• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.155-158
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• 2010

태양광전원이 연계되어 운용되고 있는 저압배전선로에 Sag, Swell 발생에 따른 태양광전원의 불안정한 운전과 태양광전원의 높은 왜형율의 Harmonic 발생에 따른 배전계통의 보호계전기(OCGR) 동작 등 전력 품질에 있어서 문제점이 발생되고 있다. 이러한 문제점은 사회적, 경제적 손실을 초래하게 되어, 전력품질(Sag, Swell, Harmonic, 모터기동)특성해석이 중요하다. 따라서 본 논문에서는 태양광전원이 연계되어 정상 운용 중인 배전계통에 대한 전력품질특성시험을 수행하기 위하여, 모의 배전계통장치와 모의 태양광전원장치, Labview용 감시제어장치로 구성한 태양광전원용 전력품질시험장치를 제작하였다. 이 시험장치를 이용하여 태양광전원 연계 시 Sag, Swell, Harmonic, 모터기동에 대한 시험을 수행하여 태양광전원이 배전계통에 미치는 영향과 특성을 분석하였다.

• Annual Conference of KIPS
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• 2001.10b
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• pp.1307-1310
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• 2001

현재 네트워크 처리 시스템의 문제점은 시스템 상태나 장애에 따른 결과를 받아서 네트워크 상태가 정상인지 비정상인지를 네트워크 운영자에게 보고하는 기능은 가지고 있지만, 장애의 기록유지와 네트워크 사용자의 문의 및 불만 상담을 처리할 수 있는 기능은 제공되고 있지 않은 상태이다. 이러한 네트워크 상에서 장애를 효과적으로 해결하기 위해서는 장애를 처리하는 네트워크 장애처리시스템(Network Trouble Management System)이 필요하다. 또한, 네트워크 장애처리시스템은 궁극적으로 네트워크 운영 방식을 획기적으로 개선함으로써 네트워크 장애로 인한 시간적, 경제적 손실을 최소화할 수 있다[1]. 본 논문에서는 장애 처리 티켓 시스템에 전문가 시스템을 접목시켜 각 분야에 고급 전문가들을 영입하고 관리할 수 있는 전문가 시스템 기반의 통합 시스템 구현함으로써 사용자에게 신뢰성 있는 고부가가치의 서비스를 제공할 수 있게 하였다.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.235-239
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• 2002

A novel ultra-narrow linewidth DFB laser in the extended FBG ring cavity having kHz linewidth is presented. The method of linewidth compression was realized by introducing an extended fiber ring cavity into the cavity between the external FBG and the Bragg grating inside a DFB laser diode. Optimum optical feedback control was achieved by using an optical circulator and a variable optical attenuator to prevent mode hopping induced by spatial hole burning. To prove the validity of the proposed scheme, a self-heterodyne measurement set-up with fiber delay line of 63 km was utilized for the ultra-narrow linewidth measurement. A 3 dB linewidth of less than 3 kHz was demonstrated, which is resolution limited performance. This linewidth is equivalent to 3 dB linewidth of 2$\times$10$^{-8}$ nm.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.178-184
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• 1998

Optical fiber coupler is a crucial optical passive component for optical transmission systems. In this paper, we fabricate wavelength insensitive optical coupler(WIC), of two types for which the processing procedures are complicate and difficult. These couplers are fabricated by two optical fibers having either different fiber parameters or different cladding diameters. To clarify the validity, we measure the optical characteritics and compare to the data of theoretical simulation. The experiment results ref#eat that it has uniformity of about 1.0 dB and excess loss of less than 0.1 dB in the range of $1310{\pm}40nm\;and\;1550{\pm}40nm$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.4
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• pp.63-71
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• 2002

In this paper, we present microwave characteristics of traveling-wave photodetectors (TWPD) using the finite-difference time-domain method (FDTD). Current and voltage in the time domain are calculated by the FDTD. Also, characteristic impedance and propagation constant in frequency domain are obtained from the time-domain data. As the thickness of i-layer gets thicker and the waveguide width gets narrower, TWPD's show less microwave loss and higher velocity. The 50Ω impedance matching design is achieved for 2.4${\mu}{\textrm}{m}$ waveguide width and 1.2${\mu}{\textrm}{m}$ thickness of i-layer at 100 GHz.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.6
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• pp.23-29
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• 1981

By using a slot-line in combination with microstrip lines, a coplanar wide-band balun is designed and fabricated. The slot-line of balun junction is compensated to be operated in C-band(4~8GHz), and therefore the results are agreement with theoritical prediction. Experimental data are given for a 3-section Chebyshev transformer-matched balun with a balanced-to-unbalanced line impedance ratio of 2 : 1. A bandwidth from 3.5GHz to 7.0GHz is obtained with V.S.W.R. of below 1.2 : 1. Maximum insertion loss is measured as 0.9dB, and the phase difference varies linearlly within 180$^{\circ}$$\pm$5$^{\circ}$.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.4
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• pp.696-700
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• 1987

Guide modes in a graded index multinmode optical fiber are turned into clad modes when the optical fiber was bended into a perpendicular direction to its optical axes by microbending forces, which causes the loss of the guiding optical power. The theories reported on this microbending power loss can be applied to calculation of the transmission power loss only when the beding period equals to the mode coupling length. In this paper, we obtained the general expression of the optical power transmission loss in a graded index multimode fiber bended periodically. This can be applied to the calculation of the power loss of the periodically microbended fiber with an arbitrary bending shape and period. Also, by using the beam theory in mechanics, we could derive the expression of the displacement of the optical fiber caused by the external force which bends the fiber into a periodic trapezoidal shape. Experiments were carried out to determine the dependence of the power loss on the period of the microbending forces. Experimnetal results were in good agreement (in the same order of the magnitude) with theoritical values derived in our work within the bending period region of 2mm-10mm.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.53-59
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• 2000

Based on the polarization selectivity of fiber-to-planar waveguide coupler, a novel fiber optic polarizer has been designed and fabricated. The large structural birefringence of a metal-clad planar waveguide enables the polarizer to have wide operating wavelength range. The polymer and gold were used for the guiding layer and cladding layer of the planar waveguide, respectively. The experimental results showed that either TE or TM polarized lightwave could be created by adjusting the thickness of planar waveguide. Operating wavelegth range satisfying more than 16㏈ polarization extinction ratio was 130nm. The average insertion loss of fabricated devices was order of 0.5㏈.

• Journal of IKEEE
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• v.18 no.4
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• pp.456-462
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• 2014

Scintillators were polished in four steps using polishing paper, to reduce the optical loss occurring at their cross section when radiation detectors are fabricated with plastic scintillators. We studied the correlation between the polishing steps and detection efficiency and assessed the detection characteristics that are dependent in the polishing steps. Our results showed that the detection efficiency increased by approximately 7.75 times for a detector that used a scintillator polished in four steps, compared to a detector that used an depolished scintillator. For detectors fabricated using scintillators polished in different steps, better detection characteristics were obtained in terms of the activity, distance, and location of radiation, compared to detectors fabricated with an depolished scintillator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.119-127
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• 2004

This paper reports on the simulation study of gigabit-capable Passive Optical networks (GPON) using WDM focused on single light source per each channel, and proposes using 1550nm VCSEL for light sources. Proposed system uses high speed direct-modulated light sources, in which the merit is able to maintain a low loss. to support broad bandwidth, and to lower network configuration cost. We conformed simulation study on the transmission of the downstream 2.5Gbit/s, upstream 1.25Gbit/s, 622Mbit/s which was recommended by ITU-T G.984.1. We measured the transmission margin and examined the feasibility of proposed system.