We experimentally demonstrate the ultrafast and high-repetition capabilities of a polarization-discriminating symmetric Mach-Zehnder (PD-SMZ) all-optical switch. This switch, as well as an original symmetric Mach-Zehnder (SMZ) all-optical switch, is based on a highly efficient but slowly relaxing band-filling effect that is resonantly excited in a passive InGaAsP bulk waveguide. By using a mechanism that cancels out the effect of the slow relaxation, ultrafast switching is attained. We achieve a switching time of 200 fs and demultiplexing of 1.5 Tbps, showing the applicability of the SMZ or PD-SMZ all-optical switches to optical demultiplexing of well over 1 Tbps for the first time. High-repetition capability, which is another important issue apart from the switching speed, is also verified by using control pulses at a repetition rate of 10.5 GHz. We also discuss the use of nonlinearity in a semiconductor optical amplifier to further reduce the control-pulse energy.

We experimentally demonstrate the ultrafast and high-repetition capabilities of a polarization-discriminating symmetric Mach-Zehnder (PD-SMZ) all-optical switch. This switch, as well as an original symmetric Mach-Zehnder (SMZ) all-optical switch, is based on a highly efficient but slowly relaxing band-filling effect that is resonantly excited in a passive InGaAsP bulk waveguide. By using a mechanism that cancels out the effect of the slow relaxation, ultrafast switching is attained. We achieve a switching time of 200 fs and demultiplexing of 1.5 Tbps, showing the applicability of the SMZ or PD-SMZ all-optical switches to optical demultiplexing of well over 1 Tbps for the first time. High-repetition capability, which is another important issue apart from the switching speed, is also verified by using control pulses at a repetition rate of 10.5 GHz. We also discuss the use of nonlinearity in a semiconductor optical amplifier to further reduce the control-pulse energy.

The authors observed the correlation between electromagnetic noise and trace of discharge on surface for various surface areas of Cu in opening copper (Cu)-carbon (C) electrodes. In the case of Cu (anode)-C (cathode), the duration of sporadic burst noise generated by discharge becomes longer when Cu surface area is increased, and trace of discharge (melting area) distribute widely on electrodes. Also the forms of the burst noise in the start of arc are classified, and the traces of discharge correspond to each forms. The forms of the burst noise depend on the pattern which the trace of discharge are formed. As these results, the authors showed the correlation between form of burst noise and trace of discharge on electrode surface.

We investigated a radio interferometer for geodetic use that incorporates commercially available fiber-optic links modulated in the radio-frequency range, and a method for compensating for the delay occurring in the links. With this type of radio interferometer, we can perform baseline analysis without the need for estimating the clock difference between observation stations, which causes a relatively large error in the vertical component of the estimated position of the station. Another advantage of the interferometer is utilization of phase delay, which improves the accuracy of delay determination considerably. By analyzing the interferometer's signal-to-noise ratio, we estimated the practicable cable length to be 58.0 km. The results of preliminary experiments with short optical fiber links show that the differences in the cable delays of the fiber-optic links can be compensated for by calibration signals which make a round trip between the analysis station and the observation sites, and that phase delay can be measured successfully.

In designing ASIPs (Application Specific Integrated Processors), the papers investigated so far have almost focused on the optimization of the CPU core and did not pay enough attention to the optimization of the RAM and ROM sizes together. This paper overcomes this limitation and proposes an optimization algorithm to define the best ratio between the CPU core, RAM and ROM of an ASIP chip to achieve the highest performance while satisfying design constraints on the chip area. The partitioning problem is formalized as a combinatorial optimization problem that partitions the operations into hardware and software so that the performance of the designed ASIP is maximized under given chip area constraint, where the chip area includes the HW cost of the register file for a given application program with associated input data set. The optimization problem is parameterized so that it can be applied with different technologies to synthesize CPU cores, RAMs or ROMs. The experimental results show that the proposed algorithm is found to be effective and efficient.

We have proposed an algorithm to apply perfectly matched layer (PML) absorbing boundary condition to the noncubic cell time-domain method. The extended method has a merit of flexibility in truncating the computational domain by the use of a curvilinear PML. In this paper we apply a circular PML for computing the scattered fields of a dielectric cylinder or cylindrical shell of arbitrary cross section shape. Numerical results are presented to demonstrate the accuracy of this method.

This paper describes a new approach to analyze nonlinear characteristics of propagating waves in a ferrite material. As to the formulation of the wave in a ferrite medium, the analysis in this paper is not taken under the assumption of a sinusoidal steady state using Polder tensor permeability, but taken by directly differentiating the gyromagnetic equation in time domain without any linear approximations. Then it is combined with Maxwell equation in FDTD procedure. As a result, intensity-dependent nonlinear responses of the propagating wave are confirmed, and the nonlinearity is seen in only the right-hand polarization wave. It is also found that an effect of the damping term in the equation of the motion of the magnetization has nonlinear characteristics for wave propagation.

An efficient finite element-integral equation method is presented for calculating scattered fields from conducting objects. By combining the integral equation solution with the finite element method, this formulation allows a finite element computational domain terminated very closely to the scatterer and thus results in the decrease of the resultant matrix size. Furthermore, we employ a new integral approach to establish the boundary condition on the finite element terminating surface. The expansion of the fields on the integration contour is not related to the fields on the terminating surface, hence we obtain an explicit expression of the boundary condition on the terminating surface. Using this explicit boundary condition with the finite element solution, our method substantially improves the computational efficiency and relaxes the computer memory requirements. Only one matrix inversion is needed through our formulation and the generation and storing of a full matrix is not necessary as compared with the conventional hybrid finite element methods. The validity and accuracy of the formulation are checked by some numerical solutions of scattering from two-dimensional metallic cylinders, which are compared with the results of other methods and/or measured data.

High- and low-reflection Bragg gratings with a flat-top spectral response free from ripples are proposed. Add/drop filters are created based on gratings photoinduced on planar waveguides by using the new design schemes. The measured spectral responses for the high and low reflection gratings are in good agreement with the calculated ones, and show the flat-top spectral responses.

Two new algorithms are introduced, respectively called syndrome erasing and double syndrome decoding, which permit to achieve fast error correction with a wide class of cyclic codes.

A technique for generating the standard EM fields with arbitrary wave impedance at the center of a TEM cell is proposed in this letter. We can realize the experimental system and obtain the measured results to agree well with the calculated results. This technique is useful for the EMS test and the calibration of EM probe because the wave impedance can be easily adjusted only with step attenuator.

A new type of fiber Fabry-Perot interferometer buried in a fiber connector housing was proposed. The transmission spectra revealed double peaks due to birefringence in the fiber and the peak separation showed a temperature dependence as large as -7. 7 MHz/deg, which was 2 orders of magnitude larger than that estimated from the thermal characteristics of its component materials.

We discuss the uniqueness of 3-D shape reconstruction of a polyhedron from a single shading image. First, we analytically show that multiple convex (and concave) shape solutions usually exist for a simple polyhedron if interreflections are not considered. Then we propose a new approach to uniquely determine the concave shape solution using interreflections as a constraint. An example, in which two convex and two concave shapes were obtained from a single shaded image for a trihedral corner, has been given by Horn. However, how many solutions exist for a general polyhedron wasn't described. We analytically show that multiple convex (and concave) shape solutions usually exist for a pyramid using a reflectance map, if interreflection distribution is not considered. However, if interreflection distribution is used as a constraint that limits the shape solution for a concave polyhedron, the polyhedral shape can be uniquely determined. Interreflections, which were considered to be deleterious in conventional approaches, are used as a constraint to determine the shape solution in our approach.

The structure of bidirectional syndrome decoding for binary rate (n-1)/n convolutional codes is investigated. It is shown that for backward decoding based on the trellis of a syndrome former HT, the syndrome sequence must be generated in time-reversed order using an extra syndrome former H*T, where H* is a generator matrix of the reciprocal dual code of the original code. It is also shown that if the syndrome bits are generated once and only once using HT and H*T, then the corresponding two error sequences have the intersection of n error symbols, where is the memory length of HT.

It is shown from the Hilberts theory that if the real function Π(θ) has no zeros over the interval [0, 2π], it can be factorized into a product of the factor π+(θ) and its complex conjugate π-(θ)(=). This factorization is tested to decompose a real far-zone field pattern having zeros. To this end, the factorized factors are described in terms of bicomplex mathematics. In our bicomplex mathematics, the temporal imaginary unit "j" is newly defined to distinguish from the spatial imaginary unit i, both of which satisfy i2=-1 and j2=-1.

We propose a mechanically tunable passively mode-locked semiconductor laser with a high repetition rate using a simple configuration with a moving mirror located very close to a laser facet. This scheme is demonstrated for the first time by a novel micromechanical laser consisting of an InGaAsP/InP multisegment laser with a monolithic moving micro-mirror driven by an electrostatic comb structure. The main advantage of this laser is the capability of generating high-quality mode-locked pulses stabilized by a phase-locked loop (PLL) with low residual phase noise in a wide repetition-rate tuning range. This paper describes the basic concept and tuning performances utilizing the micromechanical passively mode-locked laser in 22-GHz fundamental mode-locking and in its second-harmonic mode-locking.

The H-polarized diffraction by a wedge consisting of perfect conductor and lossless dielectric is investigated by employing the dual integral equations. Its physical optics diffraction coefficients are expressed in a finite series of cotangent functions weighted by the Fresnel reflection coefficients. A correction rule is extracted from the difference between the diffraction coefficients of the physical optics field and those of the exact solution to a perfectly conducting wedge. The angular period of the cotangent functions is changed to satisfy the edge condition at the tip of the wedge, and the poles of the cotangent functions are relocated to cancel out the incident field in the artificially complementary region. Numerical results assure that the presented correction is highly effective for reducing the error posed in the physical optics solution.

This paper presents a method of analyzing the electromagnetic field inside an equipment housing. The electromagnetic field is assumed to be coming from outside and coupled into the housing through an aperture on the housing surface. The analysis is based on the transmission-line modeling method. Results of the analysis show a good agreement with the results of measurement. Also, it is found that the coupling through the aperture shows peaks at some frequencies that depend almost only on the structure of the housing and aperture and, therefore, can be estimated at the time of equipment design.

Scattering data from radar targets are analyzed in the time-frequency domain by using wavelet transform, and the scattering mechanisms are investigated. The wavelet transform used here is a powerful tool for the analysis of scattering data, because it can provide better insights into scattering mechanisms that are not immediately apparent in either the time or frequency domain. First, two types of wavelet transforms that are applied to the time domain data and to the frequency domain data are defined, and the multi-resolution characteristics of them are discussed. Next, the scattering data from a conducting cylinder, two parallel conducting cylinders, a parallel-plate waveguide cavity, and a rectangular cavity in the underground are analyzed by using these wavelet transforms to reveal the scattering mechanisms. In the resulting time-frequency displays, the scattering mechanisms including specular reflection, creeping wave, resonance, and dispersion are clearly observed and identified.

This paper presents a method to analyze and minimize output errors of 2-D non-separable FIR filters with finite wordlength. Finiteness in the wordlength causes output errors, which can be analyzed in the frequency domain when the statistics of input signals are known. The output errors can be minimized by optimizing responses corresponding to all levels of input impulses. A new ROM-based filter structure is proposed in which the optimized impulse responses are stored in the ROM. The output signals are generated by superposing the impulse responses corresponding to the input levels. Many simulation results confirm that the output signals of the proposed filters have far less errors compared to conventional filters. The hardware size of the ROM-based filters is estimated and compared with that of conventional structures. The proposed structures are more effective than the conventional ones especially when the signal wordlength is short.