• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.177-179
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• 2003

본 논문에서는 $0.35{\mu}m$ CMOS 공정을 이용하여 2.5 Gbps로 동작하는 광 송수신기를 설계하였다. 광 송수신기의 구성을 보자면, 전기 신호를 빛 신호로 전환하여 주는 레이저 다이오드(LD) 구동부와 레이저 다이오드에서 나오는 빛 신호를 수신하여 이를 다시 전기 신호로 바꿔주는 포토 다이오드(PD) 구동 부분으로 구성된다. LD 구동부는 LD의 문턱전류 이상을 공급하는 바이어스 부분과 신호레벨의 모듈레이션 전류를 공급하는 부분으로 구성된다. 디자인된 송신기는 바이어스 전류를 10 mA 정도 공급하여주며, 모듈레이션 전류를 15 mA 정도 공급한다. 수신기는 current decision 부분과 output buffer 부분으로 구성되어 PD로부터 나오는 전류를 다시 디지털 레벨의 전압신호로 바꾸어 주며 디자인된 수신기는 넓은 동작 영역을 가진다.

• Proceedings of the Korean Reliability Society Conference
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• 2004.07a
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• pp.147-151
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• 2004

In this study, an optical fiber assembly directly coupled with a laser diode or a photo diode is designed to confirm high reliable optical coupling efficiency of optical transmitter(Tx) and receiver(Rx). The optical fiber assembly is fabricated by soldering an optical fiber and a Kovar ferrule using a glass solder after inserting an optical fiber through a Kovar ferrule. The Kovar which has good welding characteristics is applied to introduce laser welding technique. The glass solder has excellent thermal characteristics such as thermal shift delamination compared with PbSn, AuSn solder previously used usually. Furthermore, the glass solder doesn't need fiber metalization and this enables low cost fabrication. However, the glass soldering is high temperature process over 35$0^{\circ}C$ and the convex shape after solidification due to surface tension causes the stress concentration on optical fiber. The stress concentration on the optical fiber increases the optical insertion loss and possibility of crack formation. The shape of glass solder was designed referring to 2-D Axi-symmetric FEM simulation. To test the mechanical reliability, mechanical vibration test and shock test were done according to Telcorida GR-468-Core protocol. After each test, the optical loss of the stress distributed fiber assembly didn't exceed 0.5 dB, which passes the test.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.7-13
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• 2007

In the optical module for optical communications, the flip chip bonding is used fer the precise alignment of the optical fiber and optical device. In flip chip bonding, the optical device is aligned and welded while observing the alignment mark of substrate and chip by using flip chip bonder in order to bond the optical device at the exact position. In this research, optical passive alignment method of photodiode(PD) flip chip bonding is suggested for low cost optical subassembly. By using the visible He-Ne laser (633nm wavelength), photodiode is easily aligned with emitting spot on the optical fiber with the help of stereoscopic alignment system. We compensated wavelength dependent deviation about 4m to find out real alignment position of 1550nm input laser by ray tracing. The maximum optical coupling efficiency between the optical fiber and photodiode was about 23.3%.

• ETRI Journal
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• v.28 no.1
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• pp.1-8
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• 2006

A novel all-optical gain-controlled (AOGC) bidirectional amplifier is proposed and demonstrated in a compact structure. The AOGC function using fiber Bragg grating (FBG) pairs controls both directional signals independently, and combinations of optical interleavers and isolators suppress Rayleigh backscattering (RB) noise. The amplifier achieves high and constant gain with a wide dynamic input signal range and low noise figure. The performance does not depend on the input signal conditions, whether static-state or transient signals, or whether there is symmetric or asymmetric data traffic on bidirectional transmission. Transmission comparison experiments between invariable symmetrical and random variable asymmetric bidirectional data traffic verify that the all-optical gain control and bidirectional amplification functions are successfully combined into this proposed amplifier.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.466-471
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• 2014

An asynchronous optical packet-switching (AOPS) node with load-balancing capability can achieve better performance in reducing the high packet-loss ratio (PLR) and time delay caused by unbalanced traffic. This paper proposes a novel dynamic load-balancing algorithm for an AOPS node with limited buffer and without wavelength converters, and considering the data flow distribution and service levels. By calculating the occupancy state of the output ports, load state of the input ports, and priorities for data flow, the traffic is balanced accordingly. Simulations demonstrate that asynchronous variant data packets and output traffic can be automatically balanced according to service levels and the data flow distribution. A PLR of less than 0.01% can be achieved, as well as an average time delay of less than 0.46 ns.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.477-479
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• 1997

The preparation of mach-zehnder inteferometric optical modulator and the properties of electrode and modulation bandwidth for high speed optical communications were described. The results of fabricated optical modulator was that optical 3-dB bandwidth 4.7GHz, driving voltage 6V and fiber-waveguide-fiber insertion loss 4.5dB for TM mode respectively.

• ETRI Journal
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• v.37 no.6
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• pp.1120-1128
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• 2015

We propose a pseudo optical N-level pulse-amplitude modulation (PO PAM-N) signal using a few externally-modulated lasers (EMLs) operating at different wavelengths, which is suitable for upgrading the transmission speed over an optical link of < 10 km single-mode fiber with low-cost components. To compare a PO PAM-N signal with that of a standard optical PAM-N signal, we perform experiments for evaluating the performance of a 51.56-Gb/s PO PAM-4 signal and standard 51.56-Gb/s optical PAM-4 signal. The receiver sensitivity (at $BER=10^{-5}$) of the PO PAM-4 signal is 1.5 dB better than the receiver sensitivity of a standard optical PAM-4 signal. We also investigate the feasibility of PO PAM-N (N = 4, 8, and 16) signals operating at 103.12 Gb/s, considering relative intensity noise, timing jitter, extinction ratio (ER) of EMLs, and dispersion. From the results, a PO PAM-8 signal performs better than PO PAM-4 and PO PAM-16 signals at 103.12 Gb/s. Finally, we suggest a timing control method to suppress the effect of dispersion in a PO PAM-N signal. We show that the tolerance to dispersion of a 103.12-Gb/s PO PAM-8 signal can be improved to ${\pm}40ps/nm$ by applying a proposed scheme.

• ETRI Journal
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• v.24 no.2
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• pp.97-108
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• 2002

Optical Border Gateway Protocol (OBGP) is an extension to BGP for Optical Cross Connects (OXCs) to automatically setup multiple direct optical lightpaths between many different autonomous domains. With OBGP, the routing component of a network may be distributed to the edge of the network while the packet classification and forwarding is done in the core. However, it is necessary to analyze the stable convergence functions of OBGP in case of lightpath failures. In this paper, we first describe the architecture of the OBGP model and analyze the potential problems of OBGP, e.g., virtual BGP router convergence behavior in the presence of lightpath failure. We then propose an OBGP convergence model derived from an inter-AS (Autonomous System) relationship. The evaluation results show that the proposed model can be used for a stable OBGP routing policy and OBGP routing convergence under lightpath failures of the optical Internet.

• Journal of the Optical Society of Korea
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• v.7 no.2
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• pp.47-52
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• 2003

Effect of soaking temperature on erbium doping of the optical fiber core during solution doping procedure, especially in the modified chemical vapor deposition (MCVD) process, was investigated. The concentration of dopants such as $Er^{3+} and Al^{3+}$ in the preforms and the optical fibers measured by the electron probe microanalysis (EPMA) and the optical spectrum analyzer (OSA) was found to increase with decreasing the soaking temperature. The increase in the concentration of the $Er^{3+}$ is attributed to the precipitation of the erbium due to the decrease in the solubility as well as the increase of capillary force and viscosity of the doping solution by decreasing the temperature.

• ETRI Journal
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• v.35 no.1
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• pp.1-6
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• 2013

In this paper, we present an implemented serial 40-Gb/s receiver optical subassembly (ROSA) module by employing a proposed TO-CAN package and flexible printed circuit board (FPCB). The TO-CAN package employs an L-shaped metal support to provide a straight line signal path between the TO-CAN package and the FPCB. In addition, the FPCB incorporates a signal line with an open stub to alleviate signal distortion owing to an impedance mismatch generated from the soldering pad attached to the main circuit board. The receiver sensitivity of the ROSA module measures below -9 dBm for 40 Gb/s at an extinction ratio of 7 dB and a bit error rate of $10^{-12}$.