Data Transfer System Research Articles

Application of the Green Function Method to the Problem of the Temperature Dependence of Characteristics of Vertical Cavity Semiconductor Lasers

In designing modern communication lines, telecommunications, and information processing centers, an important problem is to create laser radiation sources with a wide modulation band, ultra-small size, high efficiency, and low current consumption. In many cases (high-speed transmitters, parallel optical signal processing systems, etc.) it is necessary to produce two-dimensional laser matrices. In modern systems, radiation sources of special configuration are used, namely, vertical cavity surface emitting lasers (VCSEL's), in which the direction of laser radiation is perpendicular to the plane of constituent layers. A laser of this type has numerous advantages: small resonator length (transverse diameter is 1−20 μm), sufficiently high modulation speed, low threshold current (record values are several microamperes), low control current, radiation of a single transverse mode, circular cross-section of the radiated beam, high reliability, high efficiency, and a wide operating temperature range (−50−130° C). Due to the fast development of VCSEL technology and fabrication, it became possible to use these devices in modern data transfer systems [1-3]; therefore, one must seriously study device characteristics, threshold current, transverse mode structure, and temperature properties. VCSEL-based experiments showed that the relaxation oscillation frequency can be as high as 71 GHz. Moreover, the maximum realized modulation bandwidth for devices with oxidized layer is 17 GHz. This band narrowing is related to the internal processes of carrier transport and capture [9]. The width of the modulation band can be increased by increasing the doping level of the active region and suppressing higher-order modes. With increasing current, the lasers of the type considered (VCSEL) begin to radiate multiple modes [4], and this results in the widening of the optical spectrum and restricts the use of VCSEL's in high-speed systems. The authors of [5, 6] explained this feature of the VCSEL operation by the effect of spatial hole burning. This effect modifies the distribution of the refraction factor and amplification in the cavity. Due to the presence of current spreading and the complicated heating process of the device, an appreciable temperature difference between the active region and the substrate appears to give rise to an increase in the refraction factor [7]. It should be noted that the effect of spatial hole burning and the injected carriers affect the behavior of transverse modes in different ways. In this paper we present a method taking account of the laser temperature variation for a model that describes the carrier distribution and optical field inside the cavity.

Fundamentals of videogrammetry — A review

With the advent of inexpensive and powerful CCD- (‘video-’) cameras and associated image data transfer and processing hardware novel measurement systems, based on these components, are of great potential for human movement recording. This contribution gives an introduction to the fundamentals of ‘videogrammetry’, a measurement technique based on the principles of ‘photogrammetry’. We will discuss the concept of the multi-image (more than two CCD-frames) measurement mode, the bundle adjustment with its variants for point positioning, orientation and calibration, the notions of precision and reliability, system aspects including some details on CCD-cameras and image data transfer, calibration and self-calibration, algorithms for high precision image measurements, and finally show a typical application example. Besides being a highly automated measurement technique, videogrammetry provides for high accuracy (a relative accuracy of 1: 10000 can be reached in trajectory determination with standard components) and truly real-time data processing capabilities. In addition, a great number of particles (> 100) can be measured and tracked simultaneously, and surfaces and their deformation can be determined. Therefore, the videogrammetric technique is of great interest for applications in biomechanics, sport, animation, and virtual reality generation and control.

Many hands make light work: optics in the service of instrumentation and measurement

The advance of photonics in the latter part of the 20th Century represents one of the most important developments and a vital aspect of the exploitation of the technology that began with the invention of the laser. The engineer's rather belated response to that technology has now been highly successful in stimulating a range of developments, including optical-fibre technology. The `many hands' who have made light work over the last few decades have contributed a range of devices and techniques to complement optical communications and data transfer systems. This paper gives an overview of their underpinning technology and their development as effective devices and provides pointers to the way forward.

The WA Hospital Morbidity Data System: an evaluation of its performance and the impact of electronic data transfer.

The paper evaluates the performance of the Hospital Morbidity Data System, maintained by the Health Statistics Branch (HSB) of the Health Department of Western Australia (WA). The time taken to process discharge summaries was compared in the first and second halves of 1995, using the number of weeks taken to process 90% of all discharges and the percentage of records processed within four weeks as indicators of throughput. Both the hospitals and the HSB showed improvements in timeliness during the second half of the year. The paper also examines the impact of a recently introduced electronic data transfer system for WA country public hospitals on the timeliness of morbidity data. The processing time of country hospital records by the HSB was reduced to a similar time as for metropolitan hospitals, but the processing time in the hospitals increased, resulting in little improvement in total processing time.

A visual basic program to pre-process MRI data for finite element modeling

Investigators use non-invasive imaging to collect geometric data for finite element models. A preprocessor is described to facilitate model generation of anatomical regions from serial Magnetic Resonance Imaging (MRI) data stored in a bitmap format. The MRI Data Transfer System is a stand-alone Windows-based program developed in VISUAL BASIC 3.0 which generates a NASTRAN input file. The program can be modified to generate input files for other solvers. The software will execute on any IBM-compatible computer which runs Windows Version 3.1 or higher. To demonstrate the software, model generation of a portion of a tibia is described.

Coherent-difference detection of optical radiation pulses

A method for recording radiation pulses by optical mixing of spectrally resolved fields is proposed. The suitability of this method for optical data transfer systems and for determination of the characteristics of ultrashort pulses is considered.

Production prototype of an engineering seismometric observation system

This article describes the ongoing development of an observation and data collection system for seismic effects parameters at hydroelectric power plants. The field sensors and their placement are discussed in considerable detail, as are the means of communicating, processing, and storing the data from the sensors. An operating prototype has been developed and tested, with satisfactory resolution of basic problems. In the prototype, there are two eight-channel digital operating stations. Transducers of types A1632m and A1612 have been successfully tested. A check of the ADC measuring board confirmed the possibility of measurments in the 120-dB dynamic range. The data transfer system was tested with good performance, and the prototype is presently ready to take to the field.

A Trial Installation of a Proposed Standard for an Agricultural Communication System

This paper proposes a detailed standard, covering a bus-based system for data transfer, monitoring and control between a personal computer and sensors and actuators in field crops with a particular view to orchards and vineyards. Specifications that form the standard cover software, protocol, electrical and hardware parameters to ensure compliance in interfacing of items developed by different constructors. Advantage has been taken of the dedicated nature of the application to provide desirable features summarized as ease of software and hardware installation and maintenance and bus powering of field sites. Software meeting the specifications has been developed for the personal computer and field stations and circuits designed and constructed to meet the electrical requirements. The details of a trial installation at a vineyard in Central Victoria, Australia are included.

A study on the development of a filing system for funduscopic images with a personal computer for Twin AMHTS.

A filing system for ocular funduscopic image data was developed by using a personal computer for the Twin AMHTS. The development of the system was tried as one of the data transfer system including image data between two similar AMHTSs named the Twin AMHTS through the information network system. The filing system is capable of storing 26782 data of ophthalmoscopic pictures with a data compression mode by using a magneto-optical disk (MOD) whose storage capacity of both sides is 616 MB. It takes no long time for retrieval and display of the image data in the filing system. Good quality of compression and decompression obtained and reproducibility of the ocular fundus picture is favorable regardless of normal or abnormal cases. As a result, it is suggested that the developed system has practical utility although it requires more improvement.

Ground water control system based on chemical sensors

A quasi-continuous monitoring system for nitrate and ammonium in ground water is described. Both parameters change dramatically in the case of a leakage of a dump site. Due to their cost efficiency and easy maintenance new potentiometric chemical sensors become more evident in the field of continuous control of ground water. The extremely selective and sensitive sensors presented here show an increased long-lasting stability as well as an improvement in the limits of detection. After addition of auxiliary reagents such sensors allow a quantitive and nearly selective determination of nitrate and ammonium. Combined with an appropriate data transfer system a cost effect continuous monitoring system is built working over more than six months without refilling.

Readout control for high luminosity accelerators

In this article we discuss some aspects of data acquisition at high luminosities and offer a set of design principles concerning readout control electronics and related software. As an example we include a brief description of a data transfer and processing system for future hadron colliders, featuring a transputer-based crate controller and a set of readout cards. This is a simplified and more efficient version of our design recently published in Nuclear Instruments and Methods. [A295 (1991) 391].

An 80 Mbytes/s data transfer and processing system

We describe hardware and software aspects of a very fast and versatile, yet conceptually simple, data transfer and processing system for use with future accelerators. It consists of a transputer-based crate controller (CC), which includes an Intel i860 microcomputer, and of a set of readout cards (RC), each containing a digital signal processor (DSP) for fast data parametrisation and compaction. The reduced data is written into a dual port memory (DPM), where it can be accessed concurrently by the transputer and transferred to a common DPM on the CC card. A crateful of data thus assembled at one place can further be processed by the powerful i860 microcomputer. Address generators (simple binary counters) are included on the crate controller and each readout card to enable direct memory access (DMA) operations, resulting in a considerable increase in data transfer speed (maximum 80 Mbytes/s). The use of a transputer as the sole controlling processor, in conjunction with DPMs, renders bus arbitration unnecessary, leading to very simple interfacing logic and operating software. The four high-speed serial links of the transputer greatly facilitate downloading of programs and intercrate communications. An Intel i960CA processor, situated on the CC card, is used for fast data transfer between crates by means of its 32-bit wide DMA channel. The operating software is written in the Occam language, which was specially developed for programming concurrent systems based on transputers.

New nibbled-page architecture for high-density DRAMs

A nibbled-page architecture which can be used to access all column addresses on the selected row address randomly in units of 8 bits at the 100 Mbit/s data rate is discussed. To realize such high-speed architecture, three key circuit techniques have been developed. An on-chip interleaved circuit has been used for the high-speed serial READ and WRITE operations. Column address prefetch and WE signal prefetch techniques have been introduced to eliminate idle time between 8 bit units. The nibbled-page architecture has been successfully implemented in an experimental 16 Mb DRAM, and 100 Mb/s operation has been achieved. The DRAM with nibbled-page mode is very effective in simplifying the design of high-speed data transfer systems. >

DATA MULTIPLEX SYSTEM (DMS) —ASPECTS OF FLEET INTRODUCTION

ABSTRACTThe Data Multiplex System (DMS) is a general‐purpose information transfer system directed toward fulfilling the internal data intercommunication requirements of a variety of naval combatant ships and submarines in the 1990–2000 time frame. The need for a modern data transfer system of the size and capability of DMS has increased as various digital control systems throughout naval ships have adopted distributed processing architectures and reconfigurable control consoles, and as the quantity of remotely sensed and controlled equipment throughout the ship has increased manyfold over what it was in past designs.Instead of miles of unique cabling that must be specifically designed for each ship, DMS will meet information transfer needs with general‐purpose multiplex cable that will be installed according to a standard plan that does not vary with changes to the ship's electronics suite. Perhaps the greatest impact of DMS will be the decoupling of ship subsystems from each other and from the ship. Standard multiplex interfaces will avoid the cost and delay of modifying subsystems to make them compatible. The ability to wire a new ship according to a standard multiplex cable plan, long before the ship subsystems are fully defined, will free both the ship and the subsystems to develop at their own pace, will allow compression of the development schedules, and will provide ships with more advanced subsystems.This paper describes the DMS system as it is currently being introduced into the fleet by the U.S. Navy. The results of its design and implementation in the DDG‐51 and LHD‐1 class ships are also presented.

Single-user capabilities in interprocess communication

Many distributed operating systems use interprocess communication (IPC) and data transfer schemes which are optimised for a particular architecture: the workstation/server model. In this model, client processes have full control over data transfer. This paper argues that server controlled data transfer is better suited to systems with a hierarchy of servers distributed across a collection of machines. The system proposed integrates a set of IPC primitives, for the exchange of control information, and a capability system for secure data transfer.

Interface between an optical communications system and the host spacecraft

AbstractThe current state of development of optical communications systems for intersatellite data transfer has reached an advanced level, with on‐orbit operations planned for the early 1990s. The technology and engineering aspects of the development of the optical system have been evaluated in some detail and are widely known, but the interfaces between the optical system and the host spacecraft are not as well understood. Many aspects of the optical interfaces have been identified, are currently under investigation and are discussed here. These include the interface support needed from the host spacecraft, such as thermal, electrical, mechanical, optical, radiation protection and contamination control; spacecraft attitude and vibrational stability; spacecraft level interface testing, such as EMI/EMC, vibration and thermal vacuum tests; and lifetime and reliability testing.

Inter‐Library Loans using TINIend

The previous issue of VINE carried a general description of the integrated library system, TINlib from Information Made Easy, concentrating on the acquisitions, cataloguing and enquiry, circulation and serials control modules. These are now about to be joined by TINlend which has been undergoing site‐testing at, amongst others, the Universities of Sussex, Aston and Durham. TINlend is available as part of the integrated TINlib system or in what the supplier refers to as ‘side‐by‐side’ mode, which is the version installed in the test sites; the aforementioned libraries are, of course, Geac sites and use versions of the Geac Library System for their mainstream automation. The connection with Geac is not accidental: the development of the package was instigated by members of the Geac Library System Users' Group who opted for a microcomputer‐based solution to their ILL automationrequirements. The strategy proposed was to run ILL administration on a micro with appropriate links to the Geac minicomputer system for data transfer. After a couple of false starts, the software development passed to Information Management & Engineering (IME) Ltd who built the system using their TINman database management product according to a detailed specification produced by the Geac libraries. These libraries have, as noted above, been helping test the product, but without any commitment to purchase. The released product is now marketed by the IME subsidiary, Information Made Easy, with the other TINlib applications' software; all enquiries about TINIend should be addressed to IME rather than the test sites.

A 16MB 3.5 inch Ba-Ferrite flexible disk drive with dual track following servo modes

A large capacity high-speed-access 3.5 inch flexible disk drive has been achieved, using a barium ferrite 3.5 inch flexible disk and newly developed sector servo technology. The flexible disk drive has a 16 megabyte unformatted capacity, a 50 millisecond average seek time and a 3 megabit/second data transfer rate. It can use both concentric track disks for conventional computer systems and spiral track disks for high speed data transfer systems, such as hard disk drive (HDD) back-up, image data storing, and so on.

Optical-fibre sensors

Optical-fibre development to date has concentrated on their use in systems for telecommunications and data transfer. The realisation that optical fibres could also be used for sensors and sensing systems has increased rapidly in recent years. Judged by the large number of publications in this area, the research effort is extensive, but few systems have yet been put to practical use. A critical review of recent developments is therefore useful at this stage. Several examples of fibre-optic sensors are given, where their selection has been dependent on the system showing some practical viability, and data having been obtained relevant to operation in a real (as distinct from purely laboratory) environment. Devices ranging from simple fibre-optic switches and pollution monitoring equipment, to highly sensitive acoustic, magnetic and rotation sensing systems are emerging, where an understanding of modal and polarisation effect in single-mode fibres is necessary, At present each sensor system tends to be aimed...

Optical-fibre sensors

Optical-fibre development to date has concentrated on their use in systems for telecommunications and data transfer. The realisation that optical fibres could also be used for sensors and sensing systems has increased rapidly in recent years. Judged by the large number of publications in this area the research effort is extensive, but few systems have yet been put to practical use. A critical review of recent developments is therefore useful at this stage. Several examples of fibre-optic sensors are given, where their selection has been dependent on the system showing some practical viability, and data having been obtained relevant to operation in a real (as distinct from purely laboratory) environment. Devices ranging from simple fibre-optic switches and pollution monitoring equipment, to highly sensitive acoustic, magnetic and rotation sensing systems are emerging, where an understanding of modal and polarisation effects in single-mode fibres is necessary. At present each sensor system tends to be aimed at specific application areas, where the form of acceptance by the user will vary. It is emphasised that such developments require engineering inputs at the earliest possible stage. The use of optical fibres for direct actuation of valves and sensors has now closed the optical control loop.