UTP (unshielded twisted pair) and F/UTP (shielded twisted pair) cables were developed and designed to help cancel out electromagnetic interference (EMI) from external sources. Set transmission performance criteria (categories) have been established for various cable grades.
What Are the Categories?
Categories are a method of classifying cables and related hardware within specific performance criteria.
The maximum horizontal cable length is 90 m (295 ft); 10 m is allowed for cords in the work area and for patch cords or jumpers in the telecommunications closet.
The maximum backbone cable length is typically 90 m (295 ft), but this number now depends on media and applications. A 90 m length assumes that 5 m (16 ft) are needed at each end for equipment cables connecting to the backbone.
The maximum length for equipment cords and patch cords or jumpers is 10 m. Up to three cords can be used totaling no more than 10 m (33 ft).
Maximum pulling tension for a 4-pair horizontal cable is 25 lbf. Excessive pulling tensions may occur during installation. Once the damage is done, reversing the effect may not be sufficient enough to correct the problem; in this scenario, cable replacement is recommended. Intermediate cable pulls within the overall cable run may be necessary to avoid exceeding the maximum pulling force.
Minimum Bend Radius
Minimum bend radius can be calculated by multiplying the outside diameter (OD) of the cable by 4. For example, if you have a cable with an OD of .250, the minimum bend radius can be determined this way:
4 x .250 = 1”
CAUTION: Exceeding the minimum bend radius can distort cable geometry and result in degradation of transmission performance.
Repositioning the cable to the proper bend radii may not correct the fault. Once the damage is done, the best option is to replace the damaged run.
There are two common places where exceeding the minimum bend radius may occur:
Installation in Temperatures Below Freezing
The minimum installation temperature for plenum cables is 0°C (32°F). If the cable has to be installed when the temperature is below 32°F, the following precautions should be taken to ensure that the jacket does not crack:
Eliminate cable stress caused by tension in suspended cable runs and tightly cinched cable bundles.
Excessive cable loading or stress can also occur if a cable is incorrectly suspended in a cable run. A recommended cable support spacing is 48” to 60” centers.
Avoid twisting of cable during installation. Excessive twisting may result in distortion of cable geometry and, in severe cases, tears in the jacket.
In addition to the above guidelines extracted from ANSI/TIA-568-C, Mohawk strongly recommends the following supplementary installation tips:
The installer must be acquainted with the connector manufacturer’s installation instructions. The correct tools, wire layout and untwist length are critical, especially in Category 6 installations. Modular jacks usually have the pair color code marked on the jack. The color code can be either T568A or T568B wiring methods. Maintain the same pin-to-pair combination throughout the installation. Changing pin-pair assignment can result in crossed pairs. Modular jacks and cross-connect blocks employ IDC connectors to complete the circuit between the cable and the hardware. The manufacturer will recommend the tools needed to terminate the cable.
Terminate with connecting hardware of the same category or higher. Any link that has substituted a lower-category component is automatically classified to that lower category.
The maximum allowable amount of untwisting during cable termination to connecting hardware is 0.5” for Category 5e and Category 6 cables. Exceeding the recommended length of untwisting may cause performance problems. The same techniques should be employed when terminating cross-connect blocks. Maintaining jacket integrity to the point of termination aids in maintaining cable geometry and NEXT isolation from adjacent cable pairs.
When terminating F/UTP cable, follow the same guidelines as listed above. Additionally, termination of the thin foil shield and drain wire are important to maintain shield continuity and shielding effectiveness from the cable to the connector. The connector manufacturer’s installation instructions should be followed for shielded cable termination.
Bridged taps and splices are not permitted as part of copper horizontal cabling requirements.
It is best to determine the lengths of several representative cable runs and adjust the NVP (nominal velocity of propagation) to correspond to the known cable lengths. If the readout for the cable length is longer than the known length, the NVP should be decreased. Conversely, if the readout for the cable length is shorter than the known length, the NVP should be increased.
The NVP values for Mohawk’s products are as follows:
A Note of Caution:
Consult the manufacturer of your test set for clarification.
|Category 5e and 6 – Permanent Link
Requirements at Specific Frequencies
The permanent link requirements include 90 m of horizontal cable and the connectors at each end. The cables to the test equipment are not part of the permanent link and are subtracted out by the test equipment.
Channel requirements include 90 m of horizontal cable and up to 10 m of equipment cords, patch cords and jumpers if you’re using a cross-connect model. The maximum length of cross-connect jumpers and patch cords in the cross-connect facility should not exceed 5 m.
For additional information and an ANSI referenced list, please contact GLOBAL ENGINEERING DOCUMENTS at 1-800-854-7179.
For additional information on cable selection, please call 1-800-422-9961 or email [email protected].
These guides have been prepared by Mohawk as an aid for installers of Mohawk category and fiber optic cables. They are not a warranty by Mohawk and should not be construed as such. Mohawk’s sole warranty with respect to its cables is set forth in the document entitled “Mohawk Warranty,” which has been or will be provided separately to installers of Mohawk category and fiber optic cables.