• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.373-376
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• 2002

An asymmetrical directional coupler with two nonidentical fibers has, for the first time, been proposed and analyzed for an EDFA gain flattening filter (GFF). The characteristics of the transmission spectra of the GFFs have been theoretically investigated for the core spacings, the coupling lengths and the fiber parameters of the asymmetrical directional coupler. The analytical results show that an EDFA gain spectrum with flatness of ~7 ㏈ can be flattened to within $\pm$0.75 ㏈ over a bandwidth of 30 nm by using the asymmetrical directional coupler-based GFF.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.24-25
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• 2003

We propose the new gain-flattened filter utilizing tapered silica-based fiber for high capacity WDM optical communication systems. The gain excursion of Gain flattening filters is less than 0.5 dB over the 40 nm(1525 nm ～1565 nm).

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.42-43
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• 2003

We propose the new gain-flattened filter utilizing tapered silica-based fiber for high capacity WDM optical communication systems. The gain excursion of Gain flattening filters is less than 0.5 dB over the 40 nm($1525nm{\sim}1565nm$).

• Journal of the Optical Society of Korea
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• v.18 no.2
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• pp.118-123
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• 2014

For multi parameter optimization of Raman Fiber Amplifier (RFA), a simple genetic algorithm is presented in the scenario of a 320 channel Dense Wavelength Division Multiplexed (DWDM) system at channel spacing of 25 GHz. The large average gain (> 22 dB) is observed from optimized RFA with the optimized parameters, such as 39.6 km of Raman length with counter-propagating pumps tuned to 205.5 THz and 211.9 THz at pump powers of 234.3 mW, 677.1 mW respectively. The gain flattening filter (GFF) has also been optimized to further reduce the gain ripple across the frequency range from 190 to 197.975 THz for broadband amplification.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.2
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• pp.90-95
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• 2009

All-optical fiber-type gain flattening filer (GFF) for an EDFA (Erbium doped fiber amplifier) were fabricated by using a FBT (fiber biconical tapered) process and the performance of the GFF was tested and athermal package was proposed. Historically, the chief contributor to gain unevenness has been the EDFA. Due to the inherent gain response of the EDFA's operation, there is always a modest imbalance in the gain applied as a function of wavelength. FBT methods have been used to make fiber type couplers and WDM filter since 1980. Attractivity of this methods was simple, cost effective and thermal stability. Simulation program tool is made to design target GFF profile for this paper. Fiber coupler manufacturing machine is modified for the GFF process. The final GFF is obtained by cascading 4 unit filter that has 6 taper stage. Test result shows 1 dB of wavelength flatness in the C band. Polarization dependent loss is under 0.15dB. The center wavelength variation is below ${\pm}$0.35nm at the temperature range of $20^{\circ}C$ to $70^{\circ}C$.

• 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.9 no.6
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• pp.413-416
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• 1998

We have flattened the gain of EDFA by using a long-period FBG filter and AOTF's. The gain and optical SNR characteristics of the gain-flattened EDFA in long-haul transmission been evaluated in a recirculating EDFA loop. The gain variation was less than 4.6 dB and the optical SNR was higher than 14 dB over 20-nm wavelength range when the optical signal went through the EDFA as many as 200 times. These results indicate that this gain-flattened EDFA is applicable for ultra long-haul WDM optical transmissions over 8000 km.

• 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.