This paper describes the optical characteristics and static fatigue reliability of a zirconia alignment sleeve, which is a component part of an optical connector with zirconia ferrules. This combination of sleeve and ferrules hardly generates any wear debris during connector insertion and removal cycles. This has reduced the cleaning frequency of the ferrule endface during cycles and greatly improved the return loss stability of the optical connectors. The zirconia alignment sleeve enables stable return loss characteristics to be achieved over a wide temperature range as it has the same thermal expansion coefficient as the zirconia ferrule. Furthermore, the gauge retention force for the zirconia alignment sleeve is defined with a view to its practical use. This force must be between 2.0 and 3.9 N to allow stable optical connections to be made under various mechanical and environmental conditions. We also clarify the conditions for a proof test by which to prevent the occurrence of static fatigue fractures in the sleeve, and we confirm the validity of the test. The static fatigue parameters for zirconia ceramics and derived from the static fatigue theory for brittle materials and fracture testing. We use these static fatigue parameters to predict the lifetime of a zirconia sleeve under working stress. An appropriate stress level for the proof test which eliminates weak sleeves, is about 3 times greater than working stress. The strength of the sleeve as demonstrated in the proof test is confirmed by accelerative stress aging. The performance of this sleeve is superior to that of a conventional copper alloy sleeve and the proof test confirms its reliability; under 0.1 FIT for 20 years of use.

As a result of examination based on a newly available data set of millimeter-wave rain attenuation measured in the UK, it is found that the ITU-R specific rain attenuation model tends to appreciably underestimate millimeter-wave rain attenuation at frequencies above about 60GHz for the UK rain climate. This tendency is very similar to that previously reported for the Japanese experimental data at frequencies up to 245GHz. Furthermore, an alternative specific rain attenuation model based on the Japanese experimental data is found to be in fairly good agreement with the experimental data in the UK at frequencies up to 137GHz.

The sidelobe canceler in radar systems is a highly computational demanding problem. It can be efficiently tackled by resorting to the QR decomposition mapped onto a systolic array processor. The paper reports several mapping strategies by using massive parallel computers available on the market. MIMD as well as SIMD machines have been used, specifically MEIKO Computing Surface, nCUBE2, Connection Machine CM-200, and MasPar MP-1. The achieved data throughput values have been measured for a number of operational situations of practical interest.

This paper describes a newly developed 22 liquid crystal optical switch for 1.3µm single-mode fiber use. This switch state can be freely set at either the cross or the bar state. The measured performance of two prototype 22 liquid crystal optical switches is given. Tests confirm that the 3 values are a maximum insertion loss of 1.5dB, a crosstalk attenuation of more than 26.1dB, and a return loss of more than 28.9dB. Requirements for optical switches for fault isolation are theoretically clarified from a LAN system view point.

With the arrival of B-ISDN, widespread usage of multicast services such as TV broadcasting and video 900 services will increase the possibility of network congestion unless efficient multiple destination routing (MDR) algorithms are used. Current MDR algorithms using link cost based on bandwidth usage or distance to compute the minimum cost routing tree do not take into account the vast amount of information collected by intelligent network (IN) databases. In this paper, we propose a multicast routing algorithm which modifies the way the cost is calculated by using the predicted traffic statistics collected by IN databases. We also show that the traffic handling characteristics vastly improved over conventional MDR algorithms.

We present an O(nN) time and O(n2) space algorithm for finding a maximum weight independent set of a circle (or overlap) graph of n chords (or intervals) on N endpoints, based on an alternative definition of such graphs. The results improve on the best previously known algorithms for this case.

We analyze the effect of overlapping technique on differential pulse position modulation (DPPM) in optical direct-detection channel when the pulsewidth and the average power of the channel are constrained. We refer to the modulation scheme employing an overlapping technique in DPPM as differential overlapping PPM (DOPPM). To avoid frame synchronization problems, we analyze the performance of DOPPM under the window scheme that results in lower bounds on the capacity and the cutoff rate of DOPPM but is easy to analyze. Under this scheme, we analyze the lower bounds on the capacity and the cutoff rate of DOPPM. It is shown that DOPPM with the window scheme has higher capacity and cutoff rate than PPM and DPPM, and also than OPPM when the average received number of photons per slot is somewhat large. The overlapping technique is thus shown to be effective on DPPM under the pulsewidth constraint when the average received number of photons per slot is somewhat large.

High-speed pulse propagation, up to several hundred Mbps or higher, will play an important role in telecommunication systems for B-ISDN. High-performance packaging, especially high-speed, high-throughput interconnection, is strongly required. For advanced telecommunication systems, giga-bit signal transmission has been developed at the multi-chip module level, and 300 to 600 Mbps signal transmission has been reached at the printed circuit board level. Electrical inter-cabinet interconnections of 150 to 300 Mbps have been achieved for up to several tens of meters. High-speed, high-throughput connectors are the key to achieving high-performance telecommunication packaging systems. Two technologies are extremely important. One is for high-density, high-pin-count connectors, and the other is for high-speed signal transmission connectors. The requirements for the connectors needed for advanced high-performance telecommunication systems are described. Several high-density, high-bandwidth connectors developed for high-performance packaging system are introduced.

This paper describes a trial coaxial surface mounted connector for PGA-type high-speed multichip modules (MCM). An MCM connector is needed to ensure testability and connection reliability of MCMs mounted on a printed circuit board. Our connector consists of a coaxial elements, a common ground housing made of conductive resin, and a ground contact spring plate. It has 68 signal contacts. We investigated the performance of this connector by experiment and simulation. Its insertion force is only about 53 gf per signal pin. The characteristic impedance is from 45.6 Ω to 61.4 Ω. The average resistance between two contacts is 28 mΩ with a deviation of less than plus or minus 5 mΩ. The insertion is -0.4 dB at 1.0 GHz. Crosstalk noise is less than 1.2%. This prototype connector can transmit pulses of up to 1.2 Gb/s, showing that it is applicable to high-speed MCMs.

The authors have studied mechanism of transition from metallic phase to gaseous phase in contact break arc. For further elucidation of the mechanism, we have carried out spectroscopic measurement. The spectrum measurement system which had high time resolution was composed using two monochromators and a bifurcated image fiber, which had one input port and two output ports. The input port received the arc light, and the two monochromators received the arc light from the two output ports, respectively. The spectral sensitivity of the two monochromators was corrected with a standard lamp. We have measured simultaneously two spectra of break arc for Ag in laboratory air, under the condition where source voltage E=48 V, load inductance L=2.3 mH, and closed contact current I0=6 A. As a result, the time-varying tendency of spectrum intensity is similar for the same element, even if the wavelength is different. And from the comparison of time average spectrum intensity, it is clarified that average intensity for gas spectrum does not attain to 10% of that for metallic atomic spectrum (Ag I, 520.91 nm). In addition, the decrease point of Ag II (ion) spectrum has been found to correspond with the peak of Ag I (atom) spectrum.

Measuring mechanical characteristics of optical disks is significant not only for designing drives but also for assuring disk interchangeability. This paper shows that the lens-movement detection method has the greatest overall potential and thus fits to a practical system for measuring mechanical characteristics. A system based on this method was constructed by developing simple and accurate capacitive sensors that can be built into an optical head to detect lens movement. The system configuration includes a precision turntable and a high-duarability reference disk to fully extract the potential. Test results show that this measuring system has adequate measuring range, accuracy, and stability. Some applications of this system are described in this paper. They show that the system is useful for evaluating and improving optical disk mechanical characteristics.

Parallel processing in speech recognition is described, which is carried out at each frame on time axis. We have already proposed a parallel processing algorithm for HMM (Hidden Markov Model)-based speech recognition using Markov Random Fields (MRF). The parallel processing is realized by modeling the hidden state sequence by an MRF and using the Iterated Conditional Modes (ICM) algorithm to estimate the optimal state sequence given an observation sequence and model parameters. However this parallel processing with the ICM algorithm is applicable only to the standard HMM but not to the improved HMM like the linear predictive HMM which takes into account the correlations between nearby observation vectors. In this paper we propose a parallel processing algorithm applicable to the correlation-considered HMM, where a new deterministic relaxation algorithm called the Generalized ICM (GICM) algorithm is used instead of the ICM algorithm for estimation of the optimal state sequence. Speaker independent isolated word recognition experiments show the effectiveness of the proposed parallel processing using the GICM algorithm.

ISO and ITU-T have developed the standard concept of the Telecommunications Management Network (TMN). This standard does not, however, specify interface implementation. The user requires an Application Programming Interface (API) that bridges user application and the TMN concept to construct a TMN-based application. This paper proposes an object oriented API (OOAPI) that is suitable for TMN-based operations system implementation. OOAPI is one interface of the Common Management Information Service Element (CMISE), and uses the Common Management Information Protocol (CMIP). OOAPI is composed of two C++ programming language constructs: Data Object and Interface object "M_User". The Data Object makes it easier for the user to access management information. The M_User provides a connection-less CMISE interface because the OOAPI handles CMIP association automatically. The M_User also provides MO location-transparency by using the OSI Directory Service. This paper compares the existing MO location-transparency schemes with the OOAPI method, and clarifies the advantages of OOAPI. This paper also indicates results from OOAPI trials, and confirms that OOAPI has sufficient performance to implement highly effective TMN operations system.

A new cell buffer implementation method, called the counter approach, is presented in this paper. A cell buffer handling CLP with the push out scheme can be implemented using this approach. Also, using this approach, an element switch for a MIN with the window scheme can be realized. The experimental element switch LSI has already been fabricated and tested. The LSI proves the applicability of the counter approach to a high-speed ATM switching system.

On the surface of contacts which are exposed to the atmosphere, the reaction with gases in the atmosphere produces contaminant films including oxides. The contact reliability is degraded by the contaminant films. Humidity in the atmospheric environment also influences on the surface of contacts. However, influence of humidity on the surface has not been clarified. In the present paper, influence of humidity on the Cu surface and the oxides (CuO + Cu2O) on it were studied with respect to the thickness of the oxide film and contact resistance characteristics both for static and for sliding contacts. The thickness was measured by ellipsometric analysis. Topographic image affected by humidification was also observed by scanning tunneling microscope (STM). In the atmospheric environment, the clean surface of Cu was found to oxidize with fluctuations of the thickness for lapse of exposure time due to the fluctuations of the humidity. It was also found that the thickness of the oxide film decreases immediately after the humidification, and increases under dehumidification. Changes in contact resistance affected by humidity was corresponding to the change in the film thickness. Immediately after humidification contact resistance decreased, and increased with dehumidification both for static and for sliding contacts. For the mechanism of the influence of humidity on the oxide, chemical reduction of hydrogen generated by decomposition of the absorbed water molecule (H2O) was derived. The clean Cu surface was oxidized by oxygen due to absorbed water molecule and atmosphere.

We introduce a procedure to determine the discrete Fourier spectra of the band-limited function from its irregularly distributed samples. The nonuniform data of the signal are represented by the non-orthogonal basis functions (non-harmonic Fourier functions) and discrete Fourier spectra of the signal. We construct a set of orthonormal basis functions from the above mentioned non-orthogonal basis functions using the Gram-Schmidt procedure. Based on the G-S procedure and the property of the orthogonalization, the spectral components of signal can be obtained by the conjugate transpose of orthonormal basis functions, their coefficients matrix and the nonuniform samples. Thus the desired signal can be obtained by the inverse Fourier transform of the determined discrete Fourier spectra. We apply this algorithm to reconstruct a band-limited low-pass and band-pass signal and show that our method provide more stable and better reconstruction than the matrix inversion method.

In the conventional protocol synthesis, it is generally assumed that primitives in service specifications cannot be executed simultaneously at different Service Access Points (SAPs). Thus if some primitives are executed concurrently, then protocol errors of unspecified receptions occur. In this paper, we try to extend a class of service specifications from which protocol specifications are synthesized by the previous methods. We first introduce priorities into primitives in protocol specification so that it always selects exactly one primitive of the highest priority from a set of primitives that can be executed simultaneously, and executes it. Then, based on this execution ordering, we propose a new protocol synthesis method which can avoid protocol errors due to message collisions, communication competitions and so on. By applying the proposed synthesis method, we can automatically synthesize a protocol specifications from a given service specification which includes an arbitraty number of processes and allows parallel execution of primitives.

It is shown that for a class of interval matrices we can estimate the location of eigenvalues in a very simple way. This class is characterized by the property that eigenvalues of any real linear combination of member matrices are all real and thus includes symmetric interval matrices as a subclass. Upper and lower bounds for each eigenvalue of such a class of interval matrices are provided. This enables us to obtain Hurwitz stability conditions and Schur ones for the class of interval matrices and positive definiteness conditions for symmetric interval matrices.

In communication protocols, the behaviour of a protocol entity is related to the behaviour of another protocol entity as they communicate under sets of communication rules (protocols). Thus, it is desirable to concentrate on the design of one protocol entity and generate the corresponding protocol entity automatically. Furthermore, it is desirable that the protocol is formal, precise and unambiguous that is, it is described using FDTs (Formal Description Techniques). In this paper, we propose a protocol synthesis algorithm in which, from a LOTOS specification of a single given entity, LOTOS specification of the corresponding peer entity is generated automatically. Unlike previous works, where FSMs (Finite State Machines) were used to synthesize protocols, we use LOTOS, which is one of FDTs developed by ISO, in our proposed synthesis algorithm. We prove that the generated protocol is logical errors free, collectively represented as deadlock free, if the given entity is in certain forms which are natural in the context of connunication protocols.

As to the method of multi-layer testing, up to now, the testing system (called PROVES) which testes effectively each N-layer protocol implement of SUT (System Under Test) using the functions of derail-points located between N-layer and (N+1)-layer protocol implements in a test system has been proposed. The test logic programs, which are embedded in the derail-points of the test system, play an important role to realize the protocol error test sequences in the test system. Namely, they modify, add, or delete the correct protocol commands/responses output from the protocol implement part of the lest system, sends these erroneous commands/responses to SUT and observes the output from SUT. This paper proposes the method of validating the correctness of test logic program using the structural properties of Petri nets without coding the test logic programs, where correctness means that the desired output can be obtained by sending or receiving the commands/responses within a constant time under the initial conditions determined uniquely by the test system and SUT. According to our experiment, it is seen that almost all of the logical errors included in the test logic programs used for the experiment can be detected by this method.