• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.41-44
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• 2000

Because of internet's growth, today's network has a serious bandwidth problem. WDM(Wavelength Division Multiplexing) is a solution of this problem. In the WDM networks, QoS(Quality of Service) is as important as bandwidth. And today's voice over IP technology makes a lot of delay-sensitive internet traffic. De]ay-sensitive internet traffic is growing up, so more QoS is needed. We proposed effective solution to assign QoS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7B
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• pp.573-582
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• 2006

In this paper, we propose a hybrid two-stage AWG-based WDM-PON architecture in order to overcome the limitations of the existing PONs and single AWG-based WDM-PONs as well as to accomodate the new services and the expandability of network. The proposed architecture employs two-stage AWG for downstream transmission and single AWG and combiners for upstream one at RN. It also employs the separated fiber with multi-wavelength for both direction. It leads to high scalability, low cost, and high capacity for transmission. In downstream transmission, the transparency can be guaranteed since the traffic is transmitted to ONU through each channel. However, several ONUs share the channel for upstream one by using WDM/TDMA scheme because the asymmetrical feature of networks is considered. The performance of the proposed one is evaluated and compared with other architectures in terms of cost, network capacity and up/downstream bandwidth.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.2
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• pp.55-60
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• 2008

Packet-switched wavelength division multiplexing (WDM) ring networks have been extensively studied as solutions to the increasing amount of traffic in metropolitan area networks, which is widely expected to be a mix of unicast and multicast traffic. In this paper we study the fairness between unicasting and multicasting in slotted packet-switched WDM ring networks that employ a tunable transmitter and fixed tuned receiver at each node and a posteriori buffer selection. We find that single-step longest queue selection algorithm generally results in unfairness between unicasting and multicasting or a lilted relative priority for multicast vs. unicast traffic. We present the various virtual output queue structures and their performance.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.3
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• pp.213-223
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• 2004

We consider the traffic grooming problem for the design of SONET/WDM(Synchronous Optical NETwork/Wavelength Division Multiplexing) ring networks. Given a physical network with ring topology and a set of traffic demands between pairs of nodes, we are to obtain a stack of rings with the objective of minimizing the number of ADMs installed at the nodes. This problem arises when a single ring capacity is not large enough to accommodate all the demands. As a solution method, an efficient algorithm based on the branch-and-price approach has been reported in the literature for the problem in which only unidirecional path switched ring (UPSR) was considered. In this study, we suggest integer programming models and the algorithms based on the same approach as the above one, considering two-fiber bidirectional line switched ring(BLSR/2), and BLSR/4 additionally. Using the results, we compare the number of required ADMs for all types of the ring architecture.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9B
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• pp.589-597
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• 2007

In this paper, a WDM metro ring consisting of access nodes with $FT-FR^n$ (Fixed Transmitter - n Fixed Receivers) is considered. A trade-off exists between node throughput and transmission fairness because the access nodes share wavelength channels. In order to eliminate the transmission unfairness and to increase throughput, the p-persistent medium access control (MAC) protocol is proposed: each node uses an empty optical slot to transmit a packet and make it available with the extraction of a transferred packet at the source access node, called source-stripping. The local empty slot can be used to transfer a head-of-line packet in the local buffer with probability p or it is used for the next downstream nodes with 1-p. The proposed MAC protocol provides better node throughput than the non-persistent protocol and exhibits better fairness index than the 1-persistent protocol in WDM ring networks. In addition, numerical analysis shows that the proposed MAC protocol maximizes the node throughput under uniform traffic conditions. For more detailed results, we use the network simulation under Poisson and self-similar traffic. Furthermore, unpredictable traffic constructed by the combination of the former and the latter is also considered. The reasonable probability of the p-persistent protocol for a given architecture can be determined through simulation.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.4
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• pp.289-294
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• 2008

Affordable traffic capacity of each node in networks is expected to reach in Tb/s range in proportion to the rapid growth of Internet users. To transmit more than Tb/s per fiber pair, WDM should be used as well as existing TDM. To increase the capacity of transmission in WDM networks, there are two ways, increasing channel speed or channel quantity. To increase the channel quantity, there are two ways, narrow spacing or expanding transmission bandwidth. To expand bandwidth, ultra-broadband optical amplifier technology is necessary. In this paper, we introduce EDFA in effect at C/L band, FRA, and some optical amplifiers in effect at S band, and analyze the development trend of various amplification technologies.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.9
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• pp.31-40
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• 1997

This paper presents a hybrid WDM/TDM channel acess protocol for high speed WDM networks based on passive double star topology. In the proposed scheme, all nodes in a network are splitted into groups forming passive double star topology and each node has a tunable transmitter and a fixed receiver. WDM channels are allocated to the groups, which are used as home channels to transmit or receive packets. TDM frames of the WDM channel are composed of the same number of slots as that of groups, and all nodes in a group transmit packets simultaneously at each slot. The proposed scheme reduces the system complexity and the number of the required WDM channels. It was proved that the proposed protocol is less sensitive to the propagation delay and maintaining its superior transmission performance by employing the efficient transmission schedule based on passive double star topology.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.1
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• pp.41-43
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• 2014

In this paper, we proposed a new protection scheme of the WDM mesh networks that can utilize the network resources efficiently while satisfying with the recovery time defined in the SLA (service level agreement). The protection scheme and the backup path are selected based on the comparison of the expected protection time with the SLA recovery time. The superior performance of the proposed protection scheme was demonstrated by comparing with ones of the existing protection schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.119-127
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• 2004

This paper reports on the simulation study of gigabit-capable Passive Optical networks (GPON) using WDM focused on single light source per each channel, and proposes using 1550nm VCSEL for light sources. Proposed system uses high speed direct-modulated light sources, in which the merit is able to maintain a low loss. to support broad bandwidth, and to lower network configuration cost. We conformed simulation study on the transmission of the downstream 2.5Gbit/s, upstream 1.25Gbit/s, 622Mbit/s which was recommended by ITU-T G.984.1. We measured the transmission margin and examined the feasibility of proposed system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.363-369
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• 2004

We propose, for the first time to our knowledge, a novel gain-clamping method for EDFA in WDM add/drop networks by introducing a disturbance observer technique. The control input signal for gain-clamping is composed of a nominal control signal and an additional control signal of compensating the gain fluctuations caused by channel add/drops. Based on disturbance observer technique, we designed the additional control signal such that it has the compensating information of estimated disturbance resulted from channel add/drops. The circuit for generating additional control signal can easily be implemented by using simple electronic devices. We proved the superiority of the new technique over the previous ones by showing simulation results of minimized dips and spikes that appear in power profile of EDFA in the process of channel add/drops.