Gain saturation of a CW-pumped erbium-doped fiber amplifier for nanosecond pulses

We report on the gain saturation property of an erbium-doped fiber amplifier for high peak 100 ns pulses. Under CW pumping conditions, the 980 nm pump power dependence of the gain saturation is precisely measured. Pump power dependence is discussed by assuming that the pulse width is much shorter than the recovery time of the erbium population inversion.     

Evaluation of TEM samples of an Mg-Al alloy prepared using FIB milling at the operating voltages of 10 kV and 40 kV

Transmission electron microscopy (TEM) samples of an Mg-Al alloy has been prepared using a Ga-focused ion beam (FIB) milling at two different operating voltages of 10 kV and 40 kV to investigate the influence of the FIB energy on the sample quality. The fine structures of the samples have been studied using a high resolution TEM, and the concentration of the implanted Ga was analysed using an energy dispersive X-ray (EDX) analysis. The result of the TEM observation revealed that point defects were introduced to the sample finally milled at 40 kV but not at 10 kV. However, crystal lattice images and electron diffraction patterns were clearly observed on both the samples. The typical influence of the FIB energy was indicated in the elemental analysis. The relative Ga concentration in the thin sample finally milled at 10 kV was 1.0-2.0 at% that is less than half of 4.0-6.0 at% of the Ga concentration in the sample finally milled at 40 kV. A comparison between the experimental results of the Ga concentration measurement with simulation was also discussed.     

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.     

Multimedia processors

This paper describes large-scale-integration programmable processors designed for multimedia processing such as real-time compression and decompression of audio and video as well as the generation of computer graphics. As the target of these processors is to handle audio and video in real time, the processing capability must be increased tenfold compared to that of conventional microprocessors, which were designed to handle mainly texts, figures, tables, and photographs. To clarify the advantages of a high-speed multimedia processing capability, we define these chips as multimedia processors. General-purpose microprocessors for workstations and personal computers (PCs) use special built-in hardware for multimedia processing, so the multimedia processors described include these modified general-purpose microprocessors. After reviewing the history of programmable processors, we classify multimedia processors into five categories depending on their basic architecture. The categories are reduced instruction set computer (RISC) microprocessors for workstations, complex instruction set computer microprocessors for PCs, embedded RISCs, low-power digital signal processors (DSPs), which are mainly used for mobile communications devices, and media processors that support PCs for multimedia applications. These five classes are then grouped into two: microprocessors with a multimedia instruction set and highly parallel DSPs. An architectural comparison between these two groups on the basis of Moving Picture Experts Group decoding applications is made, and the advantages and disadvantages of each class are clarified. Future processors, including “system on a chip,” and their applications are also discussed     

Efficient use of frequencies in terrestrial ISDB system

Requirements for a terrestrial ISDB system and the schemes for efficiently using frequencies to fulfil the requirements are discussed. One requirement of a terrestrial ISDB system is the efficient allocation of frequencies using a SFN (single frequency network). The SFN incorporates the great advantages of OFDM, which has excellent performance under multi-path conditions. The transmission characteristics of 64QAM-OFDM and the SFN capability using 64QAM-OFDM in the Kanto area, including the Tokyo metropolitan area, are analyzed. The results show that more than a 97% coverage ratio can be obtained even by using a single channel while the same area is covered currently by more than 30 analog channels. The other requirement is a scheme for efficiently using the available frequency band for various services. A transmission scheme concept called BST-OFDM (band segmented transmission-orthogonal frequency division multiplexing) is proposed as a transmission scheme for meeting the requirements of a terrestrial ISDB system. In the BST-OFDM scheme, data are transmitted in a number of OFDM blocks called a BST-segment, for which channel coding and modulation schemes can be independently defined to provide robustness in the transmission environment according to stationary, portable and mobile reception     

A 322 MHz random-cycle embedded DRAM with high-accuracy sensing and tuning

A 16 Mb embedded DRAM macro in a fully CMOS logic compatible 90 nm process with a low noise core architecture and a high-accuracy post-fabrication tuning scheme has been developed. Based on the proposed techniques, 61% improvement of the sensing accuracy is realized. Even with the smallest 5 fF/cell capacitance, a 322 MHz random-cycle access while 32 ms data retention time which contributes to save the data retention power down to 60 /spl mu/W are achieved.     

THREE‐DIMENSIONAL SEISMIC GEOMORPHOLOGY OF PALEOKARST IN THE CRETACEOUS MACAÉ GROUP CARBONATES,CAMPOS BASIN,BRAZIL

Three‐dimensional seismic data from an oilfield in the Campos Basin, SE Brazil, was used to characterize a karstified unconformity surface at the top of the Albian – Cenomanian Macaé Group. Macaé Group carbonates underwent intense karstification associated with subaerial exposure during a period of some 10 to 15 Ma resulting in the development of canyons, valleys, sinkholes and cave systems. The carbonates host commercial oil accumulations at a number of important oil fields. Understanding how the karstification process has affected the carbonates' reservoir properties is essential for future exploration, not only to improve recovery rates but also to avoid drilling‐related issues such as thief zones. In this context, this study aims to characterize the top‐Macaé Group paleokarst system by investigating the morphology of the associated reflectors recorded on seismic data, together with endokarst features in the underlying carbonate succession such as cave systems and collapse structures. The top‐Macaé Group seismic horizon can be divided into two principal geomorphological domains: highlands, characterized by abrupt relief with well‐developed erosional features; and lowlands, marked by a smoother topography. Collapse sinkholes occur in both domains and take the form of closed circular depressions. The study of endokarst features from an analysis of amplitude anomalies (bright spots) indicates the presence of heterogeneous cave systems. The interpreted data contributes to a better understanding of the spatial distribution of the paleokarst system in the Macaé Group carbonates and may assist with future hydrocarbon exploration in the Campos Basin.     

Crosstalk Countermeasures for High-Density Inductive-Coupling Channel Array

Inductive coupling among stacked chips in a package enables 1 Gb/s/channel data communications. Array arrangement of the channel increases data bandwidth, while signal may be degraded by crosstalk. In this paper, crosstalk is measured and analyzed, and crosstalk countermeasures are discussed. Received signal waveforms through the inductive coupling are measured by embedded voltage detectors on a test chip. Interference-to-signal ratio (ISR) has good agreement between the measurements and calculations. It is found that crosstalk is reduced negligibly at a certain distance. If the channels are arranged at intervals of this distance, ISR is minimized. A technique based on time interleaving is also proposed to further reduce crosstalk. A 3times17 channel array is implemented with the crosstalk countermeasures. The channel pitch is taken down to 50 mum. Inter-chip communication with data rate of 1 Gb/s/channel and bit error rate (BER) lower than 10^-9 is demonstrated     

Criteria for versatile GaN MOVPE tool:high growth rate GaN by atmospheric pressure growth

Growth rate has a direct impact on the productivity of nitride LED production.Atmospheric pressure growth of GaN with a growth rate as high as 10μm/h and also Al_0.1Ga_0.9N growth of 1μm/h by using 4 inch by 11 production scale MOVPE are described.XRD of（002） and（102） direction was 200 arcsec and 250 arcsec, respectively.Impact of the growth rate on productivity is discussed.     

The equivalent transmission-path model-a tool for analyzing errorfloor characteristics due to intersymbol interference in Nakagami-Ricefading environments

Land mobile radio systems such as car telephones and handy personal terminals used outdoors have enjoyed a remarkable evolution. To design reliable mobile radio systems, however, it is vital to have a good understanding of the impact of wave propagation characteristics on digital transmission quality in a wide variety of mobile radio environments. A very simple but general scheme for calculating irreducible bit error rate (BER) (namely, BER floor) due to intersymbol interference in frequency-selective Nakagami-Rice fading environments has been developed. The scheme, which we call the equivalent transmission-path model, plays a role in connecting wave propagation with digital transmission characteristics in a general manner. Through computer simulations assuming various types of delay profiles, we first identify key parameters of Nakagami-Rice fading dominating principally the occurrence of irreducible errors and we develop a simple method for the calculation of irreducible BER utilizing the nature or the key parameters. Then we examine the accuracy of the scheme for various types of phase-shift keying (PSK) transmission systems. Finally, based on the scheme, we show calculation examples of BER floor characteristics in line-of-sight fading environments