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• v.21 no.2
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• pp.36-40
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• 2008

Recently structural monitoring using fiber optic sensors became popular, but the fiber sensors are very difficult to apply to the real structure due to thin and fragile shape of the fiber. In this research, we developed the fiber sensor packages easy to attach or fasten to the structures and apply to the real bridge structure for measuring the strains and shape changes. The applied fiber optics sensors show the behavior of the bridge girders which have several cracks in the structure.

• Analytical Science and Technology
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• v.25 no.6
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• pp.370-374
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• 2012

As for quality evaluation of paper records, it is very important to measure acidity and moisture in paper. In the case important paper records, it should be measured directly in field. But ISO standard analytical method would be limited to measure directly in field for quality evaluation of paper records until now. Therefore it could be to use mobile small NIR spectrometer for being analyzed by direct and non-invasive method in field. The wavelength range of small spectrometer has from 900 to 1700 nm, and the surface of paper could be measured by diffused reflected optical fiber probe. Thus, the acidity and moisture could be analyzed on the paper record with from 1970 to 2003. As the result, it could be confirmed to have each more than 0.9 as the correlation of acidity and moisture. Thus, it will be possible to develope the evaluation system of paper record with mobile small NIR spectrometer and optical fiber by the result.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.4112-4112
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• 2001

The feasibility of NIR spectroscopy as a quick and nondestructive method for quality control of uniformity of coating thickness of pharmaceutical tablets was investigated. Near infrared spectra of a set of pharmaceutical tablets with varying coating thickness were measured with a diffuse reflectance fiber optic probe connected to a Broker IFS 28/N FT-NIR spectrometer. The challenging issues encountered in this study included: 1. The similarity of the formulation of the core and coating materials, 2. The lack of sufficient calibration samples and 3. The non-linear relationship between the NIR spectral intensity and coating: thickness. A peak at 7184 $cm^{-1}$ was identified that differed for the coating material and the core material when M spectra were collected at 2 $cm^{-1}$ resolution (0.4 nm at 7184 $cm^{-1}$). The study showed that the coating thickness can be analyzed by polynomial fitting of the peak area of the selected peak, while least squares calibration of the same data failed due to the lack of availability of sufficient calibration samples. Samples of coal powder and solid pieces of coal were analyzed by FT-NIR diffuse reflectance spectroscopy with the goal of predicting their ash content, percentage of volatile components, and energy content. The measurements were performed on a Broker Vector 22N spectrometer with a fiber optic probe. A partial least squares model was constructed for each of the parameters of interest for solid and powdered sample forms separately. Calibration models varied in size from 4 to 10 PLS ranks. Correlation coefficients for these models ranged from 86.6 to 95.0%, with root-mean-square errors of cross validation comparable to the corresponding reference measurement methods. The use of FT-NIR diffuse reflectance measurement techniques was found to be a significant improvement over existing measurement methodologies in terms of speed and ease of use, while maintaining the desired accuracy for all parameters and sample forms.(Figure Omitted).

• Transactions of the Society of Information Storage Systems
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• v.7 no.2
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• pp.53-59
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• 2011

We have developed a compact and high-power mode-locked fiber laser for multilayered optical memory. Fiber lasers have the potential to be compact and stable light sources that can replace bulk solid-state lasers. To generate high-power pulses, we used stretched-pulse mode locking. The average power and pulse width of the output pulse from the fiber laser that we developed were 109 mW and 2.1 ps, respectively. The dispersion of the output pulse was compensated with an external single-mode fiber of 2.5 m length. The pulse was compressed from 2.1 ps to 93 fs by dispersion compensation. The fiber laser we have developed is possible to use as a light source of multilayered optical memory. We also present a fiber confocal microscope as an alignment-free readout system of multilayered optical memories. The fiber confocal microscope does not require fine pinhole position alignment because the fiber core is used as the point light source and the pinhole, and both of which are always located at the conjugated point. The configuration reduces the required accuracy of pinhole position alignment. With these techniques we can present an all-fiber recording and readout system for multilayered memories.

• Journal of IKEEE
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• v.19 no.3
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• pp.282-287
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• 2015

In this study, an optical fiber detector was constructed by using a Ce:GAGG scintillator, optical fiber, and photomultiplier. The single crystal size of the scintillator was set to $3{\times}3{\times}20mm^3$ after simulating the counting efficiency of gamma rays in the scintillator by using the MCNPX code. The constructed detector used the standard gamma ray sources $^{137}Cs$ and $^{133}Ba$ to measure radiation and analyze the spectral characteristics of gamma rays. The resulting trend curve showed excellent linearity with an R-squared value of 0.99741, and the detector characteristics were found to vary 2% or less with distance based on comparison with the MCNPX value. Furthermore, the spectroscopic analysis of the gamma ray energy from the single-ray and mixed-ray sources showed that $^{137}Cs$ had its peak energy at 662 keV, and $^{133}Ba$ had at 356 keV. It seems that if the fiber-optics detector is used, working hours and exposure of worker can be reduced.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.449-453
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• 2003

In a broadband erbium-doped fiber source for fiber optic gyroscope, a pump-polarization scrambling scheme is used to suppress the polarization dependence of the source mean wavelength. The degree of polarization of the pump is reduced to 1.4% by applying proper modulation depth to the polarization modulator where 10 m-long single-mode fiber is wound on a cylindrical PZT. In the case of using the pump-polarization scrambler as well as the output depolarizer, the mean-wavelength variations due to the random change of polarization are measured to be less than our measurement limit of 5 ppm.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.6
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• pp.373-379
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• 2006

Vibration-based structural health monitoring is one of non-destructive evaluation (NDE) techniques for civil infrastructures. This paper presents a novel fiber optic accelerometer system to monitor civil engineering structures and a successful application of the novel sensor system for measuring ambient vibration of a real building structure. This sensor system integrates the Moire fringe phenomenon with fiber optics to achieve accurate and reliable measurements. The sensor system is immune to electromagnetic (EM) interference making it suitable for difficult applications in such environments involving strong EM fields, electrical spark-induced explosion risks, and cabling problems, prohibiting the use of conventional electromagnetic accelerometers. A prototype sensor system has been developed, together with a signal processing software. The experimental studies demonstrated the high-performance of the fiber optic sensor system. Especially, the sensor was successfully used for monitoring a real building on UCI (University of California Irvine, USA).

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.311-318
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• 1994

We fabricated fiber-optic polarizers utilizing polarization selective mode coupling between the guided mode of a fiber and the surface plasmon mode supported by a thin aluminium film deposited on the polished side of a fiber. AI thin films with various thicknesses were coated onto the 633 nm, 830 nm, 1.3 fJITI single mode fibers. The maximum extinction ratio was higher than 30 dB for most of the samples and the best result was 42 dB at 90 A film thickness, with 1.3 fJITI single mode fiber. The insertion loss ranged from 0.2 dB to 1.5 dB.1.5 dB.

• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.91-96
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• 2000

We propose a novel in-line fiber optic circular polarizing mirror utilizing cholesteric lIquid crystal (CLC) polymer [11m for the fiber laser applications. Ions matrix representation of this device has been derived and venfied experimentally. In a Fabry-Perot cavity configuration, a CLC fiber optic rmrror has been used to achieve longitudinal mode suppression as well as to obtain passively mode~locked laser operations with 630 fs laser pulses via nonlinear polarization evoluhon.oluhon.

• Current Optics and Photonics
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• v.2 no.3
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• pp.226-232
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• 2018

We propose a triangular-multicore hollow optical fiber (TMC-HOF) design for uncoupled mode-division and space-division multiplexing. The TMC-HOF has three triangular cores, and each core has three modes: $LP_{01}$ and two split $LP_{11}$ modes. The asymmetric structure of the triangular core can split the $LP_{11}$ modes. Using the proposed structures, nine independent modes can propagate in a fiber. We use a fully vectorial finite-element method to estimate effective index, chromatic dispersion, differential group delay (DGD), and confinement loss by controlling the parameters of the TMC-HOF structure. We confirm that the proposed TMC-HOF shows flattened chromatic dispersion, low DGD, low confinement loss, low core-to-core crosstalk, and low crosstalk between adjacent modes. The proposed TMC-HOF can provide a common platform for MDM and SDM applications.