This paper reviews the operation, design, and performance of the uni-traveling-carrier-photodiode (UTC-PD). The UTC-PD is a new type of photodiode that uses only electrons as its active carriers and its prime feature is high current operation. A small signal analysis predicts that a UTC-PD can respond to an optical signal as fast as or faster than a pin-PD. A comparison of measured pulse photoresponse data reveals how the saturation mechanisms of the UTC-PD and pin-PD differ. Applications of InP/InGaAs UTC-PDs as optoelectronic drivers are also presented.

We developed a polarization-independent and reserved-band-less complementary spectral inverted optical phase conjugation (CSI-OPC) device using dual-band difference frequency generation based on highly efficient periodically poled LiNbO3 waveguide technologies. To examine the nonlinearity mitigation in a long-haul transmission using a large number of OPCs, we installed a CSI-OPC device in the middle of a pure silica core fiber-based recirculating loop transmission line with a length of 320km. First, we examined the fiber-input power tolerance after 5,120-km and 6,400-km transmission using 22.5-Gbaud PDM-16QAM 10-channel DWDM signals and found a Q-factor improvement of over 1.3dB along with enhanced power tolerance thanks to mitigating the fiber nonlinearity. We then demonstrated transmission distance extension using the CSI-OPC device. The use of multiple CSI-OPCs enables an obvious performance improvements attained by extending the transmission distance from 6,400km to 8,960km, which corresponds to applying the CSI-OPC device 28 times. Moreover, there was no Q-factor degradation for the link in a linear regime after applying the CSI-OPC device more than 16 times. These results demonstrate that the CSI-OPC device can improve the nonlinear tolerance of PDM-16QAM signals without an excess penalty.

RF Variable Gain Amplifiers (RF-VGA) are important components for integrated TV broadcast receivers. Analog and digital controlled RF-VGAs are compared in terms of linearity and an AGC loop architecture suitable for digitally controlled RF-VGA is proposed. Further linearity enhancement applicable for CMOS implementation is also discussed.

Optical phase conjugation (OPC) is an all-optical signal processing technique for mitigating fiber nonlinearity and is promising for building cost-efficient fiber networks with few optic-electric-optic conversions and long amplification spacing. In lumped amplified systems, OPC has a little nonlinearity mitigation efficiency for nonlinear distortion induced by cross-phase modulation (XPM) due to the asymmetry of power and chromatic dispersion (CD) maps during propagation in transmission fiber. In addition, the walk-off of XPM-induced noise becomes small due to the CD compensation effect of OPC, so the deterministic nonlinear distortion increases. Therefore, lumped amplified transmission systems with OPC are more sensitive to channel spacing than conventional systems. In this paper, we show the channel spacing dependence of NZ-DSF transmission using amplification repeater with OPC. Numerical simulations show comprehensive characteristics between channel spacing and CD in a 100-Gbps/λ WDM signal. An experimental verification using periodically poled LiNbO3-based OPC is also performed. These results suggest that channel spacing design is more important in OPC-assisted systems than in conventional dispersion-unmanaged systems.

The block-based fast transmission scheme, which is one of typical stored video delivery schemes, is reasonable in terms of its bandwidth efficiency and tolerance to the delay jitter, etc. However, it causes packet loss because of its burst data transmission method. Thus, we propose a slotted multicast scheme for MPEG video based on the block transmission scheme to maintain a higher quality and to include time constraints. We define two delivery units, the "GoPs Group" and the "Frame Type," on the basis of the MPEG characteristics with periodical NACK feedback from the clients. The former is tolerant to burst packet loss, and the latter gives priority to important frames. Our block multicast has two phases: a "Transmission Phase" and a "Retransmission Phase." In the former, a server multicasts a block, and in the latter, a server retransmits lost packets using multicast according to the proper delivery unit. We evaluate our proposal from some viewpoints with a computer simulation. We also measure the quality of the video reflected the result of a computer simulation. From these results, we confirm performance effectiveness of our proposal.

Lasing action in GaInAs/GaInAsP quantum-wire structure, fabricated by two-step OMVPE growth, electron beam lithography, and wet chemical etching techniques, was obtained for the first time at 77 K with pulsed current injection. GaInAs quantum-wires with size of 10 nm thick and about 30 nm wide were completely separated and embedded in GaInAsP optical confinement layers so as to form a separate-confinement-heterostructure quantum-wire (SCH-QW) laser. The evidence of quantum-wire levels was confirmed by comparing its emission spectrum with that of quantum-film (QF) structure both experimentally and theoretically. The results indicate that there is no serious defects or damages in the laser operation of quantum-wires fabricated by the combination of electron beam lithography, wet chemical etching, and regrowth techniques.

Autonomous distributed manufacturing systems (ADMS) consist of multiple intelligent components with each component acting according to its own judgments. The ADMS objective is to realize more agile and adaptive manufacturing systems. This paper presents the introduction of context-dependent agents (CDAs) in ADMS that switch strategies depending on system conditions to achieve better performance than can be realized by agents that use the same strategies under all system conditions. For the real-time job scheduling problem, the paper presents a basic CDA architecture and the results of an extensive empirical evaluation of its performance relative to other rule-based schemes based on several common indices for real-time dispatch.

For a service-oriented architecture-based system, the problem of synthesizing a concrete model (i.e., behavioral model) for each peer configuring the system from an abstract specification-which is referred to as choreography-is known as the choreography realization problem. A flow of interaction of peers is called a scenario. In our previous study, we showed conditions and an algorithm to synthesize concrete models when choreography is given by one scenario. In this paper, we extend the study for choreography given by two scenarios. We show necessary and sufficient conditions on the realizability of choreography under both cases where there exist conflicts between scenarios and no conflicts exist.

A single-chip 512-point FFT processor is presented. This processor is based on the cached-memory architecture (CMA) with the resource-saving multi-datapath radix-23 computation element. The 2-stage CMA, including a pair of single-port SRAMs, is also introduced to speedup the execution time of the 2-dimensional FFTs. Using the above techniques, we have designed an FFT processor core which integrates 552,000 transistors within an area of 2.82.8 mm2 with CMOS 0.35 µm triple-layer-metal process. This processor can execute a 512-point, 36-bit-complex fixed-point data format, 1-dimensonal FFT in 23.2 µsec and a 2-dimensional one in only 23.8 msec at 133 MHz operation. The power consumption of this processor is 439.6 mW at 3.3 V, 100 MHz operation.

0.15 µm CMOS transistors have been fabricated. TiSi2 salicide was used for the gate electrode and source/drain to reduce parasitic resistance. Electron beam (EB) lithography was used for the gate patterning. Since the channel impurity was implanted only around the gate to reduce the junction capacitance, a reasonably short ring oscillator delay of 33 ps was obtained at 1.9 V supply voltage. The parasitic resistance and capacitance contribution on the delay time was analyzed by SPICE simulation. It was shown that the localized channel implant is effective for scaling the delay time and power consumption, because the source/drain size difficult to scale down to as small as the gate length.

This paper evaluates the code efficiency of the ARM, Java, and x86 instruction sets by compiling the SPEC CPU95/CPU2000/JVM98 and CaffeineMark benchmarks, from the aspects of code sizes, basic block sizes, instruction distributions, and average instruction lengths. As a result, mainly because (i) the Java architecture is a stack machine, (ii) there are only four local variables which can be accessed by a 1-byte instruction, and (iii) additional instructions are provided for the network security, the code efficiency of Java turns out to be inferior to that of ARM Thumb. Moreover, through this efficiency analysis it should be stressed that there exists the high potential of constructing a more efficient code architecture by taking minute account of the customization of an instruction set as well as the number of registers.

2.4 GHz-band wireless LAN system based on a new standard, IEEE 802.11g, has been taking a great attention as it provides the attractive features such as low cost, unlicensed spectrum use, and high speed transmission rate up to 54 Mbps. However, 2.4 GHz radio frequency band is also used for Industrial, Scientific and Medical (ISM) devices such as microwave ovens, and the man-made noise leaked from ISM devices is known to be one of the major causes of the degradation in the performance of wireless communications systems using 2.4 GHz radio frequency band. In this paper, we evaluate the bit error rate (BER) and the throughput performances of WLAN system based on IEEE 802.11g standard (IEEE 802.11g WLAN system) under man-made noise environment, and discuss the effect of man-made noise on the performance of IEEE 802.11g WLAN system. Numerical results show that the BER and the throughput performances of IEEE 802.11g WLAN system are much degraded by the influence of man-made noise.

In card-based cryptography, a deck of physical cards is used to achieve secure computation. A shuffle, which randomly permutes a card-sequence along with some probability distribution, ensures the security of a card-based protocol. The authors proposed a new class of shuffles called graph shuffles, which randomly permutes a card-sequence by an automorphism of a directed graph (New Generation Computing 2022). For a directed graph G with n vertices and m edges, such a shuffle could be implemented with pile-scramble shuffles with 2(n + m) cards. In this paper, we study graph shuffles and give an implementation, an application, and a slight generalization. First, we propose a new protocol for graph shuffles with 2n + m cards. Second, as a new application of graph shuffles, we show that any cyclic group shuffle, which is a shuffle over a cyclic group, is a graph shuffle associated with some graph. Third, we define a hypergraph shuffle, which is a shuffle by an automorphism of a hypergraph, and show that any hypergraph shuffle can also be implemented with pile-scramble shuffles.

Event structures are a well-known modeling formalism for concurrent systems with causality and conflict relations. The flow event structure (FES) is a variant of event structures, which is a generalization of the prime event structure. In an FES, two events may be in conflict even though they are not syntactically in conflict; this is called a semantic conflict. The existence of semantic conflict in an FES motivates reducing conflict relations (i.e., conflict reduction) to obtain a simpler structure. In this paper, we study conflict reduction in acyclic FESs. A necessary and sufficient condition for conflict reduction is given; algorithms to compute semantic conflict, local configurations, and conflict reduction are proposed. A great time reduction was observed in computational experiments when comparing the proposed with the naive method.

Multi-band WDM transmission beyond the C+L-band is a promising technology for achieving larger capacity transmission by a limited number of installed fibers. In addition to the C- and L-band, we can expect to use the S-band as the next band. Although the development of optical components for new bands, particularly transceivers, entails resource dispersion, which is one of the barriers to the realization of multi-band systems, wavelength conversion by transparent all-optical signal processing enables new wavelength bandtransmission using existing components. Therefore, we proposed a transmission system including a new wavelength band such as the S-band and made it possible to use a transceiver for the existing band by performing the whole-band wavelength conversion without using a transceiver for the new band. As a preliminary verification to demonstrate multi-band WDM transmission including S-band, we investigated the application of a novel wavelength converter between C-band and S-band, which consists of periodically poled lithium niobate waveguide, to the proposed system. We first characterized the conversion efficiency and noise figure of the wavelength converter and estimated the transmission performance of the system through the wavelength converter. Using the evaluated wavelength converters and test signals of 64 channels arranged in the C-band at 75-GHz intervals, we constructed an experimental setup for S-band transmission through an 80-km standard single-mode fiber. We then demonstrated error-free transmission of real-time 400-Gb/s DP-16QAM signals after forward error correction decoding. From the experimental results, it was clarified that the wavelength converter which realizes the uniform lossless conversion covering the whole C-band effectively achieves the S-band WDM transmission, and it was verified that the capacity improvement of the multi-band WDM system including the S-band can be expected by applying it in combination with the C+L-band WDM system.

With the rapid developments in the Internet of Things (IoT), low power wide area networks (LPWAN) framework, which is a low-power, long-distance communication method, is attracting attention. However, in LPWAN, the access time is limited by Duty Cycle (DC) to avoid mutual interference. Packet-level index modulation (PLIM) is a modulation scheme that uses a combination of the transmission time and frequency channel of a packet as an index, enabling throughput expansion even under DC constraints. The indexes used in PLIM are transmitted according to the mapping. However, when many sensors access the same index, packet collisions occur owing to selecting the same index. Therefore, we propose a mapping design for PLIM using mathematical optimization. The mapping was designed and modeled as a quadratic integer programming problem. The results of the computer simulation evaluations were used to realize the design of PLIM, which achieved excellent sensor information aggregation in terms of environmental monitoring accuracy.

This paper proposes graph linear notations and an extension of them with regular expressions. Graph linear notations are a set of strings to represent labeled general graphs. They are extended with regular expressions to represent sets of graphs by specifying chosen parts for selections and repetitions of certain induced subgraphs. Methods for the conversion between graph linear notations and labeled general graphs are shown. The NP-completeness of the membership problem for graph regular expressions is proved.

Multiple wireless communication systems are often operated together in the same area in such manufacturing sites as factories where wideband noise may be emitted from industrial equipment over channels for wireless communication systems. To perform highly reliable wireless communication in such environments, radio wave environments must be monitored that are specific to each manufacturing site to find channels and timing that enable stable communication. The authors studied technologies using machine learning to efficiently analyze a large amount of monitoring data, including signals whose spectrum shape is undefined, such as electromagnetic noise over a wideband. In this paper, we generated common supervised data for multiple sensors by conjointly clustering features after normalizing those calculated in each sensor to recognize the signal reception timing from identical sources and eliminate the complexity of supervised data management. We confirmed our method's effectiveness through signal models and actual data sampled by sensors that we developed.

This report will present an expression for the mechanical behavior of a drum-wound dual coated fiber and an analytical expression for the microbending loss in single mode dual coated fibers. These analytical expressions are then compared with experimental drumwinding microbending loss results to determine their validity.