• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.2
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• pp.1-5
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• 2007

Wavelength-division multiplexed (WDM) networks are emerging to be the right choice for the future transport networks. In WDM networks, the optical layer provides circuit-switched lightpath services to the client layer such as IP, SONET and ATM. The set of lightpaths in the optical layer defines the virtual topology. Since the optical switches are reconfigurable, the virtual topology can be reconfigured in accordance with the changing traffic demand pattern at theclient layer in order to optimize the network performance. We present a new approach to the virtual topology reconfiguration and loadbalancing problem for wavelength-routed, optical wide-area networks under dynamic traffic demand. By utilizing the measured Internet backbone traffic characteristics, our approach follows the changes in traffic without assuming that the future traffic pattern is known. For the simulation traffic modeling, we collected the data from real backbone traffic. Experiments show that the standard deviation compared to previous technique is reduced.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1666-1671
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• 2022

The structure of a high-power gain-flattened long wavelength band (L-band) optical amplifier was optimized, which was implemented for 64-channel wavelength division multiplexed optical signals with a channel spacing of 50 GHz. The output characteristics of this L-band amplifier were measured and analyzed. The amplifier of the optimized two-stage amplification configuration had a flattened gain of 20 dB within 1 dB deviation between 1570 and 1600 nm for -2 dBm input power condition. The noise figure under this condition was minimized to within 6 dB in the amplification bandwidth. The gain flattening was realized by considering only the characteristics of gain medium in the amplifier without using additional optical or electrical devices. The proposed amplifier consisted of two stages of amplification stages, each of which was based on the erbium-doped fiber amplifier (EDFA) structure. The erbium-doped fiber length and pumping structures in each stage of the amplifier were optimized through experiments.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.11
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• pp.17-22
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• 2005

In this study, we suggested wave-variable Bragg lattice using the characteristic of the Bragg wave that varies according to the change of the temperature imposed on the optical fiber lattice device, and experimented using a simulation test. We analyzed the results of the FBG change according to the change of the temperature obtained in the variable FEG computer simulation and experiment to suggest optimal data. Therefore, utilizing wave-variable optical filter through FBG allows us to combine other channels beyond optical fiber lattice device wave, and can be used as a helpful device in the Dense Wavelength Division Multiplexed system with a channel intervention of 0.08nm(10GHz).

• Smart Structures and Systems
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• v.1 no.1
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• pp.63-82
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• 2005

This paper introduces a technology for robust and low maintenance cost sensor network capable to detect accelerations below a micro-g in a wide frequency bandwidth (above 1,000 Hz). Sensor networks with such performance are critical for navigation, seismology, acoustic sensing, and for the health monitoring of civil structures. The approach is based on the fabrication of an array of high sensitivity accelerometers, each utilizing Fabry-Perot cavity with wavelength-dependent reflectivity to allow embedded optical detection and serialization. The unique feature of the approach is that no local power source is required for each individual sensor. Instead one global light source is used, providing an input optical signal which propagates through an optical fiber network from sensor-to-sensor. The information from each sensor is embedded onto the transmitted light as an intrinsic wavelength division multiplexed signal. This optical "rainbow" of data is then assessed providing real-time sensing information from each sensor node in the network. This paper introduces the Fabry-Perot based accelerometer and examines its critical features, including the effects of imperfections and resolution estimates. It then presents serialization techniques for the creation of systems of arrayed sensors and examines the effects of serialization on sensor response. Finally, a fabrication process is proposed to create test structures for the critical components of the device, which are dynamically characterized.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1427-1433
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• 2003

This paper presents the routing and wavelength and timeslot assignment problems for a circuit-switched time division multiplexed (TDM) wavelength-routed networks. In this paper, we propose an efficient distributed control protocol for establishing lightpath dynamically. The protocol uses backward reservation to reduce the chance of blocking. We use aggressive reservation method with usable multiple channels and select only one in multiple channel. We show through simulation that the proposed protocol improves the success rate in TDM-based lightpath establishment and the proposed aggressive reservation method improve blocking probability with appropriate reservation channel count.

• Journal of electromagnetic engineering and science
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• v.3 no.2
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• pp.79-85
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• 2003

In this paper, we investigated the degree of compensation for distorted optical pulse of wavelength division multiplexed(WDM) channel with initial frequency chirp generated in optical transmitter. The WDM channel signal distortion is due to chromatic dispersion, self phase modulation(SPM) and cross phase modulation(XPM) in fiber. The considered system is 3 ${\times}$ 40 Gbps intensity modulation direct detection(IM/DD) WDM transmission systems, which adopted mid-span spectral inversion(MSSI) as compensation method. We confirmed that the effect of initial frequency chirp on compensation for signal distortion due to a SPM is gradually decreased as a dispersion coefficient of fiber becomes gradually small. But, in the aspect of a compensation for signal distortion due to both SPM and XPM, the effect of initial frequency chirp on compensation is gradually decreased as a dispersion coefficient of fiber becomes gradually large.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.297-298
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• 2009

파장 분할 방식의 광섬유 격자 센서의 멀티플렉싱 능력을 향상시키기 위하여 이중 격자의 파장 간격 변조로 구분되는 다중 광섬유 격자 센서 시스템을 제안하였으며, 서로 다른 파장 간격을 가지는 센서의 상태와 위치를 정확히 구별할 수 있는 방법을 연구하고 씨뮬레이션을 통하여 확인하였다. 또한 변형력 하에서 광섬유격자 센서들간의 스펙트럼 중첩으로 불명확한 브래그 피크를 최급 강하법(steepest descent method) 알고리즘을 사용하여 약 3 pm이내의 표준편차로 결정할 수 있었다.

• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.181-185
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• 1998

Gain characteristic of concatenated erbium-doped fiber amplifiers(EDFA) are studied with a recirculating EDFA loop. For a non-flat gain EDFA, the 3 dB gain bandwidth was reduced to 6 nm after the 20th EDFA. However, for an optimized gain flattened EDFA, in a simple configuration, the 5 dB gain bandwidth was found to be 9nm, even after the 100th EDFA, corresponding to 8000km transmission. This results suggest that the simple optimized flat gain amplifier could be a good candidate for ultra-long distance wavelength division multiplexed transmissions.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.3-9
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• 2006

Among many fabrication methods of composite materials, filament winding is the most effective method for fabricating axis-symmetric structures such as pressure tanks and pipes. Filament wound pressure tanks are under high internal pressure during the operation and it has the complexity in damage mechanisms and failure modes. Fiber optic sensors, especially FBG sensors can be easily embedded into the composite structures contrary to conventional electric strain gages (ESGs). In addition, many FBG sensors can be multiplexed in single optical fiber using wavelength division multiplexing (WDM) techniques. In this paper, we fabricated several filament wound pressure tanks with embedded FBG sensors and conducted some kinds of experiments such as an impact test, a bending test, and a thermal cycling test. From the experimental results, it was successfully demonstrated that FBG sensors are very appropriate to composite structures fabricated by filament winding process even though they are embedded into composites by multiplexing.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.132-133
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• 2000

최근, 인터넷 등의 보급으로 인하여 급증하는 다양한 형태의 정보를 효과적으로 전송하기 위하여 파장분할다중화 광통신시스템 (wavelength division multiplexed optical communication system: WDM)이 활발히 개발 및 보급되어 왔다. 가변 광감쇠기는 각 파장별 광신호의 세기를 균일하게 하여 장거리 전송을 가능하게 하는 WDM시스템의 핵심 소자이다. 폴리머 소자는 제작이 간편하고 가격이 저렴할 뿐 만 아니라 다른 소자와의 집적이 용이하고, 열광학 계수가 실리카에 비하여 10배 정도 커서 구동전력을 크게 줄일 수 있는 등의 장점으로 인하여 폴리머 광감쇠기가 활발하게 연구되어 왔다$^{(1)}$ . 본 논문에서는 미세 가공된 멤브레인형$^{(2)}$ 도파로를 이용한 저전력 폴리머 가변 광가쇠기에 관한 것이다. (중략)