Transceivers flash at gigabit speeds

Aug. 1, 1995

Transceivers flash at gigabit speeds


The evolution of a desktop computer from a simple data processing box to a high-end development and data manipulation terminal has heightened the need of many companies to install fiber-optic based local area network architectures for more efficient two-way transport.

These LANs offer the capability of real-time information exchange among multiple users and the promise of affordable prices. As the isolation of the personal computer desktop box slowly yields to a dedicated switched circuit network that is locally controlled, new markets have evolved that provide add-on personal computer components and technology solutions to manage the optical links between individual data processing stations and campuswide facilities.

Finisar Corp. in Mountain View, CA, has been developing high-speed data transfer technologies since 1988. It owns several patents that have established short-wave, multimode gigabit optics as a technical standard codified by the American National Standards Institute Fibre Channel Committee in 1993.

Two other major vendors of ultra high-end LAN transceivers include AT&T Network Cable Systems and Ancor Communications Inc. in Minnetonka, MN. Ancor and Finisar have also structured subcomponent agreements with such high-technology companies as Hewlett-Packard Co. and IBM. Similar to other sectors of the microelectronics business, large data communications companies use each others` products and are also key competitors in the marketplace. For example, Terry Anderson, vice president for systems development at Ancor, says, "We are using AT&T chips and Finisar Optics as the framework for our asynchronous transfer mode-compatible Fibre Channel platform."

According to Carl Reeder, a network connectivity consultant in Palo Alto, CA, "Tapping a central server by means of high-speed transceiver modules is more cost-effective than investing in a group of workstation boxes with large amounts of processing power." He also notes that five years ago, "Ethernet was a state-of-the-art application, but does not adequately deal with today`s bandwidth bottleneck issue."

Finisar provides connectivity products that allow transport of data at rates to 2 gigabits per second over multimode fibers capable of covering distances to 20 kilometers. For a speed- comparison check, integrated services digital networks now being nationally promoted by the regional Bell operating companies are capable of data transfer rates approaching 128 kilobits per second.

The building blocks for the 1-Gbit/sec Fibre Channel solution supports a variety of media, including multimode and singlemode fiber and 75-ohm coaxial cable. They address the bottleneck of available bandwidth among clustered workstations, massively parallel mini-computers, mainframes and mass-storage peripherals.

Integrated optical transceiver

Finisar`s FTR-8510 unit, for example, is an integrated optical transceiver that combines a transmitter, receiver and link controller in a 1.5ٴٲ.4-inch package installed on the host platform. This unit is fully compatible with the American National Standards Institute X3T9.3 specification for Fibre Channel. Finisar developed the transceiver for multimode fiber at 850 nanometers for links to 500 meters.

The FTR-1311 transceiver is used for singlemode fiber at 1310 nm for links to 20 km. The singlemode transceiver eliminates a 1-meter fiber pigtail that attaches most singlemode modules to their optical connectors. No bulkhead adapter is needed, and no protection or mounting is necessary for the fiber pigtail.

Ancor`s suite of LAN adapters can handle data transfer rates ranging from 25 megabytes per second to 1.0625 Gbits/sec. The FCS Sbus adapter comes in two versions--266 megabaud and 1.065 gigabaud. Each works across singlemode and multimode fiber and 75-ohm coaxial-cable networks.

The chief technology macro-market competitor to the Finisar LAN solution is 100-megabit-per-second Ethernet architectures. AT&T spokesperson Sam Gronner says that vendors will still be able to squeeze out a lot of life from Ethernet with a switching solution. The limiting factor for Ethernet, however, is that only one user at a time can access the channel, which effectively lowers the available bandwidth by the number of terminals looped in series.

Network bottlenecks

According to Jay Sherfey, manager of high-performance network communications at AT&T Microelectronics Division, "The Fibre Channel gigabit solution overcomes the bottlenecks inherent in today`s networks, where the bandwidth seems to evaporate as the load of the network reaches its daily peak."

The Fibre Channel standard allows multiple users to ship data at 1 Gbit/sec, which, according to Finisar President Jerry Rawls, would "increase available bandwidth by the same number of users connected to the network." Thus, a network of 1000 users with a basic access rate of 1 Gbit/sec could form a network with a total capacity of 1 terabit per second.

"Technology aside," Rawls says, "the value of the application will drive the adoption of hardware." Those key applications have to do with what he terms visualization and simulations. Rawls notes that Fibre Channel is often referred to as SCSI-96 because it is expected to become the successor to the small computer system interface-2 common today in high-performance machines.

According to Reeder, "The slowest part of any company`s local area network today is point-to-point transport, and such companies as Finisar and Ancor have been successful in going up against AT&T to advance solutions for gigabit data transfer." He suggests that tapping a central server by means of high-speed transceiver modules is more cost-effective than investing in a group of workstation boxes with large amounts of processing power.

Key applications for ultra-high-end local area network solutions involve large amounts of bandwidth that are necessary for engineers to share and manipulate the necessary data; 100-Mbit/sec transmissions attainable by means of high-end Ethernet are not suitable for pixel-intensive tasks.

Other applications include image transfer for medical diagnostics (CAT scan and MRIs) where extremely high resolution is required for accurate analysis. High resolution is "bits and color" intensive, and compression algorithms, including Motion Picture Experts Group and Joint Photography Expert Group, may not be satisfactory because of the percentage (albeit very small) of resolution loss that could hinder analysis.

Finisar`s transceiver is platform-neutral, because it can be integrated with an interface/adapter card designed to function with a particular architecture such as that available from IBM, Macintosh and Silicon Graphics Inc. Rawls predicts that the architecture will eventually mature to the point where "on one side it`s native to the computer, and on the other, it`s simply transport."

The limiting factor, however, is that while data can be reliably shipped at 1- to 2-gigabit rates, most standard computers are not capable of processing and storing information at that rate. Rawls says that computer operating systems that can efficiently handle data at 1-Gbit/sec transfer rates still have to be designed.

The good news is that Intel`s Pentium-based systems typically ship with next-generation protocol control information-type buses. A standard PCI slot on a computer can already handle data throughput at 132 Mbits/sec in burst rates, which fits into the parameters built into Finisar`s 1-Gbit/sec capacity (132 Mbits ¥ 8 = 1.056 Gbit/sec peripheral cards). q

Paul A. Palumbo writes from Seaside, CA.

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