In this paper we review the recent progress and basic technology of vertical cavity surface emitting lasers together with related parallel surface operating optical devices. First, the concept of surface emitting lasers is presented, and then currently developed device technologies will be reviewed. We will feature several technical issues, such as multi-layer structures, 2-dimensional arrays, photonic integration, etc. Lastly, future prospects for parallel lightwave systems will be discussed.

In this paper we study the problem of scheduling a tree-structured program on multiprocessors so as to minimize the total execution time, which includes communication delay between processors. It is assumed in the problem that a sufficiently large number of processors are available. It is known that if the program structures are restricted to be out-trees, the problem can be solved in O(n2) time, where n denotes the number of modules of a program. However, this problem is known to be NP-hard if the program structures are allowed to be in-trees. Up to now, no optimal algorithm, except an obvious one, was known for the latter case while some approximation algorithms were shown. We present an optimization algorithm with a nontrivial time bound O((1.52)nn log n) for the in-tree case.

In this paper we review the recent progress and basic technology of vertical cavity surface emitting lasers together with related parallel surface operating optical devices. First, the concept of surface emitting lasers is presented, and then currently developed device technologies will be reviewed. We will feature several technical issues, such as multi-layer structures, 2-dimensional arrays, photonic integration, etc. Lastly, future prospects for parallel lightwave systems will be discussed.

A rigorous theoretical method for predicting "ratio of desired signal power to interference power [c/i]" and "ratio of signal power to noise plus interference power [c/(n+i)]" where both desired and interference signals vary with time under the Nakagami-Rice fading conditions is presented. An alternative simple prediction method which is more desirable from the viewpoint of engineering application is then proposed. Prediction errors given by the simple method are evaluated by comparing to the errors given by the rigorous method, and it is confirmed that the simple method gives reasonable accuracy. This method is expected to serve in the development of frequency re-use technologies and the coordination of various systems for mobile satellite communications in the near future.

Transmittance distribution along a horizontal line in LCDs addressed by amorphous silicon TFTs was investigated using measurements and calculations. Nonuniformity of the distribution, in which the transmittance increased with increasing distance from the left edge of the LCD, was observed in a 10 inch diagonal TFT-LCD. The cause of the nonuniformity was attributed to the decrease in voltage drop due to the gate source parasitic capacitance and the increase in gate voltage fall time due to large line resistance, based on the measurements of voltage drops in TFT test elements and calculations considering the decrease in voltage drop. The distribution could be improved by reducing the line resistance and parasitic capacitance in the actual LCD.

A fast Viterbi decoding technique with path reduction in optical channels is presented. This decoding exploits the asymmetric characteristic of optical channels. In the decoding trellis, the branches with low or no possibility being correct path are eliminated based on the detected signal level. The number of Add-Compare-Select (ACS) operations which occupy the dominant part of Viterbi decoding is considerably reduced due to branch eliminations, and fast decoding is realized by decoding asynchronously to received sequence. The reduction of the number of ACS operations is derived for the codes with rate 1/2. It is shown that the number of ACS operations is considerably reduced compared with the conventional Viterbi decoding. The bit error probability of the proposed decoding is derived for noiseless photon counting channel. It is also shown that the decoding technique can be applied to the cases using avalanche photo diode (APD) based receiver with dark current noise at a cost of negligible degradation on the bit error probability.

We review the role of optics in interconnects, analog processing, neural networks, and digital computing. The properties of low interference, massively parallel interconnections, and very high data rates promise extremely high performance for optical information processing systems.

This paper presents a new connected associative memory neural network. In this network, a threshold function which has two dynamical parameters is introduced. After analyzing the dynamical behaviors and giving an upper bound of the memory capacity of the conventional connected associative memory neural network, it is demonstrated that these parameters play an important role in the recalling processes of the connected neural network. An approximate method of evaluationg their optimum values is given. Further, the optimum feedback stopping time of this network is discussed. Therefore, in our network, the recalling processes are ended at the optimum feedback stopping time whether a state energy has been local minimum or not. The simulations on computer show that the dynamical behaviors of our network are greatly improved. Even though the number of learned patterns is so large as the number of neurons, the statistical properties of the dynamical behaviors of our network are that the output series of recalling processes approach to the expected patterns on their initial inputs.

This paper proposes a knowledge-based design method of a protocol of a communication network system based on the knowledge-based design methodology for computer communication systems. In the proposed method, two knowledge models, i.e., the communication network architecture model (CNAM) and the communication protocol architecture model (CPAM), are introduced and a protocol design task is modeled as a successive transformation process of these knowledge models. Giving CNAM which represents the users' requirements concerning a communication network system, the requirements specification of a protocol is derived from CNAM and represented as CPAM. Then, the detailed requirements specification of a protocol is also derived from CPAM and represented by the formal description technique (FDT-Expressions). The derivations of CPAM and FDT-Expressions are executed by the transformation rules which represent the mappings between knowledge models. Due to formally defined knowledge models and mappings, the proposed method provides a framework of a systematic support of knowledge-based protocol design. In this paper, the formal definitions of CNAM and CPAM are given, then the derivation process of FDT-Expressions of a protocol is also formalized based on these knowledge models. Furthermore, a design example is demonstrated by using LOTOS as one of the FDT-Expressions of a protocol.

A new MOS linear operational transconductance amplifier (OTA) for the up-to-4 MHz range OTA-C filters is proposed. The proposed OTA is designed using a new linearizing technique based on bias-current modulation, to compensate nonlinearities in the transfer characteristic of the conventional current-source-biased source-coupled pair. The design and SPICE simulation are presented in detail, assuming the implementation by the typical p-well CMOS process. The simulation of a 3.58 MHz OTA-C band-pass filter built with the proposed OTAs showed close agreement with the desired performance.

This article briefly looks at the future of telecommunication education in the universities as it evolves from present concerns and trends. Five year bachelor's programs and top-down curricular design will be common. Textbooks supplemented by advance organizers, instruction and testing according to individual learning styles and global integration of education using multi-media services and broadband technology will be some of the other features. Finally, the importance of industry-university partnership in all aspects of engineering education is emphasized.

We propose Polarization-Shift-Keying (POLSK) homodyne system using phase-diversity receivers and theoretically analyze its bit-error-rate (BER) performance. Since the proposed system uses polarization modulation and homodyne detection, it can cancel the phase noise and is attractive at a high bit-rate transmission. It is found that the receiver sensitivity of the proposed POLSK homodyne system is the same as that of POLSK heterodyne system and is much better than that of DPSK phase-diversity homodyne systems at high signal-to-noise ratio (SNR). We also cosider theoretically the effect of the fluctuation of state of polarization (SOP) on the BER performance of POLSK homodyne system.

The heterointerfaces of Al0.3Ga0.7As/GaAs single quantum wells (SQWs) and the characteristics of SQW lasers grown on Si substrates with Al0.5Ga0.5As/Al0.55Ga0.45P intermediate layers (AlGaAs/AlGaP ILs) entirely by metalorganic chemical vapor deposition (MOCVD) are reported. The effects of thermal cycle annealing on the crystallinity and the lasing characteristics of GaAs/Si are also reported. By using the AlGaAs/AlGaP ILs, SQWs with a specular surface morphology and a smoother heterointerface can be grown on a Si substrate. Thermal cycle annealing is found to improve the crystallinity of GaAs/Si and to contribute to room-temperature continuous-wave operation of lasers on Si substrates. The combinations of the techniques of AlGaAs/AlGaP ILs and thermal cycle annealing improve the lasing characteristics: an average threshold current density of 1.83 kA/cm2, an average differential quantum efficiency of 52%, an internal quantum efficiency of 83%, an intrinsic mode loss coefficient of 23cm-1, a differential gain coefficient of 1.9cm/A, and a transparency current density of 266 A/cm2, which are superior to those of the two-step-grown laser on a Si substrate. The improvements of the lasing characteristics result from the smooth heterointerfaces of the AlGaAs/AlGaP ILs.

The characteristics of a LiNbO3 light modulator using the resonant YBa2Cu3Oy superconducting electrode were studied on the basis of the calculated results of surface resistances and transmission losses. The two-fluid model and the conventional transmission theory were used for the calculations. It was found that the modulation depth of this modulator using the YBCO electrode at 77 K was 7.5 times that using the Al electrode at room temperature. The drive voltage for the phase modulation of π radians was estimated to be a very low value of 2.3 V.

The VSTEP concept and its practical application in the form of an LED-type pnpn-VSTEP demonstrating low power consumption through electro-photonic operational modes are both shown. Further, with focus primarily on the new laser-mode VSTEP with high-intensity light output and narrow optical beam divergence, the design features such as threshold gain and optical absorptivity, device fabrication, and characteristics are explained. The possibility of ultimate performance based mainly on electrical to optical power conversion efficiency, important from the application viewpoint of optical interconnection, are also discussed. Also, as two examples of functional optical interconnection achieved by VSTEP, serial-to-parallel data conversion and optical self-routing switches are shown. Finally, future opto-electronic technologies to be developed for two-dimensionally integrable surface-type optical semiconductor devices, including the VSTEP, are discussed.

In this paper, some classes of arithmetic circuits are introduced that capture the computational complexity of computing the determinant of matrices with entries either indeterminates or constants from a field. An arithmetic circuit is just like a Boolean circuit, except that all AND and OR gates (with fan-in two) are replaced by gates realizing a multiplication and an addition, respectively, of two polynomials over some indeterminates with coefficients from the field, and the circuit computes a (formal multivariate) polynomial in the obvious sense. An arithmetic circuit is said to be skew if at least one of the inputs of each multiplication gate is either an indeterminate or a constant. Then it is shown that for all square matrices M of dimension q, the determinant of M can be computed by a skew arithmetic circuit of (q20) gates, and is shown that for all skew arithmetic circuits C of size q, the polynomial computed by C can be defined as the determinant of a square matrix M of dimension (q). Thus the size of skew arithmetic circuit is polynomially related to the dimension of square matrices when it is considered to represent multivariate polynomials in both arithmetic circuits and the determinant. The results are extended to some other classes of arithmetic circuits less restricted than skew ones, and by using such an extended result, a difference and a similarity are demonstrated between polynomials represented as the determinant of matrix of relatively small dimension and those polynomials computed by arithmetic formulas and arithmetic circuits of relatively small size and degree.

We propose parallel rate-variable punctured convolutional coded PPM in photon communication to achieve high energy information efficiency Ie for desired bit error rate (BER) and transmission bandwidth. We theoretically show the BER performance, bandwidth expansion factor β and necessary Ie to achieve BER10-6 of the proposed systems for some combinations of code rates. It is found that the proposed system can achieve high Ie for desired BER and β by selecting a suitable combination of code rates depending on the channel conditions. Moreover, it is showm that the proposed system has better BER performance than RS-coded PPM in the range of small β.

We propose Polarization-Shift-Keying (POLSK) homodyne system using phase-diversity receivers and theoretically analyze its bit-error-rate (BER) performance. Since the proposed system uses polarization modulation and homodyne detection, it can cancel the phase noise and is attractive at a high bit-rate transmission. It is found that the receiver sensitivity of the proposed POLSK homodyne system is the same as that of POLSK heterodyne system and is much better than that of DPSK phase-diversity homodyne systems at high signal-to-noise ratio (SNR). We also cosider theoreically the effect of the fluctuation of state of polarization (SOP) on the BER performance of POLSK homodyne system.

The heterointerfaces of Al0.3Ga0.7As/GaAs single quantum wells (SQWs) and the characteristics of SQW lasers grown on Si substrates with Al0.5Ga0.5As/Al0.55Ga0.45P intermediate layers (AlGaAs/AlGaP ILs) entirely by metalorganic chemical vapor deposition (MOCVD) are reported. The effects of thermal cycle annealing on the crystallinity and the lasing characteristics of GaAs/Si are also reported. By using the AlGaAs/AlGaP ILs, SQWs with a specular surface morphology and a smoother heterointerface can be grown on a Si substrate. Thermal cycle annealing is found to improve the crystallinity of GaAs/Si and to contribute to room-temperature continuous-wave operation of lasers on Si substrates. The combinations of the techniques of AlGaAs/AlGaP ILs and thermal cycle annealing improve the lasing characteristics: an average threshold current density of 1.83 kA/cm2, an average differential quantum efficiency of 52%, an internal quantum efficiency of 83%, an intrinsic mode loss coefficient of 23 cm-1, a differential gain coefficient of 1.9 cm/A, and a transparency current density of 266 A/cm2, which are superior to those of the two-step-grown laser on a Si substrate. The improvements of the lasing characteristics result from the smooth heterointerfaces of the AlGaAs/AlGaP ILs.

We study the computational power of PC=P. We give a characterization of the class via single Turing machines. Based on the characterization, we give combinatorial problems that are Pm-complete for the class.