• Current Optics and Photonics
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• v.1 no.1
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• pp.23-28
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• 2017

The laser has been regarded as the potential illumination source for the next generation of projectors. However, currently the major issues in applying the laser as an illumination source for projectors are beam shaping and laser speckle. We present a compact solution for both issues by using a vibrating diffractive optical element (DOE). The DOE is designed and fabricated, and it successfully transforms the circular Gaussian laser beam to a low speckle contrast uniform rectangular pattern. Under a vibration frequency of 150 Hz and amplitude of $200{\mu}m$, the speckle contrast value is reduced from 67.67% to 13.78%, and the ANSI uniformity is improved from 24.36% to 85.54%. The experimental results demonstrate the feasibility and potential of the proposed scheme, and the proposed method is a feasible approach to the miniaturization of laser projection display illumination systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.1
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• pp.269-280
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• 1996

We proposed a symbolic substitution method based on an optical correlator for an optical parallel addition. In the proposed symbolic substitution method, we used redundant binary number of the symbolic substitution rules as a number system and chose MAC3E filter which had very low sidelobes and good correlation peak compared with SDF filter as the optical correlation filter. We encoeded input numbers property to increase the discrimination capability and divided inpt patterns into 5 groups of the same addition results to minimize the number of symbolic substitution rules. Through the computer simulation, we confirmed the proposed method was suitable to implement the optical parallel adder.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.462-469
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• 1988

Choromatic dispersion of single mode optical fibers limits the maximum bit rate in the single mode optical transmission systems. In this paper we calculate chromatic dispersion and dispersion parametes(zero dispersion wavelength, dispersion slope) for concatenated single mode optical fibers form the chromatic dispersion and dispersion parameters of individual single mode optical fibers, and compare theoretical valuse with those measrued by double demodulation method. Calculated values are coincident with measured ones reasonably. The standard deviation is 0.77-1.28nm for zero dispersion wavelength and 0.56-0.75PS/km.nm2 for dispersion slope. The standard deviation of zero dispersion wavelength is inverse proportional to the optical fiber lenght.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6B
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• pp.568-574
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• 2009

320km optical transmission link for 128 channel DWDM (dense wavelength-division-multiplexing) signals is simulated and fabricated. An optical fiber amplifier for the link is composed of a distributed Raman amplifier and dual C/L-band EDFAs which are optimized for the performances of an optical amplifier obtained from the simulation. Gain and NF of the optimized EDFAs are above 19dB and below 7.5dB, respectively. The resultant OSNRs (optical signal to noise ratios) of the link are average 25dB on each band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5B
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• pp.404-413
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• 2003

Optical Internet consists of IP domain and optical (WDM) domain, where the wavelength routing (WR) and optical burst switching (OBS) are the promising switching technologies in the optical domain. In this paper, we perform the simulations on the WR network and the OBS network, and compare their performances. It is verified from our simulations that the OBS network performs better than the WR network when the same network resources are given.

• Journal of The Korean Astronomical Society
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• v.32 no.1
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• pp.7-16
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• 1999

Open clusters are useful tools to investigate the structure and evolution of the Galactic disk. We have started a long-term project to obtain UBVI CCD photometry of open clusters which were little studied before, using the Doyak 1.8 m telescope of Bohyunsan Optical Astronomy Observatory in Korea. The primary goals of this project are (1) to make a catalog of UBVI photometry of open clusters, (2) to make an atlas of open clusters, and (3) to survey and monitor variable stars in open clusters. Here we describe this project and report the first results based on preliminary analysis of the data on four open clusters in the survey sample: Be 14, Cr 74, Biu 9, and NGC 2355. Isochrone fitting of the color-magnitude diagrams of the clusters shows that all of them are intermediate age to old (0.3-1.6 Gyrs) open clusters with moderate metallicity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7C
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• pp.641-652
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• 2002

We introduce a new ultra-large capacity time- and wavelength-division hybrid optical switching system, called ESCIMONET(Easily SCalable Interconnected Multiwavelength Optical NETwork). We describe its architecture, principle of operation, and performance characteristics. ESCIMONET is very effective system in terms of its handling capacity versus number of wavelength needed. It can handle n$^3$number of channels using only n number of different wavelengths. The insertion loss of the whole system is less than conventional optical switching system so that the number of optical amplifiers in the system can be minimized. We analyzed the performance of the system by investigation the characteristics of the buffer used in the system such as throughput and average waiting time of the signal in a buffer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8A
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• pp.657-662
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• 2003

The OPM(optical performance monitoring module) is needed in order to monitor optical performance. the most importance of OPM is to measure the wavelength of optical signal. In the past time, it was very difficult to get the wavelength value because they used pilot tone. Since then, using AWG(arrayed waveguide grating) and AOTF(acousto optic tuneable filter), the wavelength and the transmission qualify for multi channel signal have been monitored. In this paper, we chose the fiber fabry-perot wavelength variable filter which be evaluated for optical resolution ability to excellent, so that FBG(fiber bragg grating) was used for setting reference wavelength because chose a wavelength variable filter.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.77-84
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• 2005

We prepared the new nonlinear optical chromophores that show fairly high microscopic nonlinearity through intramolecular charge transfer. Phenothiazine and carbazole units played an important role to contribute high electron donability and connect the resonance pathway via conjugative effect in the cyclized ring beside the aromatic ring. Theoretical calculation, electrochemical analysis, and absorption spectroscopic study gave us useful information about the energy states and microscopic nonlinearities of two serial chromophores. We compared the microscopic nonlinearities of four chromophores with the conjugation length and electron donability in the push-pull type NLO chromophores. The effect of gradient donability and lengthening the conjugation were investigated on the electronic state and microscopic nonlinearity.

• Molecules and Cells
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• v.44 no.11
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• pp.851-860
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• 2021

Label-free optical diffraction tomography (ODT), an imaging technology that does not require fluorescent labeling or other pre-processing, can overcome the limitations of conventional cell imaging technologies, such as fluorescence and electron microscopy. In this study, we used ODT to characterize the cellular organelles of three different stem cells-namely, human liver derived stem cell, human umbilical cord matrix derived mesenchymal stem cell, and human induced pluripotent stem cell-based on their refractive index and volume of organelles. The physical property of each stem cell was compared with that of fibroblast. Based on our findings, the characteristic physical properties of specific stem cells can be quantitatively distinguished based on their refractive index and volume of cellular organelles. Altogether, the method employed herein could aid in the distinction of living stem cells from normal cells without the use of fluorescence or specific biomarkers.