• 센서학회지
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• 제21권6호
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• pp.429-433
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• 2012

In this paper, we reduced the optical noise interference in a visible light communication system using two color LEDs. In the transmitter, the original and the inverted signals of the transmitted data modulated a red LED and a blue LED, respectively. In the receiver, a differential detector which is composed of two photodetectors and an optical red filter detected the mixed signal radiated from the two LEDs. In an environment that the optical noise from a fluorescent lamp exists, the signal-to-noise ratio in this system was improved by about 20dB compared to that in the conventional system which uses a single LED and a single photodetector.

• 한국통신학회논문지
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• 제33권2A호
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• pp.198-203
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• 2008

In this paper, we consider the diffuse type of indoor wireless optical communication (WOC) system. To find the channel characteristics of indoor wireless infrared communication system, we investigate the simulation process to get the impulse response of diffuse type and analyze the scenario of the indoor structure which we have built. The simulation results of the impulse response include power ratio and time delay due to bounce times. We get and discuss the receiving power distribution according to six configurations which have different transmitter and receiver positions and reflection coefficients of the indoor structure assumed. The results of this paper are useful to design the indoor wireless optical communication systems.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.1109-1112
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• 2002

A non-coherent synchronous all-optical code-division multiple-access (CDMA) network is proposed. In this network, symmetric codes derived from prime sequence codes are used. We present the construction of symmetric codes and show that the pseudo-orthogonality of the new codes is the same as that of the original prime-sequence codes while the cardinality of the new codes is larger than that of the prime sequence codes and the modified prime codes in the same field GF(p). Therefore, an optical CDMA LAN using symmetric codes can have a larger number of potential subscribers. The new codes allow designing fully programmable serial all-optical transmitter and receiver suitable for low-loss, high-capacity, optical CDMA LANs. It is also shown that compared to systems using modified prime codes the proposed system can achieve better BER performance for low received chip optical power.

• 한국전자통신학회논문지
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• 제2권1호
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• pp.40-45
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• 2007

수백Km 정도의 섬과 섬 섬과 내륙을 해저광케이블로 연결하는 경우 일반 국가간의 500Km이상의 장거리의 중계기 증폭 시스템과 달리 송신단 및 수신단, 광케이블에 EDFA 기술을 적용하여 무중계 시스템을 설계할 수 있다. 중계기가 없음으로 해서 중계기에 공급하는 전력시스템, 동튜브가 내장된 해저케이블, 중계 증폭시 필요한 여기 파장공급용 Laser Diode등이 필요가 없어 고신뢰성 및 경제적인 시스템을 구성 할 수 있다. 그러나 중계 증폭을 하지 않는 만큼 저손실의 광케이블을 사용하여야 한다. 이러한 광증폭 제약 요소들을 고려하여 장거리 무중계 시스템을 고찰 하였다.

• 센서학회지
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• 제26권6호
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• pp.408-413
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• 2017

In this paper, we newly developed a byte-inverted transmission method for flicker-free visible light communication (VLC). The VLC transmitter sends original data in the former half period of the clock, and inverted data and in the latter half period of the clock. The VLC receiver receives the original data in the in the former half period of the clock. In this system, we used 480Hz clock that was generated from the 60Hz power line. The average optical power of the LED array in the transmitter is constant, thus flicker-free, in the observation time longer than the period of the clock that is about 2ms. This period is shorter than the maximum flickering time period (MFTP) of 5ms that is generally considered to be safe. This configuration is very useful in constructing indoor wireless sensor networks using LED light because it is flicker-free and does not require additional transmission channel for clock transmission.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(5)
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• pp.113-116
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• 2000

In this paper presents the portable wireless ECG data detection and diagnosis system based on discreet wavelet transform. An algorithm based on wavelet transform suitable for real time implementation has been developed in order to detect ECG characteristics. In particular, QRS complex, S and T waves may be distinguished form noise, baseline drift or artifacts. Proposed telemetry system that a transmitting media using radio frequency(RF) for the middle range measurement of the physiological signals and receiving media using optical for electromagnetic interference problem. A standard hi-directional serial communication interface between the telemetry system and a personal computer or laptop, allows read-time controlling, diagnosing and monitoring of system. A portable telemetry system within a size. of 65${\times}$125${\times}$45mm consists of three parts: a digital signal processing part for physiological signal detect or diagnose, RF transmitter for data transfer and a optical receiver for command receive. Advantages of proposed telemetry system is wireless middle range(50m) FM transmission, reduce electromagnetic interference to a minimum. which enables a comfortable diagnosis system at home.

• Journal of information and communication convergence engineering
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• 제13권3호
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• pp.167-171
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• 2015

A radio over fiber (RoF) system is a kind of analog optical transmission system and considered as a strong candidate for the next-generation fronthaul link in the future mobile network. In RoF systems, nonlinearity compensation is essential to increase the link capacity. In this paper, we propose a nonlinearity detection and compensation scheme using a monitoring channel in RoF systems. A monitoring channel is added at the transmitter site and used for transmitting a reference signal in an RoF transmission. The nonlinearity in the RoF transmission is detected by comparing the received monitoring signal and the original reference signal at the receiver site. Finally, the nonlinearity is compensated at the receiver by giving the reverse function of the detected nonlinearity. Our results show that the proposed scheme can almost remove the error vector magnitude degradation induced by the nonlinearity in the RoF system.

• International Journal of Internet, Broadcasting and Communication
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• 제11권4호
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• pp.43-48
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• 2019

We design a reconfigurable optical node for metropolitan WDM networks, and numerically study the capability of the node in the optical signal level. Unlike a long-haul WDM system, major limitations of metropolitan WDM systems are power loss, fiber dispersion and optical signal-to-noise ratio(OSNR) degradation due to EDFAs. Therefore, we include the behaviors of transmitter and receiver, and fiber, EDFAs, and optical filters(MUX/DeMux) in numerical simulations with varying parameters over wide range. From simulation results, we can identify the maximum span numbers for OC-48 and OC-192 to achieve $BER<10^{-12}$ using the node structure at various received powers and residual dispersions.

• 대한의용생체공학회:의공학회지
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• 제21권5호
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• pp.513-517
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• 2000

본 논문에서 제안한 텔레메트리 시스템은 생체신호를 증거리로 전송하기 위한 RF 송신기와 전자파 간섭의 영향이 없는 광을 매체로하는 수신기로 구성된 시스템이다. 따라서 텔레메트리 시스템은 RF 송신부, 광 수신부 및 생체신호 처리를 위한 CMOS 원칩으로 구성되어있으며, 65$\times$125$\times$45mm의 크기이다. 제안된 텔레메트리 장점은 전자파에 노출을 최소화하면서 중거리(50m) 텔레메트리가 가능하여, 자유로운 상태에서의 모니터링이 가능하다.

• 한국통신학회논문지
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• 제25권6A호
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• pp.893-899
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• 2000

광섬유의 대역폭을 보다 효율적으로 활용하기 위한 방안으로 각각의 채널에 서로 다른 파장을 사용하여 하나의 광섬유에 동시에 전송하는 파장분할 다중화 방식(WDM, Wavelength Division Multiplexing)이 최근 주목받고 있다. WDM 전송 시스템은 광 송수신기의 비용이 고가이므로 경제적인 구축을 위해서는 최소한의 광 송수신기를 사용하여야 하고 성능 파라미터인 전송률(throghput)과 시간 지연의 분석이 중요한 의미를 갖는다. 본 논문에서는 각 노드에 단일 큐 버퍼와 각각 1개씩의 파장가변송신기(TTX), 파장가변수신기(TRX), 파장고정수신기(FRX)가 장착된 슬러티드 링 MAC 프로토콜을 통계적 접근 방법으로 분석하였으며 컴퓨터 실험을 통하여 분석의 타당성을 검증하였다.