A GaAs/AlGaAs directional-coupler-type device that use polariton propagation was fabricated and its switching operation was demonstrated. The length of the switching region is as small as 300 µm. The output signal modulation under an electric field shows typical characteristics of directional-coupler type switching. The measured operation voltage is 2 V for an operation wavelength of 805 nm at 10 K. The corresponding signal extinction ratio is 8 dB. These experimental results confirm the efficient operation of the polariton devices, which can be applied to especially small optical -switching devices with low-voltage operation.

A GaAs/AlGaAs directional-coupler-type device that use polariton propagation was fabricated and its switching operation was demonstrated. The length of the switching region is as small as 300 µm. The output signal modulation under an electric field shows typical characteristics of directional-coupler type switching. The measured operation voltage is 2 V for an operation wavelength of 805 nm at 10 K. The corresponding signal extinction ratio is 8 dB. These experimental results confirm the efficient operation of the polariton devices, which can be applied to especially small optical -switching devices with low-voltage operation.

Hierarchical macrocell/microcell architectures have been proposed for future cellular mobile communication. The performance analysis for the hierarchical cellular system becomes an important issue. In this paper, extending the analytical methods from[1][2][8], assuming that the imperfect power control follows log-normal statistics, and employing different attenuation models for macrocells and microcells, the capacity plane and outage probability of the system are examined and quantified with and without perfect sectorization. From the numerical results of parameters of IS-95 protocol, the high user capacity and lower outage probability may be expected in the case of relatively tight power control and narrower overlap between sectors. These results are compared with the previously published CDMA nonhierarchical cellular system estimation. When we employ the hierarchical cellular system, we can increase the user capacity 2.3 times with the same bandwidth 1.25 MHz than the one of the nonhierarchical cellular system.

Network monitoring is one of the most significant functions in network management to understand the state of a network in real-time. In SNMP (Simple Network Management Protocol), polling is used for this purpose. If the time interval for two consecutive polling requests is too long, then we cannot understand the state of the network in real-time. Conversely, if it is too short, then the polling message traffic increases and imposes a heavy load on the network. Many dynamic polling algorithms have been proposed for controlling the increase in the polling message traffic. However, they cannot keep track of the time variations of management information values, since their main objectives are to check whether or not a network node is active and the next polling interval is determined being independent of the time variations of the values. The existing polling algorithms are thereby not applicable to the case where monitoring the time variation of management information values is critical. This paper proposes a new dynamic polling algorithm which, by making use of Discrete Fourier Transformation, enables not only to control the increase in the polling message traffic but also to keep track of the time variations of network management information values. We show the availability of the proposed algorithm by evaluating it through both simulations and experiments in actual network environment.

In deep submicron CMOS and BICMOS technologies, antenna effects affect floating gate charge of usual floating gate test structures, dedicated to capacitor matching measurement. In this paper a new pseudo-floating gate test structure is designed. After test structure and modeling presentation, testing method and results are given for several capacitor layouts (poly-poly and metal-metal).

Recently, we proposed a low power consumption FIR switched-capacitor filter constructed with capacitors having capacitances in proportion to square roots of transfer function coefficient values. It is referred to as an FIR semi-parallel cyclic type (SPCT) filter. In this paper, we present IIR SPCT filter. It needs only a single operational amplifier, hence being low power consumption. The IIR SPCT filter has smaller total capacitance than one of the IIR parallel cyclic type (PCT) filter and better high frequency response than one of the IIR transfer function coefficient ratio (TCR) filter. As a whole, the IIR SPCT filter has middle performance of the IIR PCT and TCR filters for the total capacitance, the number of types of clock pulses, and high frequency response.

The influence of loaded capacitance on the resonant frequency of a triplate-type strip resonator is investigated through numerical simulations by means of the finite-difference time-domain (FDTD) method. This type of resonator is one of the basic components of very small high-dielectric stripline filters, named laminated planar filters. Numerical results of resonant frequencies are compared with experimental results and found to be in excellent agreement, which circumstance ensures that the FDTD method can be applied to the characterization of a wide range of laminated planar microwave devices including resonators and filters. It is also found that the resonant frequency is directly related to the square root of its line capacitance when the resonator is regarded equivalently as a series LC circuit.

This paper presents a new approach to computing symbol error probability of fast frequency-hopped M-ary frequency shift keying (FFH/MFSK) systems with majority vote under multitone jamming. For illustrating the applications, we first consider the case in which the source data rate is fixed and the hopping rate is allowed to vary. In this case, the optimum orders of diversity for several values of M are examined. Results show that M=4 outperforms other values. Then, we treat another case in which the hopping rate is fixed and the data rate is adjusted so as to obtain maximum throughput under a given constraint of error probability. In addition to the case of diversity alone, we also evaluate the performances of the fixed hopping rate case with channel coding using convolutional code and BCH code.

Complex rule conditions are commonly required to describe complicated business semantics. In these cases, efficient condition evaluation is crucial for high performance of active database systems. Most previous works used the incremental evaluation techniques, whose operations are relatively expensive due to the processing based on the exact calculation of the condition expression. In this paper we propose a new filtering technique that effectively identifies false condition in an early stage of condition monitoring. Since the results of condition evaluation tend to be false in most practical cases, an efficient filtering method can highly facilitate fast condition evaluation. The proposed filtering technique is developed based on the new perspective of database state and database operations, i. e. , a vector space model. We first present vector representations of database states, database operations, and complex condition expressions. Then, we propose a filtering method based on the properties of a vector space, called the sphere containment test. Our proposed method determines the truth value of the rule conditions only with the delta vectors maintained in main memory. We compare our method with a typical incremental evaluation method and show that the proposed method can give a significant performance enhancement.

The effectiveness of periodic dispersion compensation on single-channel 40 Gbit/s soliton transmission system was experimentally investigated. This technique requires just the dispersion compensation fibers and wideband optical filters in the transmission line, which has no difficulty to be used in the practical system. By using polarization-division-multiplexing together with periodic dispersion compensation, single-channel 40 Gbit/s transmission over 4700 km was demonstrated. Single-polarization 40 Gbit/s transmission experiments, which are more suitable for system implementation and compatible with WDM were also conducted. We investigated the transmission characteristics and pulse dynamics in different dispersion maps and in the optimized dispersion map, single-channel, single-polarization 40 Gbit/s transmission over 6300 km was successfully demonstrated.

By sacrificing approximately ten percent of the transmission speed, ultra-high speed optical time division multiplexed network can be fully operatable by the use of currently available electrical switches. The network utilizes dispersion managed quasi-solitons and transmits TDM packet which comprises of ATM cells that are introduced from a gateway through bit compression to match to the ultra-high speed traffics. The network can provide flexible bandwidth and bit on demand at burst rate of the maximum LAN speed.

Attenuated total reflection (ATR) properties and scattered light properties were measured for Ag thin films and arachidic acid (C20) Langmuir-Blodgett (LB) ultrathin films on the Ag thin films to obtain the information about their complex dielectric constants and surface roughness utilizing an excited surface plasmon polariton. The complex dielectric constants for the Ag thin films and the C20 LB films were obtained by fitting the calculated ATR curves to the experimental ones. The surface roughnesses of these films were estimated by the angular distribution of the scattered light assuming the Gaussian function as an autocorrelation function and a linear superposition of roughness spectra. The angular spectra strongly depended on the roughness parameters: the transverse correlation length σ and the surface corrugation depth δ. The experimental angular distributions were explained by some pairs of σ and δ. It was suggested that the surface roughness of the C20 LB films changed with the number of monolayers since the angular spectra varied with the number of the C20 LB monolayers on the Ag films. It is thought that the measurement of the scattered light is useful to evaluate surface roughnesses of LB ultrathin films.

The TMN that appears to operate the various communication networks generally and efficiently is developed under the different platform environment such as the different hardware and the different operating system. One of the main problems is that all the agents of the TMN system must be duplicated and maintain the software and the data blocks that perform the identical function. Therefore, the standard of the Q3 interface development cannot be defined and the multi-platform cannot be supported in the development of the TMN agent. In order to overcome these problems, the Farming methodology that is based on the Farmer model has been suggested. The main concept of the Farming methodology is that the software and the data components that are duplicated and stored in each distributed object are saved in the Platform Independent Class Repository (PICR) by converting into the format of the independent componentware in the platform, so that the componentwares that are essential for the execution can be loaded and used statically or dynamically from PICR as described in the framework of each distributed object. The distributed TMN agent of the personal communication network is designed and developed by using the Farmer model.

We demonstrate that the frequency modulated video signals in the subcarrier multiple access optical network can be satisfactorily transmitted using our proposed method, that broadens an optical spectrum by multiplying the subcarrier signals by an additional signal and that reduces optical beat interference, even if the wavelengths of four Fabry-Perot laser diodes are very close each other.

Recently, reliable Pb (Ti, Zr) O3 (PZT) thin-film capacitors with robust switching endurance were fabricated successfully by incorporating oxidizable metal and oxide electrodes. However, the reasons for the drastic improvement in the switching endurance property was not clear. Degradation of polarizations by switching is called "polarization fatigue. " This paper describes the mechanisms of polarization fatigue, and discusses ways for improving of that property from the standpoints of microstructure, and of interactions between the PZT and the electrode materials of the capacitors. It is clearly identified that the causes of the fatigue are the unexpected formation of a surface transition layer of PZT, which is strongly dependent on the crystallization process, and a decrease in the interfacial capacitances due to the accumulation of oxygen vacancies between the PZT and non-oxidizable metal electrodes with high work functions such as Pt. Oxidizable metal and oxide electrodes suppress by oxidation-reduction reactions the accumulation of oxygen vacancies. Fatigue-free PZT thin-film capacitors can be formed if oxidizable metal or conductive oxide electrodes are incorporated in columnar-grain-structured PZT thin-film. In sharp contrast, fatigue and retention properties of PZT thin-film capacitors with Ir electrodes were degraded by modification of the PZT with 1 atm%-Nb and 1 atm%-La even though its grain structures were columnar.

If the fiber dispersion of soliton transmission line is optimized, the amplifiers output power becomes almost constant for different amplifier spacing and pulse width. Numerical simulations indicate the optimal dispersion can be determined, as the ratio of amplifier spacing to dispersion length is about 0. 8 for uniform dispersion line.

We study nonlinear pulse propagation in an optical transmission system with dispersion compensation. This is particularly important for designing an ultra-fast long-haul communication system in the next generation. There exists a quasi-stationary pulse solution in such a system whose width and chirp are rapidly oscillating with the period of dispersion compensation. This pulse also has several new features such as enhanced power when compared with the soliton case with a uniform dispersion and a deformation from the sech-shape of soliton. We use the averaging method, and the averaged equation to describe the core of the pulse solution is shown to be the nonlinear Schrodinger equation having a nontrapping quadratic potential. Because of this potential, a pulse propagating in such a system eventually decays into dispersive waves in a way similar to the tunneling effect. However in a practical situation, the tunneling effect is estimated to be small, and the decay may be neglected.

The propagation of solitons in a dispersion managed link can be mainly modeled with the evolution of two parameters γ and C, related to the spectral width and the chirp. Steady propagations are shown to be possible if the average dispersion lies in the anomalous domain. With the same conditions, periodical propagations are both theoretically and experimentally demonstrated. With the help of a perturbation theory, the jitter and the signal to noise ratio are theoretically evaluated. The latter is experimentally shown to be the low power limit of terrestrial systems based on non dispersion shifted fiber. Finally, wavelength and power margins of a single channel 20 Gbit/s soliton transmission over 11 amplifier spans of 102 km show that a 400 Gbit/s Wavelength Division Multiplexed transmission could be envisaged over the same distance.

The reduction of Soliton-soliton interaction to stabilize the soliton pulse propagation in the periodic dispersion-compensated standard fiber system using optical bandpass filter has been investigated by numerical simulation, and experimentally 10 Gbit/s soliton transmission was realized without fine tuning dispersion management over 5700 km, using appropriate optical bandpass filters and polarization scrambler.

The effect of sampling-pulse pedestals, generated by pulse compression, on the temporal resolution in electro-optic (EO) sampling is studied both theoretically and experimentally. Analysis is made on how the pedestals degrade a measurement bandwidth and a temporal waveform. Based on the analysis, a practical guideline on the suppression of pedestals is also given. Gain-switched laser diode (LD) pulses adiabatically soliton-compressed using a dispersion decreasing fiber are used to confirm the theoretical results, and are successfully applied to high-temporal-resolution (>100 GHz) EO sampling measurements.