Subscriber network opticalization is the key issue for the next generation network. Fiber-optic systems have been limited to mainly big business applications, so far. Massive opticalization including home and small business customers remains the ultimate goal. Opticalization of the subscriber network needs an enormous investment and a long construction period. In order to achieve smooth evolution towards B-ISDN, the subscriber network must be effectively opticalized well in advance of full B-ISDN deployment. This paper presents the development concept of optical subscriber network. It also describes the design concept and configuration of fiber-optic subscriber systems. Deployment strategies and the developing technologies for the future subscriber network are also addressed.

Optical fiber cable systems are being developed in many countries for subscriber loops as the infrastructure to realize B-ISDN (Broadband Integrated Services Digital Network). The present systems are DLC (Digital Loop Carrier) systems which provide leased lines, POTS (Plain Old Telephone Services), and N-ISDN (Narrowband ISDN) services. Before FTTH (Fiber To The Home) networks can be implemented, their construction cost must be lowered to the level of the current metallic network. The FTTH network must also be easy to operate and maintain. In this paper, we describe optical fiber cables, splicing, and testing technologies used in the NTT cable networks, and introduce the technologies being developed to construct FTTH networks.

The essential functions of the passive double star (PDS) system are clarified by comparing them to the functions of the single star (SS) and the active double star (ADS) system. A layered structure describing the functional characteristics of the PDS system is proposed for flexible transport capability. The functions of the optical network unit (ONU) on the customer premises are systematically partitioned into four layers. The functions of the optical subscriber unit (OSU) in the central office are described using five layers. Call by call activation and deactivation techniques are described on the basis of a layered architecture. The reduction of ONU power consumption by adopting activation and deactivation control is also discussed.

Microcrystalline silicon embedded in silicon oxide has been prepared by means of a wet oxidation of porous silicon (PS) anodically produced from degenerate Si wafers in a HF solution. As the oxidation proceeded, optical absorptions of the PS specimen in the visible light region shifted obviously to the higher energy side. Visible light emission from the oxidized specimen was observed at room temperature with photoexcitation by a He-Cd laser while the as-prepared specimen emitted no visible lights. These results are discussed in relation to the quantum size effect of the microcrystalline silicon confined in the oxide matrix as well as visible emissions from as-prepared specimens produced from non-degenerate Si wafers.

Isotope dilution secondary ion mass spectroscopy (ID-SIMS) using 30Si as a spike is investigated as a quantitative analysis method for trace amounts of Si. For a standard solution of Si, the relateve standard deviation of results using this method is 5% for 0.2 µg Si, and the determination lower limit is 18 ng. Using this method, the amount of Si deposited on the Ge(100) surface by the self-limited adsorption of SiH2Cl2 is determined to be about 1.00.2 monolayer.

This paper proposes the GDV system, which provides a format-independent interface with which to access documents in various formats. It also proposes a new approach for document representation to be used in the GDV system. In this approach, a document is represented by a chain of objects, each of which belongs to a certain class and transforms access operations according to the class-specific transformation rule. A user's request is interpreted as a request to the uppermost object of the chain, transformed by objects in the chain successively, and executed by the lowermost object in the chain. The initial state of a document is an object chain containing an unidentified object. As the unidentified object identifies and divides itself, classification (and chain generation) proceeds step by step.

This letter proposes an improvement of the equivalent source method in order to give an accurate solution for the scattering of an electromagnetic plane wave by a conducting cylinder with edges.

This paper first discusses the software reusability-based development process in a lifecycle and reusable objects modification process called differentiation. Next, the supporting environment is described. Both the method and the environment allow developers to carry out requirement definitions, specification and implementation in a reusable way. Some quantitative evaluations are given about how productivity and quality have been improved by using this method and environment, based on a number of case studies made on development projects. Reusability has been largely improved by differential specification, and adjustment method and a direct transformation capability.

A novel harmonic retrieval algorithm is proposed in this paper based on Hopfield's neural network. Frequencies can be retrieved with high accuracy and high resolution under low signal to noise ratio (SNR). Amplitudes and phases in harmonic signals can also be estimated roughly by an energy constrained linear projection approach as proposed in the algorithm. Only no less than 2q neurons are necessary in order to detect harmonic siglnals with q different frequencies, where q denotes the number of different frequencies in harmonic signals. Experimental simulations show fast convergence and stable solution in spite of low signal to noise ratio can be obtained using the proposed algorithm.

A Ge/Si structure grown by chemical vapor deposition (CVD) is angle-lapped and characterized by the micro-Raman spectroscopy. Near the interface, the phonon mode due to the Si-Ge bond is clearly observed, which indicates that a SiGe alloy is formed by the solid-phase interdiffusion at the interface. The thickness of the interfacial alloy layer is about 0.2 µm. Amount of residual strain is estimated by comparing the measured phonon frequencies with those predicted from the composition profie, but the shift due to the residual strain is not appreciable. Both the interdiffusion at the interface and the nearly complete relaxation of the lattice mismatch are attributed to the high growth temperature of the CVD sample.

In this paper, a new M-estimation technique for the linear prediction analysis of speech is proposed. Since in the conventional linear prediction (CLP) method the obtained estimates are very much affected by the large amplitude residual parts, in the proposed method we use a loss function which assigns large weighting factor for small amplitude residuals and small weighting factor for large amplitude residuals which is for instance caused by the pitch excitations. The loss function is based on the assumption that the residual signal has an independent and identical t-distribution t(α) with α degrees of freedom. The efficiency of this new estimator depends on α. When α=, we get the CLP method. When the proposed method with small α is applied to the problems of estimating the formant frequencies and bandwidths of the synthetic speech by finding the roots of the prediction polynomial, we can achieve a more accurate and a smaller standard deviation (SD) estimate than that with large α. When the signal is very spiky, the proposed method can ahieve more efficient and accurate estimates than that with robust linear prediction (RBLP) method. The loss function is modified in the similar manner as the autocorrelation method. The solution is calculated by the Newton-Raphson iteration technique. The simulation results show that only few iterations are needed to reach a stationary point, the stationary point is always a local minimum and the obtained prediction filter is always minimum phase. Preliminary experiments on the human speech data indicate that the obtained results are insensitive to the placement of the analysis window and a higher spectral resolution than the CLP and RBLP method can be achieved.

Thin Si films grown on anodized porous silicon have been characterized using a high-energy ion scattering technique with related simulations of MeV ions in solids. It turned out that the simulations are necessary and very usuful for quantitative and nondestractive analysis of thin films with thicknesses less than 100 nm. In the case of the epitaxial Si films examined, it is often insufficient for the characterization of crystalline quality to measure only the channeling minimum yield, and therefore, it is emphasized that angular scans over the critical angle in the vicinity of a channeling direction must be performed for the analysis of possible imperfections in thin films. The possible imperfections observed in the epitaxial specimen are treated quantitatively.

In this paper, we analyze a photodetection process of new kind theoretically, which transforms a coherent state of light so as to lead to nonstandard property, namely, sub-Poissonian distribution of its output photoelectron during its photodetection process. The properties of the photoelectron distribution are studied used as preamplifiers of both direct-detection and homodyne detection cases.

Asynchronous Transfer Mode (ATM) switching system is expected to handle various kinds of media (such as motion video, computer data, and voice), and traffic control becomes essential to satisfy various quality requirements and to maintain efficient utilization of system resources. Priority control is one possible solution for realizing such a traffic control. In priority control, cells from various media are scheduled for transmission with different priority according to the quality class to which they belong. In this paper, we propose a new priority control method in which cells from various media are stored in their own buffer, we call it class buffer, and priority assignments are carried out based on the number of cells in each class buffer and the delay time. The number of cells in each class buffer is maintained using the counter circuit. The delay time of the cell is checked by the timer circuit for cell group, each of which consists of cells arriving during a periodical time interval. For simulation model, we consider three kinds of traffic; video, computer data, and voice, of which quality requirements are quite different. We show performance results in terms of the cell delay and the cell loss probability in our method through simulation.

This letter considers a subclass of t-symmetric error correcting/all unidirectional error detecting (t-SyEC/AUED) codes in which the information is represented in an m-out-of-k coded form, which thus can be regarded as virtually systematic for practical purposes. For t3, previous researchers proposed methods for constructing codes of this subclass which are either optimal or of asymptotically optimal order. This letter proposes a new method for constructing, for any values of t, m and k, codes that are either optimal or of asymptotically optimal order. The redundancy of the obtained code is of the order tlog2k bits when mt.

The a-Si films deposited on quartz substrates were crystallized by lateral sweep annealing in steep temperature gradient using a gas burner. Random nucleation in amorphous region was effectively suppressed in the temperature gradient, so lateral solid phase epitaxial growth from crystallites generated at the initial stage of lateral sweep annealing spread over 100 µm. Their crystallographic orientations were mostly (100).

After the intrinsic pulsed light illumination, a transient negative photoconductivity (TRANP) was observed in silicon doped with gold. The ambient temperature dependence of the TRANP-current was measured and compared with the simulated results obtained by solving rate equations. The temperature dependence of the peak value of the TRANP-current was in agreement with the simulated result. The activation energy of gold acceptor level obtained from the time constant in the recovery process was also consistent with the simulation. It was cleared from this result that the recovery process is dominated by the electron re-emission from gold acceptor level to the conduction band. It was concluded that the occurrence of the TRANP is well explained by using our model proposed before.

This article proposes, given an independently-and-identically distributed binary source, an arithmetic code-like variable-to-variable length source code whose compression efficiency achieves nearly the rate function in a range of small distortion. Inheriting advantages of arithmetic codes, the proposed code requires neither large memory capacity nor large computation time for management of messages and codewords. The Elias code, which can be regarded as an antecedent of arithmetic codes, is defined originally in terms of the first-in-first-out (FIFO) coding form. The proposed code corresponds to an extension from the Elias code refined in terms of the last-in-first-out (LIFO) coding form into one considered a fidelity criterion.

A 1/2 frequency divider using resonant-tunneling hot electron transistors (RHETs) has been proposed and demonstrated. The circuit make the best use of negative differential conductance, a feature of RHETs, and contains one half transistors than used in conventional circuits. The RHETs were fabricated using self-aligned InGaAs RHETs and WSiN thin-film resistors on a single chip. The RHETs have an i-InGaAlAs/i-InGaAs collector barrier that improves the current gain at low collector-base voltages. Circuit operation was confirmed at 77 K.

This paper describes on the transmission properties of the superconducting coplanar waveguide on LiNbO3 (LN) substrates, fabricated by YBa2Cu3Oy (YBCO) superconducting films. The films have been prepared by the reactive co-evaporation method and patterned by a wet etching process. The surface resistance of the obtained film was 0.04 Ω at 18 GHz and 77 K. It was confirmed from X-ray diffraction (XRD) that these films were highly oriented to the direction of c-axis without a secondary phase. The microwave transmission properties of these YBCO coplanar waveguides were investigated at frequencies up to 20 GHz and compared with that of the aluminum coplanar waveguide. The characteristic impedances of both coplanar waveguides were designed to be 50 Ω. It was found that the attenuation constants of these samples at 77 K were less than that of the aluminum coplanar waveguide for frequencies below 18 GHz.