Larry A. Bergman

A Synchronous Fiber Optic Ring Local Area Network for Multigigabit/s Mixed-Traffic Communication

A synchronous-ring fiber optic local area network is reported that facilitates the simultaneous transmission of packet and real-time traffic at gigabit/s rates, minimizes the amount of high-speed logic, and simplifies the user interface to the network. The novelty of the technique is based on 1) suspending in transit around the rings circumference an integral number of data frames and 2) achieving this condition by skewing the frame clock rate a small amount ( < 1 percent). Rather than use the whole data frame as one packet destined to a specific user (as in a slotted ring), we instead time multiplex many individual channels into the data frame. This technique only becomes feasible for local networks as data rates approach the Gbit/s range. This departure from other synchronous rings results in several advantages both in terms of system performance and hardware simplicity.

Bit-parallel wavelength links for high-performance computer networks

This paper describes a new interconnect and local area network transmission concept for computer communications based on spectrally encoding one or more computer words into a wavelength datagram. At physical and data link level, this system resembles an optical ribbon cable, except that all the bits pass on one fiber optic waveguide. At the network level, such fiber optic link segments can be interconnected all-optically using 2x2 optical switches into ShuffleNet or other architectures that permit a photonic packet to pass from source to destination without being incumbered with the extra delay and bandlimiting associated with electronic switching and regeneration. Unique properties of such a system include low latency (<10ns), very high bandwidth (<100Gbit/s per port), precise time alignment (<10ps) of the individual word bits over km distances, and dynamic scalability to support cluster computing and distributed supercomputing. Novel system elements disclosed in this paper include: (J) a bit parallel wavelength (BPW) fiber optic link that uniquely maintains wavelength channel time alignment, (2) an innovative parallel stepped wavelength optical transmitter that time synchronizes each laser diode element at its optical output, (3) a spectral encoder/decoder that adds fault tolerance and optical message addressing capability, and (4) a technique for transmitting and maintaining time aligned multi-X solitons as parallel bits through fiber media. Applications to teraflop high performance parallel computing and DoD input/output (I/O) bound applications are described.

Overview of fiber optics in the natural space environment

The potential applications of fiber-optic (FO) systems in spacecraft which will be exposed to the space radiation environment are discussed in view of tests conducted aboard the Long-Duration Exposure Facility and the Comet Rendezvous and Asteroid Flyby spacecraft. Attention is given to anticipated trends in the use of FO in spacecraft communications systems. The natural space radiation environment is noted to be far more benign than the military space environment, which encompasses displacement-damage effects due to significant neutron influences

WDM component requirements for bit-parallel fiber optic computer networks

The device specifications for an all optical bit-parallel WDM single fiber link for the cluster computer network community are intended for dissemination to the opto- electronic device research community to stimulate synergy between the two, ultimately leading to early availability of new devices to the computer network researchers. It is also hoped that early adoption of these devices by the research community will promote limited production of these devices by industry. Background information on our investigation of this problem will first be given. Then the detailed design of a long distance all optical bit-parallel WDM single-fiber link with 12 bit-parallel channels having 1 Gbytes/sec capacity is given. The speed-distance product for this link is 32 Gbytes/sec-km. Means to improve this speed-distance product using the pulse shepherding effect will be described. Finally, a detailed description of the BP-WDM component requirements is given.

Remote observing with the Keck Telescope from California using NASA's ACTS satellite

As a technical demonstration project for the NASA Advanced Communications Technology Satellite (ACTS), we have implemented remote observing on the 10-meter Keck II telescope on Mauna Kea in Hawaii from the California Institute of Technology campus in Pasadena. The data connection consists of ATM networks in Hawaii and California, running at OC-1 speeds (51 Mbit/sec) through optical fiber, and high data rate (HDR) satellite antennae at JPL in Pasadena and at the Tripler Army Medical Center in Honolulu. The ACTS network provides sufficient bandwidth to enable true remote observing, with a software environment identical to that used for on-site observing. In this paper, we demonstrate that while the satellite link introduces a number of difficulties and decreases overall reliability of the system, remote observing is not only feasible, but provides several important advantages over standard observing paradigms. Benefits include involving more members of observing teams while decreasing expenses, enhancing real-time data analysis of observations by persons not subject to altitude-related conditions, and providing facilities, expertise, and personnel not normally available at the observing site. Although the current bandwidth of the public Internet is insufficient for true remote observing, we nevertheless anticipate a growing role for remote observing techniques, particularly as high-speed terrestrial networking paradigms, such as ATM, become more commonly available.

Fiber Optic Experiment For The Shuttle Long-Duration Exposure Facility

This paper describes two complementary fiber-optic experiment packages that are under development for orbital exposure on the Shuttle Long Duration Exposure Facility. The intent of the experiment is to take the first step toward providing the experimental confidence and design data necessary for application of optical fiber technology on NASA spacecraft and military. satellites. Four active fiber links will be monitored at predetermined intervals on each experiment, and other components and fibers will be exposed passively. Results from the experiment will be presented in planned future publications.

WDM requirements for high-performance testbeds

This paper describes several high performance computing testbeds being developed for Ballistic Missile Defense Organization applications that are based on high speed wavelength division multiplexed (WDM) fiber optic packet network technology. By combining high speed (> 100 Gb/s per channel), low latency (< 1 us), and scalability, these WDM networks offer the possibility of creating very closely coupled meta-supercomputers for real-time theater defense applications. The testbeds consist of: (1) coarse grain architecture consisting of a few large massively parallel processor supercomputers connected by striped WDM trunks, (2) fine grain architecture consisting of clusters of workstations connected by a fast WDM packet network, and (3) a hybrid satellite/WDM fiber network for global grid. These all-optic networks are expected to enable a number of distributed teraflop applications, such as real- time image fusion, real-time radar signature analysis and modeling, very large scale simulation, and realistic synthetic scene generation. This paper describes these testbeds in more detail and their specific WDM component requirements.

Bit error rate measurement for evaluation of a fiber optic link

Digital fiber optic data link terminal modules are being developed in a number of laboratories, and often the modules take the form of black boxes without convenient access to internal signals. This paper discusses types of measurements which can be made using only the digital terminals of the link. Bit-error-rate (BER) vs signal power data can, of course, provide a means for proving overall link performance, but it can also be used to determine certain internal parameters of the receiver. The theoretical dependence of the BER vs light signal power curve shape on receiver input noise equivalent power and comparator slicing level is discussed. BER vs light signal power measurements obtained with an experimental link are presented and interpreted with the aid of the theoretical curves. The effect of other problems, such as hum or oscillation on the BER data, are mentioned. Sensitivity of the system BER to bit rate is also discussed, with application to determining system operating limits. Since BER measurements are simple to make and can easily be automated, they may prove to be a useful means for either laboratory evaluation or production-line acceptance testing of sealed terminal modules.

New advances in time aligned parallel WDM transmission

For ultra-high-speed single media parallel interconnects, an all optical single fiber WDM format of transmitting parallel bits rather than a fiber ribbon format-where parallel bits are sent through corresponding parallel fibers in a ribbon format, can be the media of choice. Here, we shall discuss the realization of a multi-km x gbytes/sec bit-parallel WDM single fiber link. The distance-speed product of this single fiber link is more than several orders of magnitude higher than that of a fiber ribbon link. The design of a 12 bit- parallel channels WDM system operating at 1 Gbit/sec per channel rate through a single fiber will first be presented. Experimental results for a two channel system operating at that rate are given. Further improvement of distance-speed product for the BP-WDM link can be obtained with JPLs newly developed 20 Gbits/sec per channel laser diode array transmitter. Also, new computer simulation results on how a large amplitude co-propagating pulse may induce pulse compression on all the co-propagating data pulses, thereby improving the shaping of these pulses for a WDM system, will be presented and discussed. The existence of WDM solitons is also shown.

High bit rate ACTS experiments for performing global science - Keck Telescope and global climate model

The ACTS wide bandwidth and high-speed switching provides for the first time the ability to establish nation-wide high data rate networks to control remote, high data rate instruments, process their data in near real-time, and to connect supercomputers for addressing Grand Challenge applications in the High Performance Computing and Communications program. To demonstrate these important satellite networking capabilities, a team is conducting an ACTS experiment entitled High Data Rate ACTS Experiments for Performing Global Science. Two elements are included in the experiment. In the first, remote astronomy will be conducted from the Caltech campus to the Keck telescope on Mauna Kea, Hawaii. In the second case, a distributed global climate model simulation will be run on a meta-supercomputer. (Author)