• 정보통신설비학회논문지
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• 제4권1호
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• pp.7-13
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• 2005

In this paper, we propose the time synchronization module on fiber optic repeater to use optic line delay for obtaining time synchronization between up-link and down-link, in the 2.3 GHz WiBro network using TDD/OFDM (Time Division Duplex/Orthogonal Frequency Division Multiplexing) Generally, when we use fiber optic repeater to remove the shade area, it occurs transmission delay which is caused by optic transmission between RAS (Radio Access Station) and fiber optic repeater and inner delay of fiber optic repeater. Because the WiBro system is adopting a TOO method and there exists the difference of switching time which is caused by these delay between up-link and down-link, it occurs ISI (Inter Symbol Interference), ICI (Inter Carrier Interference). These interference results in the reduction of the coverage. And the inconsistency between Up-Link and Down-Link switching time maybe gives rise to the interruption of communication. In order to prevent these cases, we propose synchronization module using analog optic line delay as the one of synchronizing up-link and down-link. And we propose the consideration factor for the designing time synchronization module and the feature of optic line of analog method. The measurement result of optic line time synchronization module of structure proposed is as follows, the delay error of $0.5{\mu}g$ and the insertion loss value below maximum 4.5dB in range of $0{\sim}40{\mu}s$. These results fully meet the specification of WiBro System.

• ETRI Journal
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• 제30권2호
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• pp.275-281
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• 2008

A 40 Gb/s clock and data recovery (CDR) module for a fiber-optic receiver with improved phase-locked loop (PLL) circuits has been successfully implemented. The PLL of the CDR module employs an improved D-type flip-flop frequency acquisition circuit, which helps to stabilize the CDR performance, to obtain faster frequency acquisition, and to reduce the time of recovering the lock state in the event of losing the lock state. The measured RMS jitter of the clock signal recovered from 40 Gb/s pseudo-random binary sequence ($2^{31}-1$) data by the improved PLL clock recovery module is 210 fs. The CDR module also integrates a 40 Gb/s D-FF decision circuit, demonstrating that it can produce clean retimed data using the recovered clock.

• 산업기술연구
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• 제15권
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• pp.137-146
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• 1995

The reference model for UNI (User Network Interface) of B-ISDN is consisted of three function groups (B-NTI, B-NT2 and B-TE). In this study, we constructed passive B-NT1 module which can be utilized for optical link management and repair, one of main functions of B-NT1. For the convenience of installation and management, this module is only consisted of passive optical devices. And at a local exchange center linked with the module, the broken zone of optic link is able to be monitored without interrupting services. In addition, we performed the power burget analysis for the design of efficient optic link including this module.

• Journal of the Optical Society of Korea
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• 제16권4호
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• pp.401-408
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• 2012

The amplitude error of phase modulator used in closed-loop fiber optic gyroscope has occurred by the temperature dependency of the electro-optic coefficient, and also can be due to the square-wave dither signal which is generally applied for eliminating the deadzone. This error can cause bias drift and scale factor error. This paper analyzes the temperature dependency of the modulation amplitude and the relationship with the scale factor of the gyroscope, and deals with an amplitude control method. The error calculation logic considering the dither signal is implemented on the signal processing module. The result of experiments from a prototype gyroscope shows the effect of the modulation amplitude control and a considerable improvement on performances.

• 한국광학회지
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• 제14권2호
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• pp.135-141
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• 2003

양의 열광학 계수를 갖는 실리카를 하부클래드 및 코아에 그리고 음의 열광학 계수를 갖는 폴리머를 상부클래드에 적용한 AWG(Arrayed Waveguide Grating) 파장분할 다중화 소자에 대하여 이차원 스칼라 유한차분법(Scalar Finite Difference Method; SFDM)으로 온도의존 특성을 분석한 결과, 클래드의 굴절률을 변화시키거나 실리카 코어 상부에 실리카 박막이 존재하는 구조에서 박막의 두께를 변화시켜 온도의존 특성을 조절할 수 있음을 확인하였다. 이러한 해석결과에 근거하여 폴리머 상부클래드가 적용된 AWG 소자를 제작하였으며 기존의 실리카 AWG 소자와 특성을 비교분석하였다. 폴리머 상부클래드의 도입에 의해 삽입손실 및 크로스톡은 큰 변화가 없었으나 중심파장의 온도의존성은 0.0130 nm/$^{\circ}C$에서 0.0028 nm/$^{\circ}C$ 수준으로 감소하였다.

• 한국전기전자재료학회논문지
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• 제19권5호
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• pp.427-431
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• 2006

We have studied electro-optic characteristics of reflective $45^{\circ}$ twisted nematic liquid crystal display which implement the new LC orientation using of in-cell retarder film. For the embodiment of reflective liquid crystal display, essentially the optic compensation films was always needed and attached to the outside of glass substrate. In our study, these optic compensation film were not employed in reflective LC cell. On other hand we have employed the in-cell retarder to substitute the optic compensation film and were able to orient the LC molecules using this in-cell retarder. So we have developed the reflective LC cell that has good optical performances without any additional coating process on the in-cell retarder.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.260-263
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• 2007

The importance of natural light in building is known by all of us who experienced dark rooms. The sunlight system is very important from energy saving and human welfare point of view. The system consists of light-collecting module, light -transporting module and light-emitting module. The light-collection is used light reflection mirror, a prism for lighting bent, and lens for light condensing. The transportation of collected sunlight is used polished duct, tube, pipe and specially used fiber optic cable. This paper investigate research and development trends of sunlight system for advanced product.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.389-393
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• 2003

This paper describes the design of enhanced TSSI RF Power Detector which has wide dynamic range using switch and Log amp. This Power Detector consists of low and high gain loops, and they adaptively switched by output DC voltage which is proportioned to input power level. Because Power Detector needs to separate the channel, so architecture is heterodyne system having 70MHz intermediate frequency. This proposed RF Power Detector is settle to the satisfaction of Closed loop power control system for W-CDMA optic repeater, and the obtained dynamic range cover the higher than 50dB.

• 한국광학회지
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• 제5권1호
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• pp.166-172
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• 1994

2.5 Gbps급 장거리 광통신 시스템에 소요되는 단일모우드 광섬유 부착 APD-FET 광수신모듈을 설계 및 제작하였다. 본 논문에서는 광수신모듈 제작시 고려해야 할 광학적, 전기적, 기계적 설계 및 제작 그리고 모듈의 특성평가에 대해 설명하였다. 광학적으로는 GRIN rod 렌즈와 경사 연마된 단일모우드 광섬유를 갖는 단일렌즈계로 구성하였으며 기계적으로는 광부품의 견고한 조립을 위해 레이저 용접법을 도입하였고 전기적으로는 Avalenche Photo Diode로부터의 소신호를 증폭하기 위한 GaAs FET 전치층폭기를 내장 하였다. 모듈 제작후 성능평가에서는 2.5 Gbps 속도에서 223-1의 길이를 갖는 입력광신호에 대해 $10^{-10}$ Bit Error Rate 조건에서 모듈 수신감도가 -30.3dBm으로 측정되어 국제전신전화 자문 위원회의 규격인 -26dBm은 물론 한국통신규격인 상온 -30dBm을 만족시키는 결과를 얻었다. 본 연구에서의 성공적인 모듈제작은 2.5 Gbps 광통신용 광수신모듈ㄹ의 실용화는 물론 앞으로 10 Gbps급 광통신용 광수신모듈 제작에 대한 밝은 전망을 보여주는 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.460-463
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• 1993

In this paper, The laser transmitter module is designed as the subsystem of the high repetitive laser rangefinder. The module consists of high voltage power supply, high voltage control circuits, high voltage discharger, electro-optic Q-switch driver, and laser resonator. The high voltage power supply is composed of 2-phase flyback converter. And it has 220W power level and 78% conversion efficiency. From the Q-switch driver of the crossed porro resonator, the phase retardation voltage is switched from 600V to -1500V with 200ns falling time. The module can be operated up to 15Hz. And it generates the laser pulse which has 20ns width and 80mJ.