K.H. Kim

Site diversity effect on forward link performance under unequal cell loading in DS/CDMA

Forward link analysis under SIR based power control that quantitatively describes the effect of unequal cell loading, path loss slope, target Eb/No, and handoff threshold T-ADD on wireless direct sequence code division multiple access (DS/CDMA) spread spectrum systems is presented. A maximal ratio combining (MRC-2, MRC-3) site diversity scheme is used to compare system performance for unequal number of cell users, 10 and 15 respectively. About 2.4 times home cell users increase is shown in MRC-3 unequal cell loading as compared with the equal cell loading. In both cases of MRC-2 and MRC-3, T-ADD impact is negligible in equal cell loading. For equal cell loading, average MRC-3 capacity is 1.2 times larger than that of MRC-2.

Nonlinear effects in optical fiber: Advantages and disadvantages for high capacity all-optical communication application

This paper presents, in the form of a review, some of the results of our study addressing the advantages and disadvantages of the nonlinear effects in optical fibers for their use in high-speed, high capacity, all-optical telecommunication applications. Nonlinear effects that we cover include: self-phase modulation (SPM), cross-phase modulation (CPM), stimulated Raman scattering (SRS), and stimulated Brillouin scattering (SBS). We have found that nonlinear effects can play useful and important roles in enhancing the fiber performances and creating new functions by way of fiber lasers, amplifiers, switches, logic devices, demultiplexers, signal format conversion and wavelength conversion devices. But we also have found that they can play degenerative roles limiting the performances of optical fiber communication. Trade-off between the advantages and the disadvantages of the nonlinear effects should be carefully examined in order to utilize their effects to the fullest extent.

RFID tag antenna mountable on metallic surfaces and matching method by parasitic patches

A low cost novel antenna for radiofrequency identification (RFID) tags mountable on metallic surfaces has been proposed and implemented. The proposed antenna indicates not only an easy impedance matching method with various microchip impedances but also the ability to be mounted on metallic surfaces. In this paper, the folded dipole type tag antenna with two parasitism-patches is proposed. This allows control of both the real and imaginary parts of the antenna impedance to achieve conjugate matching with the various values of the microchip impedance.

Provision of User-Centric Mobile Services in Next Generation Mobile Communication Environment

In next generation (NG) mobile communication environment, it is expected that mobile services will be user- centric and the mobile service platform will play an important role in supporting various future mobile services not only for service providers to provide services effectively but also for users to use services easily. In-this-paper,-we propose the architecture, functions and protocols of the NG mobile service platform of the NG mobile service platform which gives efficient means of connecting users and service providers to fulfill user-centric mobile services. Then we describe the NG mobile service environment with focusing on the NG service platform and how user-centric mobile services are provided in the NG mobile service environment. We then introduce the context aware follow-me (CAF) service developed as a prototype of promising NG user-centric mobile service followed by introduction of test- bed system developed to investigate feasibility of the CAF service.

All-optical wavelength conversion scheme based on 20 Gb/s RZ data

Summary form only given.High-speed all-optical wavelength converters are essential components of future wavelength division multiplexed optical networks. Semiconductor-optical-amplifier (SOA) based wavelength converters operating up to 40 Gb/s are becoming attractive because of their small size and integrability. Wavelength conversion in the SOA can be achieved either by cross-gain modulation (XGM) in a single amplifier or by cross phase modulation (XPM) in two amplifiers placed in a Mach-Zehnder interferometer (MZI). We demonstrate a hybrid scheme of a single-SOA and asymmetric MZI (AMZI) for wavelength conversion of 20 Gb/s RZ format data.

Double-path erbium-doped fiber amplifier with enhanced noise figure characteristics

Summary form only given. Efforts paid to various pump schemes such as forward, backward and bidirectional pumping have made significant contributions to highly reliable erbium-doped fiber amplifiers (EDFAs) with high gain and low noise figure characteristics. Reflective type EDFAs by using a mirror and an optical isolator were proposed to achieve a better utilization of wasted pump energy. Therefore, this double-path EDFA doubled the gain coefficient compared to that of single-path ones. However, its noise figure was worse than that of single-path EDFAs. Using a 3 nm bandpass filter (BPF) between the EDF and mirror to remove the amplified spontaneous emission (ASE) improved the noise performance. However, the BPF scheme is not suitable for wavelength division multiplexing (WDM) optical communications since the BPF simultaneously filtered out other WDM signals outside its transmission band.

Simultaneous amplification by Er-ions and nonlinear Raman phenomena in a Er-doped germano-silica fiber

It is possible to obtain a flat gain band in C and L band by Er-ions and stimulated Raman scattering in a Er-doped germano-silica fiber if the concentration of Er and background loss in a fiber core have proper values during the fiber fabrication process.

1480/spl sim/1485 nm cascaded CW Raman fiber laser

Summary form only given. Recently, distributed Raman amplifiers have been demonstrated to obtain broad gain bandwidth of the optical amplifiers. To achieve L band signal (1570-1610 nm) amplification using Raman gain in a silica fiber, a pump power at wavelengths around 1485 nm is required. In this letter we demonstrate a simple and versatile cavity configuration for a tunable cascaded Raman fiber laser which converts 1313 nm pump light to wavelengths range of 1480-1485 nm.