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Linking UTP and fiber

When Chrysler designed its new automated truck and four-wheel-drive vehicle transmission plant in Kokomo, Ind., the plan was to put all programmable logic controllers (PLC) and intelligent workstations (IWS) on the overall building network.

The network supports the traditional office automation requirements. Remote facilities - such as the guard station, the energy plant, and the wastewater station - also needed to be connected.

'We were trying to figure how to move the network into the future,' says Martin Papesh, network specialist for Chrysler in Centerline, Mich. His job is to put networks into Chrysler's manufacturing facilities nationwide and to support plant-floor systems.

'We wanted to be positioned to use higher data speeds,' Papesh says. 'We came up with the concept of putting an enclosure up in the steel trusses. The network had to be able to handle both fiber and unshielded twisted pair (UTP).'

On the plant floor, however, Chrysler faced the problem of putting fiber as close as possible to the end devices without running it down columns and incurring the risk of damage to the cable. There also was the challenge of integrating a mixed cabling environment using fiber and twisted pair.

The answer was a media converter placed high above the work area in the trusses. The converter allows short dropoffs of fiber to the devices on the floor.

The network at Chrysler's Kokomo site is designed as a fiber-distributed network, with the main distribution frame (MDF) in the data center. Several intermediate distribution frames (IDFs) are scattered around the facility floor. The MDF is connected to each of the IDFs with 24-strand fiber. Each IDF is linked to individual devices on the assembly area floor with four-strand fiber.

The basic network configuration is a star, with the data center and MDF at the center. The network has been in place for more than a year, although the plant only began full production of transmissions in February.

The distance requirements of such an installation mandated the use of fiber. The lack of noise on a fiber network was an added boost, according to Max Young, data center supervisor for the Indiana Transmission Plant. While the majority of the environment required only 10 Mbps Ethernet initially, Chrysler also looked to fiber to future-proof the cabling system - to build the infrastructure that would manage tomorrow's higher-speed environments today.

In the past, RG-58 coax had been used for the runs from the IDF. With their distance and noise limitations, however, it was not the best solution for future network expansion.

'We could see that 10Base-2 would never get beyond 10 Mbps in the near future,' Papesh says. 'We knew that the future would demand the higher speeds that fiber can support. So we went in that direction.'

James Bundza, network specialist for information services at Chrysler, says Chrysler wanted to build a fiber-distributed network. As part of this network, 24-strand fiber would be pulled across the entire backbone with four-strand fiber for the drop cable. To connect the floor devices (which had twisted pair connections) to the backbone, Chrysler needed a 10Base-T-to-fiber media converter. Chrysler calls the media converters truss enclosures.

The truss enclosures house several 10Base-T to 10Base-FL converters from Transition Networks of Minneapolis. The units convert twisted pair to fiber. The converters are compact: between six and eight of them fit into each of the truss enclosures. Based on Ethernet, they allow the network to be extended up to 2,000 meters on multimode fiber or 20,000 meters on single-mode vs. a standard 100 meters on twisted pair.

Another advantage of the media converters is their low latency when compared to repeaters or other traditional extension devices. Roundtrip delay is only 33 bit times with the Transition converters, well below the Class II rating of 92 bit times for repeaters.

ASSEMBLING A SOLUTION

Chrysler called upon Cadre Corp., Madison Heights, Mich., to manage the installation of the cabling infrastructure. To optimize the fiber deployment, Chrysler designed the distributed-fiber network to have 150 drop cables throughout the manufacturing floor. Each of these drop cables goes to a specially designed conversion rack mounted 30 feet above the manufacturing floor.

Mounted away from the work area, the fiber line is kept out of harm's way, but still provides convenient access for when the network is expanded, says Cadre project manager Mike Savel, who supervised installation of the distributed-fiber network. Each rack supports four media converters or pass-through fiber lines for areas where Chrysler chooses to run fiber directly to the shop floor. Several office areas already have fiber drops.

Because the repeaters are small - 4 x 3 x 1 inch each - several can be nestled into the compact truss boxes without sticking out or using extra space. Most of the truss boxes are 16 x 16 x 6 inches, although some are a bit larger. Papesh says there also are some wireless devices and an independent power supply housed in the truss boxes.

The network includes a number of PCs used for standard business-type office automation, printing, timekeeping, and some programming of the PLCs on the floor.

The IWS and PLCs are on the shop floor. They are connected via fiber or Category 5 through a steel media box to a series of hubs in the equipment floor above via four-strand fiber. A slave unit is directly on the 24-strand backbone that runs to another hub located in the data center. A second hub is run for the office automation network, and a third hub serves as a hot backup.

The secondary units serve as a concentration point for the data. There are nine fiber cards in the hub, each supporting eight drops for a total of 72 floor drops.

Converters connect the IWS devices. Fiber transceivers are used to connect the PLCs. Cadre is proud of the 45 A, 9 V power supply provided for this box. Of the 450 media converters installed, there has been a problem with only one, and 'Transition turned around and replaced that product overnight,' says Savel.

Chrysler installed 6,000 to 8,000 feet of 24-strand fiber and 20,000 to 30,000 feet of 12-strand and four-strand fiber at Kokomo.
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Copyright 1998 Gale, Cengage Learning. All rights reserved.

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Comment:Managed the installation of cabling infrastructure for Chrysler's fiber network
Publication:Communications News
Geographic Code:1U3IN
Date:Sep 1, 1998
Words:1026
Previous Article:Network performance: Cabling test results
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