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

• The Journal of the Korea institute of electronic communication sciences
• /
• v.1 no.1
• /
• pp.56-62
• /
• 2006

Currently, Most of the Backhual and Submarine's networks are being installed using DWDM and EDFA to deal with dramatically increasing internet traffic. In a conventional type optical system, the so-called 3R repeater, fiber non- linearity was not significant factor but it is one of the most important consideration when designing new DWDM network based on the EDFAs. To minimize the signal pulse distortion in long-haul optical network, Zero-dispersion fiber is indispensable but causes the fiber non-linearity. Therefore this conflicting problems should be managed to transmit a high-speed capacity traffic. In this paper, key technologies in DWDM submarine optic network were found out for a high capacity traffic and introduced the dispersion management way for solving the conflicting problems between Zero-dispersion and non-linearity. Lastly designed a dispersion map in section between Korea and Hong-kong.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.10B
• /
• pp.1343-1352
• /
• 2001

DWDM 전송 시스템에서 전송 용량 증대를 위하여 bit rate를 고속화하고 채널 간격을 줄이기 위해서는 전송로로 사용되는 광케이블의 분산특성이 상반되는 값을 갖도록 요구된다. 즉, 분산으로 인한 신호 왜곡을 줄이기 위해서는 광케이블의 분산이 작아야 하고, 비선형 현상을 억제하기 위해서는 분산이 커야 한다. 이러한 두 가지 상반된 분산 penalty를 동시에 해결하기 위한 방안으로 양과 음의 분산 값이 이산적으로 분포된 광섬유 케이블을 최초로 설계 및 제작하였다. 이러한 분산 분포 케이블을 위해 일반 단일 모드 광섬유(SMF)와 대응되는 음분산 값을 갖는 새로운 광섬유(NDF)를 설계 및 제조한 후, SMF의 +17 ps/km/nm 및 NDF의 -15 ps/km/nm의 분산영역이 6km의 케이블 내에 분포되도록 케이블을 제작하였다. 새롭게 개발된 케이블의 분산 값을 국지적으로는 높은 값을 가지면서도 전체적으로는 1.0 ps/km/nm의 평균 분산 값으로 NZSDF 대비 30% 이하를 가질 수 있음을 확인하였다. 또한, 제안된 케이블은 SMF 케이블과 동일한 케이블 시공 운용 환경에서도 정합함을 확인하였다.

• Journal of Applied Reliability
• /
• v.1 no.2
• /
• pp.121-138
• /
• 2001

Due to large demand for high speed and great capacity for data transfer, WDM, which uses the wavelength division multiplexing technique, is known as alternative way to satisfy those demand for its flexible network operation and management, easy network expansion with existing networks, and enhancement of efficient data transfer rate. For these reasons, a new high capacity WDM optical communication network plan was established. Therefore, the quality of currently deployed optical cables with 81.6 km in length should be assessed to ensure if high capacity WDM system could be implemented on existing optical cables. Two important characteristic parameters, Transfer Loss and PMD (Polarization Mode Dispersion), were measured to evaluate quality of existing optical cable. Transfer Loss was measured at 0.244 dB per kilometer, which is lower than the design standard value at 0.275 dB/km. The measured PMD value gave at 0.030ps/km, and it, therefore, satisfies the value recommended by ITU-T (International Telecommunication Union-T) of 0.5ps/km. In addition, the transfer characteristic for existing 2.5 Gbps and 10 Gbps system were measured and evaluated, and the results showed that error-free transfer is very much feasible. Computer simulation for DWDM system, which is likely be a future backbone network in Korea, to assess the transfer characteristic using the same condition employed for 2.5 Gbps and 10 Gbps was carried out as well. The simulation verified that a stable network operation and reliable service could be provided.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.3 no.3
• /
• pp.170-176
• /
• 2008

According to the development of Internet, DWDM system needs to improve the performance for long distance transmission international optical signals. For higher the transmission capacity, we have to raise the transmission speed and increase a number of channels. To make qualifications, there are a lot of technologies such as line coding, modulation, precious fiber, broadband amplification, dispersion and forward error correction. Especially, FEC has been considered as a progressive technology for long distance transmission to carry out high speed and large capacity traffic. This paper introduced the progress of each new generation of FEC and the way to employ by current system analyzed the coding gain.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.12
• /
• pp.35-42
• /
• 2004

In this paper, we report Mach Zehnder Interleaver of optical fiber type is fabricated by the fabrication system only for interfermeter design, and it is used $CO_2$ laser to adjust precisely the wavelength. The optical fiber is very sensitive in the thermal variation around. Thus, When fabrication the prototype, it is applied a technique to compensate the optical thermal effect because the center wavelength at the output is shifted according to the thermal variation around. it can he done by applying a substrate with high thermal expansion coefficient as well as an adjusting the position between two optical fiber couplers. Consequently, the output wavelength is shifted within 0.05 nm when the surrounding temperature varies until $60^{\circ}C$.

• Korean Journal of Optics and Photonics
• /
• v.13 no.5
• /
• pp.384-389
• /
• 2002

A new idea of the wavelength locking module for DWDM application was investigated in the present research. Only one etalon photo-diode is generally used in the internal/external wavelength locking system. For the internal wavelength locking module with 50 GHz applications, an algle tuning method of the etalon commonly applied. However, the alignment process of the etalon with the angle tuning method is limited because the lock performance is extremely sensitive accoriding to the change of the tilting angle. In an optical viewpoint, the alignment tolerance of the locker module with the etalon PD array block was good, and the precise tuning of the wavelength was possible. The characteristics of free spectral range (FSR) and peak shift of wavelength according to the tilting angle with the locker module was investigated. For the present module, the optimized initial tilting angle was experimentally obtained.

• Convergence Security Journal
• /
• v.13 no.6
• /
• pp.3-9
• /
• 2013

With the rapidly changing information communication environment and development of technologies, the informati on networks are evolved from traditional fixed form to an active variable network that flexible large variety of data can be transferred. To reflect the needs of users, the next generation using DWDM (Dense Wavelength Division M ultiplexing) transmission system and OXC (Optical Cross Connect) form a dynamic network. After that GMPLS (Ge neralized Multi-Protocol Label Switching) can be introduced to dynamically manage and control the Reconfigurable Optical Add-drop Multiplexer (ROADM)/Photonic Cross Connect (PXC) based network. This paper propose a softw are architecture of Path Computation Element (PCE) protocol that has proposed by Internet Engineering Task Force (IETF) to path computation. The functional blocks and Application Programming Interface (API) of the PCE protoco l implementation are also presented.

• Convergence Security Journal
• /
• v.13 no.3
• /
• pp.25-31
• /
• 2013

Looking at the recent value change of users and the usage pattern of network users, it is changing from simple web information, one-way information acquisition and data transmission to increase of usage of multimedia, increasing demand for security and customization, and increasing demands for free mobility. Due to this change of demand, the services which were provided individually, developed into a form which is merged, the network also seems to develop into the combined network from the individual network for individual service, and the communication network control technology which is the core technology is also rapidly developing. To reflect the users' demands, the next generation network created the multi-layer network which is based on the WDM/IP transmission system and added the to make it easy to restructure. P-OTS (Packet-Optical Transport System) can be defined as a platform that combines SONET/SDH, Ethernet, DWDM, optical transport network (OTN) switching and reconfigurable optical add-drop multiplexers (ROADMs). In this paper, we suggested that the optimum path choice be performed through diversification of the PCE-based path selection using the information of various layers altogether in the multi-layer environment, compared with the established path selection method when the path was selected using the information of each layers.

• Proceedings of the Optical Society of Korea Conference
• /
• 2003.02a
• /
• pp.246-247
• /
• 2003

In recent years, soaring traffic volumes over optical communications networks lead to the rapid advances in information communications equipments. In backbone communications networks, there has been an advance in high-density transmission through DWDM, which can simultaneously transmit numerous signals with different wavelengths. When the channel spacing is narrower, the cross-talk between channels an important parameter that guarantees to the high performance of a whole system, becomes critical. (omitted)