• Journal of Advanced Navigation Technology
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• v.28 no.1
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• pp.123-128
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• 2024

When mid-span spectral inversion (MSSI), which inverts the propagated wave into phase-conjugated wave in the middle of the entire transmission distance, is combined with dispersion-managed link, it is very effective in compensating for the wavelength division multiplexed (WDM) signal distortion due to chromatic dispersion and nonlinear effects. In this MSSI combined dispersion-managed link, the shape of the dispersion map, channel data rate, channel wavelength and wavelength spacing, etc. affect the compensation and, consequently, determine the transmission distance and capacity of the WDM signal. In this paper, the compensation according to the extinction ratio of the return-to-zero (RZ) pulse that constitutes the WDM signal in the MSSI combined distributed control link was numerically analyzed. As a result of the simulation, it was conformed that the extinction ratio to obtain the best compensation should be determined depending on the shape of the dispersion map and the size of the residual dispersion per span, which determines the specific shape of the dispersion map. These results show a significant difference from the results in a general optical transmission system, where as the extinction ratio increases, the power difference between the '1' and '0' signals increases, thereby improving reception performance.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.414-418
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• 1996

An electro-optic polymer digital optical switch was fabricated by using a photobleached waveguide and a self-aligned electrode. It features wavelength insensitive operation, fabrication tolerance and flexible design. And its possible advantages include low coupling losses to the fibers and wide bandwidths. For improving its switching performance, the guided mode profiles of the photobleached waveguides were controlled by photobleaching times to achieve optimized coupling in the branch. And the self-aligned electrode was employed to achieve both efficient overlap of the optical and electric fields and easy introduction of the adiabatically tapered electrodes. The measured crosstalks were better than -21dB at 1.32 ${\mu}{\textrm}{m}$ and 1.55 ${\mu}{\textrm}{m}$, and the extinction ratios of each output port were also more than 20 dB.

• Korean Journal of Optics and Photonics
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• v.22 no.1
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• pp.40-45
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• 2011

Design and fabrication of a TCRR (Triple-coupler Ring Resonator) filter which can provide a doubled FSR (Free Spectral Range) compared with a conventional DCRR (Double-coupler Ring Resonator) filter, are discussed. Through the use of a polymer material with a good thermo-optic property and with high contrast between core and cladding polymer, a compact TCRR filter composed of straight and curved buried waveguides of small radius is designed and fabricated. The transmission characteristics from the through and drop ports are measured using a tunable laser and a fiber array block, and the FSR is observed to be 4.4 nm, about twice that of DCRR filter, and almost the same as that obtained from the analysis using a transfer matrix method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1816-1822
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• 2003

We propose a novel structure of wavelength selective optical add/drop filter comprising two tap couplers and a fiber Bragg grating. The device has unique features including a simpler structure and a lower cost implementation as compared with existing device for the same operation. The filter performance has been measured and analyzed, experimentally. The implemented prototype filter shows good performance with no­crosstalk power penalty in a 155Mbps per channel wavelength­division­multiplexing transmission system but suffers from a relatively high loss of 3.5㏈ and 21㏈ for transmitted and dropped channel, respectively. While the dropped channel extinction ratio was more than 15㏈, the transmitted channel extinction ratio was more than 26㏈.

• Journal of Advanced Navigation Technology
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• v.8 no.2
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• pp.91-97
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• 2004

This paper presents the development of InGaAsP multiple quantum well asymmetric Fabry-Perot modulators(AFPM), which have a vertical structure and high performance and describes measurements of devices operating at 10GHz for next generation broadband wireless communication applications such as picocell systems. Advantages of the AFPM include low drive voltage, which is less than -2V, and -3dB coupling loss, good flatness of the frequency response and simple fiber alignment. A simple link demonstration has been introduced, resulting in 92dB/Hz spurious free dynamic range and 40dB inter-modulation distortion. This modulator could be use for broadband radio over fiber systems such as picocell and multiple RF links.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.50-52
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• 2001

단일 모드 광섬유의 클래딩을 코어 가까이 연마로 제거한 후 그 표면 위에 유전체와 금속 박막층이 형성된 소자의 광전달 특성을 이론과 실험으로 분석하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.295-296
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• 2009

다중 브래그 파장의 안정성 확보하고 제작비용을 줄이기 위하여 본 연구에서는 하나의 위상마스크와 스텝당 0.004도의 분해능을 갖는 탤봇 간섭계(Talbot Interferometer)로 이루어진 홀로그래픽 격자제작장치를 구성하였다. C-밴드와 L-밴드 파장 범위 내의 다중 브래그 파장 특성을 실험적으로 확인하고, 이 방법을 사용하여 서로 다른 파장의 브래그 격자를 센서부로 두고, $1{\times}6$ 광분배기와 결합시켜 화학반응조 내의 액체 온도를 측정하는 시스템을 제작하였다.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.369-374
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• 2004

In this paper, we propose a new tunable laser diode structure. The laser diode consists of a sampled-grating distributed feedback laser diode monolithically integrated with a sampled-grating distributed-Brags-Reflector. For a specific design, the possibility of continuous/discrete wavelength tuning over 27nm is confirmed by a numerical analysis using a split-step time domain model. Because the laser diode can be directly coupled with optical fiber without the intervention of the passive section, the laser diode exhibits higher output power than the conventional laser diode.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.46-47
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• 2000

고출력, 고효율, 그리고 고품질의 빔특성을 갖는 DPSSL을 개발하기 위해서는 출력빔을 저하시키는 원인인 비균일한 여기빔 분포에 의한 레이저 결정내의 열렌즈, stress 복굴절 등의 효과를 최소화하여야 한다. 지금까지 열효과를 줄여, 고출력이나 TE $M_{00}$ 모드의 레이저 빔을 얻기위한 방법으로 zigzag 슬랩 디자인$^{1)}$ , VPS 여기 시스템$^{2)}$ , Cusp 형 반사체$^{(3)}$ , 광섬유 결합$^{(4)}$ 등의 방법이 연구되어 왔다. 본 연구에서는 고출력, 고효율, 그리고 고품질의 레이저 빔특성을 동시에 만족하는 레이저를 개발할 목적으로 산란된 여기빔을 이용하는 여기구조를 고안하고 열효과가 감소된 Nd:YAG 레이저 시스템을 최적설계하였다. (중략)략)

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.102-103
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• 2000

최근 광통신 시스템에서는 파장분할다중화(WDM) 방식의 도입으로 인해, 한 개의 레이저 신호를 입사시켜 여러 개의 레이저 신호를 발생시켜 광원으로 사용하는 연구가 활발히 진행되어 왔다. Park et al.[1]은 Erbium Doped Fiber Laser(EDFL)에서 1.1nm 파장간격으로 24라인을 얻었고, Yamashita et al.[2]은 내부 에탈론 구조를 가진 EDFL에서 0.8nm 간격으로 17라인, D.Yu et al.[3]은 반사형 거울과 Circulator를 사용한 Brillouin/Erbium Fiber Laser(BEFL)에서 0.08nm 간격으로 30라인, G.J.Cowle et al.[4]은 Injection-Seed Locking을 이용한 BEFL.에서 0.09nm 간격으로 12라인 그리고 N.S.Kim et al.[5]은 내부 되먹임을 이용한 BEFL에서 0.09nm 간격으로 4라인을 각각 발생시켰다. 여기서 중요한 요소로는 발생된 레이저 신호의 안정성, 각 신호들 간의 파장간격, 레이저 신호의 수 그리고 Peak Intensity 간의 차이 등이 있는데 각 연구방식에 따라 다양한 결과를 보여준다. 본 실험에서는 향상된 되먹임 구조를 가진 BEFL에서 다파장 발생에 관한 연구를 하였다. (중략)