• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.59-67
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• 2006

We demonstrate bidirectional long-reach 35-channel dense wavelength division multiplexing-passive optical network(DWDM-PON) based on wavelength-locked Fabry-Perot laser diodes (F-P LDs). The mode control of F-P LD enhances output power at decreased the required injection power. We show packet-loss-free transmission in all 70 channels at 125 Mb/s per channel line rate through 70 km of single mode fiber without optical amplifier The DWDM-PON can consolidate a metro network into an access network by bypassing the central offices within its reach. The proposed DWDM-PON can accommodate about 80 subscribers with an EDFA-based broadband light source. Further expansion up to 100 subscribers is possible with a semiconductor-based BLS.

• The Journal of the Acoustical Society of Korea
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• v.40 no.5
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• pp.417-427
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• 2021

Long-range communication in deep waters must overcome the low data rate due to limited bandwidth. This paper presents the performance of Multiple-Input-Multiple-Output (MIMO) system to increase the data rate. In MIMO system, communication performance is degraded by crosstalk between users and an adaptive passive Time Reversal Processing (TRP) is widely used to eliminate this. In October 2018, long-range underwater acoustic communication experiment was conducted in deep water (1,000 m ~) off the east of Pohang, South Korea. During the experiment, a vertical line array was utilized and communication signals modulated by binary phase shift keying and quadrature phase shift keying with a symbol rate of 512 sps were transmitted. To generate MIMO communication signals, received signals from ranges of 26 km and 30 km is synthesized. Compared to the conventional passive TRP, the adaptive passive TRP eliminates the crosstalk between users and achieves error-free performance with an increase of output signal-to-noise ratio. Therefore, two users separated by 4 km in range achieves an aggregate data rate of 1,024 symbols/s.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.732-734
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• 2011

본 논문에서는 [SPD와 Sensing 회로를 내장한 영상 전송 및 장애관리시스템 설계 및 구현에 대하여 기술하였다. STP 케이블을 이용하여 영상신호 및 제어신호, 장애정보신호, SPD신호로 총 4종류의 신호를 STP케이블 Pair별로 구성하여 장거리(2km) 전송하도록 하여 전송거리와 배관, 배선의 제약을 해결하였고, 경제성에서도 타 케이블 보다 우위를 점하고 있으며, 각각의 카메라별 전송신호 및 영상, 장애정보와 전원공급 및 SPD 상태, 감시와 녹화를 위한 각각의 장비별 전원공급 및 SPD 상태를 이력관리와 함께 관리할 수 있는 통합 관리프로그램으로 관리자가 수백대의 카메라를 효율적으로 관리할 수 있도록 설계 및 구현하였다.

• Electronics and Telecommunications Trends
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• v.28 no.6
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• pp.63-74
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• 2013

모바일, 클라우드, 빅데이터 등 최근 IT 산업의 패러다임의 변화로 인해 매년 25% 이상 증가하는 트래픽 추세에 따라 광 가입자망의 전송 기술도 빠르게 진화하고 있다. 가입자 망의 영역 확장을 위해 분기 수, 전송 거리 확대를 위한 기술개발 및 표준화 노력 또한 끊임없이 이어지고 있다. 링크당 40Gbps 이상의 전송 속도를 요구하는 차세대 광 가입자망 기술 중의 하나인 OFDM 기반 PON은 멀티캐리어 방식으로 대용량, 장거리 전송이 가능하며, 서브캐리어 별로 서비스를 분리할 수 있고, 유연한 서브캐리어 관리를 통해 동적 대역 할당이 가능하므로 향후 유무선 융합 가입자 망에 적합한 기술로써, 기존 광 분배망의 구조 및 시설 교체없이 WDM(Wavelength Division Multiplexing)-PON(Passive Optical Network), T(Time)DM-PON 기술과 융합하여, 전송 용량을 확장할 수 있는 큰 장점을 가지고 있다. 본고에서는 OFDMA-PON 기술을 소개하고, EU, 미국 등 선진 연구 기관의 연구동향을 소개하고 향후 전망에 대해 논하고자 한다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.312-313
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• 2017

전력계통 주파수를 증대시키면 변압기를 비롯하여 전력변환기의 사이즈는 감소하나 부하에 따른 선로전압 강하가 크게 나타난다. 전력계통의 주파수는 전력전송이 이루어지는 거리에 따라 최적의 주파수로 운용한다면 전체시스템의 구성단가를 낮출 수 있다. 해외에서는 장거리전송을 위해 20[Hz] 전력전송에 대한 연구가 활발히 연구되고 있다. 항공모함과 같은 단거리 전력전송에서는 400[Hz] 전력전송을 사용하고 있다. 본 논문은 배전시스템의 주파수설정에 따른 변압기 및 전력변환기영역에서 장단점을 비교하여 경제성을 분석하여 마이크리드 시스템에 따라 그 적용 타당성을 연구하였다.

• Korean Journal of Optics and Photonics
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• v.15 no.2
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• pp.158-170
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• 2004

Wireless optical communication is expected for high-speed optical communication in the areas of saturated optical fiber communication and low population density. In this paper, we present an optical transmitter system for wireless optical communication with new design concepts different from the usual optical imaging system. The specifications are the following: the source is a laser diode(LD) of wavelength 830 nm in which the divergent angle from the tangential plane differs from that from the sagittal plane. Here, the requested transmission distances are very long range such as 500 m to 1500 m and beam diameter is 3 m at the receiver with symmetrical energy distribution. For the evaluation characteristics of this kind of non-imaging system, two optical quantities, the relative illumination distribution and energy transfer efficiency, are numerically calculated through lots of ray tracing.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.2
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• pp.90-99
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• 2007

We demonstrate an 80km-reach 64-channel DWDM-PON based on wavelength-locked F-P LDs by changing the position of the C-band BLS for upstream channels from the CO to the RN. It mitigates the necessity of the high power C-band BLS and its handling problems. It also reduces back scattering induced penalty. We obtained less than $10^{-6}$ PLRs in all 128channels through 80km SMF. We also demonstrate a 240km-reach DWDM-PON based on wavelength-locked F-P LDs by adding a bidirectional erbium-doped fiber amplifier(EDFA). We show packet-loss-free transmission in all 128channels at 125 Mb/s per channel over 240km SMF We report the detuning effect of arrayed waveguide gratings(AWGs) and crosstalk effect in the implemented system. We Propose an architecture of a next generation defense wire communication system with the demonstrated long-reach DWDM-PON.

• The KIPS Transactions:PartD
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• v.9D no.1
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• pp.127-134
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• 2002

GPS is one of today's most widely used surveying techniques. But, users can't acquire an enough accuracy in applications of the navigation or geodesy by the GPS positioning technique because of the effects of the ionosphere and troposphere and US DoD's systematic errors. The solution of these restrictions is the DGPS technique that is to eliminate the common errors and can achieve a high accuracy. Although of sufficient density for good DGPS, accuracy of positioning is just not dense enough to provide complete coverage for real-time positioning, because distances between base and rover is short. In this paper, we designed and implemened a RTK-GPS error correction signal transmission system for long-distance using the TCP/IP, which consist of TCP, UDP and IP, which allows a user to increase the distance at which the rover receiver is located from the base, due to radio modem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.706-711
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• 2012

The current visible light communication (VLC) systems have a short transmission distance and a low data rate. To overcome this, we studied on the method of appling MIMO technology to VLC. However, it is difficult to apply the original MIMO technology used in RF frequency to wireless VLC. In VLC system, a lens can be used to separate the transmitted signals. And, if we use an image sensor as the receiver, MIMO technology can be applied to LED wireless visible light communication. In this paper, we report an experiment of $2{\times}2$ LED wireless visible light communication using a commercial image sensor receiver. We show the experimental demonstration with a transmission length of 10.5 m and a data rate of 200 bit/s.

• Journal of Advanced Navigation Technology
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• v.7 no.1
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• pp.14-21
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• 2003

We investigated the optimum pump light power compensating distorted WDM signal due to both chromatic dispersion and self phase modulation (SPM). The considered system is $3{\times}40$ Gbps intensity modulation direct detection (IM/DD) WDM transmission system with path-averaged intensity approximation (PAIA) mid-span spectral inversion (MSSI) as compensation method. This system have highly nonlinear dispersion shifted fiber (HNL-DSF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that HNL-DSF is an useful nonlinear medium in OPC for wideband WDM transmission, and the excellent compensation is obtained when the pump light power of HNL-DSF OPC was selected to equalize the conjugated light power into the second half fiber section with the input WDM signal light power depending on total transmission length. By this approach, it is verified the possibility to realize a long-haul high capacities WDM system by using PAIA MSSI compensation method, which have HNL-DSF OPC with optimal pump light power depending on transmission length.