Balanced Twisted Pair Copper Cable Testing: Ensuring Proper Installation and Functioning
Balanced twisted pair copper cabling is commonly used in horizontal and backbone cabling for various communication systems. As these systems rely on seamless transmission of data, it is crucial to ensure proper installation and functioning of the cabling to avoid any network failures. That’s where balanced twisted pair copper cable testing comes into play.
This article will discuss the importance of balanced twisted pair copper cable testing and the different test methods used for backbone and horizontal copper cabling. It will also cover the two main testing configurations – Permanent Link and Channel Link – and the certification levels used to verify a cabling system’s transmission performance.
Importance of Balanced Twisted Pair Copper Cable Testing
Balanced twisted pair copper cable testing is essential to identify any issues with the installation or functioning of the cabling system. Testing ensures that the cabling system is operating at the required performance levels and that the network is transmitting data correctly. It also helps to detect any issues with the network, such as noise or interference, that may impact the system’s performance.
Test Methods for Backbone Copper Cabling
The test methods for backbone copper cabling depend on the category of cabling employed. Backbone cabling is used to connect equipment rooms, telecommunication rooms, and entrance facilities, and it requires specific testing to ensure proper installation and functioning. Test methods include verifying the cable’s resistance, attenuation, and crosstalk, among others.
Test Methods for Horizontal Copper Cabling
Test methods for horizontal copper cabling vary depending on the category of cabling used and whether the permanent link or the entire channel is being tested. The permanent link is the permanent portion of the overall cable run and consists of up to 90 meters of horizontal cabling and one connection at each end, including an optional transition/consolidation point connection. In comparison, the channel link encompasses the entire cable run, including all patch cords and cross-connections.
Field Testing and Certification
Certification test sets are used to verify that a cabling system meets the transmission performance required by the applicable standard. The test sets fall within one of four certification levels that define the accuracy of the instrument. A level 1 certification test set verifies the wire map, while a level 2 set checks for wire map, length, and polarity. A level 3 set includes all level 2 parameters and adds tests for delay skew, propagation delay, and return loss. Finally, a level 4 set includes all level 3 parameters and adds tests for power sum NEXT, power sum ACR-N, and ELFEXT.
| Twisted Pair Cable Type | Minimum Certification Level |
| Category 3 | I |
| Category 5e | IIe |
| Category 6 | III |
| Category 6A | IIIe |
The following table lists the typical tests performed on balanced twisted pair cabling systems.
Field Testing Performance Parameters – Copper Systems
| Parameter | CAT 3 | CAT 5e | CAT 6 | CAT 6A |
| Wire Map | ✔ | ✔ | ✔ | ✔ |
| Length | ✔ | ✔ | ✔ | ✔ |
| Insertion Loss (Attenuation) | ✔ | ✔ | ✔ | ✔ |
| Propagation Delay | ✔¹ | ✔ | ✔ | ✔ |
| Delay Skew | ✔¹ | ✔ | ✔ | ✔ |
| NEXT (Near-end crosstalk) Loss | ✔ | ✔ | ✔ | ✔ |
| PSNEXT (Power sum near-end crosstalk) Loss | ✔² | ✔ | ✔ | ✔ |
| Return Loss | ✔ | ✔ | ✔ | |
| ACRF (Attenuation-to-crosstalk ratio, far-end) Loss | ✔ | ✔ | ✔ | |
| PSACRF (Power sum attenuation-to-crosstalk far-end) Loss | ✔ | ✔ | ✔ | |
| AFEXT (Alien far-end crosstalk) Loss | ✔³ | |||
| ANEXT (Alien near-end crosstalk) Loss | ✔³ | |||
| PSAACRF (Power sum attenuation to alien crosstalk ratio far-end) | ✔³ | |||
| Average PSAACRF | ✔³ | |||
| PSANEXT (Power sum alien near-end crosstalk) Loss | ✔³ | |||
| Average PSANEXT | ✔³ |
²Not required for horizontal Category 3 cabling.
³Indicates test parameters that may be based on either manufacturer certification or field test results.
In conclusion, balanced twisted pair copper cable testing is critical to ensure proper installation and functioning of horizontal and backbone copper cabling. The different test methods used for backbone and horizontal cabling, along with the two testing configurations – Permanent Link and Channel Link – help to identify any issues with the cabling system. Certification levels verify a cabling system’s transmission performance and ensure that it meets the required standard. By implementing proper testing procedures, organizations can avoid network failures and ensure seamless transmission of data.
Testing Guidelines and Procedures for Balanced Twisted Pair Copper Cables
Testing and certifying copper cabling is a critical step in ensuring the proper installation and functioning of network systems. This article will cover the general guidelines and procedures for testing balanced twisted pair copper cables, as well as the various tests that should be conducted to verify the transmission performance of a cabling system.
Setting the Proper NVP
The first step in testing balanced twisted pair copper cables is to set the proper NVP (Nominal Velocity of Propagation). The NVP is a crucial factor in length measurement and affects the accuracy of other test results. While many test sets contain cable libraries that automatically load pre-set cable parameters, including NVP, it is essential to verify and set the proper NVP for the cable being tested, as parameters are subject to change.
Wire Map or Continuity Testing
Continuity testing, also known as a wire map test, is the most basic test to establish proper cabling installation. This test evaluates open circuits, short circuits, improper termination, and drain wire continuity (if applicable). Wire map field testers, or pair scanners, are the most practical tools to measure direct current loop resistance of twisted pair and ScTP. To perform this test, disconnect equipment, attach the pair scanner to one end of the cabling, diagnose and repair faulty cabling, scan a second time, and document the test results.
| Step | Action |
| 1 | Disconnect equipment. |
| 2 | Attach pair scanner to one end of cabling. |
| 3 | Diagnose and repair faulty cabling. |
| 4 | Scan a second time. |
| 5 | Document the test results. |
Length Testing
Length testing is another critical test to ensure proper cabling installation. The maximum permanent link length is 90 m, plus 2 m at each end for leads, and an additional 10% for a total of 103.4 m. The maximum channel link length is 90 m, plus 10 m for all patch leads, fly leads, and equipment leads, and an additional 10% for a total of 110 m. The 10% is to allow for NVP uncertainty. Limits are stricter for the permanent link since there are fewer components, and it is essential to set the tester to the correct type of link being tested.
Field Testing and Certification
Certification test sets are used to verify that a cabling system meets the transmission performance required by the applicable standard. Test sets fall within one of four certification levels that define the accuracy of the instrument. Specific instructions and associated calculations can be found in the BICSI Information Transport Systems Installation Methods Manual and TIA/EIA-568, along with its various addenda.
Understanding Other Test Parameters for Cable Testing
When it comes to cable testing, it’s essential to evaluate various parameters beyond basic continuity and wire mapping. These parameters include insertion loss, propagation delay, delay skew, NEXT loss, PSNEXT loss, FEXT loss, return loss, ACRF loss, PSACRF loss, AFEXT loss, ANEXT loss, PSAACRF, average PSAACRF, PSANEXT loss, and average PSANEXT loss.
Insertion Loss
Insertion loss or attenuation is the signal loss measured between a transmitter and receiver across a frequency range. The category or classification limit is used to determine whether each pair passes or fails the evaluation.
Propagation Delay
Propagation delay measures the time taken for a signal to propagate from one end of a conducting pair in cabling or connecting hardware to the opposite end of that pair. It’s expressed in nanoseconds and evaluated using category or classification limits for each pair.
Delay Skew
Delay skew is the difference between the pair with the most propagation delay and the pair with the least propagation delay. It’s evaluated from 1 MHz to the highest point and frequency of each category, expressed in nanoseconds, and determined using category or classification limits.
NEXT Loss
Near-end crosstalk (NEXT) loss measures the unwanted signal coupling from a transmitter at the near-end into neighboring pairs measured at the near-end. It’s evaluated across a frequency range and compared against category or classification limits for each pair. NEXT loss measurement must be performed at both ends of the cabling.
PSNEXT Loss
Powersum near-end crosstalk (PSNEXT) loss is the combined near-end crosstalk on a tested pair from all other operating pairs. PSNEXT loss is calculated using the results of the NEXT loss of individual combinations.
FEXT Loss
Far-end crosstalk (FEXT) loss measures the unwanted signal coupling from a transmitter at the far-end into neighboring pairs measured at the near-end. It’s expressed in dB relative to the transmit signal level. Note that FEXT is not measured and reported by field test equipment.
Return Loss
Return loss measures the difference between the test signal’s amplitude and the amplitude of signal reflections returned by the cable, expressed in dB.
ACRF Loss
Attenuation-to-crosstalk ratio, far-end (ACRF) loss is a mathematical formula used to calculate the ratio of attenuation to NEXT loss for each combination of cable pairs. Results include Pass/Fail, Worst-case ACRF loss, Worst-case frequency, or Margin.
PSACRF Loss
Power sum attenuation-to-crosstalk far-end (PSACRF) loss takes into account the combined crosstalk (statistical) on a receive pair from all far-end disturbers operating simultaneously. PSACRF loss is calculated as a power sum on a selected pair from all other pairs.
AFEXT Loss
Alien far-end crosstalk (AFEXT) loss measures the unwanted signal coupling from a disturbing pair of a 4-pair channel, permanent link, or component to a disturbed pair of another 4-pair channel, permanent link, or component, measured at the far-end.
ANEXT Loss
Alien near-end crosstalk (ANEXT) loss measures the unwanted signal coupling from a disturbing pair of a 4-pair channel, permanent link, or component to a disturbed pair of another 4-pair channel, permanent link, or component, measured at the near-end.
PSAACRF
Power sum attenuation to alien crosstalk ratio far-end (PSAACRF) is the difference in dB between the power sum alien far-end crosstalk from multiple disturbing pairs of one or more 4-pair channels, permanent links, or components, and the insertion loss of a disturbed pair in another 4-pair channel, permanent link, or component.
Average PSAACRF
Average PSAACRF is the mean of the PSAACRF measurements.
PSANEXT Loss
PSANEXT (power sum alien near-end crosstalk) loss is the power sum of the unwanted signal coupling from multiple disturbing pairs of one or more 4-pair channels, permanent links, or components to a disturbed pair of another 4-pair channel, permanent link, or component, measured at the near-end.
Average PSANEXT Loss
Average PSANEXT loss is the mean of the PSANEXT loss measurements.