Optical amplifier structures suitable for a 622Mbit/s repeater in an optical communication system containing one in-line amplifier have been investigated. Two wavelengths of 1.533µm and 1.549µm are considered for two cases, i.e., single-channel transmission and two-channel wavelength division multiplexing transmission. The basic amplifier structure is of a two-stage type where forward pumped and backward pumped erbium-doped fibers are connected with each other through intermediate optical filters and an optical isolator. First, the effect of the intermediate optical filters was clarified in optical gain and bit error rate characteristics. Then, the erbium-doped fiber length was optimized on the basis of the allowable optical loss of the optical system which was operated at a bit error rate of 10-9. As a result, the appropriate length of the forward pumped erbium-doped fiber was found to be about 20m for both cases of single-channel and two-channel wavelength multiplexing amplifiers. With the designed amplifier used in the system, the calculated allowable optical line loss was more than 90dB for both the cases.

The origin of and a method of enhancing the Optical Beam Induced Resistance Change (OBIRCH) signal for defect observation in VLSI metal interconnections is discussed based on a numerical analysis of three-dimensional thermal conduction and experimental results. The numerical analysis shows that the OBIRCH signal originates from a slight increase in the resistance of the metal line caused by laser beam heating and that its effect is influenced by the temperature of the metal layer. Both simulations and experimental results suggest that cooling the sample is preferable to detect the OBIRCH signal. The decrease in the total resistance of the metal line without any change in the amount of the resistance increase under laser illumination is found to be the main cause of the OBIRCH signal enhancement under low temperature measurement.

This paper studies the performance of a dialogue communication system which consists of two stations over a half-duplex line. When a station seizes the right to send its packets, it can consecutively transmits k packets. We analyze the transmission time of a message and the throughput performances of Stop-and-Wait, Go-back-N and Selective-Repeat protocols for the half-duplex line transmission system. Based on the analytical and numerical results, we clarify the influences of the switching and the thinking times, which exist in half-duplex line system, on the throughput performance, and give the optimal k which makes the throughput to become maximum. It is observed that the throughput performances are greatly influenced not only by the switching and thinking times but also by the average message length.

This paper presents an algorithm which sums up n binary values on an n m reconfigurable mesh in O(log n/(m log m)1/2) time. This algorithm also yields a corollary which states that n binary values can be summed up on an nlog2n/log log n reconfigurable mesh in constant time.

Recent progress on the ultrahigh-speed optical transmission experiments are reviewed including the ultrashort pulse generation, high-speed timing extraction, all-optical multi/demultiplexing. Also discussed are the latest 100 Gbit/s experiments and a scope to higher bit-rate, longer distance optical transmission.

Many previous works state that a multiple Sidelobe canceller (MSLC) with two auxiliary antennas is successful in suppressing two interference signals received simultaneously by sidelobes of a main antenna. In this paper, we show that the MSLC does not always guarantee such capability in three dimensional applications where the incident direction of interference signals is defined by two angles (elevation and azimuth). We show the singularity of the autocorrelation matrix for the auxiliary channel signals induces the degradation of the capability by analyzing characteristics of MSLC's in three dimensional applications from the view point of the eigenvalue problem. To overcome this singularity, we propose a novel MSLC controlling the placement of auxiliary antennas by means of switching over three antennas arranged triangularly. Some simulations are conducted to show the effectiveness of the proposed MSLC.

We describe a geometrical optics approach for the analysis of dielectric tapered waveguides. The method is based on the ray-optical treatment for wave-normal rays defined newly to waves of light in open structures. Geometrical optics fields are represented in terms of two kinds of wave-normal rays: leaky rays and guided rays. Since the behavior of these rays is different in the two regions separated at critical incidence, the geometrical optics fields have certain classes of discontinuity in a transition region between leaky and guided regions. Guided wave solutions are given as a superposition of guided rays that zigzag along the guides, all of which are totally reflected upon the interfaces. By including some leaky rays adjacent to the guided rays, we obtain more accurate guided wave solutions. Calculated results are in excellent agreement with wave optics solutions.

The scope of this paper is the realization of FIR digital filters with an emphasis on linear phase and maximally flat cases. The transfer functions of FIR digital filters are polynomials and polynomial evaluation algorithms can be utilized as realization schemes of these filters. In this paper we investigate the application of a class of polynomial evaluation algorithms called "recursive triangles" to the realization of FIR digital filters. The realization of an arbitrary transfer function using De Casteljau algorithm, a member of the recursive triangles used for evaluating Bernstein polynomials, is studied and it is shown that in some special and important cases it yields efficient modular structures. Realization of two dimensional filters based on Bernstein approximation is also considered. We also introduce recursive triangles for evaluating the power basis representation of polynomials and give a new multiplier-less maximally flat structure based on them. Finally, we generalize the structure further and show that Chebyshev polynomials can also be evaluated by the triangles. This is the triangular counterpart of the well-known Chebyshev structure. In general,the triangular structures yield highly modular digital filters that can be mapped to an array of concurrent processors resulting in high speed and effcient filtering specially for maximally flat transfer functions.

A local area network (LAN) can now provide high-speed data communications in a local area environment to establish distributed processing among personal computers and workstations, and the need for interconnecting LANs, which are geographically distributed, is naturally arising. Asynchronous Transfer Mode (ATM) technology has been widely recognized as a promising way to provide the high-speed wide area networks (WAN) for Broadband Integrated Services Digital Network (B-ISDN), and the commercial service offerings are expected in the near future. The ATM network seems to have a capability as a backbone network for interconnecting LANs, and the LAN interconnection is expected to be the first service in ATM networks. However, there remain some technical challenges for this purpose; one of the main difficulties in LAN interconnection is the support of connectionless traffic by the ATM network, which is basically a connection-oriented network. Another one is the way of achieving the very high-speed data transmission over the ATM network. In this paper, we first discuss a LAN internetworking methodology based on the current technology. Then, the recent deployments of LAN interconnection methods through B-ISDN are reviewed.

In a distributed-memory parallel-processing system, the overhead of data transfer among the processors is so large that it is important to reduce the data transfer. We consider the data transfer in evaluating an expression consisting of data distributed among the processors. We propose some algorithms which assign the operators in the expression to the processors so as to minimize the number or the cost of data transfers, on the condition that the data allocation to the processors is given. The basic algorithm is given at first, followed by some variations.

This paper describes a color segmentation method which is essential for automatic diagnosis of stained images. This method is applicable to the variance of input images using a three-layered neural network model. In this network, a back-propagation algorithm was used for learning, and the training data sets of RGB values were selected between the dark and bright images of normal mammary glands. Features of both normal mammary glands and breast cancer tissues stained with hematoxylin-eosin (HE) staining were segmented into three colors. Segmented results indicate that this network model can successfully extract features at various brightness levels and magnifications as long as HE staining is used. Thus, this color segmentation method can accommodate change in brightness levels as well as hue values of input images. Moreover, this method is effective to the variance of scaling and rotation of extracting targets.

Although the perception of gloss is based on human visual perception, some methods for extracting glossiness, in contrast to human ability, have been proposed involving curved surfaces. Glossiness defined in these methods, however, does not correspond with psychological glossiness perceived by the human eye over the wide range from relatively low gloss to high gloss. In addition, the obtained glossiness in these methods changes remarkably when the curvature radius of the high-gloss object becomes larger than 10mm. In reality, psychological glossiness does not change. These methods, furthermore, are available only for spherical objects. A new method for extracting glossiness is proposed in this study. For the new definition of glossiness, a spatial filter which simulates human retina function is utilized. The light intensity distribution of the curved object is convoluted with the spatial filter. The maximum value Hmax of the convoluted distribution has a high correlation with psychological glossiness Gph. From the relationship between Gph and Hmax, new glossiness Gf is defined. The gloss-extraction equipment consists of a light source, TV camera, an image processor and a personal computer. Cylinders with the curvature radii of 3-30 mm are used as the specimens in addition to spherical balls. In all specimens, a strong correlation, with a correlation coefficient of more than 0.97, has been observed between Gf and Gph over a wide range. New glossiness Gf conforms to Gph even if the curvature radius in more than 10 mm. Based on these findings, it is found that this method for extracting glossiness is useful for the extraction of glossiness of spherical and cylindrical objects over a wide range from relatively low gloss to high gloss.

This paper studies the problem of embedding a graph into a book with nodes on a line along the spine of the book and edges on the pages in such a way that no edge crosses another. Atneosen as well as Bernhart and Kainen has shown that every graph can be embedded into a 3-page book when each edge can be embedded in more than one page. The time complexity of Bernhart and Kainen's method is Ω(ν(G)), where ν(G) is the crossing number of a graph G. A new 0(mn) algorithm is derived in this paper for embedding a graph G=(V, E), where m=│E│ and n= │V│ . The number of points at which edges cross over the spine in embedding a complete graph into a 3-page book is also investigated.

Recently, efficient algorithms that exploit the separability of nonlinear mappings have been proposed for finding all solutions of piecewise-linear resistive circuits. In this letter, it is shown that these algorithms can be extended to circuits containing piecewise-linear resistors that are neither voltage nor current controlled. Using the parametric representation for these resistors, the circuits can be described by systems of nonlinear equations with separable mappings. This separability is effectively exploited in finding all solutions. A numerical example is given, and it is demonstrated that all solutions are computed very rapidly by the new algorithm.

The Minimum Covering Run (MCR) expression used for representing binary images has been proposed [1]-[3]. The MCR expression is an adaptation from horizontal and vertical run expression. In the expression, some horizontal and vertical runs are used together for representing binary images in which total number of them is minimized. It was shown that, sets of horizontal and vertical runs representing any binary image could be viewed as partite sets of a bipartite graph, then the MCR expression of binary images was found analogously by constructing a maximum matching as well as a minimum covering in the corresponding graph. In the original algorithm, the most efficient algorithm, proposed by Hopcroft, solving the graph-theoretical problems mentioned above, associated with the Rectangular Segment Analysis (RSA) was used for finding the MCR expression. However, the original algorithm still suffers from a long processing time. In this paper, we propose two new efficient MCR algorithms that are beneficial to a practical implementation. The new algorithms are composed of two main procedures; i.e., Partial Segment Analysis (PSA) and construction of a maximum matching. It is shown in this paper that the first procedure which is directly an improvement to the RSA, appoints well a lot of representative runs of the MCR expression in regions of text and line drawing. Due to the PSA, the new algorithms reduce the number of runs used in the technique of solving the matching problem in corresponding graphs so that satisfactory processing time can be obtained. To clarify the validity of new algorithms proposed in this paper, the experimental results show the comparative performance of the original and new algorithms in terms of processing time.

This paper proposes new algorithms for adaptive FIR filters. The proposed algorithms provide both fast convergence and small final misadjustment with an adaptive step size even under an interference to the error. The basic algorithm pays special attention to the interference which contaminates the error. To enhance robustness to the interference, it imposes a special limit on the increment/decrement of the step-size. The limit itself is also varied according to the step-size. The basic algorithm is extended for application to nonstationary signals. Simulation results with white signals show that the final misadjustment is reduced by up to 22 dB under severe observation noise at a negligible expense of the convergence speed. An echo canceler simulation with a real speech signal exhibits its potential for a nonstationary signal.

In this paper, we study a dynamic bandwidth control which is expected an effective use of network resources in transmitting highly bursty traffic generated by, e.g., interconnected LAN systems. First, a new LAN traffic model is proposed in which correlation of not only packet interarrival times but also packet lengths are considered. An analytic model for a LAN-ATM gateway is next introduced. It employs the dynamic bandwidth control using the proposed LAN traffic model and some performance measures are derived by it. The analytic model takes into account the probability that a bandwidth increase request may be rejected. Finally, some numerical examples are provided using the analysis method and performance comparisons between the dynamic and fixed bandwidth controls are made. As a result, it is quantitatively indicated that () if the equivalent bandwidth is used in average, the dynamic bandwidth control keeps packet and cell loss rates one to two orders lower than the fixed bandwidth control, () when the more strict QOS in terms of loss rate is requested, the dynamic bandwidth control can become more effective.

An automatic tracing algorithm of the transistor-level performance faults in the waveform-based approach with CAD-linked electron beam test system which utilizes a transistor-level circuit data in CAD database is proposed. Performance faults mean some performance measure such as the temporal parameters (rise time, fall time and so on) lies outside of the specified range in a VLSI. Problems on automatic fault tracing in the transistor level are modeled by using graphs. Combinational circuits which consist of MOS transistors are considered. A single fault is assumed to be in a circuit. The algorithm utilizes Depth-First Search algorithm where faulty upstream interconnections are searched as deeply as possible. Treatment of the faults on downstream interconnections and on unmeasurable interconnections is given. Application of this algorithm to the 2k-transistor block of a CMOS circuit showed its validity in the simulation.

There has been growing interest in Broadband ISDN (B-ISDN) based on ATM (Asynchronous Transfer Mode) technologies, since ATM is expected to support a wide range of applications through high-speed and flexible multimedia communication capabilities. This paper reviews and discusses technical issues on multimedia communication protocols and services from the integration points of view of computer and communication technologies. An ISDN-based distributed multimedia and multi-party desktop conference system called MERMAID is introduced as an example which offers highly-sophisticated functions for remote collaborations among multiple users. This system, which was developed in early 1989 and has been used for daily research work since then, involves B-ISDN key technologies related to multimedia and multicast protocols, and computer architecture for groupware applications.

This paper discusses a way of identifying the network configuration of ATM-LANs, which are composed of a number of ATM hubs. In general, a Network Management System (NMS) sets and gets the necessary data to and from the network elements. In managing an ATM-LAN, the ATM connection between the NMS and each network element, namely the ATM hub, must be established in order to get and set the necessary data. This forms a remarkable contrast with conventional LANs such as the IEEE802.3 LAN, which is a shared media network and enables broadcast communication without setting up any connection. This paper proposes a new protocol and a procedure that establishes the ATM connection between the NMS and each ATM hub, while identifying the overall network configuration. First, this paper makes clear the peculiarity of the ATM-LAN in terms of automatically identifying the network configuration. Next, the identification protocol that achieves the required properties is precisely explained. Then, the proposed identification protocol is evaluated in terms of required bandwidth and identification time.