• ETRI Journal
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• 제27권4호
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• pp.446-448
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• 2005

Using tightly focused femtosecond laser pulses, we produce an optical waveguide and devices in transparent materials. This technique has the potential to generate not only channel waveguides, but also three-dimensional optical devices. In this paper, an optical splitter and U-grooves, which are used for fiber alignment, are simultaneously fabricated in a fused silica glass using near-IR femtosecond laser pulses. The fiber- aligned optical splitter has a low insertion loss, less than 4 dB, including an intrinsic splitting loss of 3 dB and excess loss due to the passive alignment of a single-mode fiber. Finally, we present an output field pattern, demonstrating that the splitting ratio of the optical splitter becomes approximately 1:1.

• 전기학회논문지
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• 제58권5호
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• pp.1035-1040
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• 2009

We propose a new encoder/decoders based on an tune able wavelength converter(TWC) and an arrayed waveguide grating(AWG) router for large capacity optical CDMA networks. The proposed encoder/decoder treats codewords of wavelength/time 2-D code simultaneously using the dynamic code allocation property of the TWC and the cyclic property of the AWG router, and multiple subscribers can share the encoder/decoder in networks. Feasibility of the structure of the proposed encoder/decoder for dynamic code allocation is tested through simulations using two wavelength/time 2-D codes, which are the generalized multi-wavelength prime code(GMWPC) and the generalized multi-wavelength Reed-Solomon code(GMWRSC). Test results show that the proposed encoder/decoder can increase the channel efficiency not only by increasing the number of simultaneous users without any multiple-access interference but by using a relatively short length CDMA codes.

• 센서학회지
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• 제31권4호
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• pp.194-213
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• 2022

This study comprehensively reviewed four types of integrated-optic electric-field sensors based on titanium diffused lithium-niobate waveguides: symmetric and asymmetric Mach-Zehnder interferometers, 1×2 directional couplers, and Y-fed balanced-bridge Mach-Zehnder interferometers. First, we briefly explain the crystal properties and electro-optic effect of lithium niobate and the waveguide fabrication process. We theoretically analyzed the key parameters and operating principles of each sensor and antennas. We also describe and compare the design, simulation, implementation, and performance tests: dc and ac characteristics, frequency response, dynamic range, and sensitivity. The experimental results revealed that the sensitivity of the sensor based on the Y-fed balanced bridge Mach-Zehnder interferometer (YBB-MZI) was higher than that of the other types of sensors.

• 전자공학회논문지D
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• 제34D권10호
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• pp.53-59
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• 1997

In this paper, we present a 20 GHz low-loss dual-mode channel filter designed by using mode matching method. The performance of dual-mode channel filter mainly depends on iris characteristics. Therefore the exact design of iris is the key point to get good frequncy response of the filter. MOde matching technique is widely used ot design several kinds of waveguide filters because it is simple in theory and can easily calculate the scattering matrices at the discontinuities with simple structure like iris coupled filters. Additionally the effect for finite thickness of the iris in the dual-mode cavity iflter is analyzed by te full-wave method, providing the exact filter implementation without trial and error.

• 한국전자파학회논문지
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• 제14권8호
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• pp.839-844
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• 2003

위성 중계기의 무게와 부피를 최소화 하기 위하여 입력 멀티플렉서 및 출력 멀티플렉서에 사용하는 채널 필터는 이중모드 도파관 필터를 많이 사용한다. 또한 입력 멀티플렉서는 일반적으로 채널이 서로 독립적이기 때문에 이에 사용하는 채널 필터는 이중종단형으로 설계하며, 매니폴드(manifold) 형태의 출력 멀티플렉서의 경우 채널 필터는 단일종단형으로 설계한다. 본 논문에서는 위성 중계기에 많이 적용되는 단일종단 및 이중종단 이중모드 도파관 필터의 튜닝 방법에 관하여 기술하였다. 필터의 튜닝은 한쪽면이 단락된 더미 공동(dummy cavity)을 이용하며, 측정된 반사계수의 위상 응답을 계산된 이론치에 정합시키는 과정으로 튜닝을 진행한다. 이러한 튜닝방법을 4차 이중종단 이중모드 타원응답 필터와 6차 단일종단 이중모드 타원응답 필터에 적용하여 튜닝함으로써 제안한 튜닝방법의 유용성을 확인하였다.

• 한국광학회지
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• 제10권4호
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• pp.342-347
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• 1999

광소자의 소형화와 집적화 노력에 따라 광도파로의 도파폭과 곡률 반경이 작아지면서, 그 경계조건을 만족하는 도파모드와 전파상수의 변화가 심하게 되었다. 특히, 도파폭의 좁아지면서 제작 공정상의 폭조절 오차한계 내의 작은 변화에도 전파상수가 크게 변화하게 되어, 배열도파로(Arrayed Waveguide Grating, AWG)소자에서는 각 도파로 진행광의 위상이 설계와 심하게 달라지고 소자의 성능에 영향이 커지게 되었다. 광소자의 소형화에 따라 심각해지는 이러한 근사설계 오차에 의한 영향을 정량적으로 분석하고 대처하기 위해, 여기서는 유효굴절률법(Effective Index Method)과 해석적 함수해(Analytic Solution Method)를 이요하여 여러 도파로 구조를 해석하여 전파특성 변수를 얻어내었다. 또한, 이를 적용하여 자체 제작한 고기능 전산시늉기를 통해 각종 InP-, Silica-AWG 소자의 성능을 모사하였다. 모사 결과는 실제 제작된 전형적인 소자와 비교하여 매우 유사한 경향을 나타내었으며, Ridge-type Inp-AWG 소자의 경우, 도파폭의 허용공차가 0.02$\mu\textrm{m}$ 이내로 개선될 때, AWG 소자의 신호대잡음비(SNR)가 약 -25dB 이상 가능하게 되며 Rib-type Silica-AWG 소자의 경우는 도파폭 허용공차가 0.1$\mu\textrm{m}$ 정도이기만 해도 약 -30dB 이상 가능한 것으로 모사되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 센서 박막재료 반도체재료 기술교육
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• pp.111-118
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• 2002

A new lithium niobate optical modulator with a polymer buffer layer on Ni in-diffused optical waveguide is proposed for the fist time, successfully fabricated and examined at a wavelength of 1.3 mm. By determining the diffusion parameters of Ni in-diffused waveguide to achieve more desirable mode size which is well matched to the mode in the fiber, the detailed results on the achievement of high optical throughput are reported. In addition, the usefulness of polymer buffer layer which can be applicable to a buffer layer in Ni in-diffused waveguide devices is demonstrated. Several sets of channel waveguides fabricated on Z-cut lithium niobate by Ni in-diffusion were obtained and on which coplanar traveling-wave type electrodes with a polymer-employed buffer layer were developed by a conventional fabrication method for characterizing of electro-optical performances of the proposed device. The experimental results show that the measured half-wave voltage is of ~10 V and the total measured fiber-to-fiber insertion loss is of ~6.4 dB for a 40 mm long at a wavelength of =1.3 mm, respectively. From the experimental results, it is confirmed that the polymer-employed buffer layer in LiNbO3 optical modulator can be a substitute material instead of silicon oxide layer which is usually processed at a high temperature of over $300^{\circ}C$. Moreover, the fabrication tolerances by using polymer materials in LiNbO3 optical modulators are much less strict in comparison to the case of dielectric buffer layer.

• ETRI Journal
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• 제31권6호
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• pp.770-777
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• 2009

We have developed a fully functional reconfigurable optical add-drop multiplexer (ROADM) switch module using a polymer integrated photonic lightwave circuit technology. The polymer variable optical attenuator (VOA) array and digital optical switch array are integrated into one polymer PLC chip and packaged to form a 10-channel VOA integrated optical switch module. Four of these optical switch modules are used in the ROADM switch module to execute 40-channel switching and power equalization. As a wavelength division multiplexer (WDM) filter device, two C-band 40-channel athermal arrayed waveguide grating WDMs are used in the ROADM module. Optical power monitoring of each channel is carried out using a 5% tap PD. A controller and firmware having the functions of a 40-channel switch and VOA control, optical power monitoring, as well as TEC temperature control, and data communication interfaces are also developed in this study.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1996년도 학술대회
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• pp.39-43
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• 1996

This paper presents the designing scheme of the duplexer for ground station using rectangular waveguide. The duplexer consists of 2-channel bandpass filters having asymmetrical inductive window and inductive post obstacles, coupled with H-plane Apertured-coupled junction, and operating in the frequency ranges of 14.5∼14.8GHz and 11.7∼12.0 GHz which are the DBS up/downlink for the domestic Ku-band ground station.

• 한국광학회:학술대회논문집
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• 한국광학회 1990년도 제5회 파동 및 레이저 학술발표회 5th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.227-231
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• 1990

A SiO2/Si concave diffraction grating(period: 1.3${\mu}{\textrm}{m}$) for the angular dispersive element of WDM was fabricated by sandwiching the SiO2/Si plane diffraction grating between a slab waveguide and a cylindrical concave block. Using this concave grating and input/output fiber, and wavelength division demultiplexer was composed. The demultiplexer has five channels, the insertion loss of 30dB, the wavelength spacing per channel of 7nm and crosstalk of-15dB.