• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1B
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• pp.1-10
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• 2007

We propose a new approach to accommodate bidirectional asymmetric traffic demands as well as unexpected dynamic internet traffic variation in the WDM mesh network by using optical networking technologies. In the proposed scheme, an intermediate node determines the optical path based on the switching statistics of IP router of the node which characterizes the Internet traffic variation, which in effect provides a dynamic and distributed traffic control over the network. It is expected to reduce the efficiency deterioration of RWA(Routing and Wavelength Assignment) due to the real-time variation of Internet traffic so that expandability and flexibility of the network can be enhanced. In this paper, we describe a methodology for traffic behavior analysis at a node, and the decision policy of the establishment/release of optical path. In addition, we evaluate the performance of the proposed scheme through the computer simulations.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.375-378
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• 2001

A 640Gb/s very advanced ATM switching system using 0.25um CMOS VLSI, 40 layer ceramic MCM and 10Gb/s, 8 wavelength 8$\times$8 optical WDM interconnection has been fabricated. To break though the interconnection bottleneck, optical WDM interconnection is used. It has 20Gb/s 8 wavelength 8$\times$8 interconnection capability. It realizes 640Gb/s interconnections within a very small size. Preliminary tests show that 800b1s ATM switch MCM and optical WDM interconnection technologies can be applied to future high speed broadband networks

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3B
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• pp.200-208
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• 2003

In this paper, we propose an enhanced p-cycles (preconfigured protection cycles) scheme for fast restoration in WDM (Wavelength Division Multiplexing) optical mesh network with limited wavelength conversion for fast restoration. We enhanced the p-cycles to accommodate uni-directional connections to be used in uni-directional multicasting or asymmetric broadband multimedia communications with bi-directional connectivity. We applied it to WDM network with limited wavelength conversion and analyzed the result. The analysis results show that the enhanced p-cycle algorithm provides better performance in WDM optical networks with limited wavelength converter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5B
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• pp.404-413
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• 2003

Optical Internet consists of IP domain and optical (WDM) domain, where the wavelength routing (WR) and optical burst switching (OBS) are the promising switching technologies in the optical domain. In this paper, we perform the simulations on the WR network and the OBS network, and compare their performances. It is verified from our simulations that the OBS network performs better than the WR network when the same network resources are given.

• Journal of the Korea Society of Computer and Information
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• v.17 no.8
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• pp.51-60
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• 2012

I propose the 5Gbps/1.25Gbps WDM/TDM hybrid Passive Optical Network(PON) with inverse RZ(Return to Zero) code coded downstream and NRZ(Non Return to Zero) upstream re-modulation and analyze its performance by performing simulation with MATLAB. The results have shown that an optical line termination (OLT) can be connected to 8, 16 optical network unit (ONU)s with the Bit Error Rate(BER) of $10^{-9}$ when the distance between OLT and ONU is 10Km and transmitted optical powers are more than -3.8, -0.9dBm, respectively. The proposed WDM/TDM hybrid PON system can solve the problem of data rate limit in upstream which happened in the conventional TDM PON because the upstream data rate is proportional to ONU and does not require a light source in ONU and its control circuits in OLT, thus can be a useful technology for asymmetric optical subscriber networks.

• The KIPS Transactions:PartC
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• v.12C no.6 s.102
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• pp.891-900
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• 2005

This paper studies network recovery methods for WDM optical mesh networks, concentrating on improving spare resource utilization. The resource efficiency can be obtained by sharing spare resources needed for network recovery. To improve the sharability of spare resources in WDM networks, methods to share backup paths us well as spare capacity should be studied. The proposed method in this paper uses multiple ring-covers and this method provides fast and simple recovery operation by exploiting the characteristics of logical ring topology, and also provides efficient resource utilization by using multiple distributed backup paths to improve the sharability of overall spare resources in the networks. This method can provide layered reliability to network service by enabling hierarchical robustness against multiple failures. The performance results show that the proposed method provide improved resource efficiency for single failure and enhanced robustness for multiple failures.

• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.13-21
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• 2015

In recent years energy consumption has become a main concern for network development, due to the exponential increase of network traffic. Potential energy savings can be obtained from a load-adaptive scheme, in which a day can be divided into multiple time periods according to the variation of daily traffic patterns. The energy consumption of the network can be reduced by selectively turning off network components during the time periods with light traffic. However, the time segmentation of daily traffic patterns affects the energy savings when designing multiperiod logical topology in optical wavelength routed networks. In addition, turning network components on or off may increase the overhead of logical topology reconfiguration (LTR). In this paper, we propose two mixed integer linear programming (MILP) models to design the optimal logical topology for multiple periods in IP-over-WDM networks. First, we formulate the time-segmentation problem as an MILP model to optimally determine the boundaries for each period, with the objective to minimize total network energy consumption. Second, another MILP formulation is proposed to minimize both the overall power consumption (PC) and the reconfiguration overhead (RO). The proposed models are evaluated and compared to conventional schemes, in view of PC and RO, through case studies.

• 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.

• ETRI Journal
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• v.35 no.2
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• pp.253-258
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• 2013

We propose and demonstrate an efficient power-saving optical network unit (ONU) based on upstream traffic monitoring for 10-Gb/s wavelength division multiplexed passive optical networks (WDM-PONs). The power-saving mode controller uses a ${\mu}$-processor and traffic monitoring modules followed by the proposed power-saving processes to operate the sleep mode ONU. The power consumption of the ONU is effectively reduced from 19.3 W to 6.4 W when no traffic from the users is detected. In addition, we design a power-saving mechanism based on a cyclic sleep mode operation to allow a connectivity check between the optical line terminal and ONU. Our calculation results show that the WDM-PON ONU reduces the power consumption by around 60% using the proposed mechanism.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.236-240
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• 1997

We compare feedback wavelength-dependent performances of all-optical gain-clamped 980-nm pumped erbium-doped fiber amplifiers. In a 2.5-Gbps 8-channel WDM system, we have measured and compared gain compressions, signal power variations due to cross-saturation, power penalties caused by relaxation oscillations and noise figures for three different feedback wavelengths - 1532, 1543, and 1565 nm.