Recent status of the polymer optical fiber (POF) for high speed data communication and telecommunication is reviewed. The GI POF was proposed for the first time 20 years ago at Keio University, and several methodologies to fabricate GI POF have been currently proposed worldwide. In this paper, we both theoretically and experimentally verify that the most transparent GI POF can be obtained by the polymer-dopant system. The relation between the refractive index profile and the dispersion characteristics of the GI POF was quantitatively clarified. The refractive index profile of the GI POF obtained by the interfacial-gel polymerization process was controlled to enable to transmit the order of gigabit per second bit rate. Furthermore, the accurate approximation of the refractive index profile and consideration of mode dependent attenuation enabled to precisely predict the dispersion characteristics of the GI POF.

Texture has been investigated as a cue for reconstructing 3-D structure. There are various textures in a natural scene. In this paper, the regularity of alignment of texture elements was manipulated to investigate its effect on human perception. The results show that the regularity affects human perception when only the texel density gradient is given as cue or the density cue is inconsistent with the compression cue. We introduce a model based on a MAP estimation to account for the result from a viewpoint of an integration of 3-D cues. The model simultaneously estimates texture properties and 3-D surface orientation by using prior knowledge about texture and 3-D surface. The performance of the model accounts for the experimental result well.

WDM transmission experiments over cascaded sections of optical links including wavelength converting 2R-transponders have been carried out in a loop testbed. Using dispersion compensated links and simple direct modulated transponder lasers, up to 11 cascaded crossconnects and 1750 km trunk lines have been bridged with 2.5 Gbit/s NRZ signals. The limitations are given mainly due to the accumulated jitter as it is shown by numerical simulations. The results indicate, that 2R-transponders are a useful approach to a flexible WDM network design using bitrate-transparent wavelength conversion.

We have proposed and demonstrated a novel optical regenerator architecture employing electroabsorption modulators as wavelength converters. The employment of EA modulators is advantageous for high-speed operation and flexibility in the bit-rate for the pulse regeneration. In addition, the EA modulator-wavelength-converter acts also as a photo diode for clock extraction. Compensation of the optical SNR and Q-factor has been demonstrated, even in cascaded noise load. Furthermore, against dispersion loading, we have confirmed that waveform recovery and Q-factor improvement is obtained by midway insertion of the optical regenerator. The proposed architecture will offer a wide-band-electronics-free optical regenerator in multi-tens of gigabit per second WDM networks.

In this letter, the novel mapping network named self-organizing relationship (SOR) network, which can approximate the desired I/O relationship by employing the modified Kohonen's learning law, is proposed. In the modified Kohonen's learning law, the weight vectors are updated to be attracted to or repulsed from the input vector.

Aiming at wideband and flat supercontinuum generation (SC) from optical fibers in the 1.55-µm wavelength region, we study both experimentally and theoretically how SC spectra are influenced by group-velocity dispersion (GVD) of fibers. In the anomalous GVD region, since the peak power of pump pulses is kept high during propagation through the fiber by the higher-order soliton effect, the Raman effect has an adverse effect to flat and wideband SC generation. In the zero GVD region, the interplay of the third-order dispersion (TOD) and the self-phase modulation splits the SC spectrum into two main components. On the other hand, in the normal GVD region, nevertheless the SC spectrum broadens wider and smoother than those in anomalous and zero GVD regions, it is still asymmetric when TOD of the fiber can not be ignored. From these results, we find that a dispersion-flattened fiber with normal GVD is the most suitable for flat and wideband SC generation. A 280-nm wide SC spectrum with the spectral-density fluctuation less than 10 dB is actually generated from such a fiber.

We have proposed and demonstrated a novel optical regenerator architecture employing electroabsorption modulators as wavelength converters. The employment of EA modulators is advantageous for high-speed operation and flexibility in the bit-rate for the pulse regeneration. In addition, the EA modulator-wavelength-converter acts also as a photo diode for clock extraction. Compensation of the optical SNR and Q-factor has been demonstrated, even in cascaded noise load. Furthermore, against dispersion loading, we have confirmed that waveform recovery and Q-factor improvement is obtained by midway insertion of the optical regenerator. The proposed architecture will offer a wide-band-electronics-free optical regenerator in multi-tens of gigabit per second WDM networks.

We analyze the dispersion-managed optical transmission system for the non-return-to-zero (NRZ) pulse format. First, we investigate the physical image of dispersion management by computing small-signal-based transfer functions, and summarize the dependence of transmission performance on system parameters. Next, the Q-map is computed numerically to design long-distance large-capacity dispersion-managed transmission systems for a single channel in a more detailed manner. It is shown that the third-order dispersion of fibers negatively influences transmission performance, and third-order dispersion compensation is proved to be an effective method for extending the transmission distance of high bit-rate systems. Utilizing these results, guidelines can be derived for the optimal design of long-distance large-capacity NRZ transmission systems.

An approach to an MPEG decoding system with reduced memory capacity will be presented. This method relies on the simple technique of one-dimensional DPCM to recompress reconstructed Macro Block (MB) prior to being stored on frame memory. Simulation results suggest that image quality is subjectively acceptable when using approximately one-half of the memory size required by that of conventional decoder. The degradation in the signal-to-noise ratio introduced by this compression method ranged from 0.1 dB to 0.7 dB for MPEG MP@ML standard test sequences at 4 Mbps. This technique can be implemented to achieve a cost effective MPEG decoder.

Wavelet filters used in usual applications are not time-varying filters. In this paper, we present a novel method to design biorthogonal wavelet filters which are orthogonal to the input signals. We call newly designed filters time-varying lifting wavelet filters (TVLWF). Their feature is to vary the wavelet filters adapting to the input signal by tuning free parameters contained in the lifting scheme developed by Sweldens. These filters are almost compact support and perfect reconstruction. By using TVLWF, we demonstrate an application to data compression of electrocardiogram (ECG) which is one of the semi-periodic time-series signals and show that the time-varying system can be constructed easily and the proposed method is very useful for data compression.

Two error control schemes for Transmission Control Protocol (TCP) connection on a wireless network are proposed that can minimize the degradation in radio link throughput due to retransmission. One scheme is based on the discard of TCP retransmission packets, and the other is based on the suppression of transmission delay fluctuation. Simulation results show that the degradation in throughput is reduced by 7.2% by using each proposal scheme when the frame error rate is 10e-3.

WDM transmission experiments over cascaded sections of optical links including wavelength converting 2R-transponders have been carried out in a loop testbed. Using dispersion compensated links and simple direct modulated transponder lasers, up to 11 cascaded crossconnects and 1750 km trunk lines have been bridged with 2.5 Gbit/s NRZ signals. The limitations are given mainly due to the accumulated jitter as it is shown by numerical simulations. The results indicate, that 2R-transponders are a useful approach to a flexible WDM network design using bitrate-transparent wavelength conversion.

In this paper, the performance of some communication systems using chaos synchronization is evaluated and compared. A new channel model taking the attenuation, impedance mismatch and noise into account, is proposed for the performance evaluation. The evaluation of bit error rate is done for both ideal and non-ideal conditions using the channel model. It is confirmed that some chaos-based communication systems have a good performance compared with conventional analog communication schemes.

This paper describes a multibeam antenna which uses switched parasitic and switched active elements to obtain multiple simultaneous directional beams that can be steered in azimuth. A 13 element monopole multibeam array has been optimised for gain and front to back ratio. Results from numerical simulation and measurements in an anechoic chamber are presented. The 13 element array can achieve up to three beams simultaneously with a minimum gain over 360 azimuthal coverage of 1.2 dB less than the maximum gain. Located on a ground plane with diameter of 2λ at 1.5 GHz, the maximum elevation angle was 20.2 with -3 dB vertical beamwidth of 88.

Excitation of magnetostatic surface waves by slot line transducers is analyzed by using the integral kernel expansion method. The Fourier integral for the current density is derived in terms of an unknown normal component of the magnetic flux density in a slot region. The integral kernel is expanded into a series of orthogonal polynomials and then applying Galerkin's method to the resulting equation yields a system of linear equations for the unknown coefficients. Comparison of a numerical result by the present method with an experiment is in good agreement.

This paper investigates a new class of pulse compression codes in which the phase rotates clockwise, and afterward, rotates anticlockwise (or rotates anticlockwise, and afterward, rotates clockwise). The spectrum energy then concentrates to the narrower band compared to the conventional code such as the Barker code and the pulse is compressed not to the width of a single subpulses, but to the width made by a collection of several subpulses. It is revealed that, using the new code, PSL (Peak Sidelobe Level) can be reduced to -25.6 dB (1/19) -25.1 dB (1/18), which is much smaller than using the Barker code and Frank code, when the compression ratio is about 10 or larger. Furthermore, the signal-to-noise ratio after compression, the appropriate IF bandwidth and Doppler tolerance for the new code are estimated by simulation.

In this paper, a general formula of disparity estimation based on Bayesian Maximum A Posteriori (MAP) algorithm is derived and implemented with simplified probabilistic models. The formula is the generalized probabilistic diffusion equation based on Bayesian model, and can be implemented into some different forms corresponding to the probabilistic models in the disparity neighborhood system or configuration. The probabilistic models are independence and similarity among the neighboring disparities in the configuration. The independence probabilistic model guarantees the discontinuity at the object boundary region, and the similarity model does the continuity or the high correlation of the disparity distribution. According to the experimental results, the proposed algorithm had good estimation performance. This result showes that the derived formula generalizes the probabilistic diffusion based on Bayesian MAP algorithm for disparity estimation. Also, the proposed probabilistic models are reasonable and approximate the pure joint probability distribution very well with decreasing the computations to O(n()) from O(n()4) of the generalized formula.

The architecture design and test results of simulation facility named millimeter-wave Test Bed has been described. Contrast with a millimeter-wave sounder, the Test Bed proposed in this paper can characterize radio channels, received signals, target reflections and radio link performance at the millimeter-wave band of 60 GHz. For fixible simulation and analysis of the performances of newly designed millimeter-wave systems, major digital signal processing parts like a sophisticate waveform generator and an analyzer, a modulator, a demodulator, an encoder, a decoder, an equalizer in the Test Bed are implemented by a software using SPW. This software based Test Bed can be used as a "deign tool" for the simulation of the millimeter-wave communication systems very flexibly without hardware modification in different specifications. The Test Bed consists of a millimeter-wave transmitter, a receiver of 60 GHz, 1.95 GHz up/down converter as IF module and a digital signal processing module. The I/Q vector modulator and demodulator with a video bandwidth of 37.5 MHz in the Test Bed can simulate or test the application of high data rate communication systems of short distance.

This paper describes a 10-bit 40-MS/s pipelined A/D converter implemented in a 0.8-µm double-poly, double-metal CMOS process. This A/D converter achieves low power dissipation of 36-mW at 5-V power supply. A 1.5-bit/stage pipelined architecture allows large correction range for comparator offset, and performs fast interstage signal processing. For high speed and low power operation, the sample-and-hold amplifier is designed using op-amp sharing technique and dynamic comparator. In addition, fully-differential folded-cascode op amp with gain-boosting stage is designed by an automatic design tool. When 10-MHz input signal is applied, SNDR is 55.0 dB, and SNR is 56.7 dB. The DNL and INL exhibit 0.6 LSB, +1/-0.75 LSB respectively.

This paper outlines the modeling requirements of integrated circuit (IC) fabrication processes that have lead to and sustained the development of computer-aided design of technology (i. e. TCAD). Over a period spanning more than two decades the importance of TCAD modeling and the complexity of required models has grown steadily. The paper also illustrates typical applications where TCAD has been powerful and strategic to IC scaling of processes. Finally, the future issues of atomic-scale modeling and the need for an hierarchical approach to capture and use such detailed information at higher levels of simulation are discussed.