This paper reports on the bending loss insensitive single mode fiber suitable for access networks, which is applicable for wide wavelength use. Excellent attenuation stability of the fiber in the full spectrum range has been confirmed even in severe conditions such as fiber handling in mid-span access at aerial closure, cable installation/handling in indoor wirings and so on. Also, applications suitable for FTTH subscribers' use have been introduced.

In this paper, a dual level access scheme is proposed to provide two levels of access to the broadcast data; one to video signals protected for authorized users, another to extra information e.g. advertisements provided for the remaining users in the network. In the scheme, video signals in MPEG format are considered. The video contents are protected from unauthorized viewing by encrypting the DC coefficients of the luminance component in I-frames, which are extracted from the MPEG bit-stream. An improved direct sequence spread spectrum technique is used to add extra information to non-zero AC coefficients, extracted from the same MPEG bit-stream. The resultant MPEG bit-stream still occupies the same existing bandwidth allocated for a broadcast channel. At the receiver, the extra information is recovered and subtracted from the altered AC coefficients. The result is then combined with the decrypted DC coefficients to restore the original MPEG bit-stream. The experimental results show that less than 2.9% of the size of MPEG bit-stream was required to be encrypted in order to efficiently reduce its commercial value. Also, on average, with a 1.125 Mbps MPEG bit-stream, an amount of extra information up to 1.4 kbps could be successfully transmitted, while the video quality (PSNR) was unnoticeably degraded by 2.81 dB.

High-resolution spectrum estimation techniques have been extensively studied in recent publications. Knowledge of the noise variance is vital for spectrum estimation from noise-corrupted observations. This paper presents the use of noise compensation and data extrapolation for spectrum estimation. We assume that the observed data sequence can be represented by a set of autoregressive parameters. A recently proposed iterative algorithm is then used for noise variance estimation while autoregressive parameters are used for data extrapolation. We also present analytical results to show the exponential decay characteristics of the extrapolated samples and the frequency domain smoothing effect of data extrapolation. Some statistical results are also derived. The proposed noise-compensated data extrapolation approach is applied to both the autoregressive and FFT-based spectrum estimation methods. Finally, simulation results show the superiority of the method in terms of bias reduction and resolution improvement for sinusoids buried in noise.

This paper presents a novel algorithm for spectral subtraction (SS). The method is derived from a relation between the spectrum obtained by the discrete Fourier transform (DFT) and that by a subspace decomposition method. By using the relation, it is shown that a noise reduction algorithm based on subspace decomposition is led to an SS method in which noise components in an observed signal are eliminated by subtracting variance of noise process in the frequency domain. Moreover, it is shown that the method can significantly reduce computational complexity in comparison with the method based on the standard subspace decomposition. In a similar manner to the conventional SS methods, our method also exploits the variance of noise process estimated from a preceding segment where speech is absent, whereas the noise is present. In order to more reliably detect such non-speech segments, a novel robust voice activity detector (VAD) is then proposed. The VAD utilizes the spread of eigenvalues of an autocorrelation matrix corresponding to the observed signal. Simulation results show that the proposed method yields an improved enhancement quality in comparison with the conventional SS based schemes.

The phase noise has a significant effect on the M-ary PSK transmission signal, furthermore the higher-order modulation signal can not be recovered in the presence of phase noise. It is important to define exactly what is required in terms of phase noise within a particular system and to avoid expensive over-specification. Based on the analysis of allowable signal-to-noise ratio for phase reference and required phase error variance for M-ary PSK systems relative to a degradation loss objective, the general phase noise allocation method for M-ary PSK satellite communication systems has been proposed in this paper. The phase noise allocation using the proposed method is adopted for M-ary PSK multi-mode satellite communication systems. Using the oscillator phase noise model and the phase noise model of a frequency synthesizer, the required phase noise spectrum distributions are carried out and the validities of the allocated phase noise spectrums are verified by the system simulation.

This paper proposes a new robust adaptive processing algorithm that is based on the extended least squares (ELS) method with running spectrum filtering (RSF). By utilizing the different characteristics of running spectra between speech signals and noise signals, RSF can retain speech characteristics while noise is effectively reduced. Then, by using ELS, autoregressive moving average (ARMA) parameters can be estimated accurately. In experiments on real speech contaminated by white Gaussian noise and factory noise, we found that the method we propose offered spectrum estimates that were robust against additive noise.

In this Letter, a frequency-domain pre-rake transmission is presented for a direct sequence spread spectrum with time division duplex (DSSS/TDD) system under a frequency-selective fading channel. The mathematical relationship between frequency-domain and time-domain pre-rake transmissions is discussed. It is confirmed by the computer simulation that, similar to the time-domain pre-rake transmission, frequency-domain pre-rake transmission can improve the bit error rate (BER) performance. The frequency-domain pre-rake transmission shows only slight performance degradation compared to the frequency-domain rake reception for large SF.

Two methods using comparable corpora to select translation equivalents appropriate to a domain were devised and evaluated. The first method ranks translation equivalents of a target word according to similarity of their contexts to that of the target word. The second method ranks translation equivalents according to the ratio of associated words that suggest them. An experiment using the EDR bilingual dictionary together with Wall Street Journal and Nihon Keizai Shimbun corpora showed that the method using the ratio of associated words outperforms the method based on contextual similarity. Namely, in a quantitative evaluation using pseudo words, the maximum F-measure of the former method was 86%, while that of the latter method was 82%. The key feature of the method using the ratio of associated words is that it outputs selected translation equivalents together with representative associated words, enabling the translation equivalents to be validated.

There is a possibility that individuals ingest contaminants that have been accidentally mixed with food because processed foods have become very common. Therefore a detection method of small contaminants in food and pharmaceuticals is required. High-Tc SQUID detection systems for metallic contaminants in foods and drugs have been developed for safety purposes. We developed two systems; one large system is for meat blocks and the other small system is for powdered drugs or packaged foods. Both systems consist of SQUID magnetometers, a permanent magnet for magnetization and a belt conveyor. All samples were magnetized before measurements and detected by high Tc SQUIDs. As a result, we successfully detected small syringe needles with a length of 2 mm in a meat block and a stainless steel ball as small as 0.3 mm in diameter.

We propose a novel approach based on wavelet decomposition for progressive full spectral rendering. In the fourth progressive stage, our method renders an image that is 95% similar to the final non-progressive approach but requires less than 70% of the execution time. The quality of the rendered image is visually plausible that is indistinguishable from that of the non-progressive method. Our approach is graceful, efficient, progressive, and flexible for full spectral rendering.

An inverse-RZ modulation scheme for dense WDM systems is proposed. Inverse-RZ signals have tolerances to chromatic dispersion and optical bandwidth limitation. The strongly pre-filtered inverse-RZ signals can be adapted to ultra-dense WDM systems, in which the spectral efficiencies are over 1.0 b/s/Hz. We have confirmed the error-free transmission of pre-filtered and co-polarized 40-Gb/s inverse-RZ signals where the channel intervals were 37.5 GHz.

In this study, we construct balanced Boolean functions with a high nonlinearity and an optimum algebraic degree for both odd and even dimensions. Our approach is based on modifying functions from the Maiorana-McFarland's superclass, which has been introduced by Carlet. A drawback of Maiorana-McFarland's function is that their restrictions obtained by fixing some variables in their input are affine. Affine functions are cryptographically weak functions, so there is a risk that this property will be exploited in attacks. Due to the contribution of Carlet, our constructions do not have the potential weakness that is shared by the Maiorana-McFarland construction or its modifications.

We have proposed and experimentally demonstrated a novel WDM-PON downstream optical link. It is composed of a wavelength-locked FP-LD with a spectrally-sliced FP-LD as an external-injection optical source and operated as directly-modulating in a downstream-traffic transmitter. The downstream transmissions at 622 Mbps and 2.5 Gbps were performed for four channels over 25 km. The proposed WDM-PON downstream transmitter can be expanded up to eight channels by controlling an external-injection optical source of a spectrally-sliced FP-LD. Also, the transmitter has facility of multi-channel selection by controlling temperature. We verified the potential of the transmitter in WDM-PON optical link.

Photoacoustic (PA) spectra on the 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) films deposited by the vacuum evaporation were measured. The films have layered structures constructed from the perylene molecule plane structures. The crystal quality depended on the deposited substrate and the photoacoustic spectroscopy (PAS) seems to be the very useful tools to evaluate these properties from the non-radiative features. The films deposited on the three different substrate had the almost same PL spectra, but the films deposited on the glass substrate had the large non-radiative peaks in the PA spectra contrary to the films deposited on the alumina or crystal Si (100) those had the non-radiative peaks only observed at the short wavelength region.

Borrowing the notion of instantaneous frequency that was developed in the context of time-frequency signal analysis, an instantaneous frequency amplitude spectrum (IFAS) is introduced for estimating fundamental frequency of speech signal in both noiseless and adverse environments. We define harmonicity measure as a quantity that indicates degree of periodical regularity in the IFAS and that shows substantial difference between periodic signal and noise-like waveform. The harmonicity measure is applied to estimate the existence of fundamental frequency. We provide experimental examples to demonstrate the general applicability of the harmonicity measure and apply the proposed procedure to Japanese continuous speech signals. The results show that the proposed method outperforms the conventional methods with or without the presence of noise.

Some plants have air purification ability. This purification ability of plants is considered a promising method for indoor air purification because of the low cost and high purification performance. Therefore, several studies have been carried out to investigate the relationship between the air purification ability of plants and environmental conditions. Nevertheless, the purification mechanism and process have not been clarified yet. In this paper, we investigated the air purification process in plants by bioelectrical potential analysis using linear and nonlinear analysis methods. First, we showed that two types of plants have a high air purification ability; Schefflera and Boston fern. Next, we measured AC bioelectrical potential during the purifying process of plants for pollutant gas. Then, we evaluated the power spectra of time series data of the bioelectrical potential. We found that the power spectra shifted to a lower level after gas injection over all frequencies. Thus, the higher power spectrum came from possible higher physiological activities of the plant. Finally, we introduced a nonlinear analysis method from the dynamical system theory. We transformed the time series data of the potential to a higher dimensional state space using a delay coordinate, which is often used in the field of nonlinear time series analysis. The results show that the orbits in the reconstructed state space have a large variation in gas injection. These experimental results suggest that the measurement of bioelectrical potential could become a useful method for evaluating the air purification ability of plants.

We have determined the thickness and optical constants (refractive index and extinction coefficient) of each layer in the multi-layer organic light emitting diode (OLED) devices based on phosphorescent platinum octaethyl porphine (PtOEP) using a phase modulated spectroscopic ellipsometer. The thickness of each layer estimated from the ellipsometric measurement is different from the thickness measured with quartz oscillator during the evaporation of organic materials. The deviation of total multi-layer thickness is about 5%, while the deviation in each of N, N'-bis(1-naphtyl)-N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) and aluminum tris 8-hydroxyquinoline (Alq3) layers is about 20-25%. Additionally the spectra of refractive index and extinction coefficient of Alq3 and α-NPD layers are different from those that are measured using the single layer films. These results are understood by penetration of organic material from the neighboring layers in the multi-layer structure devices.

Due to the cost of multicast state management, multicast address allocation, inter-domain multicast routing of traditional IP multicast scheme, ASM leads to a search for other multicast schemes. This paper presents a new solution to the problems mentioned above based on IPv6. The proposed scheme provides an enhanced scheme supporting the strengths of SSM in basic Xcast. This is achieved by adding MLDv2 operations at recipient's side and a new control plane into existing Xcast. The proposed scheme does not only provide the transparency of traditional multicast schemes to sources and recipients, but it also enhances the routing efficiency in networks. Intermediate routers do not have to maintain multicast state, so that it results in a more efficient and scalable mechanism to deliver native multicast datagrams. Also, the seamless integration in Mobile IPv6 can support multicast efficiently for mobile nodes in IPv6 networks by avoiding tunnel avalanches and tunnel convergence. We've attempted to prove this alternative architecture by both simulation and implementation, respectively. Our approach cannot fundamentally perform for many large groups distributed widely as effectively as traditional multicast schemes. However, we believe that the resulting scheme is simple, efficient, robust, transparent, and to the extent possible, scalable in case that recipients are clustered in subnets.

Spectral-amplitude coding (SAC) techniques in fiber-Bragg-grating (FBG)-based optical code-division multiple-access (OCDMA) systems were investigated in our previous work. This paper adopts the same network architecture to investigate the simultaneous reductions of multiple-access interference (MAI) and optical beat interference (OBI). The MAI is caused by overlapping wavelengths from undesired network coder/decoders (codecs) while the OBI is induced by interaction of simultaneous chips at adjacent gratings. It is proposed that MAI and OBI reductions may be obtained by use of: 1) a source spectrum that is divided into equal chip spacing; 2) coded FBGs characterized by approximately the same number of "0" and "1" code elements; and 3) spectrally balanced photo-detectors. With quasi-orthogonal Walsh-Hadamard coded FBGs, complementary spectral chips is employed as signal pairs to be recombined and detected in balanced photo-detectors, thus achieving simultaneous suppression of both MAIs and OBIs. Simulation results showed that the proposed OCDMA spectral-amplitude coding scheme achieves significant MAI and OBI reductions.

LOTOS parallel operator, which is a binary operator, is used to combine processes in order to express their concurrency. Unlike other LOTOS operators, various possibilities exist when combining processes by the parallel operator. If two processes are selected randomly for combining, the size of the composite intermediate process after combining may be large. In this paper, we propose an algorithm for selecting two processes out of three or more processes so that the size of the intermediate process is the smallest when combined by the parallel operator. Smaller size of an intermediate process means it takes less memory space which is very important in designing verification tools for systems or communication protocols specified in LOTOS.