Various optical fiber connectors have been developed during the 20 years since optical fiber communications systems were first put into practical use. As the domain of optical fiber communication systems expanded from trunk lines to subscriber lines and customer premises the main focus changed from performance improvement to miniaturization and cost reduction. This paper describes the technical background, recent trends in standard optical connectors, and recent issues related to photonic connection technologies.

A novel signal processing technique using adaptive neural network algorithm is applied for the on-line detection of harmonic current components generated by nonlinear current loads in the single-phase diode bridge rectifier and it can efficiently determine the harmonic current components in real time. The validity of this active filtering processing system to compensate current harmonics is proved on the basis of simulation results.

This paper describes the requirements for fault recovery on photonic networks and proposes a fast restoration scheme for recovering optical networks. The proposed scheme is a type of pre-assignment restoration. The features of the scheme are that it is suitable for multi-recovery classes aimed at fine control of the optical paths and that it establishes harmonization between restoration control and distributed network control such as in IP networks. The scheme is implemented on Photonic multi protocol label switching (MPLS) routers. A restoration demonstration was performed and recovery was achieved within 500ms in the optical layer.

We propose a new scheme of indoor optical wireless LAN based on a special CMOS image sensor (CIS), which realizes a low-power compact communication module with large uplink capacity due to space division multiple access. In our scheme, all nodes and a hub utilize the CIS as a photoreceiver as well as a position-sensing device for finding the positions of the communication modules, while a single large photodiode is used in the conventional systems. Although conventional image sensors cannot detect modulated signals because they integrate photocurrents, our CIS has a high-speed readout function for receiving optical data from the specific pixels receiving optical signals. The advantages of the proposed scheme are 1) compact embodiment of the communication module due to no need of the bulky mechanical components for searching the other modules, 2) space division multiple access, which leads to 3) large capacity of uplink, and 4) applicability of simple modulation and coding schemes for optical signals. In our scheme, diffusive and narrow beam lights are complementally used for position detection and communication, respectively, which leads to the advantage 5) low power consumption of both light emitter and receiver circuits. To demonstrate two basic functional modes of our CIS: an IS (image sensor) mode and a COM (communication) mode, we fabricate an 88-pixel CIS by use of a 0.8µm BiCMOS technology. In the experiments, the image of a light source is successfully captured in the IS mode for integration time of 29.6msec and optical power of 1.1nW. After the functional mode of the pixel receiving the light is changed to the COM mode, the eye pattern of the modulated light is obtained from the pixel at frequency of 1MHz. We also fabricate a test pixel circuit with in-pixel amplifier, with which operation speed is improved to 100MHz.

Three-dimensional MEMS optical switches(3D-MEMS) and planar lightwave circuit thermo-optical switches (PLC-TOSW) are suitable for use in large-scale photonic cross-connect switches (PXCs). Usually, such large-scale optical switches are created by integrating many small switch elements (such as 12 switches). Therefore, the reliability or lifetime of the individual switch element greatly affects the reliability of the PXC system. In this paper, the effect of the number and failure probability of switch elements on PXC reliability is statistically estimated. First, the equivalent number of switch elements needed to compose a large-scale PXC is determined for the switch types mentioned above. Based on this evaluation, yields and lifetimes of switch modules are estimated for each switch type. The improvement in reliability due to switch duplication (preparing spare switches) is also estimated and discussed.

A reconfigurable coprocessor for ETSI-GSM voice coding application domain is presented, synthesized and tested. An average overall reduction of more than 55% cycles with respect to standard RISC processors with DSP features is obtained. Such improvement together with locality and temporal correlation allows a reduction of power consumption, while standard interfacing technique ensures maximum flexibility.

A high efficient HBT MMIC power amplifier with a new on-chip bias control circuit was proposed for PCS applications. By adjusting the quiescent current in accordance with the output power levels, the average power usage efficiency of the power amplifier is improved by a factor of 1.4. The bias controlled power amplifier, depending on low (high) output power levels, shows 62(103) mA of quiescent current, 16(28) dBm output power with 7.5(35.4)% of power-added efficiency(PAE), -46(-45) dBc of adjacent-channel power ratio (ACPR), and 23.7(26.9) dB of gain

Datacycle is an information delivery system designed in Bellcore . It uses broadcast delivery and multiple channels of an optical fiber to provide a large volume of information to many users. In this system, the mean access time depends on the broadcast delivery schedule because different information items (called pages) may have different popularity and there are multiple channels for concurrent broadcast delivery. In this paper, we design broadcast delivery schedules for M channels where M 2 and our objective is to minimize the mean access time. We show that this design problem can be divided into two subproblems: (1) divide the pages into M partitions such that the pages of each partition are broadcast in a distinct channel and (2) determine a broadcast schedule for the pages of each partition. We analyze and solve these subproblems, and we demonstrate that the schedules found can nearly reach a lower bound on the minimal mean access time.

A heterogeneous parallel computing environment consisting of different types of workstations and communication links plays an important role in parallel computing. In many applications on the system, collective communication operations are commonly used as communication primitives. Thus, design of the efficient collective communication operations is the key to achieve high-performance parallel computing. But the heterogeneity of the system complicates the design. In this paper, we consider design of an efficient gather operation, one of the most important collective operations. We show that an optimal gather schedule is found in O(n2k-1) time for the heterogeneous parallel computing environment with n processors of k distinct types, and that a nearly-optimal schedule is found in O(n) time if k=2.

The Quasi-Delay-Insensitive (QDI) model assumes that all the forks are isochronic. The isochronic-fork assumption requires uniform wire delays and uniform switching thresholds of the gates associated with the forking branches. This paper presents a method for determining such forks that do not have to satisfy the isochronic fork requirements, and presents experimental results that show many isochronic forks assumed for existing QDI circuits do not actually have to be "isochronic" or can be even ignored.

This paper presents our experimental results in transmission of MB34 coded signal at the rate of 9.95 Gb/s over the conventional single mode fiber. The test results showed considerable improvement in receiver sensitivity, signal-to-noise-ratio (SNR), and timing margin with MB34.

Intelligent paging uses the sequential paging technique with additional user information in order to reduce the paging delay cost and the paging load cost. Our proposed paging scheme uses distribution density information of users as required additional user information. This letter addresses an optimal paging sequence and introduces formulas to calculate the paging costs. These formulas are necessary to evaluate the performance of location management. The paging delay cost and the paging load cost for the proposed paging scheme and two other paging schemes are calculated and numerical analyses for these paging schemes are performed. Results show how the paging delay cost and the paging load cost vary as either the paging request arrival rates or the number of cells in an LA increases. The proposed paging scheme is more efficient in view of both the paging delay cost and the paging load cost.

Effects of high-frequency cyclic input and noise on interspike intervals in the coupled Bonhoeffer-van der Pol (BVP) model are studied with computer simulation. When two BVP elements are weakly coupled and cyclic input or noise is added to the first element, the interspike intervals of the second element decrease non-monotonically as the amplitude of the input increases. Further, complicated bifurcations in the interspike intervals are caused by cyclic input in the coupled BVP model in the oscillating state. Effects of the coupling on small rotations due to noise and the interruption of oscillations due to cyclic input, which occur when the equilibrium point is close to the critical point, are also studied. The non-monotonic changes and bifurcations in the interspike intervals are attributed to the phase locking of the coupled elements.

We propose a method to realize soft-decision decoding for hard-detected signals. In this paper, a novel concept is introduced as "error-detected reliability. " The method is very useful for optical fiber communications (OFC) as hard detection is the only detection method for the OFC systems. We demonstrate our proposed method using the turbo code in which soft information is required for decoding. As a result, the simulation shows slight difference in the range of moderate to high signal-to-noise ratio between the proposed decoding scheme and the conventional turbo decoding scheme. Moreover, the bit error rate of 10-11 can be achieved by serial concatenation of a Reed-Solomon code and a turbo code for Q-factor lower than 8.0 dB with a bandwidth expansion ratio of 33.3%.

This paper reviews the historical development of adaptive antennas in Japan. First of all, we watch basic adaptive algorithms. In 1980s, particularly, the following issues were a matter of considerable concern to us; (a) behavior to the coherent interference like multipath waves or radar clutters, (b) signal degradation in case that the direction of arrival (DOA) of desired signal is different from the DOA specified beforehand in the adaptive antennas with the DOA of the desired signal as a prior knowledge, and (c) performance of adaptive antennas when the desired signal and interference are broadband. Although there are a lot of development and modification of adaptive algorithms in Japan, we refer in this paper only to the above-mentioned topics. Secondly, our attention is paid to implementation of adaptive antennas and advanced technologies. A large number of researches on the subjects have been carried out in Japan. Particularly, we focus on the initiative studies in Japan toward mobile communication application. They include researches of mobile radio propagation for adaptive antennas, calibration methods, and adaptive antenna for mobile terminals. As a matter of course, we also refer to adaptive antenna technologies for advanced communication schemes such as CDMA, SDMA, OFDM and so on. Finally, we take notice of some pilot products which were developed to verify the effect of the adaptive antenna in the practical environments. As the initiative ones, a couple of equipments are introduced in this paper.

We propose a new offline check system that allows refunds to be reused in payments. In this system, a shop issues a new check, called a refund check, for the change. The form of the refund check is much simpler than that of existing checks, and uses a more flexible and efficient denomination method. The new system also provides tracing mechanisms to counter criminal acts and considers the atomicity of transactions occurring in the system.

An efficient anonymous cash system based on the hash chain is presented. The new system is debit-based and vendor-independent. It also provides tracing mechanisms to reinforce controls on illegal use. The efficiency of the system results from its capacity to pay variable amounts with no additional cost. A client always makes a single blind signature, independent of the length of the chain. During payment, the client makes a single challenge-and-response or one signature, independent of the amount paid.

A soft-decision decoding scheme of low-density parity-check codes (LDPC) is proposed for hard-detected signals of optical fiber communication (OFC) systems. Based on the error detection, the proposed scheme converts the received hard-decision into soft reliability for the input of the LDPC decoder, and soft-decision decoding is performed. Simulation results under OFC channels are shown and superior performance is obtained by using the proposed decoding scheme of the LDPC codes.

Information services for drivers and passengers in land vehicles have been drastically increasing in recent years. Frequency spectra used in vehicle communications cover an extremely wide band ranging from the LF band to the millimeter-wave band. Today, a variety of properties are required of antennas depending on the types of radio systems; more than ten kinds of antennas are installed in land vehicles. Advances in such land vehicle antennas developed in Japan are reviewed in reference to antennas for broadcasting reception and mobile communication systems. Typical antennas are introduced for each system, and the technology and performance are described.

The paper overviews and surveys Japan's reflector antennas for earth stations and radio telescopes since the 1960's. Some interferometers for radio astronomy are included. Japanese original technologies regarding reflector antenna design and measurement are also described. There are 35 figures and 3 tables.