• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.40 no.4
• /
• pp.21-26
• /
• 2003

In this paper, a channel spacing-tunable sampled fiber gratings(SFGs) is proposed, and analytically and experimentally investigated. The channel spacing of the proposed SFGs can be tuned by simply changing the period of the external pressure on the fiber Bragg gratings(FBGs). The channel spacing of 1.4nm was tuned to 0.8nm by changing the pressure period from 580${\mu}{\textrm}{m}$ to 1000${\mu}{\textrm}{m}$ The experimental results agree well with the theoretical results.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.12
• /
• pp.43-49
• /
• 2000

In this paper, a novel wavelength selectable multi-channel OADM(Optical Add/Drop Multiplexers) is proposed and experimentally demonstrated. The proposed OADM drops simultaneously more than one channel among many channels with small wavelength tuning by using one sampled grating and FBGs, Interchannel crosstalk (or interchannel rejection ratio) better than 20[dB] has been shown experimentally.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.2
• /
• pp.55-60
• /
• 2008

Multi-wavelength Erbium-doped fiber(EDF) ring laser was developed by using a sampled fiber Bragg grating reflecting multiple wavelengths, which was formed by impressing periodical pressure on the outside of a fiber Bragg grating. The wavelength spacing was varied to 4.1nm, 1.41nm and 0.82nm, by pressing the grating with the pressure period $200{\mu}m$, $580{\mu}m$ and $1000{\mu}m$, respectively.

• Korean Journal of Optics and Photonics
• /
• v.16 no.6
• /
• pp.485-489
• /
• 2005

I have investigated a scheme for suppressing stimulated Brillouin scattering in optical fibers. The scheme makes use of a sampled Bragg grating fabricated within the fiber used for transmitting intense Q-switched pulses. The grating is designed such that the spectrum of the Stokes pulse generated through stimulated Brillouin scattering falls entirely within its stop band. I show numerically that the number of sampled fiber Bragg gratings in 1 m is applied directly to suppressing stimulated Brillouin scattering rather than the coupling coefficient. This prevents the build up of the backward-propagating Stokes wave and mitigates the deleterious effects of stimulated Brillouin scattering. The simulation shows that 15 ns pulses with 1 kW peak power can be transmitted though a 1 m-long fiber with little energy loss using this scheme.

• Proceedings of the KIEE Conference
• /
• 2007.10a
• /
• pp.109-110
• /
• 2007

본 논문에서는 베이시안 초해상도 영상처리시 저해상도 영상들을 고해상도 격자에 맞게 정합해서 업샘플링(upsampling)을 하는 새로운 방식에 대해 제안한다. 제안하는 업샘플링 방식은 각 장을 따로 보간하는 방식과 달리 여러 저해상도 영상의 고주파 정보가 고해상도 영상 격자의 모든 위치에 적절히 영향을 미칠 수 있도록 여러 장의 저해상도 영상의 고주파 정보를 함께 사용하여 보간한다. 보간하는 방법은 B-스플라인 (B-Spline) 기반 비정규 리샘플링(non-uniform resampling)을 기반으로 초해상도 영상처리에 맞도록 적용한다. 실험결과를 통해 일반적으로 적용되는 0-삽입(zero-padding) 업샘플링 방식과 쌍일차 보간법(bilinear interpolation) 등을 적용할 때의 효과를 살펴보고, 제안하는 방식이 일반적인 방식을 사용하는 것에 비해 정량적, 정성적으로 고해상도 정보를 더 정확히 생성해내는 것을 확인한다.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.8 no.6
• /
• pp.899-905
• /
• 2013

In this paper, we focus on how to calibrate multi-cameras easily and how to efficiently detect quad-copters with small-numbered particles. Each particle is a six dimensional vector that is composed of 3D position and 3D orientation of a quad-copter in the space. Due to curse of dimensionality, that leads to explosive computational costs with a large amount of high-dimensioned particles. To detect efficiently, we need to put more particles in very promising spaces and few particles in other spaces. Though computational cost is lowered by minimizing particles, in order to track a quad-copter with multiple cameras in real-time, multiple images from the cameras should be synchronized and analyzed. Therefore, lots of the computations still need to be done. Because of this, GPGPU(General-Purpose computing on Graphics Processing Units) is implemented for parallel computing. This method has been successfully tested and gives accurate results in practical situations.

• Korean Journal of Environmental Biology
• /
• v.39 no.4
• /
• pp.526-535
• /
• 2021

Spatial sampling design plays an important role in GIS-based modeling studies because it increases modeling efficiency while reducing the cost of sampling. In the field of agricultural systems, research demand for high-resolution spatial databased modeling to predict and evaluate climate change impacts is growing rapidly. Accordingly, the need and importance of spatial sampling design are increasing. The purpose of this study was to design spatial sampling of paddy fields (11,386 grids with 1 km spatial resolution) in Korea for use in agricultural spatial modeling. A stratified random sampling design was developed and applied in 2030s, 2050s, and 2080s under two RCP scenarios of 4.5 and 8.5. Twenty-five weather and four soil characteristics were used as stratification variables. Stratification and sample allocation were optimized to ensure minimum sample size under given precision constraints for 16 target variables such as crop yield, greenhouse gas emission, and pest distribution. Precision and accuracy of the sampling were evaluated through sampling simulations based on coefficient of variation (CV) and relative bias, respectively. As a result, the paddy field could be optimized in the range of 5 to 21 strata and 46 to 69 samples. Evaluation results showed that target variables were within precision constraints (CV<0.05 except for crop yield) with low bias values (below 3%). These results can contribute to reducing sampling cost and computation time while having high predictive power. It is expected to be widely used as a representative sample grid in various agriculture spatial modeling studies.

• Korean Journal of Optics and Photonics
• /
• v.15 no.6
• /
• pp.485-489
• /
• 2004

We demonstrated numerically that both the chromatic dispersion and the dispersion slope could be compensated by using purely phase-sampled superstructure fiber Bragg gratings provided with chirp of coupling coefficient along the wavelength axis. Also, we propose a purely phase-sampled Bragg grating for dispersion and dispersion slope compensation by introducing a chirp in coupling coefficient and sampling function. The bandwidth of all reflected channels can be equalized.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.11a
• /
• pp.739-741
• /
• 2005

컴퓨터 게임 지리정보시스템(GIS), 가상현실 분야 등에서 환경 표현의 기반이 되는 지형 렌더링 기술은 매우 중요하다. 최근 LIDAR와 같은 3D 스캐닝 기술은 보다 정밀하고 정확한 지형 데이터를 제공한다. 하지만, 실시간 렌더링을 위해 사용되는 대부분의 방법들이 DEM이나 DTED와 같은 정규격자(uniform grid) 데이터에 최적화 되어 있기 때문에, LIDAR 데이터와 같은 비정규 데이터에는 적합하지 않다. 또한 방대한 LIDAR 데이터는 일반 PC에서 처리가 쉽지 않다. 본 논문에서는 대용량 비정규 데이터에서의 빠르고 효율적인 렌더링 방법을 제안한다. 샘플 데이터의 공간적 분포에 따라 정규격자를 생성하고, 이 격자에 맞도록 LIDAR 데이터를 재샘플링(resampling)하여 DTED와 같은 형태로 변환한다. 기하 재구성된 데이터에 연속적인 상세단계(CLOD)기반의 쿼드트리 알고리듬을 적용하여 지형을 효율적으로 렌더링한다.

• Korean Journal of Optics and Photonics
• /
• v.17 no.6
• /
• pp.489-492
• /
• 2006

We demonstrate a beat frequency-Switchable dual-mode external cavity laser hybrid integrated on planar lightwave circuit with an FP-LD and a sampled grating as external reflector. The dual-mode external avity laser was able to switch its beat frequency from 132GHz to 406GHz by changing LD current from 50mA to 55mA.