• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.236-240
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• 1997

We compare feedback wavelength-dependent performances of all-optical gain-clamped 980-nm pumped erbium-doped fiber amplifiers. In a 2.5-Gbps 8-channel WDM system, we have measured and compared gain compressions, signal power variations due to cross-saturation, power penalties caused by relaxation oscillations and noise figures for three different feedback wavelengths - 1532, 1543, and 1565 nm.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2464-2466
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• 1998

A switch is a component with two or more ports that selectively transmits, redirects, or blocks optical power in a fiber transmission line. Our switch uses rotation mechanism using stepping motor, hence the common optical fiber can scan and allign to one of the arrayed N optical fibers to provide optical path by electronic precise control. The developed switch is consisted of switching module and its control module. The performance parameters of a switching loss and a repeatability are considered very important. We performed the study to reduce the switching loss and improve the repeatability of switch. The switch can be widely used as a test instrument of optical device and of optical cable in factory, also of optical cable monitoring systems.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.412-414
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• 1999

통신용전원으로서의 전력저장시스팀(BESS)은 전기요금이 싼 심야시간(또는 필요시간)에 2차전지(축전지)를 이용하여 전력을 저장하고 최대 부하시나 필요한 시기에 전력을 방출하는 시스팀을 말한다. 이 시스팀은 축전지의 충분한 사용과 최대전력제어에 의한 전기요금 절감측면 등에서 상당히 효율적이라 할 수 있다. 본 논문에서는 이러한 전력저장시스팀을 통신용전원으로 활용하기 위한 방법과 실지 적용시 고려사항, 기대효과 및 개략적인 경제성 비교 둥을 통하여 전력저장시스팀의 통신용전원 적용방안을 검토하고자 한다.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1277-1279
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• 2000

통신용 전원시설의 고장은 거의 모든 통신서비스의 중단을 일으킬 수 있기 때문에 통신용 전일시설의 신뢰성은 매우 중요하다. 그 중 통신시스템에 직류 전원을 직접 공급하는 정류시스템은 가장 중요한 전원시스템으로 분류될 수 있다. 현재 여러 전화국 및 무인국사에서 운용되는 정류시스템은 전원관리시스템에 의해 실선으로 감시되고 있으나 중단없는 서비스제공을 위해서는 전원관리시스템과 통신을 통해 효율적으로 감시 및 제어가 이루어져야 한다. 따라서 한국통신에서는 이러한 요구에 부응하기 위하여 소형, 경량화 및 자연냉각방식등을 채택하여 운용유지보수 효율이 향상되고, 전원관리 시스템이 통신을 통해 시스템 감시 및 제어가 가능한 신형 정류기 개발을 완료하였다.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1612-1620
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• 2016

This paper presents the dynamic excitation control of a siphon-turbine coupled pico-hydro powered cage rotor induction generator and load matching for off-grid electricity generation. Through the proposed dual-role of the current-controlled voltage source converter (VSC), acting as static synchronous compensator and load controller, real and reactive power are dynamically controlled in a decoupled manner with a self supported DC-bus. The proposed scheme entails minimal computation for ensuring the rated (set) capacity of real power. The scheme also exhibits fault immunity for protection, thus enabling the effective handling of constant power electrical loads presented by base telecom station towers in remote locations. The performance of the system is evaluated under MATLAB/Simulink and is experimented through a developed hardware prototype. Simulation and experimental results show close conformity and validate the effectiveness of the proposed scheme.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.6
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• pp.72-77
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• 1980

We analyze several problems concerning the operation of the optical feedback prebias control scheme in the loser diode optical transmitter and present a LD simulation circuit as a way of adjusting the component's optimum value without using the Laser - triode. 1.5% light power decrease was observed between the temperature range of $0^{\circ}C$ and 36$^{\circ}C$ in which the total light power of LD was used for feedback loop and fairly good operation was demonstrated when a star coupler was employed as a beamsplitter by which approximately 1% portion of the light power was feedbacked.

• Proceedings of the IEEK Conference
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• summer
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• pp.23-26
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• 2004

Five-port reflectometer which consists of a ring with 5 arms (two inputs, three outputs) and three RF power detectors has been used as a vector network analyser, a demodulator in the homodyne receiver as well as in Phase Looked Loop (PLL) and so on. Calibration of five-port reflectometer is an important task. In this paper, we present a calibration method of five-port for a propagation channel sounder. The method is based on measurement of the phase differences between the three voltages at the five-port's outputs in order to determine the ratio of two input incident waves. The frequency channel sounder based on five-port is calibrated for each frequency from 2.2 GHz to 2.6 GHz with 1 MHz step. This method can also determine the absolute delays of each propagation path in the propagation channel. The calibration method is validated using measurement data.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.879-880
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• 2006

The subject of this paper is to recognize the stable state of EEG using wavelet transform and power spectrum analysis. An alpha wave, showed in stable state, is dominant wave for a human EEG and a beta wave displayed excited state. We decomposed EEG signal into an alpha wave and a beta wave in the process of wavelet transform. And we calculated each power spectrum of EEG signal, an alpha wave and a beta wave using Fast Fourier Transform. We recognized the stable state by making a comparison between power spectrum ratios respectively.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1073-1075
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• 2001

현재 한국통신에서는 전원공급방식을 크게 직류전원공급방식 및 교류전원공급방식으로 구분하여 공급하고 있다. 이러한 직류전원 및 교류전원으로 이원화된 통신서비스용 전원설비를 운용함으로써 대용량의 통신설비에 전원공급 시 국사상면의 부족현상이 심화될 뿐만 아니라 전력소비량증가 등 많은 문제점이 대두되고 있다. 따라서 본고에서는 우선 직류 및 교류전원공급방식의 특성 및 실제로 교류전원을 직류전원으로의 전환방안과 대체 시 얻는 장/단점 및 경제적 이득에 대해 서술하고자 한다.

• Information and Communications Magazine
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• v.15 no.8
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• pp.13-20
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• 1998