• Journal of Internet Computing and Services
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• v.8 no.4
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• pp.41-49
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• 2007

Ethernet passive optical network(EPON) is the next-generation technology for supporting services of high-quality at low-cost. In the EPON, all optical network units(ONUs) have to share a limited uplink channel for upstream data. In order to satisfy bandwidth demands of users on high-capacity local access networks(LANs), the optical line terminal(OLT) efficiently divides and allocates time slots of uplink channel to all ONUs. We discuss previous schemes for dynamic bandwidth allocation(DBA), such as interleaved polling with adaptive cycle time(IPACT) and sliding cycle time(SLICT). In this paper, dynamic right sizing of maximum-windows(DRSM), as a novel bandwidth allocation service, is proposed for more effective and efficient time slot allocation of the uplink channel. DRSM which is based on past information of bandwidth allocated by OLT calculates maximum available bandwidth and dynamically alters the maximum window size for the next ONU. This scheme does not only exert every effort to meet bandwidth demands of ONUs with the possible scope, it also seeks fairness of bandwidth allocation among ONUs.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.167-168
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• 2009

We propose a new computing method for Fourier hologram of 3D objects captured by lens array. Fourier hologram of the two objects which positioned at different distances can be calculated using multiple orthographic view images. The size of the Fourier hologram is in proportion to the number of the orthographic view images. By repeating the orthographic view images, the size of the Fourier hologram can be increased. The principle is verified by numerically reconstructing the hologram which is synthesized from the orthographic images captured optically.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.52-58
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• 2000

Signal propagation in nonlinear optical fiber is analyzed numerically by using SS-FEM (Split-Step Finite Element Method). By adopting cubic element function in FEM, soliton equation of which exact solution was well known, has been solved. Also, accuracy of numerical results and computing times are compared with those of Fourier method, and we have found that solution obtained from using FEM was very relatively accurate. Especially, to reduce CPU time in matrix computation in each step, the matrix imposed by the boundary condition is approximated as a sparse matrix. As a result, computation time was shortened even with the same or better accuracy when compared to those of the conventional FEM and Fourier method.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.9 s.339
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• pp.19-28
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• 2005

Coherent parallel rays from some special angle form interference pattern that seems like a diffraction lattice. This is a hologram which is expressed by 1 dimensional information. I suggest to call this as 1 dimensional hologram By using 1 dimensional hologram it is possible to make a display device. Simple optical computing structure can calculate interference pattern fast.

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.60-64
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• 1997

An image processing algorithm is presented that can identify the orientation as well as the left/right side (parity) of the digitized radiographs. The orientation was found by computing the mean square deviation between the sampled gray values along the center and their best-fit linear regression relations. The parity was determined by comparing the area difference between two thresholded images of the left and the right side around the heart, which is assumed to be around the center of the image. This method was tested with 86 images with their orientations intentionally rotated. The rotation was limited to multiples of 90 degrees, as this was the way the rotation is most likely to happen in the clinical environment. We obtained positive responses for 85 out of 86 images subject to the screening.

• Journal of the Optical Society of Korea
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• v.13 no.4
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• pp.451-455
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• 2009

We present a numerical procedure that compensates for tilt phase aberration in in-line digital holography by computing the period of interference patterns in the reconstructed phase image. This method enables the reconstruction of correct and accurate phase information, even if strong tilt aberrations exist. Example applications of tilt aberration compensation are shown for a tilted plate, a micro-lens array, and a thin film transistor. This method is convenient because it uses only one hologram and no hardware to minimize the tilt aberration.

• Journal of the Optical Society of Korea
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• v.8 no.3
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• pp.115-121
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• 2004

In this paper, we propose a new algorithm to generate elemental images in a computer generated integral imaging system. By comparing the computing time of this algorithm with that of the existing algorithm, we prove the efficiency of this algorithm. Two more algorithms considering the finite size of each pixel are also proposed. These algorithms enhance the quality of the integrated image while generating the elemental image as fast as the existing algorithm.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.49.3-50
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• 2016

Two major radiative transfer (RT) techniques have been developted to model late-type galaxies: approximate RT and Monte Carlo (MC) RT. In the approximate RT, first proposed by Kylafis & Bahcall, only two terms of unscattered (direct) and single-scattered intensities are computed and higher-order multiple scattering components are approximated, saving computing time and cost compared to MC RT. However, the approximate RT can yield errors in regions where multiple scattering effect is significant. In order to examine how significant the errors of the approximate RT are, we compare results of the approximate RT with those of SKIRT, a state-of-the-art MC RT code, which is basically free from the approximation errors by fully incorporating all the multiple scattered intensities. In this study, we present quantitative errors in the approximate RT for late type galaxy models with various optical depths and inclination angles. We report that the approximate RT is not reliable if the central face-on optical depth is intermediate or high (${\tau}_V$ > 3).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.275-278
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• 1998

In recent years, miniaturization has become the key factor in the development of mobile communication system. Portable communications and computing devices suffer from two conflicting requirements which are device size to be as small as possible and large, high resolution display. These problems can be solved by virtual display. Any display in which the user views an image through an optical system is a virtual display. It provides a display which is high resolution, appears large to the viewer and at the same time occupies little physical space. In this study, handhold units of mobile communication was investigated through use of the SLA(Scanned Linear Array). The basic SLA mechanism comprises a linear array of LED's, a magnifying lens, and a scan mirror. To optimize virtual image, we investigated optical system design and operating condition for each part.

• Electronics and Telecommunications Trends
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• v.31 no.6
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• pp.13-20
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• 2016

실리콘 포토닉스 기술은 컴퓨터를 비롯한 여러 전자, 통신 기기들이 광 정보를 송수신하는 데 표준 실리콘을 이용하는 기술로, 기존 실리콘 반도체 기술과 호환될 수 있는 기술이다. 전자와 광의 융합기술로 실리콘 칩 사이, 또는 칩 내에서 빛으로 데이터를 주고받아, 데이터 전송속도를 획기적으로 올리면서도 전력 소모량을 크게 줄일 수 있는 것이 가능하다. 고성능, 저 생산비용과 낮은 소비전력 등의 장점 때문에, 전 세계적으로 실리콘 포토닉스 핵심기술/실용적 플랫폼 연구개발 및 상용화 경쟁이 이루어지고 있다. 본지에서는 실리콘 포토닉스 기술의 간략한 개요, 현재 동향 및 기술 이슈, 그리고 ETRI에서 연구개발된 실리콘 포토닉스 기술과 더불어 그 발전 전망에 대해 기술한다.