• The KIPS Transactions:PartC
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• v.11C no.5
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• pp.677-682
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• 2004

In the present paper routing and wavelength assignment (RWA) in optical WDM networks is considered. Previous techniques based on the combination of integer linear programming and graph coloring are complex and require extensive use of heuristics. Such methods are mostly slow and sometimes impossible to get results due to infeasibility. An alternative approach applied to RWA employs on the greedy algorithm for obtaining the maximum edge disjoint paths. Even though this approach is fast, it produces a solution for any connection request, which is very far from the optimal utilization of wavelengths. We propose a novel algorithm, which is based on the maximum flow technique to obtain the maximum quantity of edge, disjoint paths. Here we compare the offered method with previous maximum edge disjoint paths algorithms ap plied to the RWA.

• The Journal of the Korea Contents Association
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• v.4 no.2
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• pp.68-75
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• 2004

In this paper, n study a distributed establishment scheme to setup lightpath in WDM/TDM Network considering user traffic characteristics. We propose a GBTA(guaranteed-bandwidth time-slot allocation) algorithm which assigns time-slots according to the requred traffic so that it can utilize given network resources efficiently in RWTA(routing and wavelength time-slot assignment) schemes. We consider traffic specification on the basis of ATM traffic classes. Also, in order to increase link utilization and minimize blocking probability, we extend distributed lightpath establishment protocol based on GBTA algorithm. In order to establish lightpath in distributed WDM/IDM network, we use backward resonation protocol that resewes resource with recent information. We use DOWTns(Distributed Optical WDM/TDM ns) that is extended from NS(Network Simulator), in order to verify proposed GBTA-based optical wavelength routed network.

• Journal of Digital Convergence
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• v.17 no.8
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• pp.229-235
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• 2019

As the demand for broadband multimedia including the Internet explosively increases, the advancement of the subscriber network is becoming the biggest issue in the telecommunication industry due to the surge of data traffic caused by the emergence of new services such as smart phone, IPTV, VoIP, VOD and cloud services. In this paper, we have developed WDM(Wavelength Division Multiplexing)-PON(passive optical network) based on the 1-Gigabit Reach Externder (RE) technique to reduce optical core. Particularly, in order to strengthen the market competitiveness, we considered low cost, miniaturization, integration technique, and low power of optical parts. In addition, we have developed a batch system by integrating all techniques for reliability, remote management through the development of transmission distance extension and development of capacity increase of optical line by using RE technology in existing PON network. Based on system interworking with existing commercial 1G PON devices, it can be worthy of achievement of wide nationalization and optical core reduction by using this developed system. Based on these results, we are studying development of 10G PON technology.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.833-837
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• 2007

In this study, we have fabricated a gain flattened erbium-doped optical fiber amplifier. Gain flattening filters were realized by the strain-induced long period fiber gratings, which are made of periodically arrayed metal wires. Using the filter of $550{\mu}m$ period, spontaneous emission amplified at C-band wavelength by a 980nm pumping laser was flattened within 1dB of gain ripple. The performance of the simultaneous multi channel amplification was measured using a fabry-perot laser diode. Amplification ratio was above 20dB. This amplifier can be applied to the long distance transmission system based on a wavelength division multiplexing for boosting an attenuated signal.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.8
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• pp.27-33
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• 2001

The performance of the ordinary Fiber Bragg Grating(FBG) sensor strain measurement system, which uses Fabry-Perot filter for scanning wavelength, has limitation for application because of hysteresis characteristics of PZT element in the filter, slow scan rate of the filter and the high cost of system. We proposed and experimented a multiple FBG sensor system using light emitting diode(LED) as a light source and adapting Code Division Multiplexing(CDM) method to separating out individual sensor signal. Output signals for a applied static and dynamic strain and crosstalk levels between sensor signals were measured. The price of the system is very loss and the response speed is very fast. Crosstalk levels between sensor signals below - 30 dB were demonstrated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.534-543
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• 2000

In this paper, when the current optical communication system is used for the DWDM. The FBG filter for the DWDN is able to reduce the interferences between the adjacent channels. In this paper, therefore, we find the relection spectrums for the three types of induced index changes, that is, uniform, Gaussian apodized, and raised-cosine apodized. From the obtained result in this paper, we can see that uniform FBG does not fit, and that the smaller the maximum induced index change $\sigma$ is and the larger the value of parameter C in the raised-cosine apodized FBG and G in the Gaussian apodized FBG are the fitter they are on the narrow filter for DWDM.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.561-563
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• 2000

최근 인터넷에 대한 수요의 증가로 인해 데이터 트래픽이 음성 트래픽을 초과하는 단계로 이르고 있으며 또한 이동통신 가입자의 급증으로 인한 트래픽도 상당한 것으로 알려져 있다. 이렇게 폭증하는 망에 대한 요구를 수용하기 위해서는 단순히 광섬유를 추가로 설치하기 보다는 기존의 광섬유를 최대한 활용할 수 있어야 한다. 이를 위해 WDM 방식 광통신 시스템이 각광받고 있다. 본 연구에서는 우리나라의 실정에 적합한 트래픽을 모델링하기 위한 Pl(Population- Information factor) 트래픽 모델링 기법을 제시하며 이에 기초하여 도출된 트래픽 값으로 WBM을 수용하는 전력통신망 모델을 설계한다. 전력통신망 설계와 특성 분석을 위하여 Visual C로 시뮬레이션 툴을 개발하였으며, 본 결과는 향후 WDM을 수용한 전광전송망을 구축할 때 활용될 수 있다.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.1
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• pp.6-12
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• 2010

Fiber optic sensor using fiber Bragg grating(FBG) probes is used for monitoring strain and temperature distributed on the wide surfaces of large structures. In this paper, in order to use many FBG probes in one optical fiber line, we propose a complex multiplexing technology which is composed of two techniques, one is time division multiplexing and another is wavelength division multiplexing. However, we only investigate the characteristics of time division multiplexing because FBG sensors basically can be operated by wavelength division multiplexing. We calculate the optimal reflectivities and the lengthwise location of five FBG probes in serial connection in order to obtain the unique reflected intensities from the FBG probes. We fabricate five FBG probes with the reflectivities of 13%, 16%, 25%, 40% and 80%, which are determined by the theoretical calculation, and observe the signal reflected from each FBG in the time domain from the experiment. There are differences between experimental and theoretical results caused by the signal noise and the differences of reflectivities of FBG probes. But the experimental results shows the reflected signals of five FBG probes which prove the availability of complex multiplexing.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.59-67
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• 2006

We demonstrate bidirectional long-reach 35-channel dense wavelength division multiplexing-passive optical network(DWDM-PON) based on wavelength-locked Fabry-Perot laser diodes (F-P LDs). The mode control of F-P LD enhances output power at decreased the required injection power. We show packet-loss-free transmission in all 70 channels at 125 Mb/s per channel line rate through 70 km of single mode fiber without optical amplifier The DWDM-PON can consolidate a metro network into an access network by bypassing the central offices within its reach. The proposed DWDM-PON can accommodate about 80 subscribers with an EDFA-based broadband light source. Further expansion up to 100 subscribers is possible with a semiconductor-based BLS.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.444-444
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• 2022

하천 수심 계측은 수심을 사람이 직접 계측하거나 초음파 기반 유속계 (ADCP) 등 최신 계측기기를 이용하여 간접적으로 계측을 실시하고 있다. 하지만 사람이 직접 하천에서 수심을 측정하는 것은 위험이 동반되고, 수심자료의 측정오차가 크게 발생한다. 따라서 수심측정에서 직접 측정 방식의 한계를 극복하기 위해, 초분광 영상의 반사도와 수심이 높은 상관관계를 보이는 것을 활용하여, 초분광 영상 기반 수심 산정 기법을 개발하였다. 초분광 영상 기반 수심 산정 기법은 복수의 파장이 존재하는 초분광영상으로부터 두 개의 파장대의 밴드를 추출하여 모든 경우의 수에 대해 밴드비를 산정한 후, 실측수심과 밴드비 간의 회귀분석을 실시하여 상관계수가 가장 높은 회귀식을 찾아내는 방식이 최적 밴드비 분석법에 기반한다. 최적 밴드비 분석법을 통해 획득된 높은 상관성의 밴드비-수심 관계식을 이용하여 수심을 추정할 수 있다. 이러한 방법은 직접 수심 측정 방식에 비해, 높은 해상도와 밀도, 양질의 데이터를 수집할 수 있는 장점이 있다. 과거 연구에 따르면 저수심부에서의 높은 정확도의 수심추정 결과를 보였지만, 고수심부에서는 실측수심과의 오차도 높아지는 등 정확성이 떨어지는 경향을 보인다. 따라서 본 연구에서는 보다 효율적인 수심계측을 할 수 있도록 최적 밴드비 분석법을 활용한 수심추정에서 신뢰성 있는 수심의 범위를 파악할 수 있는 방법을 제시하고자 한다. 본 연구에서는 대상지역으로 낙동강 본류와 황강 지류 합류부로 선정하였고, 초음파 기반 유속계(ADCP)와 드론을 활용하여 실측수심과 초분광 영상을 취득하였다. 민감도 분석을 위한 수심자료를 0.5m 단위로 분할하였으며, 구간별로 최적 밴드비 분석을 실시하였다. 그 결과, 구간별로 산정된 상관계수와 평균제곱근오차 (RMSE)를 통해 정확도가 높은 구간을 구별할 수 있었다. 또한 해당 구간을 초과하는 수심은 초분광 영상을 통해 추정이 어려운 것으로 판단되며, 분석한 구간까지를 최대 추정 가능 수심으로 정의하였다. 마지막으로 검증을 위해 최대추정가능수심으로 판단된 구간까지의 데이터만 활용하여 최적 밴드비 분석법을 적용하여 상관계수나 평균제곱근오차 결과의 개선여부 확인을 통해, 본 연구에서 제시한 방법이 정확한 최대추정가능수심 구간을 산정할 수 있는지 확인하였다.