Based on the MSN algorithm, an adaptive algorithm capable of controlling antenna patterns by phase weight only is derived. Then, an algorithm for phase nulling convenient in case not needing adaptive weight control is derived. This algorithm with null directions only being the parameter is convenient for pattern synthesis and pattern improvement. Finally, two examples are presented to demonstrate usefulness and validity of the technique.
This paper deals with a popular puzzle known as Hi-Q. The puzzle is generalized: the board is extended to the size nn, an initial position of the puzzle is given, and a place is given on which only one token is finally placed. The complexity of the generalized Hi-Q is proved NP-complete.
Yutaka KATSUYAMA Nobuyuki YOSHIZAWA Yoshiaki MIYAJIMA Hiromitsu INOUE
Tensile strength of heavy metal fluoride glass fibers was investigated. The effect of proof testing on the fiber strength was evaluated theoretically and experimentally. It was found that the strength distribution of the fluoride fiber after proof testing can be predicted, based on the slow-crack growth model. This result enables to extend the cable design for silica fibers to that for fluoride fibers to assure long-term reliability.
Power reflectivity, extinction ratios and scattering loss of optical switches with intersecting waveguides are analyzed and their electrode-length dependence is investingated. The electrode is found to be several hundred microns long if the refractive index variation is about 1%. It is, therefore, anticipated that small size optical switches are realizable.
Transition phenomena associated with synchronization are investigated between van der Pol and hard-mode oscillators with slightly different frequencies interacting through linear coupling. Three types transitions between asynchronous and synchronous states appear, and power law divergence of time describing the transition is observed near the transition point.
Kazuo KOBAYASHI Yasushi TERADA Masanori HAYASHIKOSHI Takeshi NAKAYAMA Hideaki ARIMA Takayuki MATSUKAWA Tsutomu YOSHIHARA
High density and high speed nonvolatile random access memory is described. Using the conventional floating gate EEPROM process, a dynamic RAM cell has been merged into an EEPROM cell. Data stored on the DRAM cell can be backed up by the EEPROM cell. The data transfer between the DRAM and the EEPROM is executed simultaneously on all memory cells on a same word line. An experimental 16 kbit memory has been manufactured by 1.5 µm design rule CMOS process. The cell size is 17 µm17 µm and the chip size is 57.2 mm3.75 mm. The address access time of 100 ns and the page read access time of 20 ns have been achieved. A nonvolatile CAM (Content Addressable Memory) cell will also be proposed.
In this paper we consider efficient algorithms in a semi-dynamic situation, that is, input data are entered one by one while some of them may be deleted on the way and then finally we are required to solve a given problem. We evaluate such algorithms by a three tuple (Ti, Td, Tp) where Ti and Td denote the time needed for insertion and deletion of data, respectively, and Tp is the time for solving a given problem. We present efficient algorithms for several different problems including the convex hull problem, the visible-pair enumeration problem and the visibility region problem.
Katsunori MIYATAKE Shigeaki OGOSE
In high-speed digital land mobile radio communication, frequency-selective fading is the most serious obstacle to high quality transmission radio links. Diversity reception is an effective method to overcome this obstacle. In this letter, a selection combining diversity reception method suitable for coherent QPSK is proposed, and the effect on bit-error-rate (BER) performance under frequency-selective fading is described.
As a candidate for a laser structure which reduces spatial hole burning and provides narrower linewidths, we propose a coupled structure of phase shift DFBs with asymmetric cavity lengths. Mode properties of this asymmetric structure are analysed based on the transfer matrix method. It is found that its threshold gain difference between the fundamental mode and the next higher order mode is about 1.9 times larger than that of the conventional single phase-shift DFB structure, when the asymmetry parameter is optimally adjusted. The linewidth calculation taking into account the spatial hole burning effect predicts that, for a linewidth enhancement factor of α4, the minimum feasible linewidth is about 0.1 MHz, which is three times narrower than what can be achieved by the conventional single phase-shift structure.
Helmut HEIDRICH Detlef HOFFMANN
LiNbO3 switch matrices are attractive devices for small scale optical digital data interchange and service routing. This paper gives an overview on the state of the art of the first generation of photonic switch matrices as well as some future prospects.
Thomas M. HAUFF Albrecht M. OEHLER Matthias MORATZKY Walter E. HEINLEIN Werner STIEB Johann SCHULTE
A three-cladding DFSMF, Ge -and F-doped single-mode fiber was optimized with regard to fabrication tolerances and low bending loss. DFSMF cables and fused DFSMF couplers were realized for use in a low-loss WDM network. A modified refracted near-field technique for the measurement of fused-section refractive-index profiles was developed.
Hiroki MATSUMOTO Zheng TANG Okihiko ISHIZUKA
A novel comparator-based switched-capacitor voltage-to-frequency converter is presented. By using the op-amp as the comparator, it can be operated over wide frequency range. Conversion sensitivity is also insensitive to capacitance ratio and parasitic capacitances between each node and ground.
Ming CAO Yasunari MIYAKE Shigeo TAMURA Hideki HIRAYAMA Shigehisa ARAI Yasuharu SUEMATSU Yasuyuki MIYAMOTO
Lasing action in GaInAs/GaInAsP quantum-wire structure, fabricated by two-step OMVPE growth, electron beam lithography, and wet chemical etching techniques, was obtained for the first time at 77 K with pulsed current injection. GaInAs quantum-wires with size of 10 nm thick and about 30 nm wide were completely separated and embedded in GaInAsP optical confinement layers so as to form a separate-confinement-heterostructure quantum-wire (SCH-QW) laser. The evidence of quantum-wire levels was confirmed by comparing its emission spectrum with that of quantum-film (QF) structure both experimentally and theoretically. The results indicate that there is no serious defects or damages in the laser operation of quantum-wires fabricated by the combination of electron beam lithography, wet chemical etching, and regrowth techniques.
A method for constituting new multiple-simulation-type embedding networks (EM networks) is proposed. These EM networks have the multilayer structure, and each layer can be regarded as an ordinary EM network. By using this method, to constitute the complex EM networks including many different conversion parts becomes much easier, and the number of the required immittance converters decreases remarkably.
Minoru YAMADA Michihiko SUHARA
Generating mechanism of excess noise in semiconductor lasers induced by optical feedback is theoretically analyzed and experimentally examined. In case that the reflecting point is relatively far from the laser, noise gradually increases due to growing up of the external cavity modes with increasing of optical feedback. When the reflecting point is near, the lasing operation turns into unstable state abruptly with relatively large amount of feedback without showing the gradual increase of noise.
Katsusuke TAJIMA Masaharu OHASHI Yutaka SASAKI
Polarization-maintaining optical fibers with Al2O3 doped silica glass as stress-applying parts (SAPs) and fluorine doped silica glass as cladding are investigated. A high modal birefringence of 1.210-3 due to both thermally and mechanically induced stress is achived.
Atsushi TAKADA Kazuo HAGIMOTO Katsumi IWATSUKI Kazuo AIDA Kiyoshi NAKAGAWA Makoto SHIMIZU
Basic characteristics of Erbium-doped fiber laser amplifier (EDFA) pumped by laser diodes with oscillating wavelength of 1.48µm are measured. Unsaturated gain of 26 dB, 3 dB saturation output power of 1 mW, and noise figure of 5.5 dB are obtained. As a result of transmission experiment using the EDFA at 1.8 Gbit/s over 210 km, linear repeater gain of 20 dB is achieved by considering loss of optical band pass filter and power penalty due to degradation of extinction ratio. By using the basic parameters obtained experimentally, maximum regenerative repeater spacing are calculated in a direct detection transmission system with EDFA repeaters. It is clarified that theoretical regenerative repeater spacing of 5000 km can be achieved by using 50 amplifiers with gain of 20 dB and noise figure of 6 dB, including coupling loss of 0.5 dB, at a bit rate of 2 Gbit/s.
Yoshinori NAMIHIRA Yukio HORIUCHI Kiyofumi MOCHIZUKI Hiroharu WAKABAYASHI
Using an interferometric detection technique with AC modulation for searching the interference fringe signal, highly accurate polarization mode dispersion (PMD) measurement with about 0.003 ps/m resolution has been developed, and the PMD measurement in a 60 km-long installed optical submarine cabled fiber is presented. Also, fiber length dependence of PMD and comparison of the interferometric PMD measurement with other wavelength scanning PMD method are described.
Toshiaki SUHARA Hiroyuki ISHIMARU Shogo URA Hiroshi NISHIHARA
Integrated detection optics for magnetooptical (MO) disk pickup are proposed. The pickup consists of a waveguids device, external lenses, a beam splitter and a laser diode. The detection optics is constructed by integrating a trifocal focusing grating coupler and five photodiode elements in a glass-film waveguide on a Si substrate. The design considerations and fabrication are described, and experimental results are reported. The wavelength bandwidth of the devices are discussed in relation to the wavelength instability of laser diode. Although the obtained performances are not sufficient for practical application, the elementary functions, i.e., MO signal readout, focusing error detection and stabilization by multimode LD, were successfully demonstrated in the simulation experiments.
Akio SUGITA Kaname JINGUJI Norio TAKATO Katsumi KATOH Masao KAWACHI
A thermo-optic phase shifter consisting of a thin film heater deposited on a bridge-suspended silica waveguide on a silicon substrate is proposed for reducing electric power consumption of the phase shifter. A successful application to a guided-wave 22 optical switch is demonstrated. The electric power consumption has been reduced to 1/2 to 1/10 depending on the bridge structure.