Japanese terrestrial digital broadcasting (ISDB-T) began in 2003. To spread its signals throughout the country, optical fibers will be used to complement radio-wave networks. This paper describes recent applications of optical transmission of ISDB-T. It also describes our research on re-transmission with 40-GHz Radio On Fiber technology.

An efficient computational Zero-Knowledge Proof of Knowledge whose security relies on the NP-completeness of the Independent Set Problem is presented here. The proposed algorithm is constructed from a bit commitment scheme based on the hardness of the Discrete Logarithm Problem, which guarantees the fulfillment of soundness, completeness and computational zero-knowledge properties, and allows avoiding the use of the Graph Isomorphism Problem, which is present in every known Zero-Knowledge Proofs for the Independent Set Problem.

Generalized Tsume-Shogi (GTS) is Tsume-Shogi on the board of size n n for arbitrary n. The problem to decide the existence of a winning sequence of moves (where the attacker must always check) on an instance of GTS was proved to be exptime-complete by Yokota et al. (2000). This paper considers the complexity of yozume problem of GTS, which is, roughly speaking, the problem whether a given position of GTS has a winning sequence other than given sequences (though the actual rule of yozume is more complicated). The detection of yozume is an important issue in designing Tsume-Shogi problems, since the modern designing rule strongly prohibits it. We define a function problem of GTS appropriately to formulate yozume problem as its Another Solution Problem (ASP; the problem to decide the existence of solutions other than given ones). Moreover, we extend the existing framework for investigating ASPs so that it can be applied to exptime-complete problems. In particular, since the decision of correctness of given winning sequences is not easy, we establish a framework to treat ASP of function problems with promises. On the basis of these results, we prove that the decision version of yozume problem of GTS is exptime-complete as a promise problem using the existing reduction which was constructed by Yokota et al. to prove the exptime-completeness of GTS.

A new edge-coloring algorithm for bipartite graphs is presented. This algorithm, based on the framework of the O(m log d + (m/d) log (m/d) log d) algorithm by Makino-Takabatake-Fujishige and the O(m log m) one by Alon, finds an optimal edge-coloring of a bipartite graph with m edges and maximum degree d in O(m log d + (m/d) log (m/d)) time. This algorithm does not require elaborate data structures, which the best known O(m log d) algorithm due to Cole-Ost-Schirra depends on.

In this paper we give an algorithm to generates all series-parallel graphs with at most m edges. This algorithm generate each series-parallel graph in constant time on average.

Photonic crystal fiber (PCF) is a promising candidate for future transmission media due to its unobtainable features in a conventional single-mode fiber. We discuss some important problems to realize a PCF for transmission purpose. We also present recent progress on the PCF as a transmission media.

We propose a unified view to deal with two formulations of image distortion and a method for estimating the distortion parameters for both of the formulations; So far the formulations have been developed separately. The proposed method is based on image registration and consists of nonlinear optimization to estimate parameters including view change and radial distortion. Experimental results demonstrate that our approach can deal with the two formulations simultaneously.

SOBER-128 is a stream cipher designed by Rose and Hawkes in 2003. It can be also used for generating Message Authentication Codes (MACs) and an authenticated encryption. The developers claimed that it is difficult to forge MACs generated by both functions of SOBER-128, though, the security assumption in the proposal paper is not realistic in some instances. In this paper, we examine the security of these message authentication mechanisms of SOBER-128 under security channel model. As a result, we show that both a MAC generation and an authenticated encryption are vulnerable against differential cryptanalysis. The success probabilities of the MAC forgery attack are estimated at 2-6 and 2-27 respectively. In addition, we show that some secret bits are revealed if a key is used many times.

We investigate the impact of electrical band-limitation on the transmission performance of both carrier suppressed return-to-zero (CSRZ) and CSRZ differential phase shift keying (CSRZ-DPSK) format for high spectral efficiency DWDM systems. Results show that electrical band-limitation improves signal spectral compactness, leading to reduced linear crosstalk and improved tolerance against chromatic dispersion in optical fiber link without causing any degradation to fiber nonlinearity tolerance. In addition, it is shown that the electrical band-limitation is more efficient to CSRZ-DPSK signal than CSRZ signal in reducing signal degradation caused by linear crosstalk and fiber chromatic dispersion.

It is important to look for alternative forms of physical movement of people and equipments in order to assure diagnosis and maintenance tasks, especially in an environment where workers are subject to danger. An evident and classical solution is the use of the tele-operation and tele-robotics. If the tele-operation helps to solve a lot of real and technical problems, it still remains insufficient to assure an appropriate remote diagnosis and maintenance. The use of virtual reality techniques with the tele-operation can be the solution for an effective remote maintenance and diagnosis. In this paper we show the inefficiency occurred with the use of only tele-operation in the remote maintenance, we introduce our original new system where we use virtual reality techniques and 2D-3D matching (2D camera image-3D virtual objects) with tele-operation to remotely collect machinery vibration data. We explain its structure, implementation and its advantages. We finished by experimenting the system, measuring the different operating times and precision and discuss the results.

Press-induced long-period fiber gratings exhibiting strong core-to-cladding mode coupling were formed in photonic crystal fiber. Only one resonance peak was observed over a 600 nm spectral range and the resonant wavelength was tuned over the whole range by tilting a groove plate before pressing the fiber. The resonant wavelength decreased with increasing periodicity of the grating, which was opposite to the trend of the step-index conventional optical fiber. Meanwhile, the resonant wavelength increased with increasing the ambient refractive index, which was also opposite to that of the conventional optical fiber.

Optical signal processing is one of essential technologies for improving the flexibility of all-optical network. Above all, recently there have been a lot of studies regarding all-optical 2R/3R regeneration technology. However, there are few studies about all-optical 2R/3R technologies that are carried out in field environment. In this paper, we report the successful results of field trials of an all-optical 2R regeneration system based on an electro-absorption modulator for 40-Gbit/s WDM transmission systems with optical add/drop multiplexing. It was made sure that by applying the all-optical 2R regeneration system to the optical add/drop multiplexer in the 320-km-long transmission systems the transmission characteristics of the express signal after 320-km transmission and those of the dropped signal at 160-km can be made nearly the same. It is quite important that the transmission characteristics are equal for both the dropped and express channel from a point of view of the system design, and the results in this paper suggests one possible solution for this matter.

The aim of this work is to investigate the possibility of designing zero-knowledge identification schemes based on hard-on-average problems. It includes a new two-party identification protocol whose security relies on a discrete mathematics problem classified as DistNP-Complete under the average-case analysis, the so-called Distributional Matrix Representability Problem. Thanks to the use of the search version of the mentioned problem, the zero-knowledge property is formally proved by black-box simulation, and consequently the security of the proposed scheme is actually guaranteed. Furthermore, with the proposal of a new zero-knowledge proof based on a problem never used before for this purpose, the set of tools for designing cryptographic applications is enlarged.

Propagation characteristics of acoustic waves in photonic crystal fibers (PCFs) have been theoretically investigated in details. In order to evaluate acoustic band structures and guided modes for out-of-plane propagation in PCFs, analysis methods based on the finite element method are newly formulated. It is shown through numerical results that complete acoustic band-gaps (ABGs) exist in the cladding region of PCFs and that acoustic guided modes could be localized in the defect region of PCFs by the ABG effect. Furthermore, it is shown that acoustic guided modes could also be localized in the defect region of PCFs by the total internal reflection. These confinement mechanisms of acoustic waves propagating along the fiber length are completely different to those of lightwaves.

A novel optical header extraction scheme based on optical differential phase shift keying--DPSK--decoding is examined analytically and experimentally. The header is applied in front of the payload, on the phase of a pulsed optical level introduced for the duration of the header. The proposed scheme offers maximized header extraction efficiency, required by the electronics to identify the header bits and control the switch. At the same time, the payload is transmitted at maximum extinction ratio. Analytical results prove the enhanced performance of the decoding scheme with respect to the extinction ratio and in comparison to other DPSK based schemes. Moreover, the utilised scheme is cost efficient and easily upgradeable to any bit rates and adds minimum complexity at the transmitter and detector parts of the system. Finally, the implementation of the developed technique in a real optical packet switch is demonstrated, where header extraction, reading, processing and switch control using field programmable gate array--FPGA--technology is successfully demonstrated.

We report the empirically obtained conditions for the fusion splicing with photonic crystal fibers (PCF) having large mode areas. By controlling the arc-power and the arc-time of a conventional electric-arc fusion splicer, the splicing loss between two PCFs could be lowered down to 0.2 dB in average. For the splicing PCF with a conventional single mode fiber (SMF), the loss was increased due to the modal field mismatch, but still below 0.45 dB in average. The tensile strength was weakened by the splicing from 2.83 GPa down to 1.04 GPa for the PCF-PCF case and 0.89 GPa for the PCF-SMF one.

This paper discusses performance limitation of on-chip interconnects. On-chip global interconnects are considered to be a bottleneck of high-performance LSIs. To overcome this issue, high-speed signaling and large throughput interconnection using electrical wires have been studied. However the limitation of on-chip interconnects has not been examined sufficiently. This paper reveals the maximum performance of on-chip global interconnects based on derived analytic expressions and detailed circuit simulation. We derive trade-off curves among bit rate, interconnect length, and eye opening both for single-end and for differential signaling. The results show that differential signaling improves signaling performance several times compared with conventional single-end signaling, and demonstrate that 80 Gbps differential signaling on 10 mm interconnects is promising.

This paper proposes a decentralized and asynchronous replica control method based on a fair assignment of the variation in numerical data that has weak consistency for loosely coupled database systems managed or used by different organizations of human activity. Our method eliminates the asynchronous abort of already committed transactions even if replicas in all network partitions continue to process transactions when network partitioning occurs. A decentralized and asynchronous approach is needed because it is difficult to keep a number of loosely coupled systems in working order, and replica operations performed in a centralized and synchronous way can degrade the performance of transaction processing. We eliminate the transaction abort by fairly distributing the variation in numerical data to replicas according to their demands and updating the distributed variation using only asynchronously propagated update transactions without calculating the precise global state among reachable replicas. In addition, fairly assigning the variation of data to replicas equalizes the disadvantages of processing update transactions among replicas. Fairness control for assigning the data variation is performed by averaging the variation requested by the replicas. A simulation showed that our system can achieve extremely high performance for processing update transactions and fairness among replicas.

This note considers a problem of minimum length scheduling for a set of messages subject to precedence constraints for switching and communication networks, and shows some improvements upon previous results on the problem.

This paper presents two new intelligent methods to linearize the Multi-Carrier Power Amplifiers (MCPA). One of the them is based on the Neuro-Fuzzy controller while the other uses two small neural networks as a polar predistorter. Neuro-Fuzzy controllers are not model based, and hence, have ability to control the nonlinear systems with undetermined parameters. Both methods are adaptive, low complex, and can be implemented in base-band part of the communication systems. The performance of the linearizers is obtained via simulation. The simulation is performed for three different scenarios; namely, a multi-carrier amplifier for GSM with four channels, a CDMA amplifier and a multi-carrier amplifier with two tones. The simulation results show that Neuro-Fuzzy Controller (NFC) and Neural Network Polar Predistorter (NNPP) have higher efficiencies so that reduce IMD3 by more than 42 and 32 dB, respectively. The practical implementation aspects of these methods are also discussed in this paper.