• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.442-448
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• 2014

For the first time, a novel analytical model of the net gain for a Raman-EDFA hybrid optical amplifier (HOA) is proposed and its various parameters optimized using a genetic algorithm. Our method has been shown to be robust in the simultaneous analysis of multiple parameters (Raman length, EDFA length, and pump powers) to obtain large gain. The optimized HOA is further investigated at the system level for the scenario of a 50-channel DWDM system with 0.2-nm channel spacing. With an optimized HOA, a flat gain of >17 dB is obtained over the effective ITU-T wavelength grid with a variation of less than 1.5 dB, without using any gain-flattening technique. The obtained noise figure is also the lowest value ever reported for a Raman-EDFA HOA at reduced channel spacing.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.190-191
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• 2005

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.833-837
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• 2007

In this study, we have fabricated a gain flattened erbium-doped optical fiber amplifier. Gain flattening filters were realized by the strain-induced long period fiber gratings, which are made of periodically arrayed metal wires. Using the filter of $550{\mu}m$ period, spontaneous emission amplified at C-band wavelength by a 980nm pumping laser was flattened within 1dB of gain ripple. The performance of the simultaneous multi channel amplification was measured using a fabry-perot laser diode. Amplification ratio was above 20dB. This amplifier can be applied to the long distance transmission system based on a wavelength division multiplexing for boosting an attenuated signal.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.12-16
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• 2003

This paper presents a compensation method for a temperature-dependent gain tilt in L-band erbium-doped fiber amplifier using a voltage-controlled attenuator. The gain tilts in the L-band of 1570-1605 nm due to a temperature change have negative slopes, whereas they have positive slopes for the increasing optical input powers in a saturation region. The proposed method utilizes these opposite gain variations to compensate for the gain tilt over a wide range of temperature. While applying forty channels with a channel spacing of 100 GHz in the L-band and changing the ambient temperature from 0 to $50^{\circ}C$, the compensation method maintained the gain deviation within 1 dB.

• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.261-265
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• 2009

Our amplifier using an all optical method and a fixed GFF achieved automatic gain flatness throughput the C-band without any NF degradation, and simultaneously achieved a constant 25 dB gain, while input signals were varied between one channel and forty WDM channels. When thirty nine channels were added and dropped, the transient gain variation of the survival channel was not greater than the steady-state gain variation, and its wavelength dependency was negligible.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.80-81
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• 2000

최근 통신 서비스의 증가에 따라 대용량의 전송 용량이 요구되고 있으며, 이에 대한 해결책으로 파장분할다중(WDM) 방식의 광전송에 관한 많은 연구가 수행되었다. EDFA는 1550 nm 근처에서 이득 영역을 가지고 있기 때문에 장거리 광통신 시스템에 주된 광증폭기로 사용되고 있으나 파장에 따른 이득이 서로 다르게 나타나기 때문에, WDM 시스템에 이용하기 위해서는 EDFA의 이득 평탄화가 필요하며, 이에 대한 다양한 연구가 이루어지고 있다. (중략)

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.5-9
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• 2003

장주기 격자 필터를 이용한 EDFA용 이득평탄화 필터 설계에는 대역폭에 따라 한 개에서 세 개까지의 평탄화가 가능하다 이러한 필터 설계는 EDFA의 고유의 중심 파장, 크기, 대역폭에 대한 각 장주기 광섬유 격자의 중심 파장, 크기, 대역폭을 설정하여 이득평탄화를 최적화시킨다. 이득평탄화 필터의 설계를 위한 방법으로써 수동 설계통한 이득평탄화를 했으나, 신속하고 편리함을 위해 반자동 설계, 자동 설계 프로그램을 구현하였다. 이를 통한 이득평탄화 정도는, 수동이 0.38dB, 반자동 0.57dB, 자동 0.62dB 정도로 정밀한 이득평탄화를 얻을 수 있는 설계가 가능하였다.

• Journal of the Korea Furniture Society
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• v.12 no.2
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• pp.29-38
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• 2001

This study was carried out to develope a new process of flattening bamboo pieces(3 months old) by two steps of utilizing microwave oven and hot press. Internode bamboo pieces were impregnated with low molecular weight phenol formaldehyde resin (PF) under vacuum of 76 cmHg, heated in a household microwave oven in 1 minute, pressed on the temperature of $145^{\circ}C$ by the hot press for 10 minute, and then cooled by the cold press in their flattened form. The physical and mechanical . Properties of compressed flattened bamboo were as follows: 1) PF1(Mw:427) and PF2(Mw:246) sol. met the success of flattening of internode bamboo pieces in both of P. bambusoides and P. nigra var. PF2 showed the more plasticity to flatten the bamboo than PFI. The PF2 sol. with low molecular weight(Mw:246) gave the more weight gain than that of PF1 in the equal concentration. PF1 of 5% (NVC) and PF2 of 10% (NVC) sol. gave the best result for physical and mechanical properties and from a economical view point. 2) The PFI of 5% (NVC) sol. with low molecular weight decreased the water absorption of 62-63% and increased the bending strength (MaR) of 80-90%, compression strength of 43-54%. 3) The PF2 of 10% (NVC) sol. with low molecular weight decreased the water absorption of 56-57% and increased the bending strength (MaR) of 64-86%, compression strength of 39-63%.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.144-145
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• 2000

파장 분할 다중화(WDM)기술은 빠른 속도로 발전해 왔으며, 이에 대한 연구는 계속되고 있다. 전송용량의 증가에 의해 전송 채널의 수가 증가하고 이에 따라 이득 대역도 더 넓어져야한다.$^{(1)}$ 파장 분할 다중화(WDM) 시스템의 구성에서 어븀 첨가 광섬유 증폭기(EDFA)는 시스템의 핵심 요소로 각 단계마다 몇 개씩의 EDFA가 사용된다. EDFA에서는 이득의 변화가 10 ms정도로 천천히 일어나므로 입력의 평균값에 의해 이득이 결정된다. 따라서, EDFA는 모든 채널의 입력의 합이 일정할 때 이득의 상호 포화로 인한 채널 간의 누화가 없다는 장점이 있기 때문에 다채널 WDM 시스템의 광섬유 증폭기로 매우 유용하게 이용되고 있다.$^{(2)}$ (중략)

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1757-1763
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• 2014

Optical wavelength division multiplexing signals of eight non-return-to-zero 10 Gb/s channels were transmitted on the long-haul link up to 720 km. The link span was composed of 80 km single mode fiber, dispersion compensation fiber for complete compensation, and EDFAs. A circulating loop method was applied to the link experiment and the loop was optimized for the transmission link. Wavelength-dependent gain variation of EDFA was compensated using EDFAs of opposite gain slopes without expensive gain flattening filters. Average OSNR was aggravated to 22 dB and the worst OSNR channel variation was 9.7 dB after the transmission. It was confirmed by analyzing optical spectra that this OSNR variation was mainly caused by the hole burning effect of EDFA.