• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10C
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• pp.937-944
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• 2002

The current fast-growing Internet traffic is demanding more and more network capacity. Photonic packet switching offers high-speed, data rate/format transparency, and configurability, which are some of the important characteristics needed in future networks supporting different forms of data. In this paper, we define that optical backbone networks for IP transport consist of optical packet core switches and optical fibers. We propose a multi-link photonic packet switch managing as single media which unifies the whole bandwidth of multiple wavelengths on the optical fiber in the WDM optical networks. The proposed switch uses optical packet memories of output link equally as well as using the WDM buffer. So it cuts down the required number of buffers and realizes of the optical packet memory economically.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1816-1822
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• 2003

We propose a novel structure of wavelength selective optical add/drop filter comprising two tap couplers and a fiber Bragg grating. The device has unique features including a simpler structure and a lower cost implementation as compared with existing device for the same operation. The filter performance has been measured and analyzed, experimentally. The implemented prototype filter shows good performance with no­crosstalk power penalty in a 155Mbps per channel wavelength­division­multiplexing transmission system but suffers from a relatively high loss of 3.5㏈ and 21㏈ for transmitted and dropped channel, respectively. While the dropped channel extinction ratio was more than 15㏈, the transmitted channel extinction ratio was more than 26㏈.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.1381-1384
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• 2002

최근 인터넷 서비스는 최선형 서비스 제공 위주에서 실시간 멀티미디어 서비스들의 QoS 보장을 함께 지원하는 차등화된 서비스 형태로 발전하고 있다. 또한, 기존의 SONET/SDH 전송망에서 다중 기가비트 파장을 제공하는 WDM 기술이 차세대 인터넷의 중심 기술로 부상하고 있다. WDM 백본망은 Ingress와 Egress 쌍 간에 여러 lightpath를 제공하므로 각각의 광 품질에 따라 각기 다른 광 경로를 설정하여 차등화된 광 서비스를 제공할 수 있으나, 현재의 WDM 백본망은 종단간 QoS 서비스 보장을 위한 어떠한 지원도 제공하지 못하고 있는 실정이다. 본 논문에서는 다양한 실시간 멀티미디어 서비스들을 IP over WDM 백본망에 적용하기 위해, 파장을 레이블로 사용하여 QoS 제공 기능과 트래픽 분산 기능을 용이하게 수행하는 GMPLS 기술을 차등화 서비스 기술과 같이 접목하여 새로운 형태의 차등화된 광 QoS 서비스(DOS) 제공 방안을 기술 한다.

• Korean Journal of Optics and Photonics
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• v.12 no.2
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• pp.129-134
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• 2001

Novel supervisory system for WDM transmission link using conventional optical time domain reflectometry was presented. By modifying the structure of erbuim doped fiber amplifier to support bi-directional transmission at arDR pulse wavelength and launching the optical pulse into transmission link in the opposite direction of data signal propagation to avoid the distortion by cross-gain modulation, it is possible to monitor the WDM link in service. To prove the validity of proposed scheme, the supervision result of 2.5 Gbps $\times$ 8 channel WDM 320 km transmission system in service by arDR was presented. And power penalty due to monitoring was measured as smaller than 0.3 dB. .3 dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.12
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• pp.27-37
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• 2003

In the next generation Internet(NGI) based on dense wavelength division multiplexing(DWDM) technology, QoS RWA considering various QoS parameters of DWDM networks is regard as one of the key issues in providing real-time multimedia services. However, finding a qualified path meeting multi-constraints is generally NP-complete problem. It is insufficient for QoS RWA researches in DWDM networks that must consider QoS parameter as well as wavelength-continuity constraint. This paper proposes qualified path routing (QPR) algorithm with minimum computation and implementation complexity based on flooding method to accomplish QoS routing and wavelength assignment (RWA). We also introduce a QoS-based RWA mechanism considering multi-constraint such as optical signal quality attributes, survivability and wavelength-continuity constraint combined with proposed routing algorithm. Simulation results show superior efficiency of the proposed algorithms in terms of blocking probability, routing overhead and survivability ratio.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.4 s.37
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• pp.323-330
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• 2005

We fabricate PIN PD (Positive Intrinsic Negative Photo-Diode) for CWDM optical repeater and optical transmission system, and analyze theoretically the characteristics to verify the capability of device fabricated. Furthermore, we integrate CWDM filter into PD package to enhance the cost and the performance when compared to the conventional system, in which CWDM filter and PD package are linked by optical fusion splicing. The integrated CWDM PD is fabricated by three steps as follows: CWDM filter design, PD packaging, and product assembly and test. The results of measurement for PD fabricated reveal 0.5 dB bandwidth of 17 nm, isolation over 60 dB at transmission port and over 20 dB at reflection port. Also, the IMD3 for wireless communication is over 63 dBc, and the responsivity of PD presents over 0.9 A/W for 20 samples of the total 23 PD. The total insertion loss reduces about 0.4${\~}$0.7 dB due to the integrated assembly of CWDM and PD.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.186-186
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• 2011

태양전지의 효율을 증가시키기 위해서는 표면에서의 Fresnel 반사를 줄여 입사된 빛이 흡수층까지 잘 도달되도록 해야 한다. 그러나 결정질 실리콘의 경우, 굴절률이 높아 32% 이상의 표면반사율을 보이고 있어, 실리콘 태양전지 표면에 단일 또는 다중 박막의 무반사 코팅을 통해 반사율을 낮추는 방법이 널리 사용 되어 오고 있었다. 하지만, 이와 같은 코팅 방법은 열적팽창 불일치, 물질 선택의 어려움뿐만 아니라 낮은 반사율을 포함하는 파장 및 빛의 입사각 영역의 제한 등 여러 문제점을 지니고 있다. 이러한 문제점을 보완하기 위해, 표면에 서브파장의 주기를 갖는 나노구조(subwavelength structure, SWS)의 형성에 관한 연구가 활발히 진행되고 있다. 습식 식각보다 건식 식각을 이용한 SWS 제작 방법이 표면 profile을 제어하기 용이하나 패턴 형성을 위해 식각 마스크가 필요하다. 최근, 복잡하고 고가의 전자빔 또는 나노임프린트를 이용한 패턴 형성보다, 간단/저렴하며 대면적 제작이 용이한 금속 나노입자 마스크를 이용한 SWS의 제작에 대한 연구가 활발히 진행되고 있다. 또한 SWS의 무반사 특성은 표면 profile에 따라 크게 영향을 받는다. 따라서 본 실험에서는 열적 응집현상에 의해 형성되는 self-assembled Pt 나노입자 식각 마스크 및 $SiCl_4$가스를 사용한 유도결합 플라즈마(inductively coupled plasma, ICP) 장비를 이용하여 무반사 실리콘 SWS를 제작하였으며, SWS 표면 profile에 따른 구조적 및 무반사 특성을 조사하기 위해 다양한 공정조건을 변화시켰다. 실리콘 기판 위의 Pt 박막은 전자빔 증착(e-beaml evaporation)법을 사용하였고, 급속 열처리(RTA)를 통해 Pt 나노입자의 식각 마스크를 형성시켰다. Pt 나노입자들의 패턴 및 제작된 무반사 실리콘 SWS의 식각 profile은 scanning electron microscope를 사용하여 관찰하였으며, UV-VIR-NIR spectrophotometer를 사용하여 350~1050 nm 파장 영역에서의 반사율을 측정하였다. ICP 식각 조건을 변화시켜 5% 이하의 낮은 반사율을 갖는 높이가 높고 쐐기 형태의 실리콘 SWS를 도출하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.1
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• pp.188-194
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• 2011

We analyze transmission performance of radio frequency signal in WDM-ROF (wavelength division multiplexing - radio over fiber) system employing photonic crystal fiber. In a WDM-ROF system employing conventional single-mode fiber, transmission performance of radio frequency signal is analyzed depending on each WDM channel. In this case, each WDM channel experiences power fluctuation of received RF signal in remote node because of double sidebands of the modulated signal and wavelength dependent dispersion of single mode fiber. This RF power fluctuation acts as a design constraint in viewpoint of system design. By employing photonic crystal fiber (PCF) with dispersion compensation characteristics, the transmission performance of RF signal can be improved compared with the case with SMF only.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.9
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• pp.2422-2432
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• 1996

In this thesis, we analyze the Broadcast and Select Network(BSN) architecture coming up to the issues among those in the single-hip WDM networks and the degradation of performance in consequence of the traffic imbalance which well be able to be produced in these network. We propose WDM networks architecture which can support concurrency services by using Array Wavelength Tunable Filter(AWTF) with the parrallel hardware structure as a solution. For the sake of multichannel communications, we make use of the Single Control channel, Multiple Data channel(SCMD) scheme that is one of the channel architecture. Also, we compare and analize the throughput of Uniform & Nonuniform traffic conditions, and obtain the optimized number of AWTF being able to guarantee the Quality of Service(QoS) required by the enlargement of WDM netowrks and traffic imbalance. Therefore, we can make it possible that the design of the WDM networks with BSN architecture ensures the optimized performance.

• Journal of Advanced Navigation Technology
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• v.28 no.1
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• pp.123-128
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• 2024

When mid-span spectral inversion (MSSI), which inverts the propagated wave into phase-conjugated wave in the middle of the entire transmission distance, is combined with dispersion-managed link, it is very effective in compensating for the wavelength division multiplexed (WDM) signal distortion due to chromatic dispersion and nonlinear effects. In this MSSI combined dispersion-managed link, the shape of the dispersion map, channel data rate, channel wavelength and wavelength spacing, etc. affect the compensation and, consequently, determine the transmission distance and capacity of the WDM signal. In this paper, the compensation according to the extinction ratio of the return-to-zero (RZ) pulse that constitutes the WDM signal in the MSSI combined distributed control link was numerically analyzed. As a result of the simulation, it was conformed that the extinction ratio to obtain the best compensation should be determined depending on the shape of the dispersion map and the size of the residual dispersion per span, which determines the specific shape of the dispersion map. These results show a significant difference from the results in a general optical transmission system, where as the extinction ratio increases, the power difference between the '1' and '0' signals increases, thereby improving reception performance.