• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.5
• /
• pp.1123-1131
• /
• 2005

In this paper, optimal position of optical phase conjugator (OPC) for best compensating distorted WDM channels due to both chromatic dispersion and self phase modulation (SPM) in $8{\times}40$ Gbps WDM systems is numerically investigated, and the eye opening penalty (EOP) and bit error rate (BER) characteristics of overall WDM channels at this position is investigated, comparing with that in case of OPC placed at mid-way of total transmission length. It is confirmed that the compensation extents in WDM system with OPC is more improved by the shifting OPC position from the mid-way of total transmission length, depending on the modulation format and fiber dispersion coefficient. Ant it is confirmed that, from a viewpoint of the reception performance, EOP of each channel is more or less different with one another, but the BER characteristics of overall channels are almost equal.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.7
• /
• pp.1777-1784
• /
• 1998

The packet error rates of an optical packet switching node with an optical address processor using an EDFA in order to detect M-ary correlation pulses at a fiber-optical delay line matched filter output have been evaluated. Effects of A PIN diode NEP, the gain and noise figure of the EDFA, and the bandwidth of an optical filter on the packet error rate of the switching node have been compared. There is negligible error rate change depending upon the variation of the PIN diode NEP and the EDFA gain. If the bandwidth of the optical filter is below 10 times of the data rate, there is no appreciable effect on the error rate. If the noise figure of the EDFA increases, however, the power penalty increases as much as the noise figure increment at all the bit rates and for address code sets considered in this work.

• Journal of Biomedical Engineering Research
• /
• v.22 no.5
• /
• pp.431-438
• /
• 2001

Oxygen saturation of blood is defined as ratio of total hemoglobins density to oxyhemoglobins density And the accuracy of pulse oxymeter that measures the oxygen saturation of blood by a noninvasive method is influenced by a measuring environment, breathing and motion of patient. Especially when patient moved his arms and fingers, it is difficult to eliminate motion artifact because the motion artifact signal has features that are overlap or closed at normal signal in frequency domain. We propose the filtering method that construct the filter banks and a matched falter to improve the Problem. When experimented by the proposed method, the ratio regulation of the proposed methods has 4.1% below than an adaptive filter (39.7%) and a moving average filter (11.2%). So. the Proposed method will be able to get a stable ratio of SpO2.

• Progress in Medical Physics
• /
• v.11 no.2
• /
• pp.101-107
• /
• 2000

Pulse oximetry is a non-invasive optical method which measures arterial oxygen saturation with two different wavelength. We can obtain the pulsating component of the arterial blood superimposed on DC level attenuated by venous blood, skin and other nonpulsatile components. This study is based on computing algorithm of oxygen saturation using the integral ratio of pulsatile components. In this algorithm, we used the half cycle of the pulsatile signal rely on arterial contraction. It's period is about 1/4 in 1 cycle. In the result, Our algorithm with 1/4 period of 1 cycle is similar to existing model. Because of removal that A part have low amplitude and possession in long term from calculating, the effect of the motion-artifact is decrease.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.7 no.6
• /
• pp.563-569
• /
• 2002

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency DC-DC converter, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter, and an AC filter. The 20kHz switched high frequency converter is used to generate bipolar PWM pulse, and the high frequency transformer transforms its voltage twice, which is subsequently rectified by diode bridge rectifiers for a full-wave rectified 60 Hz sine wave power output. Even though the high frequency link system needs more power semiconductors, a reduced size, light weight, and saved parts cost make this system more comparative than other power conditioning systems due to elimination of 60Hz transformer.

• Journal of the Korean Vacuum Society
• /
• v.7 no.3
• /
• pp.255-260
• /
• 1998

The ionized magnetron sputtering is very useful in filling of small metal contact or via in ULSI processing with very high ionization upto 80% based on incoming flux ratio. But fairly high sputtering gas pressure is required to get high ionization, which instead gives low deposition rate and diverse incoming neutral's angular distribution. The electron quenching by heavily sputtered metals and gas rarefaction were considered the main causes of decreased ionization in this process. RF pulsing of sputtering power was proposed to solve those two problems. The results showed that 10㎳/10 ㎳ and 100㎳/100 ㎳ of on/off pulsings were optimal pulse conditions from OES measurements and also XRD of deposited Ag film showed distinct change of (111) to (200) preferred orientation. These results were analysed in a view point of neutral gas heating and cooling by high power sputtering.

• Journal of the Korean Chemical Society
• /
• v.39 no.1
• /
• pp.14-22
• /
• 1995

This paper is concerned with the design of optimal surface heating patterns that result in focusing acoustic energy inside a subsurface target volume at a specified target time. The surface of the solid is heated by an incident laser beam which gives rise to shear and compressional waves propagating into the solid. The optimal heating design process aims to achieve the desired energy focusing at the target with minimal laser power densities and minimal system disturbance away from the target. The optimality conditions are secured via the conjugated gradient method and by the finite element method along with using the half-space Green's function matrix. Good quality energy focusing is achived with the optimal designs reflecting the high directivity of the photothermally generated shear wave patterns.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.8
• /
• pp.1968-1973
• /
• 2013

We present the enhancement of narrowband modulation response of an optical source by integrating a dual-electrode distributed feedback (DFB) laser with an electro-absorption modulator (EAM). The dual-electrode DFB laser exhibits a multiple optical modes owing to a self-pulsation in GHz range. By modulating the laser and modulator sections of the integrated device simultaneously, 20-dB of narrowband modulation response enhancement at 6 GHz with 7-GHz tuning range has been observed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.18 no.6
• /
• pp.31-36
• /
• 2004

Optical coherence tomography system has been extensively studied because it has some advantages such as imaging of high resolution, low cost, and compact size configuration. In order to obtain high resolution of OCT system we configured OCT system using a femto-second laser. We measure the pulse width using autocorrelator function because a femto-second laser is ultra short pulse. And we measured the practical resolution using theoretical equation and the measurement of reference sample. It is confirmed that the proposed OCT system has 1.5 times higher resolution and un distinctive cross-sectional image than OCT system with SLD as a light source.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.10
• /
• pp.1957-1964
• /
• 1994

In this thesis, a Synthetic Aperture Rarar Processor that is possible real-time handling is implemented using CW(Continuose Wave) laser as a light source, CCD(charge Coupled Device) as a time integrator, and AOD(Acousto-Optic Device) as the space integrator. One of the advantages of the proposed system is that it does not require driving circuits of the light source. To implement the system, the linear frequency modulation(chirp) technique has been used for radar signal. The received data for the unit target was processed using 7.80 board and accompanying electronic circuits. In order to reduce the smear effect of the focused chirp signal which occurs Bragg diffrection angle of the AOD has been utilized to make sharp pulses of the laser source, and the pulse made synchronized with the chirp signal. Experiment and analysis results of the data and images detected from CCD of the proposed SAR system demonstrated that detection effect is degrated as the unit target distance increases, and the resolving power is improved as the bandwidth of the chirp signal increases. Also, as the pulse width of the light source decreases, the smear effect has been reduced. The experimental results assured that the proposed system in this papre can be used as a real time SAR processor.