Fabrication of GaInAsP/InP heterostructure lasers for 1.5 µm wavelength region by organometallic vapor phase epitaxy are discussed. Results of growth conditions, which were experimentally found important to obtain the low threshold current density (1 kA/cm2) comparable with LPE at 1.5 µm lasing oscillation are reported, such as gas switching at hetero-interfaces, maintenance of constant temperature over the growth of all layers, selection of carrier gas and doping conditions. Furthermore, OMVPE device techniques for buried heterostructure laser operating at CW condition are described. Fabrications and characterization of quantum well structure are also reported.

The single fundamental transverse mode condition, both in three-layer DH, and asymmetrical five-layer separate confinement heterostructure (SCH) laser diodes operating at 1.55 µm wavelength, has been investigated based on the effective refractive index. The simple derived formula can be applied to obtain the effective refractive index of the dominant mode in DFB laser diodes to determine the corrugation period corresponding to the designed wavelength.

This paper investigates convergence properties of a circuit simulation technique called Waveform Relaxation (WR). A general formulation of a family of WR algorithms called a generalized WR is introduced. This formulation reduces to some hitherto introduced WR algorithms in particular cases. The following two sufficient conditions for the generalized WR method to converge locally are given: ) the capacitance matrix of the circuit is block strictly diagonally dominant and a time-steplength is sufficiently small; ) the conductance matrix of the circuit has the same property and a time-steplength is sufficiently large.

The self-mixing type laser Doppler velocimter gives a simple method of directional velocimetry. The beat signal comprises the fundamental Doppler frequency as well as its harmonics, so that the waveform is like a sawtooth in which the sign of inclination reverses as the target changes the direction of its movement.

It is reported firstly that spatial filtering of laser beam by a receiving optical system such as a finite-aperture detector causes harmonic distortions of a directly modulated semiconductor laser diode when the beam irradiance is reflected partially at the submount. The theory based on geometrical optics for interference of directly emerging light and reflected light is developed and the numerical results are presented for a variety of laser structures and FM-modulation parameters.

Let G be a simple graph and α be an automorphism of G. A spanning tree T of G is said to be α-invariant if α is also an automorphism of T. We give a necessary and sufficient condition for a connected graph G to have an α-invariant spanning tree.

We show some properties of the parallel bubble sort and propose three parallel sorting algorithms on the mesh-connected processor array. These algorithms are some combinations of the parallel bubble sorts in different directions. The hardware structure and control for these algorithms are simple. These abgorithms seem to be asymptotically slower than O()-time parallel sorting algorithms. However, our computer experiments show that two of our abgorithms are faster on the average than any known algorithm on the mesh-connected model for N16384.

A new parallel algorithm for the numerical integration of ordinary differential equations is proposed. The algorithm is based on the predictor and corrector formulae and their iterative use. An equation which describes the error propagation of the proposed algorithm is derived and discussed. The reliability and convergence properties of the solutions are studied by performing the numerical experiments on a conventional computer system for some specific examples. It is found that the proposed algorithm is indeed a practical one for a concurrentt system such as a multiprocessor and a vector processor, and offers much greater computing speed than the existing algorithms.

Planar buried heterostructure GaInAsP/AlGaAs visible lasers emitting at 674 nm in wavelength fabricated for the first time and operated under room temperature pulse condition. The low threshold current of 80 mA and the output power of 5 mW/facet were obtained.

In 1978, Merkle and Hellman published two kinds of knapsack type public key cryptosystems, one of which was super-increasing type and the other was multiplicative type. However, the former was broken by Shamir in 1982 and latter was broken by Odlyzko in 1984. Recently, Chor and Rivest proposed a new multiplicative knapsack type cryptosystem based on arithmetic in GF (ph) which cannot be broken by the Odlyzko attack. This paper shows the new cryptosystem is broken if the public knapsack vector has three elements whose values are close to one another or if the primitive polynomial is known. We also present that not only the original secret-key also many other ones can decipher the cryptosystem.

In view of educational technology, we will make here a report on an education-material graphics which supports the development of sheet-type education materials such as transparency materials, instructional materials and the like. In science education there are many cases where diagrams used resemble if the disciplinary fields are analoguous with each other. Especially, with respect to demonstration experiments, there are not a few cases where a certain limited number of diagramatic units are combined variously and after modifications a diagram can be completed approximately. Based on these diagrammatic characteristics, we determine the graphic functions and definite the figure-data constrution so as to increase the productivity of material development. In this study, we also derive diagrammatic characteristics in science instructional materials mainly from chemical experiment models and determine the design criteria of education-material graphics.

This paper describes a design method of linear phase recursive FIR digital filters. The basic structure consists of a transversal part cascaded with a cyclotomic resonator, which is characterized by cycotomic polynomials and has no multipliers. The digital filters implemented by this method require the short wordlength both for multiplier coefficients and for signals in their transversal part. By introducing integer arithmetic, the filtering operation proceeds fast and exactly. As a bonus, it is possible to employ a multiplier-less implementation in most practical applications. While the stability of this type of structure requires an integer-valued impulse response, a satisfactory procedure assures the requirement. A parameter to control the approximation error is found somewhat predictively rather than tentatively.

The stage method used in the analysis of traffic or reliability models causes an increase in the number of state. For example, the k2-stage Erlang distribution is used to approximate the general type of distribution which has a coefficient of variation β1/k (ex. the 100-stage Erlang distribution is used for β0.1). This paper proposes a new type of stage method that needs only two stages to approximate a general distribution with arbitrary coefficient of variation β(0β) and presents some useful applications.

This letter compares an integration scheme with a segregation one for a loss system having two types of traffic. As a result of this comparison, the conditions under which the overall blocking probability of an integration scheme is lower than or higher than that of a segregation scheme are given.

This letter clarifies properties of cutoff rate R0 of photon channels using coherent state and photon number state as quantum state of light. The relation between cutoff rate improvement and energy saving rate is found, when one uses the number state instead of coherent state.

A PL (piecewise-linear) series kernel analogous to the Dirichlet kernel in the trigonometric series is introduced. With the aid of this kernel, some of the properties of the truncated PL series are deduced.

We present a pipeline-interval-optimum systolic implementation of priority queues which can handle usual priority queue operations at every cycle.

Primary silicone-rubber/secondary liquid-crystal-polyester (LCP)-coated optical fibers have loss increases as low as 18 dB/km even at liquid uitrogen temperatures. This result can be explained by both low contraction and the buffer effect against heat shock of the secondary LCP layer which results in less fiber bending.

Application of liquid crystal polymer (LCP) materials, having a higher Young's modulus than usual plastic materials, to optical fiber jackets and unit central members has been investigated. Novel optical fiber units thus constructed are found to exhibit ultra low thermal expansion coefficient and no optical loss change within 6060 range. Zero thermal expansion coefficient can be achieved over the wide temperature range by suitable combination of LCP materials with high and medium Young's moduli.

The BER performance of a BPSK system with sounder in the fast Rayleigh fading and cochannel interference environment is analyzed by means of the characteristic function of the decision statistic and calculating the residue, and compared with that of a DPSK system. The results show that the BPSK system with sounder can remove random FM effectively from the received fast fading signal even in the presence of cochannel interference. In addition, the optimum power distribution between the BPSK signal and sounder which minimizes the BER and the effect of a post-detection diversity are theoretically clarified.