• ETRI Journal
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• v.18 no.1
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• pp.1-14
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• 1996

We have experimentally observed and theoretically analyzed the gain dependent optimum repetition rates of a hybrid-type active and passive mode locked laser pulses in an erbium-doped fiber laser of the figure-of-eight geometry by utilizing a nonlinear amplifier loop mirror (NALM) as a saturable absorber and a directional-coupler type electro-optic modulator as an active mode locker. Transform-limited mode-locked pulses of about 10 ps width were obtained at repetition rates which correspond to harmonics of the cavity fundamental frequency and depend on the optical amplifier gain in the NALM.

• ETRI Journal
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• v.24 no.4
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• pp.259-269
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• 2002

Polymers are emerging as new alternative materials for optical communication devices. We developed two types of polymer-based devices for optical communications. One type is for ultra high-speed signal processing that uses nonlinear optical (NLO) polymers in such devices as electro-optic (EO) Mach-Z${\ddot{e}} $ hnder (MZ) modulators and EO 2${\times}$2 switches. The other is for WDM optical communications that use low-loss optical polymers in such devices as 1${\times}$2, 2${\times}$2, 4-arrayed 2${\times}$2 digital optical switches (DOSs) and 16${\times}$16 arrayed waveguide grating (AWG) routers. For these devices, we synthesized a polyetherimide-disperse red 1 (PEI-DR1) side chain NLO polymer and a low-loss optical polymer known as fluorinated polyaryleneethers (FPAE). This paper presents the details of our development of these polymeric photonic devices considering all aspects from materials to packaging.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.143-146
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• 2004

Signals of the short wave part of centimetre, millimetre and optic wave length ranges are being broadly used in the communication, location and remote sensing systems with space channels. In this case the presence of discrete non-uniform mediums like orbital debris, space dust and other discrete formations in the propagation channel may have substantial influence upon the characteristics of wave processes. and thus upon the data system quality. Mathematical models for studying the discrete non-uniform mediums effect on the characteristics of electromagnetic wave propagation are analyzed in this paper.

• Journal of Korean Physical Therapy Science
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• v.2 no.2
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• pp.533-544
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• 1995

Multiple sclerosis is a chronic, pregressive, demyelinating, disease of the central nervous system. It is named for the formation of disseminated scarlike lesions primarily in the central white mattrer of the brain and spinal cord. These plaques are commonly found in the regions of the optic tracts, third and fourth ventricles, basal ganglia, midbrain, pons, and spinal cord. Multiple sclerosis is an unpredictable disease, typically presenting with an exacerbating-remitting course, although other clinical courses have been recognized. Common clinical findings include disturbances in sensation, muscle strength, tone, fatigue, coordination, vision, communication, bladder and bowel function, and cognitive and behavioral function. Physical therapy of the patient with multiple sclerosis is centered around decreasing symptoms, improving function, prevention secondary complications, and promoting successful psychological adjustment. It requires the comprehensive efforts of a health care team to provide coordinated and continuing care.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.182-184
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• 2000

There are several facilities in Kochang distribution test center such as artificial fault generator(AFG), new distribution automation system(NDAS), communication networks (wireless and optic), lumped constant circuit, switches for distribution automation, overhead and underground distribution line. We have been field testing on remote control, data acquisition. remote metering, feeder automation and so on for distribution automation using those equipment.

• The Journal of the Acoustical Society of Korea
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• v.31 no.2
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• pp.73-78
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• 2012

The photophone, Alexander Graham Bell's device for transmitting sound through light was patented in 1880. It included the transmitter modulating and reflecting strong light like sunlight to a distant receiver which produced sound. In this working of the photophone, the discovery of the sound-emitting effect under illumination was very essential. Longing for being famous in the scientific community, Bell focused on presenting various methods for producing sounds and for maximizing the loudness by performing intensive research on the photoacoustic effect. Bell's scientific research on photoacoustics was successful in establishing himself as a scientist and laid a foundation of photoacoustic analysis. And his invention became a basis for other researchers' subsequent technologies like fiber-optic communication.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.342-344
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• 2006

During last years, large investments have been directed to development and research of nano-technological products like semiconductor, display panel, optic-fiber communication components, life technology, and ultra-precision components. All quantitative measurements at nanometre scale should guarantees accurate results and high quality. Laser interferometer is one of most famous nanometre scale devices to be able to measure metre-scale distance with nanometre scale resolution, but it is easily affected by various error causes like geometrical, instrumental and environmental factor. On the other side, capacitive sensor is robust to above error factors, but it is able to measure relatively shorter distance, under $100{\mu}m$, than laser interferometer. New error correction method for laser interferometry using capacitive sensor will be introduced in this paper.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.908-912
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• 2003

The waste heat recovery system using heat pipe was tested for the consideration of developing the high-efficiency waste heat recovery technology. Heat pipe, a effective device that can quickly transfer large amounts of heat energy using the phase change of the working fluid and the characteristics of Electric Heater Bars used for alternative heating system are introduced In this paper. In order to increase energy efficiency, the system which controls the status of electric heater bars and the temperature of heat pipe installed has developed.

• Journal of the Korea Computer Industry Society
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• v.3 no.2
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• pp.141-148
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• 2002

In this paper, brushed servo control system for industrial robot is realized under GUI environment. Brushed servo motor has 400W capacities, 1000ppr optic encoder and electric brake load. Especially, driving unit is composed of full-bridge MOSFET semiconductors with 9540 and 540 FET ICs. Control unit has PIC 16C74 microprocessor［l,2,3], RS-232 communication ports, URD current sensor, and GAL 16R8ACN. Servo control system is controlled by PID control method[5,8］ with varying control parameters and load capacities. Brushed servo control systems which are proposed in this raper are applied to industrial robot control system.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.5 s.182
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• pp.103-110
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• 2006

Automatic optical alignment modules are a key technology in optical communication system. However, the optic component assembly depends highly on manual or semi-automated alignment process. In this paper, a novel alignment mechanism with minimum degree-of-freedom has been designed and theoretical models are derived from geometric optical characteristics on collimators, optical filters and optical ray alignment. The automatic alignment control algorithm has been newly developed based on the mechanism and models, and then we make fast, precise and reliable alignment through the algorithm. The reliability of developed modules has been verified with various simulations and performance evaluations.