• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.1
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• pp.33-38
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• 2005

A cost-effective dense WDM-PON employing wavelength-locked Fabry-Perot lasers has been demonstrated. We have successfully demonstrated a dense WDM transmission of 4×622 Mb/s upstream signal with 50-GHz channel spacing over 30-km conventional single mode fiber. We have also investigated the heating noise characteristics of a wavelength-locked Fabry-Perot laser and showed the wavelength-locked Fabry-Perot laser suppresses the intensity noise of the incoherent light injected which enables a dense WDM transmission with a channels spacing of 50 GHz.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.127-129
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• 2004

대부분의 통신망 복구기법에서는 예상되는 손실에 대한 망 복구를 설계한다. 예를 들어 가장 자주 발생하는 단일 링크 손실의 경우에 대하여 100%의 복구를 보장하는 형태이다. 그러나, 예상되지 않은 손실, 즉 다중 링크의 손실과 같은 경우에는 이리 준비된 예비 자원을 가지고는 설계한대로 100% 복구를 수행할 수 없다. 이 경우에는 남아있는 예비 자원을 이용하여 손실된 트래픽의 일부만이라도 복구하여야 한다. 본 논문에서는 두 개의 링크가 동시에 손실된 경우에 트래픽의 우선순위에 기반하여 여러 단계의 계층적인 복구 견고성을 제공하여, 최상위 우선순위의 트래픽에 대해서는 100%에 가까운 복구율을 제공하는 기법을 제안한다. 제안된 기법은 단일 링크의 손실에 대비한 예비 자원만을 할당하여 다중 링크 손실의 경우에도 높은 우선순위의 트래픽에 대하여 복구 견고성을 제공한다는 점에서 그 실효성이 크다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.160-167
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• 2005

The gain-clamped EDFA has been developed to eliminate the output power change of WDM surviving channels to occur with added or dropped channels, which degrades the performance of WDM optical network. It maintains the constant gain of surviving channels when WDM channels are added or dropped in a network amplifying node. In this paper, the hi-directionally pumped gain-clamped EDFA is implemented to compensate the change of the input power by a lasing. The results show that the lasing of a short wavelength and backward propagation is the optimal condition to minimize the transient response of surviving channels in terms of the overshoot and gain saturation due to the inhomogeneous broadening effect.

• Korean Journal of Optics and Photonics
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• v.14 no.6
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• pp.578-582
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• 2003

We propose a novel structure of wavelength selective optical add/drop module comprising two tap couplers and a fiber Bragg grating. The device has unique features including a simpler structure and a lower cost of implementation as compared with existing devices for the same operation. The module performance has been measured and analyzed experimentally. The implemented prototype module shows good performance with no-crosstalk power penalty in a 155 Mbps per channel wavelength-division-multiplexing transmission system but suffers from a relatively high loss of 3.5 ㏈ and 21 ㏈ for transmitted and dropped channels, respectively. While the dropped channel extinction ratio was more than 25 ㏈, the transmitted channel extinction ratio was more than 35 ㏈.

• 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㏈.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.664-674
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• 1996

In high speed multi-wavelength networks, retransmission overhead due to desination conflict or control packet collision is one factor of performance degration because signal prpagation delay is much larger than the transmission time of data packet. In this paper, an efficient WDMA protocol with a collision avoidance mechanism is proposed for high speed WDM single-hop network with a passive star topology. In proposed protocol, each node has cource queues and routing table to store souting informatio. This architecture makes is possible to avoid any kind of collision when a node reserves the channel to transmit a data packet. High system thoughput and channel utilization can be achieved by proposed protocol since there are no discarded packets caused by any collision at transmission time. The performance of proposed protocol is evaluated in term of throughput and delay with variations in offered load. Simulation results show that the proposed protocol has superior performance to convertional protocols under nonuniform traffic as well as uniform traffic.

• Korean Journal of Optics and Photonics
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• v.24 no.6
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• pp.297-310
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• 2013

With the explosive growth of internet data traffic due to the FTTH penetration, prevalence of smart devices and cloud network service, the demand for higher bandwidth is ever increasing with the pace of more than 40% annual growth. To accommodate ultra high bandwidth traffic, optical components in each hierarchy have progressed rapidly. WDM has begun to be deployed along with higher bandwidth service in the access network. Next-generation ROADM is under development for efficient network management in the metro network. For long-haul transmission, an advanced modulation scheme based on coherent transmission technology has been adopted to enhance spectral efficiency. In this paper, core components to meet the demands of high speed, high efficiency and low power consumption will be reviewed.

• The KIPS Transactions:PartC
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• v.10C no.5
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• pp.603-610
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• 2003

On the optical network, it is important to build restoration scheme capable to network survivability in preparation of potential failure on communication route. This paper analyze the existing schemes on restoration of failure on the optical network, and propose deferred commit scheme to improve resource utilization and management efficiency. Also, the transfer flow of messages needed for transferring restoration signal are presented in a concrete way and delay time required by shared mesh restoration scheme is explained in a substantial way. Simulation-based comparative analysis of various schemes is performed.

• Journal of the Korean Professional Engineers Association
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• v.34 no.4
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• pp.41-47
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• 2001

The paper describes SR3 (Synchronous Round Robin with Reservations), a collision-free medium access control protocol for all-optical slotted packet networks based on WDM multi-channel ring topologies where nodes are equipped with one fixed-wavelength receiver and one wavelength-tunable transmitter SR3 is derived from the SRR and MMR protocols previously proposed by the same authors for the same class of all-optical networks. SRR and MMR already achieve an efficient exploitation of the available bandwidth, while guaranteeing a throughput-fair access to each node. SR3, In addition, allows nodes to reserve slots. thereby achieving a stronger control on access delays; it is thus well suited to meet tight delay requirements, as it is the case for multimedia applications. Simulation results show that SR3 provides very good performance to guaranteed qualify traffic, but also brings signigicant performance improvements for best-effort traffic. Energy effciency is an important issue for optical network since they must rely on their batteries. We present a novel MAC protocol that achieves a good energy efficiency of optical interface of the network and provides support for diverse traffic types and QoS. The scheduler of the base station is responsible to provide the required QoS to connections on the optical link and to minimise the amount of energy spend by the High speed Network. The main principles of the MaC protocol are to avoid unsuccessful actions, minimise the number of transitions , and synchronise the mobile and the base-station. We will show that considerable amounts of energy can be saved using these principles.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.7
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• pp.1359-1366
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• 2007

The recent, a large capacity of communication is required in order to it is in proportion to capacity of information communication increase and to satisfy a demand because of the demand about Internet, a multimedia service of Video of internet protocol(VoIP), Audio/Video steaming. DWDM(Dense Wavelength Division Multiplexing) technique has been emerged as the method of solving it without additional optical fiber network building and hish-speed equipment. Therefore this thesis proposed the optical filter of fiber/multilayer slab coupled structure combining it to multilayer slab waveguide by polishing the cladding of one side of fiber to design the optical filter having these functions. The optical filter proposed as the simulation result satisfies DWDM filter characteristic; 1) when the separation distance between fiber and slab is $4.15{\mu}m$ at the communication window of $1.5{\mu}m$, the polarization independence is 65nm, 2) when the center wavelengths about TM mode and TE mode are each ${\lambda}_0=1.54946\;{\mu}m$ and ${\lambda}_0=1.6144\;{\mu}m$ and, FWHM(Full at Half Maximun) is 0.1nm.