• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.24-26
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• 2005

광 간섭계는 광을 이용한 다양한 계측분야에 사용된다. 일반적인 광 간섭계의 지연단은 기계적인 광지연에 의해 저속이며, 시스템 구성상 안정성이 떨어지게 된다. 본 논문에서는 기존의 광간섭계 지연단의 기계적 방식을 배제한 광위상 변조기를 이용한 지연단을 설계하고 그 특성을 분석하였다. 제안된 광 간섭계는 1310nm 10GHz의 반복율을 갖는 광원과 광위상변조기를 이용한 전(全) 광섬유 형태로 안정한 구성을 하였다. 구성된 광간섭계는 광위상 변조기의 변조 전압, 변조 주파수의 변화에 의해 광지연시간의 쉬운 변조가 가능하였으며 최대 20ps 의 광지연시간을 얻을 수 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.294-296
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• 2005

본 논문에서는 Time Prism을 이용한 초고속 광지연을 위한 시스템을 구성하고 그 성능ㅇ르 분석하였다. 초고속 광지연을 위해 구성된 시스템은 1310nm의 15ps 펄스폭을 갖는 펄스 레이저와 광위상 변조기를 사용하여 구성하였다. 구성된 광지연 시스템은 광섬유형태로 매우 안정되며, 광위상 변조기 변조 신호의 변화를 통해 지연 시간의 조정이 가능하였다.

• Korean Journal of Optics and Photonics
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• v.27 no.5
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• pp.174-180
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• 2016

A tunable optical delay line is designed, fabricated, and characterized. The tunable delay line consists of four polymer-ring add/drop filters with delay waveguides between adjacent ones. The polymer waveguide is a buried structure, designed to be square with core width and height of $1.8{\mu}m$. The refractive indices of the core and cladding polymer are 1.48 and 1.37 respectively. The large index difference and small cross section of the waveguide enable us to realize a compact device using a small radius of curvature. Four pairs of electrodes are evaporated above the add/drop filters to provide heating currents for thermal tuning. In measurements we can identify variable time delays of 110, 225, and 330 ps in proportion to the number of delay lines.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.240-244
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• 2002

We proposed a novel temperature sensor based on the phenomena that the phase difference between principal polarization states in an optical retarder is a function of temperature. The polarization state of an optical beam is changed as it passes through the optical retarder, with the change dependent on the temperature. The temperature of the optical retarder is determined by comparison of the power difference between principal polarization states. A temperature sensor was successfully implemented using a polarization maintaining fiber of length 100 mm as the optical retarder. The change rate of phase difference on temperature was 0.236$^{\circ}C$$_{-1}$ and the measurement error was $\pm$0.038$^{\circ}C$ over the temperature region of -2.6$^{\circ}C$~3.4$^{\circ}C$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.2
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• pp.86-94
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• 2014

Optical packet switching (OPS) is being considered as one of the switching technologies for a future optical internet. For contention resolution in an optical packet switching (OPS) system, the wavelength dimension is generally used in combination with a fiber delay line (FDL) buffer. In this article, we propose a method to reduce the number of tunable wavelength converters (TWCs) by sharing TWCs for a cost-effective design of an asynchronous OPS system with a shared or an output FDL buffer. Asynchronous and variable-length packets are considered in the OPS system design. To investigate the number of TWCs needed for the OPS system, an algorithm is proposed, which searches for an available TWC and an unused internal wavelength, as well as an outgoing channel. This algorithm is applied to an OPS system with a shared or an output FDL buffer. Also, the number of internal wavelengths (i.e., the conversion range of the TWC) needed for an asynchronous OPS system is presented for cost reduction of the OPS system.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.547-552
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• 2005

We have fabricated and characterized optical delay lines for optical coherence tomography, which is composed of cylindrical PZT(piezoelectric transducer) and single mode optical fiber. The polarization mode dispersion from the optical delay lines was compensated by the polarization controllers. By applying the duplex optical delay line, we minimized the thermal drift due to optical delay lines and obtained the scan range of 2 times that of a single optical delay line. The OCT system showed resolution of $18.6\pm0.5{\mu}m$, scanning range of 1.68mm, and scanning speed of 360.4mm/s.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.119-123
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• 2010

The transmission performance of 10Gb/s optical duobinary transmitters implemented by using a Mach-Zehnder(MZ) modulator and an optical delay interferometer is presented. We investigated the theoretical impact of transmission systems by the modulator driving voltage ratio(=driving voltage/switching voltage) and the optical interferometer time delay to improve transmission distance using computer simulation. By reducing the driving voltage ratio and optimizing the partial bit time delay, the transmission performance has been improved greatly.

• Korean Journal of Optics and Photonics
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• v.18 no.4
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• pp.274-279
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• 2007

We fabricated and characterized an optical delay line for optical coherence tomography (OCT). The delay line was composed of a cylindrical piezoelectric transduce (PZT) and a single mode optical fiber. The OCT system used a duplex scanning optical delay line which was symmetrically driven in the reference and sample arms. We showed that the sinusoidal-wave was superior to a triangular-wave for driving the optical delay line for scanning depth and repeatability.

• Korean Journal of Optics and Photonics
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• v.32 no.4
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• pp.172-179
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• 2021

A near-normal-incidence ellipsometer (NNIE) is suggested as an optical critical dimension (OCD) measurement system that is highly sensitive to the bottom defect of a sample with high-aspect-ratio structured patterns. Incident light passes through a polarizer and a phase retarder in sequence, and the reflected light from the sample also passes through them, but in reverse order. The operating principle of this NNIE, where a single polarizer and a single phase retarder are shared by the incident and reflected light, is studied, and a method to determine the ellipsometric constants from the measured intensities at proper combinations of the azimuthal angles of polarizer and retarder is presented.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.234-235
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• 2008

본 논문은 계통연계형 태양광발전 시스템의 Power Conditioning System의 성능 테스트를 위한 태양광 시뮬레이터의 제어기 최적 설계에 관한 내용이다. 태양광 시뮬레이터 기술의 핵심은 정확한 에너지원의 모델링과 빠르고 안정적인 전력증폭기 제어기술에 있다. 종래의 제어기인 비례 적분제어기를 사용하는 과정에서 비례 적분 제어기 특유의 응답지연 특성으로 시뮬레이터의 동적 특성을 완벽하게 구현할 수 없기에, 응답속도가 빠르고 안정적인 제어기법인 $H_{\infty}$제어 이론을 적용하였다. 태양광 시뮬레이터의 제어기 성능평가를 위해서 태양광 시뮬레이터의 출력을 결정 하는 DC Power Amplifier의 성능실험을 하였다. DC Power Amplifier를 정전압에서 부하의 투입/제거시 비례-적분 제어기와 $H_{\infty}$제어기의 응답속도와 변동전압의 크기를 비교하여 제어기의 성능을 비교하였다.