High receiver sensitivity at 10 Gb/s using an Er-doped fiber preamplifier pumped with a 0.98 mu m laser diode

The authors report the realization of an extremely high receiver sensitivity at 10 Gb/s by using an erbium doped fiber (EDF) preamplifier pumped with a 0.98 mu m laser diode. The obtained EDF input sensitivity is -37.2 dBm (147 photons/bit). In addition, the importance of minimizing reflection from amplifier fiber ends is shown.<>     

Japan telecommunications at the crossroads

Changes introduced into telecommunications by digital technology since 1985, (when the Japanese Nippon Telegraph and Telephone Public Corp. was turned from a Government-owned monopoly to a private company, Nippon Telegraph and Telephone Corp. (NTT)) have led to a call for completely revamped approach. The main concern is to solve the problems of unequal competitive conditions existing between new common carriers and a single dominant carrier. The nature of the abovementioned changes is examined, and a proposal to split NTT into one local telephone company and one toll company is discussed, focusing on its possible effects     

Optimal queueing discipline for real-time traffic at ATM switchingnodes

Queueing disciplines at asynchronous transfer mode (ATM) switching nodes handling various kinds of real-time traffic are investigated. ATM can support various new services including voice, data, and video. However, the characteristics of superposed traffic carried by ATM are not known, and a control effective for a versatile arrival process is required. The optimal discipline which minimizes the number of cells being delayed beyond the specified maximum allowable time, and thus being discarded is derived, without assumptions on the arrival process of cells and buffer management schemes. Also discussed is implementation of the optimal discipline and a method of satisfying cell loss probability requirements of individual classes     

A novel low on-resistance Schottky-barrier diode with p-buried floating layer structure

A novel low on-resistance Schottky-barrier diode (SBD) structure with a p-buried floating layer is demonstrated by fabricating 300-V SBDs using a buried epitaxial growth technique. The fabricated SBDs realize a 50% reduction of chip area and show a possibility of higher breakdown voltage SBD of over 100 V. In addition, both the low on-resistance and the soft-recovery characteristics can be realized by the p-buried floating layer structure. The demonstrated structure is very attractive for reduction of power dissipation without electromagnetic interference noise increase.     

High energy-resolution electron energy-loss spectroscopy study of the electric structure of double-walled carbon nanotubes

Electron energy-loss spectra were obtained from two double-walled carbon nanotubes (DWCNTs) with an energy resolution of 85 meV. The spectra showed multiple peak structures between 2 and 3 eV. However, peak positions are different for these two DWCNTs. The chiral indices of CNT layers of the two DWCNTs were determined to be (29,4)(in) (17,8)(out) and (46,6)(out) (26,21)(in), respectively, by comparing experimental electron diffraction patterns with simulated ones. The spectra were also compared with simulated joint density of states, which were derived from the determined chiral indices. It was confirmed that the peak structures in the spectra are due to interband transitions intrinsic for tubular structures of graphitic sheets.     

Amplitude-division three-electron-wave interference for observing pure phase objects having low spatial frequency

A new interferometry is presented for direct visualization of pure phase objects having low spatial frequency, such as electromagnetic microfields. A thin crystal of silicon prepared using argon ion milling is installed at the standard specimen position. This silicon crystal works as an electron beam splitter and forms diffraction spots in the back focal plane. Using the objective aperture, [000], [111] and [111] spots are selected as coherent electron sources to illuminate the specimen located at the area-selecting aperture position. The lattice image of silicon is formed below the area-selecting aperture position by decreasing the electric current of the objective lens. Three defocused images of the specimen are observed in the fluorescent screen by overexciting the first intermediate lens. We have successfully visualized equipotential lines around a latex particle charged by electron beam irradiation. The computer-simulated image was consistent with the experimental image.     

0.15-μm RF CMOS technology compatible with logic CMOS forlow-voltage operation

Radio Frequency (RF) CMOS is expected to replace bipolar and GaAs MESFETs in RF front-end ICs for mobile telecommunications devices in the near future. In order for the RF CMOS to be popularly used in this application, compatibility of its process for high-speed logic CMOS and low supply voltage operation are important for low fabrication cost and low power consumption. In this paper, a 0.15-μm RF CMOS technology compatible with logic CMOS for low-voltage operation is described. Because the fabrication process is the same as the high-speed logic CMOS, manufacturability of this technology is excellent. Some of the passive elements can be integrated without changing the process and others can be integrated with the addition of a few optional processes. Mixed RF and logic CMOS devices in a one-chip LSI can be realized with relatively low cost. Excellent high-frequency characteristics of small geometry silicon MOSFETs with low-power supply voltage are demonstrated. Cutoff frequency of 42 GHz of n-MOSFETs, which is almost the same level at that of general high-performance silicon bipolar transistors, was obtained. N-MOSFET's maintained enough high cutoff frequency of 32 GHz even at extremely low supply voltage of 0.5 V. Moreover, it was confirmed that degradation of minimum noise figure for deep submicron MOSFETs with 0.5 V operation is sufficiently small compared with 2.0 V operation. These excellent high-frequency characteristics of small geometry silicon MOSFETs under low-voltage operation are suitable for mobile telecommunications applications     

A 1.71-million transistor CMOS CPU chip with a testable cachearchitecture

A 1.71-million transistor CISC CPU chip for the business computer has been developed. The chip is implemented in a 0.8-μm CMOS double-polysilicon double-metal technology. The 16.3-mm×12.7-mm device contains a 16-kilobyte cache and 192 entries TLB and operates at 40 MHz. The sustained high performance in a complexed instruction set has been realized by a large horizontal microprogram that controls two 32-b ALU's. The cache and TLB employ a 77-μm² SRAM using load resistors formed by the second polysilicon; these are accessed in one-half clock cycle and are tested at an 8 bytes per clock rate utilizing a new test strategy     

Oscillation center frequency tuning, quantum FM noise, and direct frequency characteristics in external grating loaded semiconductor lasers

Simple analytical expressions for the oscillation frequency, quantum FM noise spectrum, oscillation power spectrum, spectral linewidth, and direct optical frequency modulation efficiency in semiconductor lasers with external grating feedback are presented. Experimental results for the grating loaded AlGaAs lasers are in good agreement with the theoretical predictions. Remarkable reduction in spectral linewidth to less than 50 kHz is achieved by feeding back only 10^-3of the output power. Oscillation frequency stabilization, frequency jump behavior, and reduction in direct optical frequency modulation efficiency are also discussed.     

Semiconductor laser FSK modulation and optical direct discrimination detection

FSK signals are generated in an AlGaAs double heterostructure laser by employing an electrical equalising circuit to compensate for its nonuniform FM modulation characteristics. A 10?9 bit error rate is achieved at a 100 Mbit/s data rate in the optical direct discrimination detection with a Michelson interferometer. The optical FSK discrimination detection performance is studied in terms of receiving signal power level and laser spectral linewidth.