• ETRI Journal
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• v.7 no.4
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• pp.3-10
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• 1985

After the light from an incoherent LED was transmitted through the multimode fibers which were linked over 10 km, the nearfield power distribution reached the steady-state independent of launching conditions. It has been also found that the steady-state output power distribution showed the pattern of Gaussian function. In this steady-state Gaussian function pattern, the measured losses of fibers were very repeatable values. In case of using LD source, the speckle phenomena in near -field power distribution appeared until the distance of 10 km. And the output power distribution did not reach the steady-state shown in LED even over 20km on account of the coherence and the nonuniform lasing modes of LD. But the measured losses of fibers were nearly stable in this long distance.

• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.415-422
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• 2004

We propose and present a new multiplexed bend loss type single-mode fiber-optic sensor system for displacement measurement in order to measure the displacement of several mm of civil engineering structures such as bridges and buildings. We make a bend loss type fiber-optic sensor for measuring displacements using the signal difference between two reflection signals due to various bend losses generating at a pair of optical connectors by using the optical time domain reflectometer. And we fabricate a multiplexed bend loss type fiber-optic sensor detecting linear displacements of 4 measuring positions of an object by setting these new 4 fiber-optic sensors on a single mode fiber simultaneously. We find that the multiplexed fiber-optics displacement sensor has linearity of 0.9942, maximum displacement of 6 mm, and accuracy of 6% for 4 measuring points.

• The KIPS Transactions:PartC
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• v.13C no.4 s.107
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• pp.441-446
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• 2006

In recent years, WDM networks have received much attention as the Internet backbone networks because of the explosive growth of the Internet IP-based traffic. The Optical Burst Switching (OBS) has been proposed as an effective optical switching technology in the WDM networks. The OBS has the advantages in 1) the high usage rate of the bandwidth, and 2) no necessity of optical buffer. However, the OBS has the burst-contention problem in the networks. The deflection routing is proposed as one of means to solve this problem. In this paper, we propose a new routing method to minimize burst loss in the deflection routing based networks. In addition, we propose a QoS control method using a new routing algorithm. Finally, we show the variety of the proposed methods by computer simulations.

• Composites Research
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• v.15 no.4
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• pp.17-22
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• 2002

Small diameter composite helical springs (CS) are developed using a hot plated mold for reinforcement of common optical fiber jumper cord (OJC). The outer diameters of the springs are about 2 ~ 3mm. These springs are inserted into the OJC to protect the damage of an optical fiber from the sudden lateral load. Two types of CS, Yarn type (Y-type) and Band type (B-type), are manufactured to compare the effectiveness for the damage protection. The experimental works were conducted to check the effect of the CS covered around OJC on the mechanical and optical properties. Experimental observations show a considerable effect on the flexural resistance, hence slowing down the deterioration of the optical power by the internal damage of the fiber. Obtained main results are as follows: (1) Y-type CS has better protection abilities to lateral loading than B-types. (2) Compared with bare OJC, CS-OJC has less power loss under the loading. (3) OJC covered with the composite coil spring has a possibility for a practical usage with full fruits.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.11C
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• pp.1139-1151
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• 2002

In this paper, we propose the novel module-type optical space switch, employing time division multiplexing (TDM) method and multihop structure, in order to enlarge the capacity of the switching system. And we show that the proposed structure is superior over conventional ones, in terms of power loss, the number of the devices used, and signal to crosstalk (SXR). We also analyze the saturation throughput with the number of module M. As a result, the saturation throughput of the switching system with M modules is M+ 1-√(M$^2$+1), when the number of input port in a module (N) is large. Finally, we confirmed the cell loss rate (CLR) performance with the proposed switch through simulation. For example, when p=0.9, M=8 and N=32, to get the CLR that is less than or equal to 10$\^$-6/, the number of input buffers storage unit is greater than or equal to 6 and output buffers storage unit is greater than or equal to 52.

• Journal of IKEEE
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• v.27 no.4
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• pp.450-455
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• 2023

Among single-phase photovoltaic inverters that can avoid excessive leakage current caused by the large parasitic capacitance of photovoltaic panels, a boost converter followed by a half-bridge inverter is the simplest and has the smallest leakage current. However, due to the high DC-link voltage, the rated voltage of the switching devices is high and the switching loss is large. This paper proposes a new circuit topology which can operate as a buck-boost inverter by adding two bidirectional switches to the output side of the half-bridge inverter instead of removing the boost converter. By reducing two stages of power conversion through the high-voltage DC-link to one stage, power loss can be reduced without increasing costs and leakage current. The feasibility of the proposed circuit topology is verified by computer simulation and power loss calculation.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.4 no.2
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• pp.33-40
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• 1990

고압 수은등의 전기적 특성을 예측하기 위한 컴퓨터 프로그램을 작성하였다. 즉 고압기체방전에서 성립되는 단위체적당 에너지 평형식과 입자의 밀도에 대한 연속방정식을 방전관의 반경과 시간에 대하여 풀어서 전류값을 예측하였다. 프로그램의 수행결과, 방전광에 입력된 에너지는 방사에너지로 가장 크게 손실되며, 전도손실은 시간에 무관하게 거의 일정한 것으로 나타났다. 또한 비교적 길이가 짧은 방전관의 특성을 예측하기 위하여 음극강하를 고려하여 산정한 길이를 추정하는 방법을 개발하였다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.3
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• pp.218-225
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• 2023

An agrivoltaic system (AVS) is a combined system that generates power through photovoltaic panels (PVPs) installed above a field where a crop is cultivated. Although soil moisture is an important limiting factor for open-field crop production, particularly during spring season in Korea, it is not well considered in the utilization of AVS. Indeed, the application of water-energy-food nexus on the AVS should be necessary. In this study, the changes of soil moisture and temperature under the AVS was investigated in fallow paddy field during spring season. The AVS that has partial shading condition by PV panels was decreased soil temperature and increased soil moisture compared to open-field. Furthermore, the maximum of the change in soil moisture to the change in soil temperature had a negative correlation both on open-field and AVS under wet condition. It represents that the micro-climate under the AVS is in energy-limited condition. The open-field of relatively high soil temperature was in water-limited condition. The different behavior of soil moisture on the AVS should be considered for the sustainable agricultural system as related to water-energy-food nexus.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1982.10a
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• pp.29-32
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• 1982

본 논문은 광섬유 케이블의 설계에 있어, 케이블 공정에 따른 광손실의 증가를 최소로하는 케이블의 구조 및 광케이블의 포설에 따른 잔류 응력의 억제 등, 장기간 동안 케이블의 전송특성을 유지하며, 광섬유의 파단 방지를 목표로 고려해야할 사항을 논하였다. 광섬유의 특성을 유지하기 위해서는 광섬유 제조시 사용되는 재질 및 적정 Dimension 설정이 필요하며 광섬유 파단 방지를 위해 CABLE내에 TENSION MEMBER를 수용하는 구조를 검토, 광섬유 CABLE 포설시 광섬유의 파단 확률을 감소시키며, 광섬유의 잔류응력을 억제하는 관점에서 케이블 구조를 설계하였다.

• The Optical Journal
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• s.134
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• pp.26-31
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• 2011

레이저 프로젝터에서 스크린을 조사할 경우 원리적으로 광 손실이 크기 때문에 발생한 스펙클은 시간적으로 독립적인 다수의 스펙클 패턴을 화상에 중첩해서 그 평균 조작에 의해서만 본격적으로 저감할 수 있다. 평균조작에 대한 매우 높은 시간적 다중도를 실현하는 수단으로서 스크린 투영광로 중에 삽입한 확산판을 정현함수적으로 진동시키는 진동확산판 방식이 유망하다. 이 원고는 Kubota Shigeo 교수(도쿄대학 생산기술연구소 1부)가 월간 Optronics(통권 349호)에 기고한 내용으로, 필자는 향후 이러한 전자 액추에이터가 Miniature화 되고, 스펙클 저감 디바이스로서 보급되기를 바란다고 밝혔다.