• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.7
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• pp.52-60
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• 2009

In this pater, a CP-DRA(Circularly Polarized Dielectric Resonator Antenna) using cross-slot-feed is studied to enhance the gain and axial ratio bandwidth. First, a single layer CP-DRA is studied as a reference for comparison. Then a new type of multilayer CP-DRA is proposed to enhance the gain and axial ratio bandwidth. In consideration of the antenna gain enhancement, the spacing between the elements of the multilayer CP-DRA is examined through analysis of the radiation performance of a 2$\times$2 planar amy of DRAs with a spacing of 0.7$\lambda_0$ and 1.2$\lambda_0$ using CST Microwave Studio. The measured result shows that the gain and bandwidth of the multilayer structure is approximately twice that of the single layer one. In the case of the array antenna in which the spacing between multilayer CP-DRA element is 1.2$\lambda_0$, a grating lobe is reduced, in contrast to what we can expect from a conventional antenna array. The gain is 13.4dBi and axial ratio bandwidth is 0.8GHz.

• Proceedings of the Optical Society of Korea Conference
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• 1990.07a
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• pp.123-132
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• 1990

The method of characteristic matrix used in the calculation of multi-layered optical coating is applied to the analysis of DFB waveguide with arbitrary structure of grating by plecewise approximation where the DFB structure is devided into many sections in which the gain and period, amplitude and phase of DFB structure are assuced to be constant in each section. The DFB structure with two section is analyzed using this method of C-matrix. The possible applications for photonic devices using DFB waveguides are proposed.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.80-81
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• 2000

최근 통신 서비스의 증가에 따라 대용량의 전송 용량이 요구되고 있으며, 이에 대한 해결책으로 파장분할다중(WDM) 방식의 광전송에 관한 많은 연구가 수행되었다. EDFA는 1550 nm 근처에서 이득 영역을 가지고 있기 때문에 장거리 광통신 시스템에 주된 광증폭기로 사용되고 있으나 파장에 따른 이득이 서로 다르게 나타나기 때문에, WDM 시스템에 이용하기 위해서는 EDFA의 이득 평탄화가 필요하며, 이에 대한 다양한 연구가 이루어지고 있다. (중략)

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.5-9
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• 2003

장주기 격자 필터를 이용한 EDFA용 이득평탄화 필터 설계에는 대역폭에 따라 한 개에서 세 개까지의 평탄화가 가능하다 이러한 필터 설계는 EDFA의 고유의 중심 파장, 크기, 대역폭에 대한 각 장주기 광섬유 격자의 중심 파장, 크기, 대역폭을 설정하여 이득평탄화를 최적화시킨다. 이득평탄화 필터의 설계를 위한 방법으로써 수동 설계통한 이득평탄화를 했으나, 신속하고 편리함을 위해 반자동 설계, 자동 설계 프로그램을 구현하였다. 이를 통한 이득평탄화 정도는, 수동이 0.38dB, 반자동 0.57dB, 자동 0.62dB 정도로 정밀한 이득평탄화를 얻을 수 있는 설계가 가능하였다.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.2
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• pp.81-89
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• 1999

Among various wavelength conversion technologies, that using the cross-gain modulation in laser diode makes it possible to deal with the high speed signal quite simply and efficiently. In this paper, presented was the applicability of an improved time-domain large-signal dynamic model as a CAD tool to analyzed the characteristics of SSGDBR(Superstructure Grating Distributed Bragg Reflector) laser diodes used for wavelength converters. Using this model, it was shown that this kind of wavelength converter can provide the widely tunable wavelength conversion of the high speed data above 10 Gbps. We also investigated the effect of input optical power and the bias current on the characteristics of the device such as extinction ration and eye diagram. The modeling results show very similar trend to the experimental reports.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.10
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• pp.21-25
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• 2014

Scan capabilities of Fabry-Perot cavity (FPC) antennas are investigated for the case of a $4{\times}1$ thinned array placed inside the cavity. The FPC array antenna has higher maximum gain and lower sidelobe level (SLL), but the maximum scan angle of the thinned array is 14-17% lower than the patch array alone, due to increased mutual coupling in the FPC structures. However, unlike the bare thinned array, the SLL of FPC array does not suffer from the grating lobe problem even though it has a relative large element spacing of more than $1.0{\lambda}_0$.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.321-326
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• 2003

We constructed grating- tuned external cavity semiconductor lasers using Littman and Littrow configuration, for which the wavelengths are tuned by rotation of the grating. This wavelength tunable semiconductor laser is one of the main devices of WDM optical communication. In Littman configuration, the wavelength range of about 60 nm (The C- and L-band range of 1,530~1,590 nm) was obtained by changing the incidence angle of the grating about $\pm$1$^{\circ}$ from the incidence angle of 70$^{\circ}$. In the 40 nm tuning range, the output power variation was less than 1.25 ㏈ and the side mode suppression ratio(SMSR) was 32 ㏈. In Littrow configuration (The incidence angle and the first order diffraction angle is the same, i.e. $\alpha$=$\delta$), the wavelength tuning range was about 80 nm for the same conditions used in Littman configuration except the incidence angle ($\alpha$=49$^{\circ}$). In 60 nm tuning range, the output power variation was less than 1.5 ㏈ and SMSR was 35 ㏈.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.10 s.113
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• pp.1000-1006
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• 2006

In this paper, the gain of the square hem antenna is enhanced with $3{\times}3$ latticed aperture. In order to get the uniform field distribution on the aperture, the different thicknesses of dielectric plates for the phase compensation are inserted into the center and the edge of the aperture respectively. The proposed horn antenna is designed at 12.5 GHz band, and then the analysis of the field distribution on the aperture is performed by using FDTD method. The radiation pattern is also calculated from the analysis. Based on the measured data, it is verified that the gain of a horn antenna with latticed aperture is 18 dBi and this is 2 dB gain enhancement compare with a normal horn antenna without latticed aperture.

• 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.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.57-60
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• 2001

In order to extend the life time of building and civil infra-structure, nowadays, patch type fibrous composite materials are widely used. Retrofitted concrete columns and beams gain the stiffness and strength, but they lose toughness and show brittle failure. Usually, the cracks of concrete structures are visible with naked eyes and the status of the structure in the life cycle is estimated with visible inspection. After retrofitting of the structure, crack visibility is blocked by retrofitted composite materials. Therefore, structural monitoring after retrofitting is indispensible and self diagnosis method with optical fiber sensor is very useful. In this paper, We try to detect peel out effect and find the strain difference between main structure and retrofitting patch material when they separate each other.