Bong Kyu Kim

Radio-over-fiber system using fiber-grating-based optical CDMA with modified PN codes

In this work, we propose the fiber Bragg grating (FBG)-based optical code-division multiple-access (CDMA) with the modified pseudorandom noise (PN) codes for the radio-over-fiber (ROF) systems, and we numerically analyze the characteristics of the proposed system. By the proposed FBG-based optical CDMA with the modified PN codes and spectrally uniform intensity light sources, it is possible to construct interference-free optical CDMA for ROF systems.

Suppression of polarization dependence in a two-mode-fiber acousto-optic device.

We present a theoretical and experimental analysis of the polarization dependence of a two-mode-fiber acoustooptic device, taking into account the residual stress in the fiber and the ellipticity of the core. We successfully demonstrate the suppression of the polarization dependence by relieving the residual stress, using thermal annealing.

A new family of 2-D wavelength-time spreading code for optical code-division multiple-access system with balanced detection

We propose a new family of 2¿D wavelength-hopping/ time-spreading code for optical code-division multiple-access systems with balanced detection, and we numerically analyze the characteristics of the proposed system. By using the proposed decoding scheme, the undesired interference is efficiently eliminated. The proposed scheme has the enhanced performance and allows for a large number of simultaneous users compared with the 3-D and other balanced codes for differential detection.

Performance comparison between Manchester and inverse-RZ coding in a wavelength re-modulated WDM-PON

We compare the performance of wavelength re-modulated WDM-PON implemented by Manchester or IRZ coded downstream and NRZ re-modulated upstream, and investigate effects of bit-rate difference between downstream and upstream on the two coding schemes.

Nonlinear strain response of two-mode fiber-optic interferometer

Experimental and theoretical investigation of a nonlinear response of a two-mode fiber interferometer to axial strain is described. It is discovered that the nonlinearity dramatically increases as the wavelength approaches the cutoff wavelength of the second-order mode (LP(11)).

The finite element analysis of internal stresses during sequential build-up of lamination-based thick-film multilayer substrates

The thermomechanical behavior of multilayer structures is a subject of perennial interest. Among various multilayer structures, we provided a thorough investigation on the lamination-based thick-film multilayer substrates, or the multichip module substrates. Firstly, we offered an in-depth look at the composite bean analysis (CBA) recently suggested for thick-film multilayer structures. The calculated substrate bow values using the CBA model were compared with the measured values and calculated values from numerical analysis. The magnitude and distribution of biaxial, shear, and peel stresses in thick-film multilayer substrates during sequential build-up of thick-film polymer dielectrics were calculated and discussed. Secondly, for users’ convenience, the most widely-used analytical methods for microelectronics applications were summarized along with the CBA model, and their possible applications were suggested.

Dual heterodyne polarization diversity demodulation for fiber-optic interferometers

A novel method is described for the simultaneous suppression of polarization and phase bias induced signal fading in fiber-optic interferometers based on differentially frequency shifted orthogonal polarization components. An experimental demonstration proved the operating principle with a high sensitivity of 28 /spl mu/rad//spl radic/(Hz).

A new family of 2-D wavelength/time spreading code for optical-code division multiple-access system with balanced detection

We propose a new family of two-dimensional wavelength-hopping/time-spreading code for optical code-division multiple-access systems with balanced detection, and we numerically analyze the characteristics of the proposed system. By using the proposed decoding scheme, the undesired interference is efficiently eliminated. The proposed scheme has enhanced performance and allows for a large number of simultaneous users compared with the three-dimensional and other balanced codes for differential detection.

EXPERIMENTAL STUDIES ON PHASE EQUILIBRIA OF PEG-WATER-DEXTRAN/AMMONIUM SULFATE SYSTEMS AND PARTITIONING OF ALBUMIN INTO TWO WATER-CONTINUOUS PHASES

The clouding points and equilibrium concentrations of PEG/dextran/water and PEG /ammonium sulfate/water systems were experimentally determined for different molecular weights of PEG by titration method and direct determination of concentrations. In phase diagrams of PEG-water with ammonium sulfate or dextran, the addition of salt or dextran induced the phase separation of PEG-rich phases near the PEG-lean phases having the different partitioning of PEG. The concentrations of PEG in PEG-rich phases increase as the amounts of PEG or salt and dextran increase, while the concentrations of PEG in aqueous media decrease in any cases. The higher the molecular weight of PEG has, the wider the two-phase regions are. In dextran DT10 systems, the partition coefficients of egg albumin into PEG-lean phases increase with concentrations of dextran and the molecular weight of PEG. In ammonium sulfate systems, the partitioning coefficients showed a maximum, having lower partitioning at the very high and low concentration of salts. It is also observed that as the amounts of albumin increase, the partitioning of albumin into PEG-lean phase increases.

Experimental Demonstration of Bipolar Optical Spectral Encoding CDMA with Modified PN Codes

Experimental demonstration of bipolar spectral encoding CDMA with modified PN codes is presented. Spectral encoding is achieved with EDFA ASE and AWG filters. We measured bit-error rate performance of 1.25 Gbps optical CDMA signal transmission.