• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.433-439
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• 2003

In this paper, we proposed a novel true time-delay (TTD) feeder for phased array antennas (PAAs) using fiber Bragg gratings (FBGs) and fibers coated with Cr/Au film. This structure requires less number of FBGs than the previously proposed FBG TTD feeders since one FBG is replaced with a metal film reflector in a strand of optical delay line connected to each antenna element and also provides the flexible wavelength selection since the metal film shows wide reflectance spectrum. A TTD for 10 GHz linear PAAs capable of steering beams in three different directions at 0$^{\circ}$and $\pm$30$^{\circ}$has been built. Experimental results on time delays are in good agreement with those calculated at all the steering angles. A 10 GHz linear array antenna with eight antenna elements red from the proposed TTD has been designed and the far-field radiation pattern or this antenna has been obtained by simulation.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.130-136
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• 2002

Device makers want to make higher density chips as devices shrink, especially WSix poly stack down is one of the key issues. However, EPD (End Point Detection) time delay was happened in DPS+ poly chamber which is a barrier to achieve device shrink because EPD time delay killed test pattern and next generation device. To investigate the EPD time delay, a test was done with patterned wafers. This experimental was carried out combined with OES(Optical Emission Spectroscopy) and SEM (Scanning Electron Microscopy). OES was used to find corrected wavelength in WSix stack down gate etching. SEM was used to confirm WSix gate profile and gate oxide damage. Through the experiment, a new wavelength (252nm) line of plasma is selected for DPS+ chamber to call correct EPD in WSix stack down gate etching for current device and next generation device.

• Journal of the Optical Society of Korea
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• v.20 no.3
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• pp.335-342
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• 2016

We demonstrate an optical asynchronous transfer mode/wavelength division multiplexing (OATM/WDM) optical access network, using a router based on an optical header decoder to conduct next-generation communications. The router consists of a decoder or hardware analysis processing of the header bit and switches. The router in the OATM/WDM optical access network is a key technology by which to satisfy subscribers’ requests, including reliability, cost efficiency, high speed, large-capacity transmission, and elevated information security. In this study, we carry out experiments in which a header decoder delivers to 16 and 32 subscribers with a single wavelength in the router. These experiments confirm the decoder’s successful operation via hardware using 4 and 5 header bits. We propose that this system may significantly contribute toward the realization of an optical access network that provides high-quality service to subscribers of next-generation communications.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.141-145
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• 2011

We theoretically investigated dispersion tolerance of an optical duobinary transmitter employed a Mach-Zehnder modulator and an optical filter. Compared to the optical transmitter based on a Mach-Zehnder modulator and an optical delay interferometer by optimizing the applied voltage for improving the dispersion tolerance, the demonstrated duobinary transmitter provides improved receiver sensitivity and higher dispersion tolerance while maintaining narrow spectral bandwidth.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.102-108
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• 1991

Utilizing self-phase modulation effects of a dispersion-shifted fiber and delay-line characteristics of two gratings, mode-locked 80 ps pulses at 1.319${\mu}{\textrm}{m}$ wavelength from a Nd: YAG laser are compressed down to 2.1 ps. These pulses are further compressed down to 340 fs using higher order soliton effects in a common single mode fiber.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.3-4
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• 2006

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.447-454
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• 2003

Optical burst switching (OBS) has been proposed to reduce the use of fiber delay lines (FDLs) and to realize the optical switching paradigm of the next-generation ail optical networks. The OBS can provide improvements over wavelength routing in terms of bandwidth efficiency and core network scalability via statistical multiplexing of bursts. Recently, another challenging issue is how to upport quality of service (QoS) in the optical burst switching networks. In this paper, we propose a deflection routing scheme to guarantee the QoS for the OBS networks to detour lower priority burst forward to the deflection routing path when congested. A big advantage of the proposed scheme is the simplicity of QoS provision, that comes from the simple QoS provisioning algorithm. Also, the QoS provisioning scheme be able to make efficient networks by fairly traffic distributing with the reduce of the use of FDLs at core routers. The QoS provisioning scheme has been verified to reliably guarantee the QoS of priority 0, 1, 2 burst and to efficiently utilize network resources by computer simulations using OPNET As results, the end-to-end delay of high priority burst is improved, and the network efficiency is also improved.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.3
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• pp.213-219
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• 2017

Recently, the Internet Protocol Television (IPTV) services have become very common, enabling various Internet-based services as well as watching TV. In the IPTV system, a Set-Top box (STB) plays a key role as a network terminal device that transmits and receives realtime multimedia contents. In addition, the IPTV networks are usually supported by broadband optical fiber-base network such as fiber-to-the-home (FTTH), However, a general IPTV STB is regarded as one of the local area network (LAN)-attached devices while sharing the bandwidth of the LAN (e.g., Ethernet). In order to overcome the limited bandwidth utilization by fully facilitating the broadband bandwidth (e.g., 1 Gbps) of the optical fiber-based network, we propose a new FC (Fiber Channel)-embedded IPTV STB which can be directly attached to the optical fiber network. Then, we verify that the impacts of the proposed FC-embedded IPTV STB by organizing the the FC-AL (Fiber Channel-Arbitration Loop) network equipped with the FC-embedded IPTV We measures the average Start-up Delay, Average Reject Ratio and the Number of Concurrent Users through extensive simulations to investigate the performances of the suggested FC-AL-based IPTV network. Surprisingly, the IPTV network architecture with the proposed FC-embedded IPTV STBs has an excellent average start-up delay of less than 10 msec, an acceptable average reject ratio of less than 3 % as well as a linear increase of the number of concurrent users when extending the architecture. This reveals that the proposed FC embedded STB has a superior impacts on the performance of the entire IPTV network by effectively utilizing the broadband bandwidth of the fiber optic-based network.

• Journal of Industrial Technology
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• v.13
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• pp.89-96
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• 1993

In this paper, an OPS(Optical Protection Socket) unit is designed and prototyped for the application in the optical CPN(Customer Premises Network). The OPS unit, which plays an important role in the CPN for the enhanced network reliability, is consisted of $1{\times}2$ optical fiber splitter, combiner, and $1{\times}1$ optical switch to be a hybrid-typed unit. Various considerations, about power burget and optical information loss have given the most practical design for OPS. From the measurement of the realized OPS unit, it has proved such as the pertinent switching delay time with minimum data loss, the perceptive ability on the ONU degradation, the switching ability on the ONU malfunction.

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.591-596
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• 2004

In this paper, a photonic RF true-time delay based on a partially side-polished fiber Bragg grating with heating electrode has been proposed and fabricated. It features continuous voltage-controlled operation, requiring no mechanical perturbation and no moving parts. For an RF signal carried over an optical signal, the time delay has been obtained by controlling the voltage applied to the electrode and thus adjusting its reflection positions from the fiber grating via the thermooptic effect. The achieved time delay is about 100 ps with the electrical power consumption of 280 mW.