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.

The Heart Rate Variability (HRV) analysis has become vigorous these days. One reason for this is that the HRV analysis investigates the dynamics of the autonomic nervous system activities which control the HRV. The Integral Pulse Frequency Modulation (IPFM) model is a pulse generating mechanism model in the nervous system, that is one of the models which connects the HRV to the autonomic nervous system activities. The IPFM model is a single frequency component model; however, the real HRV has multiple frequency components. Moreover, there are refractory periods after generating action potentials are initiated. Nevertheless, the IPFM model does not consider refractory periods. In order to make sure of the accuracy and the effectiveness of the integral function (IF) method applied to the real data, we consider the absolute refractory periods and two frequency components. In this investigation, the simulated HRV was made with a single and double frequency component using the IPFM model with and without absolute refractory periods. The original generating function of the IPFM model was demodulated by using the instantaneous heart rate tachogram. The power of the instantaneous pulse rate per minute was analyzed by the direct FFT method, the IF FFT method without the absolute refractory periods, and the IF FFT method with the absolute refractory periods. It was concluded that the IF FFT method can demodulate the original generating function accurately.

Dense WDM techniques that exploit the enormous bandwidth of dispersion-shifted fibers (DSFs) while avoiding the impairments due to nonlinear effects are described. First, the nature of four-wave mixing (FWM), the dominant impairment factor in WDM transmission systems, is investigated using DSF installed in the field and laboratory experiments. This provides useful information for the practical design of WDM networks based on DSF. Second, practical techniques to reduce FWM impairment, unequal channel allocation and off-lambda-zero channel allocation (equal channel allocation in the novel 1580 nm band) along with gain-shifted erbium-doped fiber amplifiers for the 1570 to 1600 nm band, is described. Comparisons between off-lambda-zero and unequal channel allocation are provided in terms of the maximum transmission distance for various numbers of channels. Two schemes to immunize WDM systems against group velocity dispersion, span-by-span dispersion compensation and optical duobinary format, are presented. The combination of unequal channel allocation with off-lambda-zero channel allocation as well as the combination of two bands: the conventional 1550 nm band and the novel 1580 nm band are proven to be very useful in expanding the usable bandwidth of DSFs.

This paper describes the design of polarization insensitive InP-based arrayed waveguide gratings (AWGs), and the characteristics of fabricated devices. The use of a deep-ridge waveguide structure made the fabrication of compact polarization-insensitive AWGs possible. As a result, a low crosstalk (-30 dB) 8-channel AWG and a large-scale (64 channel) AWG with 50 GHz channel spacing could be fabricated. An integrated circuit containing an 8-channel AWG with photodetectors is also described.

High- and low-reflection Bragg gratings with a flat-top spectral response free from ripples are proposed. Add/drop filters are created based on gratings photoinduced on planar waveguides by using the new design schemes. The measured spectral responses for the high and low reflection gratings are in good agreement with the calculated ones, and show the flat-top spectral responses.

To expand signal wavelength bandwidth in long-haul, large-capacity WDM transmission systems, we investigated gain-equalizers (GEQs) for Erbium doped fiber amplifiers (EDFAs). We applied GEQs using Mach-Zehnder type filters with two different free-spectral-ranges (FSRs) to accurately compensate for the EDFAs gain-wavelength characteristics. The 1st GEQ with a longer FSR was the main GEQ to compensate for the overall gain-wavelength characteristics, and the 2nd GEQ with a shorter FSR was the secondary GEQ to compensate for the resultant gain undulation after the 1st GEQ. The 2nd GEQ had low maximum loss and long period of equalization-spacing compared to the 1st GEQ. We designed that the FSR for the 1st GEQ was twice the signal wavelength bandwidth, and the FSR for the 2nd GEQ was two thirds of the signal wavelength bandwidth. To compensate for the asymmetry in the EDFAs gain-wavelength characteristics, we designed that the 2nd GEQ minimum-loss wavelength was shorter than the 1st GEQ maximum-loss wavelength. Using a circulating loop with a 21-EDFA chain, we confirmed the signal wavelength bandwidth expanded by the above GEQs. We also investigated the trade-off relationship between the signal wavelength bandwidth and the optical signal-to-noise ratio, as the parameter of the number of the 1st GEQ inserted in the EDFAs chain. The achieved signal wavelength bandwidth after 10,000-km transmission was 12 nm. We successfully transmitted 170 Gbit/s (325. 332 Gbit/s) WDM signals over 9,879 km employing high alumina codoped EDFAs and Mach-Zehnder type filters with long FSRs.

Input-wavelength-insensitive tunable wavelength conversion was achieved in the range of 1530 to 1560 nm using cascaded semiconductor laser wavelength converters (a DFB laser and an SSG-DBR laser). The power penalty in the wavelength conversion of input signal between 1530 and 1555 nm, where the wavelength ranged between 1537 and 1557 nm, is less than 1 dB for 5 Gbit/s signals.

Electron and hole transport in polymethylphenylsilane (PMPS) containing anthracene units in the polymer backbone (PMPS-AN) has been studied by time-of-flight and electrophotographic measurements. It is found that the hole transport of PMPS-AN is non-dispersive and exhibits thermally activated behavior. The anthracene incorporation to the polymer backbone of PMPS slightly decreases the hole drift mobility of PMPS-AN because of the increase in energetic disorder. In PMPS-AN, the electron transport, which has not been observed in organic polysilanes, is clearly seen. In contrast to the hole transport, the electron transport exhibits anomalous dispersion of the transit times and the electron drift mobility is independent of temperature. It is suggested that the electron transport is due to geometrical disorder of electron hopping sites (anthracene units). From the electrophotographic measurements, we discuss the applicability of PMPS-AN to photoreceptors and estimate the Schubweg of electrons in PMPS-AN.

A single-chip GaAs Transmit/Receive (T/R)-MMIC front-end has been developed which is applicable to 1. 9-GHz personal communication terminals such as digital cordless phones. This chip is fabricated using a planar self-aligned gate FET useful for low-cost and high-volume production. The chip integrates RF front-end analog circuits a power amplifier, a T/R-switch, and a low-noise amplifier. Additionally integrated are a newly developed voltage-doubler negative-voltage generator (VDNVG) and a control logic circuit to control transmit and receive functions, enabling both a single-voltage operation and an enhanced power handling capability of the switch, even under a single low-voltage supply condition of 2 V. The power amplifier incorporated onto the chip is capable of delivering a 21 dBm output power at a 39% efficiency, and a 30 dB associated gain with a 2 V single power supply in the transmit mode. The gain and efficiency are higher than those of the previously reported amplifier operating with a 2 V single power supply. The VDNVG produces a step-up voltage of 2. 9 V as well as a negative voltage of -1. 8 V from a 2 V power supply, operating with a charge time of less than 0. 25 µs. The control logic circuit on the chip has a newly designed interface circuit utilizing the step-up voltage and negative voltage, thereby enabling the chip to handle high power outputs over 24 dBm with a low operating voltage of 2 V. In the receive mode, a 1. 7 dB noise figure and a 0. 6 dB insertion loss are achieved with a current dissipation of 3. 6 mA. The developed MMIC, which is the first reported 2 V single-voltage operation T/R-MMIC front-end, is expected to contribute to the size and weight reductions in personal communication terminals.

We have improved the optical beam induced resistance change (OBIRCH) system so as to detect (1) a current path as small as 10-50 µA from the rear side of a chip, (2) current paths in silicide lines as narrow as 0. 2 µm, (3) high-resistance Ti-depleted polysilicon regions in 0. 2 µm wide silicide lines, and (4) high-resistance amorphous thin layers as thin as a few nanometers at the bottoms of vias. All detections were possible even in observation areas as wide as 5 mm 5 mm. The physical causes of these detections were characterized by focused ion beam and transmission electron microscopy.

This paper newly proposes the CMT/IM/DD system for universal radio access networks where radio base stations (RBSs) and an optic backbone network are universally available among different radio services and providers. In the proposed system, the Chirp Fourier transformer at an RBS, converts the received FDM multiple radio service signals into optical TDM format signals, then transfers them over the optic fiber-link. This paper is focused on the discussion about the performance on the up-link of the CMT/IM/DD system. A new type of the configuration of CMT and the direct demodulation for the CMT signal are also proposed, and the SNR considering inter-symbol and inter-channel interferences caused by the CMT is theoretically analyzed. Analysis results show that the overall SNR performance of the CMT system is superior to the conventional SCM system when the number of radio channels is more than 26.

We propose and evaluate a single-bit adaptive step-size closed-loop power control (AS-CLPC) scheme which is adaptable to a dynamically changing radio channel. We also investigate the effect of the mobile terminal (MT) velocity on system performance when the proposed AS-CLPC scheme is employed. The proper power control constant of the AS-CLPC scheme is obtained by solving a polynomial equation. Compared with the IS-95 single-bit fixed step-size CLPC scheme, the proposed single-bit AS-CLPC scheme can reduce link margin (LM) by about 3 dB when the outage probability is below 0. 03 and a single fading path reception in the base station is assumed. System performance such as link availability and throughput can be improved by utilizing this proposed CLPC scheme in the outdoor radio propagation channel where time-selective fading occurs.

We fabricated a tunable and polarization-insensitive arrayed-waveguide grating (AWG) 1616 multiplexer that operates around the wavelength of 1. 55 µm using fluorinated polyimides. The wavelength channel spacing was 0. 8 nm, and the 3-dB passband width was 0. 26 nm. The insertion loss at each channel was from 8 to 12 dB, and the crosstalk was less than -28 dB. The transmission pass wavelength was tuned over a wide range of 6 nm by heating from 24 to 64. The slope of the temperature dependence of the pass wavelength was -0. 15 nm/, which is ten times that of a silica-based multiplexer. Polarization-insensitivity was achieved by fabricating a film AWG multiplexer, which was formed by removing the silicon substrate and annealing at 350. The polarization-dependent wavelength shift was smaller than the spectrum analyzers wavelength resolution of 0. 1 nm.

Testing for delay faults is very important in the verification of the timing behavior of digital circuits. When a circuit which is unable to operate at the desired clock speed is identified, it is necessary to locate the delay fault(s) affecting the circuit in order to remedy the situation. In this paper, we present a path-tracing method of multiple gate delay fault diagnosis in combinational circuits. We first present the basic rules for deducing suspected faults based on the multiple gate delay fault assumption. Next, in order to improve diagnostic resolution, we introduce rules for deducing non-existent faults based on the fault-free responses at the primary outputs. Using these rules, we present the detailed method for diagnosing multiple delay faults based on paths sensitized by test-pairs generated for marginal delays and gate delay faults [7]. Finally, we present results obtained from experiments on the ISCAS '85 benchmark circuits. The experimental results show the effectiveness of our method.

In this paper, we propose several novel methods to decrease propagation error for multiple access interference cancellation techniques in asynchronous DS/CDMA. To increase spectral efficiency, the system wherein transmitting signal power of each user is assigned with exponential law and multiple access interference successive cancellation is used in the receiver has been discussed. However, when the number of active users is increased, propagation error occurs in the receiver. Thus, the improvement effect of spectral efficiency in the system has been degraded. In this paper, we propose novel methods to decrease these propagation errors for the system. These novel methods are quasi-maximum likelihood method that means maximum likelihood in considering the signal of the next user when the signal of the arbitrary user is demodulated, feedback method that means the demodulation error of the stronger users in transmitting signal power is estimated after several users, demodulations and the error is corrected, and combination method that is a combination of quasi-maximum likelihood method and feedback method. And we evaluate their performances by computer simulation and show that the combination method is effective for the reduction of the propagation error.

This paper proposes the Dual Zipfian Model addressing how to describe HTTP access trends in large-scale data communication networks, and discusses how to design the capacity of address cache tables in an edge router of the networks. We show that destination addresses of packets can be characterized by two types of Zipf's law. Fundamental concept of the Dual Zipfian Model is in complementary use of these laws, and we can derive the relationship between the number of accesses and the number of destination addresses. Experimental results show that the relation gives a good approximation. Applying this relation, we derive cache hit probabilities of the address cache table that incorporates high-speed address resolution. Using the probabilities, design issues including the capacity of the cache tables and aging algorithms of cache entries are also discussed.

This paper presents a novel transmission diversity scheme for code division multiple access system. Conventional diversity receivers in mobile stations require space and complicated circuits, however, the proposed diversity schemes present significant diversity effect without any diversity equipment at the mobile station. It is possible to use the transmitter diversity at the base station by using the feature of time division duplex (TDD) which has strongly correlated fading patterns in both forward and reverse link. Computer simulation is performed to evaluate the performance of the proposed systems for single user environment. The performance of the system 1, which select best situated antenna, is analyzed and the BER performance for multiple access is presented.

It is important to know phase offsets of a binary code in the field of mobile communications because different phase offsets of the same code are used to distinguish signals received at a mobile station from those of different base stations. When the period of the code is not very long, the relative phase offset between the code and its shifted code can be found by counting the number of bits delayed from the code of the same bit streams. But as the period of the code increases, it becomes difficult to find the phase offset. This paper proposes a new method to calculate the phase offset of a binary code. We define an accumulator function, which is used to calculate the phase offsets between the code and its shifted code. Also the properties of the accumulator function are investigated. This number theoretical approach and its results show that this method is very easy for the phase offset calculation. Its application to the code division multiple access (CDMA) system to define a reference code is given. The simple circuit realization of the accumulator function to calculate the phase offset between the received code and receiver stored replica code is described.

This paper describes new millimeter-wave ICs based on flip-chip bonding using micro bumps on a low cost silicon substrate, named millimeter-wave flip-chip ICs (MFICs). They have significant advantages such as good performance, low cost and excellent flexibility in the active device selection which makes them superior to conventional monolithic microwave integrated circuits (MMICs). In order to demonstrate these advantages, a K-band front-end block for a broadband wireless communication equipment was designed and fabricated. This front-end block consists of four MFIC chips: a low noise amplifier (LNA), a down converter and two medium power amplifiers. These chips are designed to satisfy stable operation conditions using a simplified model derived for micro bump bonding (MBB). In experimental measurements; the LNA using heterojunction field-effect transistors (HFETs) had an 18 dB gain, the down converter using an HFET had a 9. 5 dB conversion loss, and two power amplifiers using heterojunction bipolar transistors (HBTs) had saturated powers of 13. 0 dBm and 11. 7 dBm, respectively. The performance for each of the developed ICs agreed with the designed values, and satisfied circuit requirements. These results show that the MFIC technique is a potential technology for manufacturing multi-functional millimeter-wave ICs.

This paper describes new IC design concepts using flip-chip bonding technologies for microwave and millimeter-wave circuit integration. Two types of bonding technologies, stud bump bonding (SBB) and micro bump bonding (MBB) are introduced, and their applications to microwave and millimeter-wave ICs are presented. Receiver front-end hybrid IC (HIC) for cellular and PHS handsets using SBB and new millimeter-wave ICs on Si substrate called millimeter flip-chip IC (MFIC) using MBB have been designed and fabricated to prove their advantages. These flip-chip bonding technologies are experimentally proven to provide excellent solutions for high performance and compact-sized ICs with low-cost. The HIC concept is applicable consistently over a wide range of devices from RF/microwave to millimeter-wave region.