• Journal of the Optical Society of Korea
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• v.4 no.1
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• pp.14-18
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• 2000

We have investigated gain flattening of EDFA systems with or without a gain equalizer for WDM long-haul transmission using a re-circulating EDFA loop. Without a gain equalizer, gain variation as small as 2.9 dB was achieved over the 10-nm band of a 100 cascaded EDFA system by the inversion principle. With a gain equalizer based on all-fiber acousto-optic tunable filters, two different config-urations of EDFAs were tested. For a single-stage EDFA scheme, the 21-nm band has shown 3.8 dB of gain variation at 17.4 ∼ 20.3 dB of OSNRs after the 100the stage of EDFAs. For a dual-stage EDFA scheme, a wider bandwidth of 34 nm has shown 3.6-dB variation after 40 cascaded EDFAs.

• ETRI Journal
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• v.34 no.6
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• pp.838-846
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• 2012

This paper proposes a cost-effective hybrid-type power budget extender (PBEx) that can provide a high power budget of over 45 dB in an asymmetric 10-Gb/s Ethernet passive optical network (10/1G-EPON). The hybrid-type 10/1G-EPON PBEx comprises a central office terminal (COT) and remote terminal (RT) module supporting four channels and uses a coarse wavelength division multiplexing (CWDM) technology between the COT and RT for a reduction of fiber cost and efficient access network design. The proposed 10/1G-EPON PBEx can provide over a 40-km reach and 128-way split per CWDM wavelength with no modification of a legacy 10/1G-EPON system and can satisfy the error-free service in $10^{10}$ packet transmission.

• Korean Journal of Optics and Photonics
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• v.21 no.6
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• pp.235-240
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• 2010

We fabricate highly birefringent photonic crystal fiber with new structure using a stack and draw method. Fabricated fiber has two big air holes, one at each side of the outside air cladding region, leading to core ellipticity during the drawing process. Birefringence of the fabricated Hi-Bi PCF is measured to be $2.29{\times}10^{-4}$ (at 1550 nm).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.473-483
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• 2004

In this paper, we numerically investigated the optimum pump light power best compensating for pulse distortion due to both chromatic dispersion and self phase modulation (SPM) as a function of channel input power in 8 channel ${\times}$ 40 Gbps wavelength division multiplexing (WDM systems. Also we investigated the allowable maximum channel input power dependence on modulation format and fiber dispersion coefficient in the various pump light power of OPC. The considered WDM transmission system is based on path-averaged intensity approximation (PAIA) mid-span spectral inversion (MSSI) compensation method, which has highly-nonlinear dispersion shifted fiber (HNL-SDF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that optimal pump light power of HNL-DSF OPC depend on modulation format, initial channel input power, total transmission length and fiber dispersion. But optimal pump light power of HNL-DSF OPC must be selected to make power conversion ratio to almost unity. And we confirmed that, if we allow a 1 dB eye opening penalty (EOP), the tolerable maximum channel input power is increased by using RZ than NRZ as modulation format when pump light power of HNL-DSF OPC is not optimal value but another values.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.462-469
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• 1988

Choromatic dispersion of single mode optical fibers limits the maximum bit rate in the single mode optical transmission systems. In this paper we calculate chromatic dispersion and dispersion parametes(zero dispersion wavelength, dispersion slope) for concatenated single mode optical fibers form the chromatic dispersion and dispersion parameters of individual single mode optical fibers, and compare theoretical valuse with those measrued by double demodulation method. Calculated values are coincident with measured ones reasonably. The standard deviation is 0.77-1.28nm for zero dispersion wavelength and 0.56-0.75PS/km.nm2 for dispersion slope. The standard deviation of zero dispersion wavelength is inverse proportional to the optical fiber lenght.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.11B
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• pp.1903-1908
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• 2000

사다리형 디지털필터는 일반적으로 IIR 필터의 직접형, 병렬형 또는 종속형과 비교하여 주파수응답 감도가 뛰어나기 때문에 최근 많이 이용되고 있다. 사다리형 디지털필터는 모델의 형식에 따라 연분수 전개가 다르고 주어지는 전달함수에 따라 실현 가능한 형식과 불가능한 형식이 있다. 본 논문에서는 연분수 형태의 제 III 사다리형 디지털필터를 모델로 하여 방형성 결합기와 광섬유를 이용한 사다리형 광섬유필터의 실현조건과 설계방법을 논하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.9B
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• pp.1203-1208
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• 2001

1545∼1560nm 파장의 C 대역에서 0.8nm 간격의 16 채널 WDM을 갖는 펌프 LD 타입의 2단 이득 제어 어븀 첨가 광섬유증폭기(GC-EDFA)를 버스트 패킷 모드 광스위칭 시스템에 사용하기 위하여 실험을 통해 입증하였다.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1126-1127
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• 1999

연산자 분리 시영역 모델을 이용하여 광섬유 커플러 ADM(add-drop multiplexer)의 필터링 효과를 분석하였다. 이 모델은 방향성 결합기나 브래그 격자를 포함하는 소자의 해석에 유용하다. 본 논문에서는 비대칭 구조를 고려했으며 결합계수, 코어의 반경, 개구수, 굴절율 변조 등의 파라미터를 이용하여 최적의 필터링 효과를 얻기 위한 구조를 설계하였다.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.331-337
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• 2003

This paper represents 50 ㎓ narrow band pass filters for fiber optical communication fabricated by dual ion beam sputtering method. We have analyzed the characteristics of the TA$_2$ $O_{5}$ and $SiO_2$ single layers in order to optimize the process conditions for the 50 ㎓ narrow band pass filters, and controlled the film thickness uniformity to less than 0.1 nm deviation by dual peak spike filter pre-deposition. We designed and fabricated 50 ㎓ narrow band pass filters that consist of 216 layers including 4 cavities based on quarter wave optical thickness. Class substrates with high thermal expansion coefficients were used to reduce the film stress. Anti-reflection coating at the rear side of the substrate was also needed to reduce the optical thickness errors of the Optical Monitoring System caused by multiple beam interference between the front side and the rear side of substrate. The optical characteristics of this 50 ㎓ narrow band pass filters are insertion loss of 0.40 ㏈, pass band ripple of 0.20 ㏈, and pass bandwidth at -0.5 ㏈ of 0.20 nm. and isolation bandwidth at -25 ㏈ of 0.6 nm, which satisfy specifications of dense WDM system in fiber optical communications.tions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.535-541
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• 2005

This paper proposes a hybrid optical lines composed of single-mode fiber(SMF) and multi-mode fiber(MMF) for gigabit-capable Passive Optical Network(GPON) using a WDM method with a single light source per each channel, and reports the results of transmission performance the proposed lines. The transmission link uses a direct modulated DFB-LD for high speed downstreams at the optical line terminal(OLT) of central office(CO) and a low cost SFP type transceiver for low-speed upstream in optical network unit(ONU). To split or combine the transmission channels, wavelength MUX/DEMUX are used in the optical line section, and MMFs not longer than 1 km are attached to the SMF lines at the ONU side of the WDM-PON links. We have performed the transmission experiment on the downstream of 2.5 Gbit/s, and 1.25 Gbit/s, and the upstream of 1.25 Gbit/s, and 622 Mbit/s which are recommended by ITU-T G.984.2. The transmission margin and feasibility of the proposed links have been tested to be suitable up to 2.5 Gbit/s transmission.