Optical loss increase in optical fibre coated with silicone resin containing Si?D

One possible origin of the loss increase phenomenon with heat treatment at 200°C (H2 evolution from the coating material) has been investigated, using optical fibre coated with silicone resin containing the Si?D group. Although OH absorption at 1.4 ?m increases with 200°C heat treatment, no OD peak is observed. It is suggested that silicone resin containing no Si?H and Si?CH2?CH2?Si groups is appropriate as a coating material as no H2 evolution is present.     

Light modulator using piezoelectric films with waveguides

A light modulator using piezoelectric films based on optical interference of the Mach-Zehnder type has been proposed and demonstrated. The modulator is constructed with two optical waveguides joined to each other at both ends to divide the incident light and to recombine them, and each waveguide is fabricated on a polyvinylidene fluoride (PVDF) film to serve as a voltage-driven phase-shifter.     

Low-power chip interconnection by dynamic termination

A low-power dynamic termination scheme is proposed and demonstrated as a way to reduce power dissipation for high-speed data transport. In this scheme, the transmission lines are terminated only if the signals change. The gate of a switching MOS transistor connected to a termination resistor is driven by differentiating the transmission signal with a resistor and a capacitor. The power dissipation of the terminating resistor can be reduced to 1/5 in the conventional determination scheme, and overshoot can be reduced to 1/5 that in the open scheme. This scheme is promising for use with palm-top equipment, facilitating high-speed low power operation     

K-vector determination of whistler mode signals by using amplitudedata obtained by a spacecraft borne instrument

A straightforward method for determination of k-vector (wave normal) direction of a whistler mode signal observed onboard spacecraft consists in measuring three components of the wave magnetic field with their instantaneous amplitudes and phases. In that method, one needs to send by telemetry a total wave form of a signal, which requires much larger bandwidth than for sending amplitudes only. The present study develops another method of determination of the wave normal direction based only on the amplitude data; the method is checked using Omega signal observations by the Akebono satellite. It should, however, be noted that the sense of k-vector is not determined by this proposed method     

Demonstration of 100 Gbps optical packet switching using header processor based on 48-bit longest prefix matching

Wire-rate packet processing and its energy saving for over 100 Gbps speed of line are major issues to be resolved in optical packet switching (OPS) networks. For that purpose, we newly develop a high-speed, deterministic-latency electronic header processor based on longest prefix matching (LPM) for searching optical packet destination addresses (OP-DAs). This paper reports the successful experimental results of electronic header processing based on LPM search of up to 48 bits and optical switching of 100 Gbps optical packets by the use of the header processor. We demonstrate 48-bit LPM-capable optical packet switching. We also demonstrate IP packet transfer and 32-bit LPM-capable optical packet switching. In the latter demonstration, the 32-bit OP-DA of optical packets is directly copied from the 32-bit destination address of Internet Protocol version 4 (IPv4) packets. This result indicates that OPS networks can be deployed with electronic IP networks by the use of integrated network operation between OPS and IP networks.     

Interactive multimedia communication systems for next-generationeducation using asymmetrical satellite and terrestrial networks

We propose a new concept of a hierarchical network structure for remote education. This system combines broadband satellite networks and simple terrestrial communication networks effectively to meet the demands of point-to-multipoint communications. Remote education experiments have been conducted using the proposed satellite communication networks. The results of network characteristics and degree of satisfaction are discussed. Acceptable communication quality was achieved ensuring an interactive lecture environment     

The influence of dopant species on thermal stability of NiSi film

We investigated the relationship between thermal stability of NiSi films and the implanted dopant species on Si substrates. The most stable NiSi layer appeared on Boron-implanted Si substrate, where the formation of pseudo-epitaxial transrotational structure was observed, just in case that the dose of boron is more than 5e15 atoms/cm². This unique crystallographic orientation of NiSi film on Boron-implanted substrate is a key role of thermal stability because thermal stress at grain boundary can be diminished by peculiar arrangement of transrotational domains, owing to the anisotropy in coefficient of thermal expansion (CTE) of NiSi.     

A New Approach to Suppress the Effect of Machining Error for Waveguide Septum Circular Polarizer at 230 GHz Band in Radio Astronomy

A new stepped septum-type waveguide circular polarizer (SST-CP) was developed to operate in the 230 GHz band for radio astronomy, especially submillimeter-band VLBI observations. For previously reported SST-CP models, the 230 GHz band is too high to achieve the design characteristics in manufactured devices because of unexpected machining errors. To realize a functional SST-CP that can operate in the submillimeter band, a new method was developed, in which the division surface is shifted from the top step of the septum to the second step from the top, and we simulated the expected machining error. The SST-CP using this method can compensate for specified machining errors and suppress serious deterioration. To verify the proposed method, several test pieces were manufactured, and their characteristics were measured using a VNA. These results indicated that the insertion losses were approximately 0.75 dB, and the input return losses and the crosstalk of the left- and right-hand circular polarization were greater than 20 dB at 220–245 GHz on 300 K. Moreover, a 230 GHz SST-CP was developed by the proposed method and installed in a 1.85-m radio telescope receiver systems, and then had used for scientific observations during one observation season without any problems. These achievements demonstrate the successful development of a 230 GHz SST-CP for radio astronomical observations. Furthermore, the proposed method can be applicable for observations in higher frequency bands, such as 345 GHz.     

Gate length scalability of n-MOSFETs down to 30 nm: Comparisonbetween LDD and non-LDD structures

Gate length scalability of LDD and non-LDD n-MOSFETs are investigated in terms of resistance to short-channel effects. Extremely small gate electrodes are delineated using electron beam direct writing and highly selective dry-etching techniques. An LDD MOSFET with As-implanted 15-nm-deep junctions shows a superior scalability down to 30 nm. In contrast, in the case of a non-LDD MOSFET having Sb-δ-doped 18-nm-deep junctions, the drain induced barrier lowering (DIBL) mechanism limits the minimum gate length to around 80 nm, at which favorable device operation is achieved. The difference between built in potential of source/drain junctions (around 0.1 eV) of LDD and non-LDD devices is found to remarkably affect short channel characteristics in the sub-0.1-μm region     

Photodetectors monolithically integrated on SOI substrate foroptical pickup using blue or near-infrared semiconductor laser

We made photodetectors on a silicon-on-insulator (SOI) substrate by a 0.35-μm BiCMOS fabrication process to detect the signal light used in an optical disk system. Investigating their characteristics at two wavelengths, 410 and 780 nm, for different structures, we found that the thickness of the silicon crystalline layer on the insulator strongly affected the frequency response at the longer wavelength, while the cutoff frequency was over 500 MHz for the shorter wavelength. We also simulated the frequency response