A new optical limiter system including a viscoelastic polymer waveguide has been studied. The transmittance of this waveguide is changed by the feedback voltage proportional to the optical output power and hence the power of the optical output beam is suppressed to a constant value. Typical characteristics are demonstrated for a polyvinyl-alcohol thin film waveguide with a prism coupling.

This letter proposes a new-type electrostatically-driven fiber-optic micromechanical switch by fabrication of a 32-element switch array and examines its switching performances. Low-loss and high-extinction-ratio characteristics are confirmed.

The objective of this article is to investigate whether or not a network containing one capacitor, one inductor, and three resistors is able to realize a given biquadratic function. This information should be sought before any synthesis procedure is attempted. It is hoped that the technique may be extended to higher order networks.

This paper presents an analytical approach to the error performance of Trellis Coded 8-PSK with Viterbi decoding, over a Hard-Limited (HL) satellite channel. Although an error probability of Trellis Coded Modulation (TCM) depends on the transmitted sequence in general, we treat a sequence independent TCM composed of a convolutional code of rate 2/3 and constraint length 3 combined with 8-PSK. The channel is considerered to be disturbed by up-link and down-link cochannel interference (CCI) apart from both up-link and down-link noise. It is assumed that the system band is sufficiently wide so that the signal and each interference pass without distortion. For the non-Gaussian characteristics of received signal due to the nonlinearity and CCI, the moments of path metric is employed in the analysis. The first event error probability is obtained by the moments with the aid of the Gram-Charlier expansion without the knowledge of the actual probability density function (pdf) of the metric related with the non-Gaussian characteristics. The bit error probability is derived through the transfer function method. Numerical results of coded 8-PSK are presented for both hard-limited satellite channels and linear terrestrial channels with a comparison to uncoded QPSK.

The diffraction losses of transverse modes of a surface emitting laser are studied by beam propagation method and the condition of single mode operation that when the diameter of one side mirror is about 5µm, fundamental transverse mode operation can be achieved, is given.

A simple adaptive scheme is proposed for controlling the length of time-steps for numerical simulation of Hopfield's networks.

Scattering problem of an electromagnetic beam wave by a rectangular pit on a perfectly conducting substrate is rigorously analyzed. The pit is the canonical model of an optical disk pit. The numerical results of the far field patterns are presented for the various pit depths.

An end-coupled stripline filter is analyzed by the current normal mode expansion method. It is shown that the frequency characteristics are well described with finite number of current normal modes which are existed in the frequency range of interest. This fact intimates the possibility of synthesizing the circuit by Foster-type equivalent circuit.

This letter proposes a mechanical single-mode fiber-optic switch which interconnects a pair of probe fibers and pairs of line fibers to perform fault testing. The 16-channel switch array is fabricated and the switching performance is confirmed to be excellent.

This paper presents an analysis of a multi-hole directional coupler attached to an overmoded circular waveguide. The directional coupler is analized as a boundary value problem, and is solved numerically by a virtual cavity method. The approximate analysis of a small hole coupling coefficient is verified by this analysis. Numerical results indicate that the mutual coupling between holes is not negligible for calculating the directivity of the directional coupler.

An optical logic operation is reported which can perform by means of a spatial filtering. As the data encoding for the spatial filtering, the methods which used the diffraction grating is studied.

This study is concerned with modeling an elastomer impact problem when a mass experiences a collision with the contact pad mounted on the underlying linear dynamic structure. The contact pad which consists of the viscoelastic material is modeled by a linear or nonlinear contact stiffness and the analytical form of frequency response obtained by a Fourier spectral analyzer is utilized in modeling the underlying dynamic structure. One linear model and one nonlinear model are introduced and their characteristics are analyzed. The result shows that the predicted impact forces match the measured responses fairly well.

A fully automatic, high-speed splicing machine for optical fiber ribbons has been developed to construct high-count optical cable lines in subscriber loops. Design procedure and detail performance of this machine is discussed in this paper. The developed machine achieves an average splice loss of less than 0.1 dB and a splicing time of about 2 min. for multi-mode five-fiber ribbons.

For investigating the validity of the two exclusion criteria in the ANSI safety guide revised in 1982, this paper examines numerically the specific absorption rate (SAR) in the lossy sphere simulating a human head exposed to the microwave near-fields due to a half wavelength dipole antenna. The SAR patterns on the spherical surface are calculated with respect to the antenna input powers and the frequencies.

This letter clarifies properties of system using squeezed state signal in photon channel with energy loss. It is found that error rate of squeezed state system is always superior to that of coherent state, and that reduction of optimum squeezing parameter is allowed by optimization taking into account loss in comparison with optimization of transmitter squeezed state.

Magnetic, mechanical, and chemical properties of amorphous Co-based alloys (Fe-Co)75(SizB1z)25 and (Fe-Co-Ru)75(Si0.2B0.8)25 having zero magnetostriction were studied for use as recording/playback head cores. Preferable Si/(SiB) ratio (z) for high saturation induction and high permeability is between 0.15 and 0.2. Small addition of Ru is found to improve wear resistance. A suitable alloy (Fe-Co-Ru-Cr)75(Si0.2B0.8)25 for audio heads has been developed with values of B108.2 kG, Hc20 mOe, and µ1(1 kHz)8,000. Comparing with a commercial sendust head, three features of the amorphous-alloy head were observed: high wear resistance, low bias current, and high output level at high frequencies.

The perfect shuffle interconnection is widely used in parallel processing hardware, mostly in multistage configurations. However it is rarely applied to VLSI arrays except for the case of realizing FFT or sorting. This is due to the fact that control methods to load data into cells have not been established yet. VLSI arrays using the interconnection have a potential possibility to realize some kinds of computations more efficiently than ones using other interconnections. This paper analyzes properties of the perfect shuffle interconnection to apply it to parallel computations by VLSI arrays, especially existence of a cell into which a given pair of inputs are loaded and a control method to make pairs on cells are discussed. The properties presented become basis to realize parallel computations by VLSI arrays using the perfect shuffle interconnection.

Image segmentation which identifies the regions of image objects by thresholding gray levels of pixels on the basis of histogram information is treated. The main aim of this paper is to obtain the statistical performance of the image thresholding method whose threshold is determined on the basis of the squared-distortion criterion and Lloyd's algorithm for the normalized gray level histogram. In order to obtain the performance, it is assumed that the normalized histogram is governed by a mixture of generalized Gaussian p.d.f.'s, which provides a wide range of expression as histogram approximations of real images. The performance of the method using Lloy's algorithm is evaluated through the misclassification probabilities for variation of the parameters of the mixed p.d.f. in comparison with optimum thresholding and valley thresholding. Moreover, a discrete histogram model obtained by quantizing the continuous histogram is studied. These results offer us the global and systematic performance of the image thresholding methods.

Spatial color image transmission characteristics in the optical graded-index (GRIN) fibers are investigated in order to transmit two-dimensional spatial images. Color images can be transmitted through the GRIN fibers, when lasers of primary colors with adjusted powers are used at the input of the GRIN fiber and an achromatic optical system is applied at the output. The transmitted images through the GRIN fibers are degraded due to the refractive index profile aberration and chromatic aberration at the wavelengths of the primary colors λ10.442µm (He-Cd laser), λ20.532µm (the second harmonic of the YAG laser) and λ30.694µm (Ruby laser). The profile aberration is related to the coefficient of the fourth order term D4 of the refractive index profile of the GRIN fiber and the color aberration is ascribed to the wavelength dependence of the on-axis refractive index, n0, and the focusing parameter, lt, of the fiber. The minimum focusing depth, i.e. the profile aberration, is achieved for the minimum mode dispersion of a GRIN fiber with D40.8 at each wavelength of the primary colors. Also the minimum distance between the longitudinal positions of the on-axis (χiyi0) and off-axis (χi50µm, yi0) point images in the fiber (D40.8) becomes identical value of about 52µm at three different wavelengths of λ1, λ2, and λ3 for a transmission length of 51.965 m. For the GRIN fiber with D40.8, the longitudinal color aberrations for the on-axis and off-axis point image transmission are almost equal and the fiber does not have lateral aberration for the considered transmission length. The number of propagation modes in a GRIN fiber is different at each wavelength, so that, the intensities of the transmitted images at λ2 and λ3 are smaller than those at λ1. Therefore, the powers of the lasers which are used as of the sources of the primary colors should be adjusted in order to obtain output images with almost equal intensities at the wavelengths. The compensation of the longitudinal aberration for two-dimensional spatial color image transmitted through the GRIN fiber with D40.8 can be achieved using more than two rod lenses of different materials.

The nonuniformity of signal constellation on coded phase/frequency modulation is investigated to obtain further improvement on the error performance over conventional uniformly spaced coded phase/frequency modulation. The analytical method for evaluating the Euclidean distance of nonuniform FSK/PSK signal is presented. In particular, the joint design of m/(m1) systematic convolutional encoders and nonuniform 2FSK/2mPSK are considered, and especially for 2FSK/4PSK and 2FSK/8PSK the behavior of the free Euclidean distance is evaluated by varying the modulation index, the rotation angles which determine the nonuniform signal constellation, and the mapping rule by set partitioning. The results show that by designing compared with the conventional coded uniform phase/frequency modulation may be obtained without increasing average or peak power or changing the bandwidth of the transmitted signals. The maximum value of the free Euclidean distance of codes can be obtained when the PSK signal constellation of one carrier frequency is the same as those of the other carrier frequency, and the mapping rule used in coded uniform FSK/PSK system is not always good enough when the nonuniformity in the signal constellation is introduced.