• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.397-399
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• 2003

파장분할다중화방식(WDM-Wavelength Division Multiplexing) 네트워크는 차세대 전송망으로서 주목받고 있다. 광경로들의 집합으로서 WDM 네트워크의 가상 토폴로지가 정의되는데, 각각의 광경로를 정의하는 광학 스위치들이 재구성 가능하기 때문에, 가상 토폴로지 또한 재구성 가능하게 된다. 이러한 WDM 네트워크의 특징은 IP, SONET, ATM과 같은 클라이언트 층이 요구하는 트래픽 패턴에 따라 가상 토폴로지를 재구성함으로서 네트워크 성능을 최적화시킬 수 있게 된다. 본 논문에서는 시간에 따라 변화하는 트래픽 패턴 하에서 가상 토폴로지를 재구성하면서, 각 광경로의 트래픽에 대한 로드벨런싱을 수행하는 기법을 제시한다. 이 기법은 기존의 기법들과 달리 미래의 트래픽 패턴을 알고 있다는 가정을 필요로 하지 않으며, 동적인 워터마즈 결정을 통해 전범위에서의 로드벨런싱을 수행하게 된다.

• The Transactions of the Korea Information Processing Society
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• v.7 no.12
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• pp.3952-3963
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• 2000

This paper considers the WRA(Wavelength and Houting Assignment) problem on all-optical tree networks using WDM(Wavelength Division Multiplexing). Each link between a pair of request nodes on all optical networks is assigned different wavelengths because of technical constraint. On the basis of this, we give an polynomial time algorithm to assign wavelengths to the all patbs of a arbitrary tree network using divide and conquer method. The time complexity of this algorithm is O(Q. R), in which Q is the request nodes for all to'all communication in a tree topology and U is the maximum number of wavelength. Also we implemented our algorithm using C in Pentium II 233MHz and analyzed performance results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.12
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• pp.3310-3329
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• 2023

This work designs an eighteen-channel bidirectional Intensity Modulation with Direct Detection (IM/DD) Wavelength Division Multiplexing-Passive Optical Network (WDM-PON) system. The proposed system meets the requirement of the ITU-T 5G fronthaul link suggested design in G-series Recommendations-Supplement 66. The newly designed system, with a 25Gb/s/λ data rate (450Gbps as a system capacity), has been tested and simulated using OptiSystem V.19 software. The system has been evaluated by the BER with respect to variable the optical span and CW laser power. Based on the ITU-T recommendations, the simulation results demonstrate that this system might be used as an F1 and as an Fx 5G fronthaul link for functional split choices starting from options 1 to 7a. These options are required under 25Gbps/λ for each upstream and downstream link direction. Furthermore, the proposed system utilized a bidirectional single-mode optical fiber within short optical spans of up to 10 km. The proposed system is characterized by a low-cost, simple, DSP-free and amplifier-free system with a reasonable system capacity.

• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.464-469
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• 2016

All-optical non-return-to-zero (NRZ) -to- return-to-zero (RZ) data-format conversion has been successfully demonstrated using a semiconductor optical amplifier in a fiber-loop mirror (so-called SOA-loop mirror) with a continuous-wave (CW) holding beam. The converted RZ signal after pulse compression has been used to create a 40 Gb/s OTDM (Optical Time Division Multiplexing) signal. Here is proposed an NRZ-to-RZ conversion method without any additional optical clocks, unlike conventional methods based on optical AND logic. In addition, it has the merit of operating at various bit-rate speeds without any controlling device. Moreover, it has a simple structure, and it can be used for all-optical bit-rate-flexible clock recovery.

• Journal of the Optical Society of Korea
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• v.10 no.4
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• pp.174-177
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• 2006

We propose a new technique to minimize gain-transient time of wavelength-division-multiplexing (WDM) signals in erbium-doped fiber amplifiers (EDFA) in channel add/drop networks. We have dramatically reduced the gain-transient time to less than $3{\mu}sec$ by applying, for the first time to our knowledge, a disturbance observer with a proportional/integral/differential (PID) controller to the control of EDFA gain. The $3{\mu}sec$ gain-transient time is the fastest one ever reported and it is approximately less than 1.5% of $200{\mu}sec$ gain-transient time of commercially available EDFAs for WDM networks. We have demonstrated the superiority of the new technique by performing the simulation with a numerical modeling software package such as the $Optsim^{TM}$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1569-1574
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• 2003

최근에 VOD, HDTV, 라이브 스트리밍 등의 서비스가 늘어나면서 가입자들은 광대역 서비스를 요구하고 있다. 이를 가입자에게 제공하기 위해서는 광대역폭을 지원할 수 있는 FTTH(Fiber to The Home)의 실현이 필수적이며, FTTH의 고비용과 설비 문제를 해결하기 위한 대안으로 PON(Passive Optical Network)이 부상하고 있다. PON은 네트워크를 시스템이 아닌 소자로 구성해, 일정거리까지는 하나의 광 회선을 설치하고 스플리터를 중심으로 여러 개로 회선을 분배하는 것이다. 이 또한 스플리터의 한계로 분배할 수 있는 회선이 제한적이며, 이를 해결하기 위한 방법으로 WDM(Wavelength Division Multiplexing)-PON이 고려되고 있다. 이에 본 논문에서는 WDM-PON에 적용할 수 있는 Ethemet 기반의 광 송수신 채널 유닛을 설계하였다. 채널 유닛은 1000BASE-T Ethernet 신호를 입력받아 파장별 DFB-LD에 직접 변조하는 방식을 사용하여 구현하였다

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.8
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• pp.51-57
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• 2004

We have analyzed the effect of out-band dispersion in the cascaded fiber Bragg Elating(FBG) based optical add-drop multiplexers(OADM) when bypassed wavelengths contain SCM signals. In order to compute this impairment the dispersion characteristics of FBG have been analytically calculated by solving their coupled wave equations, and the Fourier method is applied to IMD analysis. The out-band dispersion effects over WDM/SCM signals are analyzed under different and common system situations as: ITU channel spacing(100, 50, 25 GHz), channel density parameter, frequency extension of the SCM plan, modulation characteristics, FBG length, etc. From this results, the transport of WDM/SCM signals in future DWDM transport networks could be limited by this effect which has to be taken into account for designing future networks.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.1
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• pp.36-45
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• 2010

This paper shows a multiplexing technique to maximize the application of a moire-fringe based fiber optic sensor to lots of structure. Especially, a novel fringe-based fiber optic sensor was proposed to overcome the difficulty of multiplexing of a previous moire-fringe-based fiber optic sensor. The novel fringe-based fiber optic sensor is composed of a single reflective fringe and two optical fibers. Therefore, the multiplexing is easily realized because of the simplicity of optic structure inside the sensor. This paper also proposed four models of the multiplexing techniques. The models are based on a wavelength division multiplexing(WDM) technique and a time division multiplexing(TDM) one. Basically, the models would be profitable for a general extrinsic fiber optic sensor such as the fringe-based fiber optic sensor. Finally, the real optic system was manufactured by using the proposed model and successfully examined to prove the feasibility of the model for the application.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.685-689
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• 2003

오늘날 급격히 증가되고 있는 광 대역 멀티미디어 서비스, 초고속 대용량 인터넷 서비스 등을 가입자에게 제공하기 위해서는 광 가입자망 기반의 네트워크 구성이 필수적이다. 최근 효율적이고 경제적인 광 가입자망 구축을 위한 기술들이 빠르게 개발됨에 따라 효율적인 네트워크 구성이 가능하게 되었다. 이중 대표적인 기술로 PON(Passive Optical Network)을 이용하여 ONN(Optical Network Unit)를 공유하는 방식의 WDM(Wavelength Division Multiplexing)-PON 기술이 있으며, 이를 이용한 FTTH(Fiber to The Home)시스템에 대한 개발이 활발히 이루어지고 있다. 본 논문에서는 100BASE-TX 및 1000BASE-T Ethernet 신호를 입력받아 파장별 DFB-LD에 직전 변조하는 방식을 사용하여 WDM-PON 시스템에 적용할 수 있는 광 송수신기를 설계하고 이를 구현하였다.

• Journal of information and communication convergence engineering
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• v.6 no.1
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• pp.15-18
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• 2008

WDM is an incredibly promising technique in which multiple channels are operated along a single fiber, providing the facilities of terabit per second bandwidth. Thus, the survivability of WDM networks becomes critical for the success of the next generation internet architecture. Despite the fact that the path-based proactive restoration scheme guarantees 100% restoration as it computes a backup light path while the primary light path is being set up, this method results in additional capacity consumption. In this paper, an ideal technique is proposed that modifies the active multi-backup paths method and results in a better restoration scheme. Based on a theoretical analysis, a new method is shown to reduce the number of hopes as well as the restoration time.