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두 광파의 비팅과 주파수차이 검출기를 이용한 광파 로킹에 관한 연구
유강희 忠州大學校 2002 한국교통대학교 논문집 Vol.37 No.3
This paper describes a new lightwave locking technique which can be used in tuning the wavelength of a local VCO laser diode to the reference wavelength fed from optical network. The optical signals from the reference laser source and local slave VCO laser are heterodyned on a photo detector, resulting in the microwave RF signal corresponding to the difference frequency between two input optical signals. The optical frequency locking exp reference RF signal source in off-set frequency locking loop. Through experiments are carried out using 1550 nm VCO DFB laser diode and 1.5[GHz]eriments with the calculated parameters, we confirmed that the off-set frequency locking loop simply develops an error component that is proportional to the frequency difference between heterodyned optical signals and a reference 1.5[GHz] oscillator for the loop locking.
유강희 충주대학교 2006 한국교통대학교 논문집 Vol.41 No.-
A full 360° reflection type analog phase shifter has been realized with four varactors and 90° branch coupler. The analytic formulars for the phase shift and insertion loss have been derived and applied to the design of the circuit. A new design technique for the large phase shift is applied using short stub microstripe lines. Through the experiment using the microstrip line and varators, the phase of 10GHz signal is controlled to the 0-12V DC voltage with the phase shift range of 360°. The achieved insertion loss of less than 3dB are achieved over all phase states.
유강희 韓國交通大學校 2013 한국교통대학교 논문집 Vol.48 No.-
This paper describes the procedure to get full mesh connectivity in WDM ring networks. The number of wavelengths as well as maximum hop numbers are calculated for both odd and even number of nodes on the ring to get full mesh connectivity. Using matrix approach, optimal wavelength assignment algorithm for the full mesh connectivity is presented. Additional work presented is the performance comparison among several types of WDM ring networks such as fiber-mesh, WDM-XC, WDM-ADM. We observe the trade-off between link cost and node cost in WDM ring networks for the performance comparison.
광 부호분할 다중접속 가입자 전송망에서의 잡음영향 연구
유강희 忠州大學校 2007 한국교통대학교 논문집 Vol.42 No.-
Noise characteristics of the frequency domain optical CDMA system has been analyzed for the system performance. It is found that the excess intensity noise is the important factor in case of the high power optical input signal at the receiver. As a result, the suppression of the excess intensity noise is very important to design the stable frequency domain optical CDMA system compare to the suppression of the other noises such as thermal() noise, shot() noise and spontaneous emission beat() noise. This paper describes the calculated result of the noise analysis.
유강희 한국교통대학교 2014 한국교통대학교 논문집 Vol.49 No.-
An analysis on the transmission performance of the subcarrier intensity modulated wireless optical communication link has been carried out in the presence of noise and atmospheric turbulence. Atmospheric turbulence causes fluctuations in the both intensity and phase of the received light signal, impairing link performance. The BER of the turbulence induced optical wireless link according to the SNR is derived. The receiver sensitivity at the given BER is calculated due to the SNR as well as the turbulence level. This paper described the calculated results of the receiver sensitivity as well as BER according to the variation of subscriber number and SNR.
광섬유를 이용한 컬러TV신호 3채널의 주파수 분할 다중 전송시험
유강희,서완석,강민호,Yu, Gang-Hui,Seo, Wan-Seok,Gang, Min-Ho 한국전자통신연구원 1984 전자통신 Vol.6 No.4
Frequency division multiplexed 3ch. Color TV signals have been transmitted via optical fiber by employing $1. 3\mum$ InGaAsP DH-laser diode, graded index optical fiber and Ge-APD as optical components. Overall system margin of 20 dB was realized at weighted SNR of more than 49 dB. With this system margin, measured DG and DP were less than 10% and $5^{\circ}$respectively. Throughout this experiment, it was confirmed that multichannel TV signals could be economically transmitted over optical fiber in short haul networks. This paper describes system outlines and hardware implementation results.
가변 캐패시터와 Branch Coupler를 이용한 반사형 아날로그 위상 변위기 연구
유강희 한국통신학회 2004 韓國通信學會論文誌 Vol.29 No.3A
Varactor 다이오드와 branch coupler를 이용한 반사형 아날로그 위상 변위기 설계에 대하여 기술하였다. 1단의 위상 변위기로 위상 변위를 크게 하기 위하여 마이크로 스트립 stub기법을 사용하였으며 2.260GHz 주파수대에서 제작 결과 170$^{\circ}$의 위상이 변화함을 확인하였다. 측정된 삽입손실을 3㏈ 이하이었고. 반사 손실은 12㏈ 이상이었다. 본 논문에서는 설계 기법과 제자 및 실험 결과를 상세히 기술하였다. A low loss reflection type analog phase shifter which is realized with two varactors and branch coupler. is described. A new design technique for the large phase shift is applied using short stub microstripe lines. This paper presented the realization of design and experimental results. Through the experiment using the duroid microstrip line and varactors, the phase of 2.26GHz signal is controlled to the DC voltage with the phase shift range of 170$^{\circ}$. The achieved insertion loss of less than 3㏈ and the return loss of mote than 12㏈ are achieved over all phase states.
광 부호분할 다중전송에서 부호길이에 따른 BER 영향분석
유강희 忠州大學校 2011 한국교통대학교 논문집 Vol.46 No.-
BER characteristics of the optical code division multiple transmission due to code length has been analyzed. Using the given subscriber number as well as input optical power, the network performance factors such as SINR, BER are calculated. The performance become better according to increasing code length as well as input optical power. But subscriber number increase make performance wrong due to interference. This paper describes the calculated results of the SINR as well as BER according to the variation of code length.
주파수 분할다중 무선 광전송 시스템에서 수신 광전력과 전송속도에 의한 BER 성능 연구
유강희 한국교통대학교 2015 한국교통대학교 논문집 Vol.50 No.-
A Study on BER Performance of the frequency division multiplexed optical wireless transmission system has been carried out in the presense of atmospheric turbulence as well as various factors which infulence the received SNR. Random changes of refractive index due to atmospheric turbulence which results from a varyring temperature and air pressure make the optical intensity fluctuation. The ISI caused by the optical intensity fluctuation of the propagated optical signal make the BER performance degradation. The SNR of the received optical signal which is affected by various factors such as received optical power, multiplexed subscriber numbers and transmission speed also degrade the BER performance. This paper described the calculated results of BER performance according to the atmospheric turbulence as well as the received optical power and transmission speed.