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Select the right hardware: a good interconnection strategy takes time and study.


Integrating fiber optics into the latest system designs is becoming popular for premises communications wiring. In addition to basic point-to-point links, fiber is being incorporated into backbone wiring applications such as:

* channel extensions and PBX nodal links;

* data and voice multiplexing such as 3270, T1, and RS-232;

* and local-area networks (LANs) such as Token Ring, Ethernet, and emerging Fiber Distributed Data Interface (FDDI) standards.

The cabling plant is an important element of the premises communications, system. It serves as the transmission highway for the system electronics.

The cabling plant includes fiber-optic cable, cable assemblies, connectors, splices, interconnection hardware, and testing instruments.

In order to specify fiber-optic hardware, you must first determine cable fiber count and routing design. Required at all splice points and cable termination points, this hardware includes splice closures, trays, organizers, cabinets, patch panels, and wall outlets. A flexible interconnection system using the proper hardware allows for future growth and easy reconfigurations.

Interconnection hardware should accept different types of cables and splices, and be compatible with all types of OEM computer systems.

All types of commonly used fiber-optic connectors should fit in the hardware--including the ST-compatible, Biconic, FC, D4, and SMA. Though the ST-compatible connector is emerging as the de facto standard in the premises industry, other connector types are required with some equipment.

The hardware construction should also be considered, as the unit's main function is to store and protect splices and terminations. The minimum bend radius of fiber-optic cables must be maintained, and adequate cable strain relief points are needed. Labels on the hardware serve as system records, so that interconnection documentation can be completed right on the units.

Ungradeability is a must. With advancements in premises communications systems, hardware is required to take a system all the way to the desk-top--from the highest-fiber-count patch panels to information outlets at the workstation.

Outside Plant Hardware

Outside plant products should be capable of withstanding environmental conditions. Hardware may become damp, wet, or directly exposed to weather conditions while still protecting splices and connectors.

The most commonly used outdoor hardware is the splice closure, used to protect fiber-optic splices. The splices are generally considered permanent connections that are rarely, if ever, remade. Closures are designed for use in buried, underground, or aerial environments. When assembled, the closure is completely sealed from moisture by use of sealing tape, cords, and paste.

The consideration of fiber count and the use of multi- or single-mode fiber are the major determining factors in closure selection. Closures are available in a wide range of sizes, from low to high fiber counts, to accommodate different requirements.

In many instances, closures require specially designed tools such as drills, tensioning tools, and closure measuring tapes. Siecor has modified the standard closure to allow installation using only standard tools. This simplifies the procedure and shortens installation time.

Outside plant products are also needed in areas where moisture may be a factor, such as in parking garages or basements. A wall-mountable product, such as Siecor's Outside Building Entrance Terminal, is needed to house splices or to house connectors.

For areas that may flood, splice closures are required. Generally these will be used for splice points but can accommodate terminations as well.

The building entrance terminal is best suited for wall mounting where limited environmental protection is needed.

These housings should store either splices or connectors.

Both indoor and outdoor hardware sometimes require splice trays at points where splices are stored.

Fiber-optic splice trays used to organize and protect splices are designed to ensure the minimum fiber bend radius is maintained.

They should be able to store various splicing methods, including both mechanical and fusion splicing.

Intrabuilding Hardware

For indoor hardware, first identify the termination method to be used. Options include pigtail splicing, preconnectorization, factory connectorization, field connectorization, and direct selicing. The selection of the best, most cost-effective method for your system should be carefully considred. Siecor supports all these methods, identifying advantages and tradeoffs for each.

Secondly, determine the mounting location of your hardware. Products are designed for rack mounting, wall mounting, and workstation applications. The rack-mounted hardware generally is installed in a standard 19-or 23-inch equipment rack or cabinet. Rack space normally is available in locations where communications equipment is installed--equipment rooms and computer rooms, for example. Wall-mounted hardware is installed where rack space is not available, and space is at a premium. Such locations include wiring closets and satellite closets. The workstation products allow fiber-optic outlets to be installed directly at the desk. This permits jumpers to adapt to workstation equipment.

Thirdly, identify the fiber count for your system, allowing for current needs as well as future system upgrade. Modular products permit room to grow and rearrange the system.

Intrabuilding hardware is used in the main distribution frame at the building entrance, riser wiring closets, floor and satellite wiring closets, and in the workstation area.

The main distribution frame often serves as the demarcation point between the outdoor cable and indoor cable. Hardware here houses the highest fiber counts in the building. In most instances, the rack-mounted hardware is used. Units can be field-terminated, shipped prewired with interconnection sleeves and pigtails mounted in modules and routed to the splicing area, or shipped with pre-connectorized multi-fiber cables installed.

Sometimes it is applicable to have hardware at this location which can accommodate both splices and connectors. For example, the Siecor Fiber Distribution Frame can serve as a cross-connect or interconnect point. The FDC patch panel serves as an interconnection and splice point.

From the main distribution frame, proceed to riser locations. Riser wiring closets are the drop points for riser cables on each floor. Hardware here stores and protects terminations used at the individual floors. Typically, fiber counts will be 12-36 fibers. Direct connectorization may be more feasible in these wiring closets, to permit easy rearrangement and upgrade when needed. Rack or wall mounting may be used, depending on the application's requirements. Often space is limited in these closets. Siecor usually recommends a patch panel here, such as the Cabinet Mounted Interconnect Center, to support both splice and connector use.

The floor wiring closets and satellite wiring closets on each floor are the remote points for wiring to each workstation. "Closet" may actually be a misnomer in many instances, as the hardware often is not located behind a closed door. This remote wiring site may be on an office wall, so security is important. The hardware at a satellite closet is usually mounted on a wall. Aesthetics can play a role here, so the units must be low profile. Typical fiber counts are 12 per satellite.

System rearrangement must be easy, so features such as access to the connectors from the front and back of the unit are valuable. Strain relief provisions and fiber-retaining guides are helpful, and a lockable hasp helps ensure system security.

Though connectors will most often be used because of the need for easy system rearrangement, some applications may call for splicing. Indoor splice points are similar to the splice closure point, without the environmental protection. They provide cable strain relief, buffer tube or cable sub-unit storage, and a mounting provision for splice trays. Knockouts on all corners allow for multiple cable entry locations.

Once in the work area or at the workstation, an interconnection device to house a few connectors for each desk is required. This low-cost, low-profile unit must blend into the office aesthetics. Up to four fiber connections to accommodate both voice and data communications are usually required. Easy and safe rearrangement must be accommodated.
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Copyright 1990 Gale, Cengage Learning. All rights reserved.

Article Details
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Author:Hawkins, Paul D.
Publication:Communications News
Article Type:tutorial
Date:Mar 1, 1990
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