Runlength-limited block codes are investigated. These codes are useful for storing data in storage devices. Since most devices are not noiselss, the codes are often required to have some error-control capability. We consider runlength-limited codes that can correct or detect unidirectional byte errors. Some constructions of such codes are presented.

An accurate numerical solution is presented for the electromagnetic scattering from infinite strip gratings attached to both sides of a dielectric slab. This structure is a model of polarization discriminating devices. The period of the strips is common to both planes, but the widths and the axes may be different. The direction of propagation and the polarization of an incident plane wave are arbitray. We derive a set of singular integral equations and solve it by the moment method, where the Chebyshev polynomials are successfully used as the basis and the testing functions. This method is accurate and effective owing to the incorporation of the edge condition and the decomposition of the kernel functions into the singular and the regular parts. Numerical calculations are carried out for the purpose of designing polarization discriminators, and it is shown that the band width is widened by decreasing the permittivity of the slab. The cross-polarization characteristics at skew incidence are also discussed.

The effect of mesage-class dependent threshold-type scheduling on queueing delay and resequencing delay for the M/M/n queueing system is analyzed. We first derive the expressions for the state transition equations, mean queueing delay, resequencing delay and total delay for the M/M/n queueing system shared by C different message classes under a threshold-type scheduling in which the threshold values depend on the message class at the head of queue and the number of messages in the buffer. Next, the numerical calculation and the computer simulation are carried out for the queueing system with two servers. It is found that the message-class dependent threshold-type scheduling is effective to reduce the resequencing delay of some specific message class, which can not be attained under the conventional threshold-type scheduling, and thus, the proposed scheduling can satisfy the different requirements of the different message classes, such as minimizing only queueing delay or total delay including resequencing delay.

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.

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.

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.

It often occurs in the acoustic environment that a specific signal is contaminated by the additional noise of non-Gaussian distribution type. In order to extract exactly the various statistical information of only specific signal from the observed noisy data, a stochastic signal processing by use of digital computer is essential. In this study, a stochastic method for estimating the probability function of the specific signal embedded in the additional noise is first theoretically proposed in a suitable form for the quantized level observation. Then, the effectiveness of the proposed method is experimentally confirmed by applying it to the observed data in the acoustic environment.

The characteristics of an optical functional integrated circuit and its applications are discussed. This circuit is based upon a Mach-Zehnder interferometer type waveguide device employing thermo-optic effect. This circuit is compact, cost-effective and practical. One proposed application is an optical loopback circuit to test both OCU loop 1 and DSU loop C. This optical loopback circuit with an attenuator and space switches is formed on a common silicon substrate, and using this circuit both loopback and line tests are independently available at the same access point. The other is an optical selector. This optical selector with WDM-MUX/DMUX and space switches is formed on a common silicon substrate, and using this selector, wavelength selection from medium density WDM (MDWDM) signal can be performed. Each MDWDM signal carries both AM and FM-FDM video signals modulated by Subcarrier Multiplexing (SCM) techniques. This selector can be wired in point-to-multipoint configurations to home video appliances.

Analysis of the propagation of circularly symmetric fields is made using the finite-difference beam-propagation method. After testing the accuracy of this method, we analyze the guided-mode transmission of connected fibers whose core radii are different. The propagation behavior of the unguided-mode field generated at the junction is revealed using a transparent boundary condition.

In this paper, we propose a method to simulate the curve surface of the initial height in the movement of the electronic wire bonder using the experimental data. For given measured data (xk, yk, zk (k=1, 2, , m)), we propose an algebraic surface of n-th degree as a methematical model of the initial height surface. The AIC method is a method of evaluating the goodness of a given model. The maximum likelihood model is selected by comparing with the AIC value of each model for n=0, 1, 2, 3, , 11. Useing this model, the initial raise position of the electronic wire bonder can be controlled by computer programing and can make the movement of wire bonder full-automatic. As a resurt, the well-arranged wiring and reliable contacting can be obtained.

The quality of polycrystalline silicon films and electrical characteristics of polycrystalline silicon gate metal-oxide-semiconductor (MOS) capacitors were investigated under various processing conditions, including phosphorus doping. The stresses observed in Si films deposited in the amorphous phase show complex behavior during thermal treatment. The stresses in as-deposited Si films are compressive. They change to tensile with annealing at 800, and to compressive after an additional annealing at 900. The kind of charges trapped in the SiO2 film during the negative constant current stress in Polycrystalline silicon gate MOS capacitors differ with the maximum process temperature. The trapped charges of samples annealed at 800 were negative, while those of samples annealed at 900 were positive.

Diffusion of phosphorus impurities from a polycrystalline silicon films into a silicon substrate was investigated as a function of the mean concentration of phosphorus in a polycrystalline silicon film at the first diffusion stage. We presented that good control of the redistribution of implanted phosphorus impurities was possible by optimizing the normalized dose, which is the value: [the total dose of phosphorus impurities]/[the polycrystalline silicon film thickness], in the case of samples both with and without an arsenic doped layers. In the range where the normalized dose was less than 1.52.51020 cm-3, deeper junctions were formed in samples with an arsenic doped layer. In the range where the normalized dose was more than 1.52.51020 cm-3, however, deeper junctions were formed in samples without any arsenic doped layer rather than in samples with an arsenic doped layer. These results mean that formation of the junction in the device structure where a high concentration phosphorus doped polysilicon layer is stacked on to the high concentration arsenic layer embeded at the surface of the substrate can be restricted by optimizing the normalized dose. Moreover, a trade-off relationship between suppressing phosphorus diffusion and maintaining low contact resistance against normalized doses was also observed.

A passive double star (PDS) optical subscriber system which employs a newly proposed flexible access and frequency division duplex transmission system has been reported. For the flexible access and efficient channel usage in subscriber PDS system, a modified pipe-line polling with a call-by-call basis channel assignment has been proposed. This access system has a wide covering range which exceeds 10km or more. A newly proposed pulsed PSK transmission and a baseband transmission are used for a single wavelength bi-directional transmission for to and from the central office. A pulsed FM single subcarrier transmission system is also proposed for the analog CATV distribution system, which is overlaid with wavelength division multiplexing on the bi-directional transmission system. The equipments for the pulsed PSK and the pulsed FM transmission can be realized with all digital circuits. Moreover, the pulsed signal's modulation nature has eased the requirement for the laser diode characteristics, such as linearity and RIN. These features are effective for the compact and cost effective transmission systems.

Silicon-on-insulator (SOI) films fabricated by the wafer bonding technique were studies with capacitance-voltage (C-V) and deep-level transient spectroscopy (DLTS) measurements. For our expereiments, two kinds of SOI wafers were prepared. Many voids were present in one sample (void sample), but few voids were in the other sample (no void sample). Before annealing, two DLTS peaks (Ec-0.48 eV and Ec-0.38 eV) were observed in the SOI layer of the void sample. For the no void sample, different two DLTS peaks (Ec-0.16 eV and Ec-0.12 eV) were observed. The trap with an activation energy of 0.48 eV was annealed out after 450 annealing for 24 h. On the other hand, other traps were annealed out after 450 annealing for several hours. During annealing at 450, thermal donors (TDs) were formed simultaneously. In usual CZ silicon, a DLTS peak of TD was observed around 60 K. In the no void sample, however, a TD peak was observed at a temperature lower than 30 K. This TD was annihilated by rapid thermal annealing. This suggests that the TD with a shallower level was formed in the no void sample after annealing at 450.

Relational query languages like SQL and QUEL require the users to understand the complex detabase structure. This is a burden on end users, especially novice end users who access the database on a casual and infrequent basis. To alleviate the need to know the logical database origanization, this paper proposes the use of a semantic data model, known as the Enhanced Entity-Relationship (EER) model, as a front-end to the relational systems. A formal, high-level Visual Knowledge Query Language (VKQL) has also been designed for this interface. This language provides for knowledge abstraction as the user communicates only domain knowledge with the system without any implication on the storage structure or search strategies. A translation algorithm is also described in this paper to translate VKQL queries to Standard SQL equivalents.

A new channel stop design for submicton local oxidation of silicon (LOCOS) isolation was presented. The n-channel stop was designed with boron implanation after forming LOCOS, while the p-channel stop was constructed with high energy phosphorus or arsenic implantation before or after forming LOCOS. These optimized channel stop designs can extend an isolation spacing to the submicron region without a decrease in junction breakdown voltage and an increase in junction leakage current. Narrow channel effects were found to be effectively suppressed by optimum channel stop design issues.

Operation of a newly proposed semiconductor optical modulator based on absorption control by electron depletion around a p-n junction is demonstrated, forming preliminary structures of waveguide-type as well as panel-type (or surface-illuminated type) devices. The optical absorption is occurred at the intrinsic energy levels in the band structure not at the extended state into the band-gap. Performance of 35 dB on-off extinction ratio for 4 V variation of the applied voltage was obtained in a waveguide type device. Validity of the proposed mechanism were confirmed by getting large change of the absorption coefficient of around 5000 cm-1 over wide wavelength range of 30 nm.