• Journal of KIISE:Information Networking
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• v.30 no.1
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• pp.1-8
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• 2003

In this paper. we develop an analytical model to evaluate the virtual topology reconfiguration phase of optical Internet networks. To counter the continual approximation problem brought by traditional heuristic approach, we take the traffic prediction into consideration and propose a new heuristic reconfiguration algorithm called Prediction based Multi-stage Reconfiguration approach. We then use this analytical model to study the different configuration operation policies in response to the changing traffic patterns in the higher layer and the congestion level on the virtual topology. This algorithm persists to decide the optimal instant of reconfiguration easily based on the network state. Simulation results show that our virtual topology management Policy significantly outperforms the conventional one, while the required physical resources are limited.

• Electronics and Telecommunications Trends
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• v.27 no.3
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• pp.164-174
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• 2012

향후 10년 내에 전 세계적으로 인터넷 인구가 50억 명에 이르고 사물지능통신의 발달로 인해 인터넷에 접속되는 기기가 1,000억 대로 급증할 것으로 전망된다. 또한, video 콘텐츠를 비롯한 초대용량 서비스, 무선 인터넷 서비스 등이 활성화되고, 트래픽이 폭증할 것으로 예측된다. 그러나 60년대 후반에 만들어진 인터넷은 이러한 새로운 서비스의 등장 및 인터넷 트래픽의 폭증에 적절히 대응하기에는 많은 한계를 가지고 있다. 따라서 미국, EU, 일본 등 선진국들은 네트워크의 양적인 확충은 물론, 새로운 인터넷 기술을 개발하고 그 구조를 재설계하기 위해서 경쟁적으로 대대적인 투자를 전개하고 있다. 광가입자망은 이러한 급변하는 가입자망의 변화에 효과적으로 대처할 수 있는 기술로써, 인터넷 서비스 사업자와 가입자를 연결하는 중요한 네트워크이다. 본고에서는 대표적인 광가입자망 기술인 TDM-PON(Time Division Multiplexing-Passive Optical Network) 및 WDM-PON(Wavelength Division Multiplexing-Passive Optical Network)의 전반적인 기술 현황, 국제 표준화 동향 및 시장 동향에 대해 소개하고, 앞으로 미래를 대비하기 위해 필요한 광가입자망의 기술개발 방향에 대해 논하고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.12C
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• pp.1197-1206
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• 2002

Recently, the research on the construction of optical Internet backbone networks using WDM has been actively progressed. In this paper, we propose the offset based service-differentiation scheme in optical burst switching (OBS) networks. We classify the services into two classes; high class and low class. The proposed scheme decides the offset time of high class so as to satisfy the required burst loss rate (BLR) of services according to the service-differentiation ratio (SDR). The SDR may be set depending on the environment of OBS network and user's requirements, our scheme decides the BLR of high class by using the required SDR and conservation law. Finally, we use the offset time decision (OTD) algorithm to determine the offset time of high class. The proposed scheme is evaluated through simulation. The result of simulation is compared with that of analysis to verify the proposed scheme.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.589-593
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• 2014

Terahertz (THz) communication has important applications in high-speed and ultra broadband wireless access networks. The THz modulator is one of the key devices in a THz communications system. Wavelength division multiplexing (WDM) can expand the capacity of THz communications systems, so research on multi wavelength THz modulators has significant value. By combining photonic-crystal and THz technology, a novel type of multi wavelength THz modulator based on a triple-lattice photonic crystal is proposed in this paper. Compared to a compound-lattice photonic crystal, a triple-lattice photonic crystal has a larger gap width of 0.196. Simulation results show that six beams of THz waves can be modulated simultaneously with high performance. This modulator's extinction ratio is as large as 34.25 dB, its insertion loss is as low as 0.147 dB, and its modulation rate is 2.35 GHz.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2495-2497
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• 1998

Fiber optic facilities are increasingly being deployed in loop applications for both busines and residential areas. These facilities support a variety of communications services that include high speed data and video using leading technologies such as Synchronous Optical Network (SONET), Wavelength Division Multiplexing(WDM). This proliferation of fiber optic facilities combined with the increasing pressure on network operators to reduce costs are fostering increased automation to reduce labor costs associated with providing and maintaining communications services. Effective fiber management and accurate records can improve the reliability and integrity of the future telecommunications networks and the quality of customer services. This paper describes the trend forward and the need for the deployment of Fiber Administration System (FAS) into the operations enviroment of a typical network provider.

• Journal of KIISE:Information Networking
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• v.36 no.4
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• pp.360-368
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• 2009

Recently, broadband access networks have been competitively deployed all over the world with the development of various multimedia services for such a network. ETRI(Electronics and Telecommunications Research Institute) built the FTTH(Fiber-To-the-Home) service center to develop a next-generation equipment and a high-quality service/platform as well as to promote domestic industry in the field of optical communication. The FTTH service center has a variety of test equipments such as FTTH standard testbed for a BMT(bench mark test), a network operation center, and IPTV service equipments. Also, ETRI deployed a new type of commercial optical access networks cooperating with ISP(Internet Service Provider). This paper presents the performance evaluation of FTTH E-PON(Ethernet Passive Optical Network) system as a platform for TPS(Triple Play Service) based on QoS(Quality of Service) and QoE(Quality of Expericence) issues. This FTTH E-PON system is successfully demonstrated as an optical access network system by commercial network service provider and the FTTH service center of ETRI.

• Convergence Security Journal
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• v.13 no.3
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• pp.25-31
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• 2013

Looking at the recent value change of users and the usage pattern of network users, it is changing from simple web information, one-way information acquisition and data transmission to increase of usage of multimedia, increasing demand for security and customization, and increasing demands for free mobility. Due to this change of demand, the services which were provided individually, developed into a form which is merged, the network also seems to develop into the combined network from the individual network for individual service, and the communication network control technology which is the core technology is also rapidly developing. To reflect the users' demands, the next generation network created the multi-layer network which is based on the WDM/IP transmission system and added the to make it easy to restructure. P-OTS (Packet-Optical Transport System) can be defined as a platform that combines SONET/SDH, Ethernet, DWDM, optical transport network (OTN) switching and reconfigurable optical add-drop multiplexers (ROADMs). In this paper, we suggested that the optimum path choice be performed through diversification of the PCE-based path selection using the information of various layers altogether in the multi-layer environment, compared with the established path selection method when the path was selected using the information of each layers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1C
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• pp.1-10
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• 2002

With the explosive growth of the number of Internet users and Internet-related services, the research on construction of broadband Optical Internet by using WDM technologies is actively is actively progressed. In this paper, we design the offset time decision (OTD) algorithm for supporting the QoS in optical networks based on optical burst switching (OBS), which is the new switching paradigm, and evaluate the performance of it. The proposed algorithm determines a reasonable offset time considering traffic load of network and the number of wavelengths to guarantee the burst loss rate (BLR) of high priority Internet traffic as a QoS parameter. In order to design the proposed OTD algorithm, firstly we make the new burst loss formula, which includes the effect of offset time. The decision of offset time corresponding to the requested BLR, however, should use the reverse formula of proposed one, thus we are not able to use it without any changes. In this paper, we define the heuristic loss formula (HLF) that can be changed into reversed formula by using the proposed formula and proportional equation considering its characteristics. Finally we show the OTD algorithm to decide the offset time by using HLF. We show that the requested BLR is guaranteed under various traffic load with the determinded offset time by using the proposed OTD algorithm.

• Journal of Internet Computing and Services
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• v.10 no.2
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• pp.171-177
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• 2009

Optical packet switching(OPS) is a strong candidate for the next-generation internet, since it has a fine switching granularity at the packet level for providing flexible bandwidth, and provides seamless integration between WDM layer and IP layer. Optical packet switching have been studied in two categories: OPS in synchronous and OPS in asynchronous networks. In this article we are focused on contention resolution of OPS in asynchronous networks. The hybrid buffer have been addressed, to reduce packet loss further as one of the alternative buffer structures for contention resolution of asynchronous and variable length packets, which consists of the FDL buffer and the electronic buffer. The OPS design issue for the limited number of TWCs and internal wavelengths is important in the aspect of switch cost and resource efficiency. Therefore, an hybrid buffer structured optical packet switch and its scheduling algorithm is presented for considering the limited number of TWCs and internal wavelengths, for contention resolution of asynchronous and variable length packets. The proposed algorithm could lead to the packet loss improvement compared to the legacy LAUC-VF algorithm with only the FDL buffer.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.1
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• pp.44-52
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• 2000

This paper is contented with packet transmission scheduling problem for repeating all-to-all broadcasts in WDM optical passive-star networks in which there are N nodes and k wavelengths. It is assumed that each node has one tunable transmitter and one fixed-tuned receiver, and each transmitter can tune to k different wavelengths. The tuning delay represents the time taken for a transmitter to tune from one wavelength to another and represented as ${\delta}$(>0) in units of packet durations. We define all-to-all broadcast as the one where every node transmits packets to all the other nodes except itself. So, there are in total N(N-1) packets to be transmitted for an all-to-all broadcast. The optimal transmission scheduling is to schedule In such a way that all packets can be transmitted within the minimum time. In this paper, we propose the condition for optimal transmission schedules and present an optimal transmission scheduling algorithm for arbitrary values of N, k, and ${\delta}$ The cycle length of the optimal schedules is $max{[\frac{N}{k}](M-1)$, $k{\delta}+N-1$}.