• ETRI Journal
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• v.29 no.5
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• pp.682-684
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• 2007

A new scheme to alleviate contention in optical burst switching networks is proposed. It consists of preventively reserving resources in a node, to be used if resources are busy on the next hop node. The burst is sent back to the preceding node and then resent forward. Simulations are carried out to assess the feasibility of the proposed scheme. Its performance is compared with that of contention resolution based on deflection routing.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.457-459
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• 2005

OBS(Optical Burst Switching) 망에서 우선 순위를 보장해 주기 위해 채널 선정 방식(preemptive channel reservation scheme)이 제안되어 왔다. 채널 선점으로 인해 drop된 버스트의 크기가 OBS 망의 전체 성능에 영향을 끼치는 요소인데도 불구하고 기존의 채널 선점 방식은 선점될 채널 선택 시에 버스트의 채널 사용 시간(elapsed time)만을 고려하고 있다. 따라서 본 논문에서는 각 버스트의 채널 사용 시간과 버스트 길이의 합이 작은 채널을 선택하는 선점 방식으로써 Length-based Smallest Elapsed time Selection(LSE)을 제안한다 시뮬레이션을 통하여 제안하는 LSE 방식이 기존의 SE(Smallest Elapsed time)에 비해서 버스트 손실 성능 면에서 우수함을 알 수 있었다.

• Korean Journal of Optics and Photonics
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• v.12 no.5
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• pp.401-405
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• 2001

We propose a novel channel-switching transmission filter using segmented chirped fiber Bragg gratings (CFBG's) each of which has separate transmission bands in the reflection spectrum of the CFBG. The segmented CFBG's are made by using specially designed slits. The separated reflection spectral bands of the segmented CFBG's are controlled by the attached fiber stretchers, and the controlled reflection bands are used to choose the channels independently. Tunability of the transmission spectra is experimentally demonstrated in WDM transmission experiments.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.146-150
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• 2002

1.55${\mu}{\textrm}{m}$ PnpN optical thyristor as a smart optical switch has potential applications in advanced optical communication systems. PnpP optical thyristors operating at 1.55${\mu}{\textrm}{m}$ are proposed and fabricated for the first time. In the optical thyristors, we employ InGaAs/InP multiple quantum well (MQW) for the active n- and p-layers. The thyristors show sufficiently nonlinear s-shape I-V characteristics and spontaneous emission. In the OFF-state, the device has a high-impedance up to switching voltage of 4.03(V). On the other hand, it has low-impedance and emits spontaneous light as a light-emitting diode in the ON-state voltage of 1.77(V), and switching voltage is changed under several light input conditions. It can be used as a header processor in optical asynchronous transfer mode (ATM), as a hard limiter in optical code division multiple access (CDMA) and as a wavelength converter in optical WDM systems.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.231-234
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• 2008

In this paper, we propose a novel electrode structure for superb transmittance in super in-plane switching (S-IPS) mode while keeping the features of the conventional SIPS mode such as the capability of initial LC alignment. The optimization of the electrode made it possible to enhance the light transmittance approximately by 14 % in comparison to the conventional S-IPS cell.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.105-108
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• 2005

We demonstrate an electro-optical device based on the flexoelectric effect of a short-pitched cholesteric liquid crystal. By using a dual-frequency switchable nematic, a small amount of chiral dopant and a small amount of phase-separated polymer localized on the surface, we were able to create a device that operates in amplitude (flexoelectric) and phase(dielectric) modes. At high frequency the dual frequency liquid crystal suppresses the phase mode at higher voltage, which improves the switching speed, and thereby preserving the in-plane-switching mode.

• The KIPS Transactions:PartC
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• v.10C no.3
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• pp.317-324
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• 2003

In this paper, we propose the ATM based Passive Optical Network (PON) using the optical CDMA scheme with optical switches and PN codes in time domain. We also propose the bipolar optical receiving correlator for PN codes. As optical CDMA is performed by driving directly an optical switch on-off switching with PN codes, the number of distinct code sequences can be increased and the flexibility in assigning PN codes can be improved. Finally we theoretically analyze the signal-to-interference -plus-noise ratio and the bit error probability of regenerated signal and compare the performance of proposed scheme compared with ATM based PON using conventional optical CDMA with optical delay lines.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1B
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• pp.109-116
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• 2004

Optical Burst Switching (OBS) technology has drawn much attention as a promising solution for IP/WDM networks. OBS has the features such as the offset time, the delayed reservation and the burst assembly. In particular, the burst assembly, which assembles IP packets into the data bursts, has a great impact on the performance of OBS network. In this paper, we compare the performance of three different burst assembly schemes and investigate their impact on the performance of OBS network.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.315-319
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• 1997

In photorefractive crystals, light deflection is achieved by dynamic photorefractive volume grating, which is induced by the interference of two writing beams. In this paper, we implemented and analyzed the light deflector using Ce-SBN:60 crystals, which is doped with CeO$_2$ and photorefractive effect is induced by low intensity. And we measured maximum coupling coefficient, effective charge density, diffraction efficiency as the intensity ratio and response time.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.796-799
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• 2006

We studied the nematic liquid crystal (NLC) alignment capability by the Ion beam (IB) alignment method on a NDLC (Nitrogen doped Diamond Like Carbon) as a C:H thin film, and investigated electro-optical (EO) performances of the IB aligned In plane switching (IPS) cell with NDLC surface. A good LC alignment by IB exposure on a NDLC surface was achieved. Monodomain alignment of the IB aligned IPS cell can be observed. The good electro-optical characteristics of the IB aligned IPS cell was observed with oblique IB exposure on the NDLC as a-C:H thin film for 1min.