Completion of a $3 million campus network in three months is result of an electrical contractor's becoming a telecommunications installation specialist.

Princeton Theological Seminary in Princeton, N.J., has a state-of-the-art, fiber-optic, backbone network that allows Gigabit Ethernet transmission speeds for data transfer. To upgrade transmission speeds from 10 Mbit, network consultant Charles Everet, Applied Automated Engineering, Penington, N.J., specified a new 12-fiber, loose-tube, gel-filled cable backbone to interconnect 40 buildings, located on two separate campuses, in a star topology. (A layout of 27 three-story residential apartments and a multipurpose building containing the data center and main distribution frame are located on one campus. The second cluster, consisting of 12 networked school buildings, is about a half mile away.) The 12-fiber indoor-/outdoor-rated cable consists of eight 62.5/125 micron multimode fiber strands and four 50/125 micron single-mode fiber strands. A multiplexed, T1 (1.554 megabit per second), copper-based telephone line serves as the network bridge, connecting the two sections of the fiber-optic network.

The old network backbone could not support the continuing demand for high data rates. From this, the network consultant recognized the limitations of the EIA 568-based copper cable. This was, and still is, a powerful argument for the installation of the high-capacity medium, which may serve as the network backbone on the two sections of the campus for many years.

Underground raceway details. For the most part, Powers Electric Co. Inc., Bordentown, N.J., installed the optical fiber backbone cable in an existing underground conduit system at the school campus, which covered about six square blocks. However, at the larger apartment complex, the contractor dug over three miles of trenching to place banks of Schedule 40 PVC rigid conduit at a 4-ft burial depth.

Trenching allowed installers to lay PVC pipe into place separated by spacers, depending on the quantity of pipe per trench. Once the pipe was in place, Powers covered the duct bank with fill and restored the landscape.

Powers selected a 4-ft burial depth because the school campus has a layout of concrete encased steam pipes (for central heating purposes) with the bottom of the encasement at a 3-ft depth. The apartment complex also has a layout of buried heating pipes, although they're scheduled for replacement. Thus, throughout the campus, the duct banks are below any of these steam lines as well as below gas and water utility lines.

Powers prepared the layout of duct banks and 14 manholes at the housing campus using a CAD program, which integrates with other project drawings. The number of bends between manholes generally has a maximum limit of 180 degrees.

After the installation of all duct runs, the contractor carefully measured the length of each cable that would extend from the network origin point to the entry point of each building, allowing sufficient extra cable (about 28 ft inside the building for termination and a storage loop).

Although it considered placing inner duct within the PVC plastic conduit, the contractor rejected its use after the New Jersey State Department of Transportation offered its experience of being unable to maintain watertight integrity at joints with innerduct in conduits. Also, it was easier for electricians to make up sweeps and bends with plain conduit sections.

Backbone cable installation details. All optical fiber cables came to the job site on self-supporting cable reels, factory preterminated, and with a pulling eye at both.

Packaging protected each terminated-fiber strand, making it easy to prepare the pulling lines used to place the cables and avoid any damage during the installation. Type SC connectors terminated all fiber-optic cable strands. (Because owner Gabby Dibaczy had no experience with fiber terminating and lacked the equipment for doing it, he appreciated receiving all the cabling tested and ready for installation. However, since completing the school project, he set up a "clean room" in his shop for preterminating optical fiber cable. He also has a new panel truck fitted out to perform the same function in the field.)

Building entry details. An optical fiber cable coming into a building enters what is called a vertical integration array (VIA) modular cross connect system. This system supports any type of media and cabling. The cabinet design allows for future expansion as the cabling system changes, and it simplifies cabling management when patching and setting up the cross connection of distribution cables.

The cabinet (frame) is about 16 in. high. The individual cabling modules slide into the chassis vertically. Since the ports are oriented vertically on individual cards, the installer can put different media side by side, instead of on top of one another. This vertical alignment of distribution ports allows the fiber cable to fall in the same plane as the concentrator (hub) ports, which are usually mounted just above. The patch cords don't overlap or cross over the face of the chassis to create a mess of patch cord wires.

For handling Cat. 5 twisted pair copper cabling, the module has 24 data connector cutouts and a grounding bar.

Later on, the contractor found the VIA frame could conveniently accommodate coaxial cable, in addition to fiber and twisted pair conductors. During the project, Powers also received a contract to install a closed-circuit TV system throughout both campuses. The contractor assigned single-mode fiber strands in the backbone cable to carry the CCTV signals. As shown in Photo 3, on page 68, Powers pulled a blank module cover and installed a TV conversion module for the RG-6 coaxial cable runs at each VIA frame. If the contractor had used horizontally mounted patch panels instead, it would have had to install a 96-port F coupler panel.

At the rear of the frame, installers can neatly organize entering cabling and secure them with multiple tie-down hardware points.

Interior cabling details. Powers installed a variety of cable conveyance systems within the buildings to support the cabling runs, which depended on the building materials and surfaces encountered in each space. In particular, surface metal raceway runs are widely used for outlet device runs in classrooms. As shown in Photo 4, below, they're also used in larger area cross section sizes to protect cable bundles above and below dropped ceilings.

The contractor installed a mock-up of a two-channel, surface metal raceway system in an empty apartment for approval before it began wiring all of the apartments.

During the roughing-in phase, Powers took care not to bend the cabling too tightly, pull too hard, or otherwise damage the cables.

At a desk or workstation location, the contractor terminated the horizontal distribution cable at appropriate media outlets.

Powers tested the FO cabling system for end-to-end attenuation using an optical light source and power meter. In this process, a technician tests each fiber segment individually to determine if any losses occurred during installation. In addition, Powers used an optical time domain reflectometer (OTDR) tester to locate and measure power losses at a connector, splice point, or other components.

The contractor also tested all Cat. 5 UTP data cables using appropriate handheld testers and recorded the test results for inclusion into final client reports.

Powers' technicians are trained and certified by the manufacturer of the network communication equipment, the cable management systems, and cable conveyance systems. The contracting firm also purchased the fiber optic cable from the same manufacturer.

Compliance to standards. This project complies with the three most important telecom standards currently in use. The first, EIA/TIA-568A Commercial Building Telecommunications Wiring Standard, covers the planning and installation of building wiring and the selection of media. The second, EIA/TIA 569 Commercial Building Standard for Telecommunications Pathways and Spaces, covers the pathways, or routes, carrying the telecom wires and cables, and the related equipment rooms. The third, EIA/TIA-606 Administrative Standard for the Telecommunications Infrastructure of Commercial Buildings, deals with the documentation of cables, termination hardware, cable pathways telecommunications closets, and other telecommunication spaces, along with grounding.




Sidebar: Ethernet Delivered Over Optical Fiber

Ethernet only gets bigger, better, stronger and faster (especially faster) as it ages. It's a bus-based network and is the most widely used type of four established network architectures [including Token Ring, Fiber Distributed Data Interface (FDDI), and Asynchronous Transfer Mode (ATM)].

Ethernet originally began with coaxial cable as the primary bus cable, but optical fiber has replaced coaxial cable to extend the usable distance. It uses a "one transmit, all receive" operational method. Ethernet versions using fiber include 10Base-F (10 Mbits/sec) and 100Base-F (100Mbits/sec), as well as the 1000Base-SX and 1000Base-LX (1 gigabit per second) standard for short- and long-wavelength applications, respectively. The 1000Base-LX can carry 1Gbps Ethernet over 3-km distances. The 1000Base-SX can carry 1-Gbps over 500-m distances.

Three factors may drive this growth. First, the most critical one is the ability of gigabit Ethernet to work within existing topologies - especially in network backbones - without requiring infrastructure overhauls. Secondly, demands for network bandwidth are increasing. Thirdly, the technology offers the potential to simplify network design and management by displacing traditional routers in many situations.