Tatsuya FUCHIGAMI Yutaka YOKOO Katsunori UGAWA Masaaki KAWASE
Optical loss increase of SP-optical fiber cable at low temperature was investigated theoretically and experimentally. Estimation formula was presented for the relation between excess fiber length and optical loss increase. It was clarified that excess fiber ratio normalized by pipe radius of less than 0.005 was required to suppress optical loss increase at 40 to be less than 0.1 dB for 1 km in cable length.
Osamu SHIMOMURA Kazunobu OHHASHI Yoshitaka SASAZAWA Kazumasa IDE Kisei KOMORI
In the KDP solution Fe3 and Cr3 have a higher content in the crystal separated early. Therefore, it is possible to purify the KDP solution by removal of the crystal separated early as a method contrary to the usual recrystallization method.
A Rayleigh backscattered signal over a 64 km single-mode fiber has been successfully observed by a long-range OTDR utilizing a 1.5µm LD and an InGaAs/InP APD cooled to 0 with a Peltier's thermodevice, which improves 9.0 dB in the detector sensitivity in comparison with a Ge-APD at room temperature.
Hiroshi NISHIWAKI Hiroyuki ARAI Naohisa GOTO
This letter presents an approximate analysis for coupling coefficients of a multi-slotted directional coupler to diagnose propagating modes in an output waveguide of a gyrotron. The coupling coefficients are calculated approximately and verified by a rigorous analysis.
Hajime SHOJI Yasuhiko ARAKAWA Yoichi FUJII
Bistable operation in inhomogeneously excited semiconductor lasers is discussed theoretically considering gain dispersion effects. The results indicate a significant dependence of bistable properties on lasing wavelength when the wavelength is fixed by some selection mechanisms such as distributed feedback structures.
Koichi WAKITA Masashi NAKAO Yuichi KAWAMURA Hajime ASAHI
A large on/off ratio with low drive voltage optical modulation is realized by using waveguide InGaAs/InAlAs multiple quantum well (MQW) structures grown by molecular beam epitaxy (MBE). These waveguide MQW optical modulators have a modulation on/off ratio of 90:1 (19.5 dB) at a driving voltage as low as 2.5 V.
Zukowski's theorem on a monotone onvergence of the Waveform Relaxation (WR) is slightly generalized. The sequence of iterated waveforms in the WR method is proven to converge monotonically for a system where the time derivative of variables reduces to a quase-monotone increasing function by a liner transformation of the variables. This result is then applied to a class of MOS digital circuits, and a sufficient condition on the topology of the circuit and input waveforms is derived such that the sequence of iterated waveforms in the WR method applied to the circuit converges monotonically.
Keiichi UCHIMURA Junji MICHIDA Shinji NOZU Teizo AIDA Hiroshi ECHIGO Tasuku TAKAGI
This letter deals with a newly developed automatic system, which measures the rate of malfunction of digital circuits owing to noise induced by breaking electric contacts. In this system, a personal computer is used for the detection and the count of the malfunction in the digital circuit. Its experimental results are reported here.
Masaaki DOI Minoru KAWANO Isamu KATO Koki SATO
A new fabrication method of a star coupler has been described. It is fabricated by stacking polymer films and then sticking them by a heat press. Using this method, the star coupler can be produced very easily and has square core cross sections. The 5-port multimode star coupler made on an experimental basis has an output power variation of 0.9 dB and an insertion loss of 3 dB.
This paper reviews the experimental data that have been reported since 1980 on long-wavelength (λ1µm) optical reflectometry and discusses the different approaches being used. The principles of both the optical time domain reflectometry (OTDR) and the optical frequency domain reflectometry (OFDR) are presented. The experimental data of 35 technical papers mostly on single-mode OTDR which includes optical source wavelength, launching power, length and type of the test fiber, types of the optical source and receiver, etc, are discussed and classified into three categories as: (1) moderate-distance OTDR using a semiconductor laser diode (2) long-distance OTDR using a Nd: YAG laser and (3) coherent OTDR. The principle of the heterodyne-OTDR and its expected advantages over conventional direct-detection-OTDR are also discussed.
Yasuyuki KATO Toshio OOYANAGI Akihiko ISHIKURA Mitsuru MIYAUCHI
A new stuffing-pulling fusion technique for the mass fusion splicing of single-mode fibers is presented, where the fiber spliced-region is pulled after the fiber end faces are fused and stuffed to each other. The characteristic feature of this technique is that the stuffing and pulling strokes are varied, based on the observation of fiber end face gaps for every splice. This technique can reduce splice loss to a half in comparison with the conventional method.
Hiroo UKITA Yoshitada KATAGIRI
The light output of a injection laser in a short (several µm) external cavity has been investigated both experimentally and theoretically. The amplitude modulation ratio of the light output signal reaches maximum where the drive current is below the threshold lasing current. An antireflection coated (ARC) laser diode is useful in increasing the light signal.
Tatsuki WATANABE Masayuki MATSUMOTO Tekken LI
In most of the voltage-mode CMOS-multiple-valued-logic circuits published so far, distinct voltage levels are used for the logic values and the logical operations are carried out by binary circuits through converting once multiple-valued imputs to binary signals. In this case, encoder circuits are employed for the multiple-valued outputs. Such voltage-mode circuits are not always competitive with binary circuits except for the reduced number of pins for IC realization. In this letter, new CMOS logical-sum (Max) and logical-product (Min) circuits which can perform directly multiple-valued-logic operations without converting multiple-valued inputs to binary signals are presented. As the proposed circuits have the same property of low-power dissipation as usual CMOS inverters, they are suited for binary circuit use as well. In two-input case, each of the logical-sum and logical-product circuits is composed of a pair of PMOS and NMOS transistors and, except for the number of inputs and the circuit-function, the circuit configuration is the same as that introduced by Sugano, Tarui and Asada. The transient characteristics of the proposed circuits obtained by SPICE-2 simulations are shown. In this letter, logical values 0, 1, 2, and 3 are represented by voltage levels 0 V, 2 V, 4 V and 6 V respectively.
Tadashi KATO Ryoichi ARAI Shuichi TAKANAMI
A modified cosine equalization effective for equalizing both amplitude and phase has been developed with a simple circuit. It slims asymmetrical read-back waveforms in digital magnetic recording devices more effectively than without phase equalization.
Takeshi KONDOH Osamu FUJIWARA Kazuo KATOH Takashi AZAKAMI
This letter presents a method for visualizing the 2-dimensional distribution of electrostatic charge, which is based on the principle of the X-ray CT. For confirming the possibility of this method, the focusing images of the simple model are also demonstrated by a computer computation.
Masanobu OHHATA Tohru TAKADA Masayuki INO Masao IDA
A novel level shift circuit for Low Power Source Coupled FET Logic (LSCFL) is proposed that effectively lowers the power supply voltage. Master-slave T-type flip-flops (T-FFs) with reset function using a three level series gate are designed employing the new level shift circuit, and fabricated using the BP-SAINT process. It is demonstrated that this advanced T-FF operates with a power supply voltage of -1.8 V, which is 30% less voltage than the conventional LSCFL.
Coplanar silicon-coupled bridge type Josephson junctions with recessed niobium electrode structure were fabricated with a new planarization process and Josephson current was observed for the device with an electrode spacing of 50 nm. This device structure has potential to a three-terminal supercouductive device controlled by an insulated gate.
Shuichi FUJITA Makoto HIRANO Koichi MAEZAWA Takashi MIZUTANI
A high-speed potential of an n+-Ge gate AlGaAs/GaAs MISFET has been confirmed by a ring oscillator and a frequency divider performances. The circuit was based on SCFL with 1.0 µm gate-length MISFET's. The delay time was 42.4 ps with a power dissipation of 8.9 mW/gate. A maximum toggle frequency of 11.3 GHz with a power dissipation of 219 mW per T-F/F has been achieved at room temperature.
Akira IINO Mikio OGAI Kunihiro MATSUBARA
Sodium and potassium contained in natural silica tubes have been found to migrate into the central part of germania doped silica fiber during drawing process after secondary ion mass spectrometry (SIMS) measurements. Migrated such impurities caused the structural change of germania doped silica glass, which raised hydrogen induced loss increases in infrared wavelength region.
Shinzo MUTO Akitoshi ANDO Osamu YODA Takayuki HANAWA Hirosi ITO
The tuning property of the fiber sheet type dye laser has been studied. When the array of the active fibers doped with a laser dye in a plastic core is pumped by a pulsed N2 laser, the fiber dye laser emission with narrow spectrum is obtained in wide wavelength region.