Structured Wiring System Primer |
APPENDIX |
The scope of this structured wiring system primer is specific to a single building location. For this primer, the building has 4 floors with approximately 100 users per floor. FIGURE C-1 depicts the sample building layout and cabling distribution viewpoint.
The following design criteria will be used as a guideline for designing a structured wiring system within this single building location:
When designing a horizontal workstation cabling system, first obtain a floor plan. The second step is to calculate the maximum physical distance from the wiring closet to the workstation outlet. This ensures you are within distance limitations for the type of cabling used. FIGURE C-2 shows a sample building floor plan and design approach.
A structured wiring system has six foundational building blocks—building cabling entrance, data center or equipment room, backbone cabling, telecom room/wiring closets, horizontal cabling, and workstation/office location. This primer reviews each building block and provides guidelines for what you need to assess, design, and implement them.
Prior to the AT&T divesture and breakup in 1984, the term Bell entrance referred to the bundled, twisted-pair cabling entering the building with proper electrical protection and grounding. The actual physical path into a building was a metallic conduit entering into the bottom floor of a building. Inside of the metal conduit was the bundled, twisted-pair cabling from the central office telephone switch. With new construction, the building entrance is a metallic conduit path providing a physical path into the building. Service providers install fiber optic cabling bundling voice, TV, and Internet. A cable path or conduit path may be needed to extend from the Bell entrance to the data center or equipment room.
The building has a single metallic conduit that acts as the building entrance for outdoor cabling. A data center resides on the basement floor where all cabling is terminated. Termination of a copper wire means a physical connection is made between the actual copper wire and wiring block (e.g., a 66-block for terminating voice copper cables or a 110-block for terminating data copper cables onto RJ-45 patch panels). The local service provider has brought in two separately sheathed fiber optic cables with multiple strands each. These fiber cables support bundled voice, data, and Internet connectivity for the entire building.
The outdoor fiber cabling must extend to the data center or equipment room where the fiber optic cabling can be terminated with SC connectors in a fiber optic patch panel. This is shown in FIGURE C-3.
The building will typically have a clean room, data center, or equipment room. This centrally located room will house computer equipment, network equipment, and the building’s backbone cabling system. Battery backup, redundant network switches, and generator backup power are part of the environmental controls needed to support a highly available network.
Note the network side rack on the left in FIGURE C-4 and the workstation cabling side rack on the right. Cross-connections are made via an RJ-45 patch cable between the Layer 3 PoE+ switch and the workstation cabling.
If VoIP is used, there is no need for copper backbone cabling unless analog phone lines are needed in various locations. Multimode and single-mode fiber cables are typically installed from the data center to each wiring closet, providing long-term growth and high-speed backbone connections (10GigE, 40GigE, 100GigE, etc.). Bundled unshielded twisted-pair cabling in 25-pair, 50-pair, or 100-pair is needed only if a wired digital phone system is utilized.
Fiber connectors include the following and have different applications:
TABLE C-1 summarizes the distance limitations for various fiber optic cabling and 850 μM and 1300 μM wavelengths.
Telecom rooms or wiring closets are centrally located on floor plans. They are needed to support backbone cabling and horizontal workstation cabling and LAN equipment. In addition, LAN switches are installed here to provide workstation connections to the LAN via a patch cable. Wireless access points (APs) connect to LAN switches in the wiring closet supporting Wi-Fi user connectivity. Wiring closets are typically positioned to be no greater than 90 meters to the furthest workstation outlet. This distance will support high-speed Ethernet connections to the workstation outlet on 4-pair UTP cabling.
This is the workstation cabling that emanates from the closest wiring closet to the workstation outlet. For ceilings that have air conditioning flow, plenum-rated cabling sheaths are required for installation above the ceiling. You will need to pull and install 100-Ohm, 4-pair UTP cabling in Cat 3, 5, 5e, 6, and 6e specifications to support voice and data connectivity. Transmission speeds and distance limitations are shown in TABLES C-2 and C-3, respectively.
Each 4-pair UTP workstation cable should be terminated onto an RJ-45 connector at the workstation outlet. Using a consistent pin configuration for voice and data jacks, the RJ-45 connector and corresponding patch panel in the wiring closet must be wired the same (i.e., both ends must use the same RJ-45 pin configuration as EIA 568A or EIA 568B to ensure end-to-end connectivity). FIGURE C-5 depicts a block diagram that includes the wiring closet, the horizontal workstation cabling, and the workstation outlet.
With any structure wiring system, installation, testing, and as-built documentation are a must to have as part of the overall system.
Installations must be in compliance with BICSI, TIA, EIA, low-voltage electrical, and local building codes. All structured wiring system installations must pass a fire inspection by the county fire marshal as part of new construction building occupancy permit releases.
All UTP cabling must be continuity tested, end-to-end from the workstation outlet through the entire cabling infrastructure to the workstation patch panel in the wiring closet. Distance, attenuation, signal-to-noise, crosstalk, and continuity testing are required for all UTP cable pairs.
All fiber optic cabling must be continuity tested, end-to-end from the ST fiber patch panel all the way to the data center where the main equipment room ST fiber patch panel is. An optical time domain reflectometer (OTDR) is needed to measure distance, attenuation, and continuity for each fiber strand.
A certified cabling system requires a battery of tests performed on the installed cable plant. This include testing for distance, continuity, attenuation, noise, and GigE network transmission speeds on UTP. This type of testing assures that the newly installed cabling system will support the electrical specifications of the electronics that are installed, including VoIP and GigE, to the workstation outlet. Fiber optic testing includes measuring distance, attenuation, and splice points using multiple optical wavelengths.
When performing a certification test on unshielded, twisted-pair transmission media, the following tests should be performed along with requirements for the cable plant’s “as-built” documentation:
All physical cables (UTP or fiber), when terminated onto a patch panel, must be properly labeled on both ends of the cable.
All workstation outlets will have a corresponding voice RJ-45 jack and data RJ-45 jack number, which need to correspond to an equivalent RJ-45 jack in the wiring closet RJ-45 patch panel.
All cabling documentation should be provided in a spreadsheet or database such that the final as-built documentation can be reviewed and accepted with official test results.
TIA/EIA standards were updated in 2015 under revision D.
For more information: https://www.tiafotc.org/ansi-tia-568-d/
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