• 정보저장시스템학회논문집
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• 제1권1호
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• pp.53-57
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• 2005

In order to measure signal quality of optical disc such as CD or DVD, jitter is used traditionally. The signal attained from a disc by optical pick-up is processed by analog circuits. And then, binary signal can be obtained by using proper silcer. After the signal is changed into binary format, jitter is calculated as a time difference between the binary signal and the reference time. Jitter is used to express the signal quality. In this paper, a new method that is able to offer more precise measurement of the signal quality fur high density optical disc than the jitter is proposed. We named it LPSNR (Level Peak Signal to Noise Ratio). The relationship between bER (bit error rate) and LPSNR is shown in the paper.

• 한국정보통신학회논문지
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• 제10권2호
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• pp.220-223
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• 2006

채널 레벨 컨트롤러는 DWDM(Dense Wavelength Division Multiplexing) 방식의 OXC(Optical Cross Connect), OADM(Optical Add/Drop Multiplexer), 광 증폭기(EDFA : Erbium Doped Fiber Amplifier) 등의 시스템에서 채널별 광 신호의 세기를 조절하여 시스템의 신뢰성을 높이는 중요한 제어기다. 본 논문에서는 12채널 VOA(Variable Optical Attenuator) 4개를 사용하여 40채널의 광 신호 레벨을 제어할 수 있는 컨트롤러를 구현하였다. 각 채널의 광 신호 레벨을 제어하는데 하나의 마이크로프로세서가 5개의 채널을 제어하고 총 8개의 마이크로프로세서로 40채널을 분산 제어하도록 구성하였다. 또한 외부와 통신을 하고 사용자로부터의 명령을 각각의 마이크로프로세서에 전달하기 위한 마이크로프로세서를 추가하였다. 출력 되는 광 신호의 세기를 측정하여 VOA를 제어하고 VOA 출력에서 바로 PD(Photo Detector)로 입력하였다. 일반적으로는 AWG(Arrayed Waveguide Grating) 출력에서 광 신호를 다시 분파하여 PD에 입력하는 방법으로 매우 복잡하다. 본 연구는 이를 개선하여 매우 간단한 방법으로 다 채널의 광 신호를 제어 할 수 있었다.

• 전자공학회논문지B
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• 제30B권5호
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• pp.34-42
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• 1993

Due to the low loss, broadband and accurate short time delay properties of optical fiber, it has attracted as a delay medium for high speed and broad-band signal processing. In this paper, we consider the coherent optical fiber filter of lattice structure, which uses coherent light sources and consists of directional couplers and optical fiber delay elements.The differences between the optical fiber filter and the ordinary digital filter are 1) the coupling coefficients of directional couplers are restricted between 0 and 1. 2) the optical signal is divided into ${j\sqrt{a}}and\;{j\sqrt{1-a}}$ at the directional coupler. Considering these restrictions, the design formulae and condition of realibility for optical fiber filter of lattice structure which makes the optimal use of optical signal energy are derived.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 하계학술발표회
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• pp.224-226
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• 2000

Consumer electronics is rapidly digitalized invoking the necessity of digital signal transmission. Moreover, even in consumer electronics, occasionally signal speed is over 1Gbps and long distance transmission(over 5 meters) is required. For these requirements, even though optical transmission is ideal, cost problem has blocked up its entrance to consumer market. However, inexpensive and high speed optical devices such as VCSEL, PIN or MSN PD with large detecting area and low capacitance and Plastic Optical Fiber have been developed so that optical solution can be compete with electrical one in consumer electronics.

• 제어로봇시스템학회논문지
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• 제10권3호
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• pp.239-248
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• 2004

Optical coherence tomography(OCT) is high resolution imaging system which can see the cross section of microscopic organs in the living tissue. In this paper, we analyze the relation between the light source and the resolution of modulated signal in Michelson interferometer. We construct 1-D OCT signal processing hardware such as amplifiers, filters, and demodulate electronic signals from the photo detector. In order to get 2-D OCT image, the synchronization among optical delay line, sample stage and A/D converter is dealt with. In experiments, we verify analog and digital signal processing blocks which apply to the stacks of glasses. Finally we aquire high resolution 2-D OCT image with respect to the onion tissue. We expect that this result can be applied to the medical instrument through performance improvement.

• 한국통신학회논문지
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• 제28권5A호
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• pp.323-332
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• 2003

본 논문에서는 광원이 불필요하며 단일 광섬유를 통하여 양방향 전송이 가능한 base station용 광송수신기 모듈을 제안하였다. 제안한 시스템에서는 써큘레이터와 Mach-Zehnder 변조기로 구성된 ring-type의 base station에서 central office로부터 하향 전송된 광신호의 일부를 재사용하여 상향신호 전송에 사용한다. 시스템의 성능을 평가하기 위해서 IS-95 CDMA 신호 전송을 통한 ACPR 특성과 14개의 캐리어 신호 전송을 통한 CNR을 측정하였다.

• 한국전자파학회논문지
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• 제16권5호
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• pp.494-500
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• 2005

본 논문에서는 광섬유 커플러를 이용하여 차동 검출기를 구성하고 무선광시스템에서 잡음광 소거에 활용하였다. $1\times2$광섬유 커플러를 이용하여 수신광을 2개로 분리해서 수신하면 동일한 지점의 잡음광을 2개의 포토다이오드에서 동시에 검출하는 효과가 발생한다. 따라서 잡음광의 공간분포의 변화가 심하게 발생하는 환경에서도 2개의 포토다이오드의 위치 차이로 인한 출력 전압의 변동이 나타나지 않아 잡음 소거 효과가 높아진다. 광필터를 사용한 단일의 광검출기에 비하여 광섬유 커플러를 사용한 차동검출기에서 신호대 잡음비를 약 8 dB 개선하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(2)
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• pp.270-273
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• 2000

We have fabricated and analyzed photodiodes for optical link with Si pin structures. As the results of experiment, the web patterned photodiode(type C) with $p^{+}$-guard ring showed low junction capacitance of 6~7 pF at $V_{R}$=-5V and high separation ability for optical signal(dark current : $\leq$ 5 nA, optical signal current : $\geq$ 340 nA) due to the small effective $p^{+}$-n junction area and the expanded electric field region. The fabricated Si pin photodiode can be applicable for detecting an optical signal with the wavelength of about 660~670 nm. It can also be integrated with the twin well CMOS structure to develope an one chip based optical receiver IC. IC.C.

• Journal of the Optical Society of Korea
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• 제15권3호
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• pp.222-226
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• 2011

We demonstrated the feasibility of an amplified wavelength-division multiplexed passive optical network (WDM-PON) architecture based on broadband light source (BLS) seeded optical sources and a novel bidirectional reach extender. Our bidirectional reach extender could provide an amplification of both downstream and upstream signals as well as a BLS output for the upstream WDM signal generation. An error-free 1.25 Gb/s signal transmission over a 100-km long single-mode fiber was achieved in a bidirectional WDM-PON using BLS seeded reflective semiconductor optical amplifier (RSOA) sources.

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 하계학술발표회 논문집
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• pp.309-310
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• 2008

Polymer optical waveguides are fabricated with high-index materials deposited to strengthen exciations of evanescent field whose birefringence is utilized for optical sensing. Optical sensing properties are examined as a function of time, using different types of analyte solutions to extract noise-free signal induced by evanescent field birefringence. It is observed that sensing signal can be free of initial noise that may obscure real signal recognition, when glycerol is used for sensing characterization, due to slow accumulation process following adsorption of analyte material onto the sensing surface of the waveguide.