Test parameters and Fault Analysis of Copper link in Integrated Wiring

The Integrated Wiring technology has developed over the years. To meet the requirements of devices for higher transmission media performance, the Integrated Wiring standards have been gradually upgraded, the performance of cabling system components has evolved from Category 3 to Category 5, Category 5, Category 6, and category 7. Each time, the link transmission bandwidth has been further improved. To ensure the stability and reliability of the system at a higher transmission rate, each standard upgrade requires more strict consideration of the transmission capacity of the link. From the perspective of integrated wiring systems and products, various detailed testing indicators have been developed for the standard, the capability of link transmission can be recognized. I have taken into account that technicians who have just entered the cabling industry cannot determine or locate faults of unqualified parameters during acceptance or repair of engineering link faults, this article describes the testing parameters of various cabling systems for reference.

1. Contact Map Wire Map)

The test of the wiring diagram verifies the connection relationship between the two ends of the line and the core of the RJ45 plug. In terms of contact points, the two Connection Methods T568A and T568B are generally followed. There is no difference in performance between the two methods, but the same method must be used for construction in the project.

Wiring Diagram faults include open circuit, short circuit, crossover, error pairs, and string winding.

1.1 open circuit: refers to the disconnection of one or more core wires in the end of the 8-core cable. The general solution is to check the Crimping of the module and distribution frame ends and jumper crystal headers, this problem is the most common error in the project and can be avoided during end-to-end connection. The Jumper should adopt the original shape Jumper as much as possible to improve the implementation efficiency in the project with multiple information points.

1.2 short circuit: a line fault caused by one or more core wires connecting to each other. The troubleshooting method can be used to locate the fault point by using the time domain reflection technology of the test instrument. Based on the location of the short-circuit point, determine whether the problem occurs at the connection point or between the cable to quickly troubleshoot the fault.

1.3 cross: this problem is generally caused by negligence during cabling. This situation is easy to appear in some brands of cables, because the core and secondary colors of these cables are usually pure white, during construction, it is easy to mix the positions of the right white core Cables. The VCOM cables are strictly designed in accordance with the standard. The secondary Core Cables all contain the primary stripe, which can reduce the probability of this problem.

1.4 error: the line on both sides of the line to adjust the color, this problem often occurs on one side of the use of T568A, the other side of the use of T568B construction error. It should be noted that in the 100Base-TX network, this method can be used for direct connection of Dual-host NICs according to the principle of sending and receiving by line, which is not allowed in the project.

1.5 string winding: a new transmission line pair is formed from different winding pairs. As a result, the transmission core lines 3 and 6 are formed by different winding pairs, this layout method breaks the balance principle of twisted pair wires. Although the connectivity test is normal with the common disconnection tester, the 3-and 6-Core Cables may have a great number of nearby traces, leading to network connection failure, this problem often occurs on the connection link that directly creates the crystal head.

2. link Length)

Currently, the maximum cable length of a twisted pair link in the Integrated Wiring System is 100 meters. If the length exceeds the specified value, the attenuation and delay are too large, affecting network transmission. The length of the telephone system is not limited to 100. An important factor affecting the length test is the NVP value, which means "the speed at which the signal is transmitted in the cable and the percentage of light speed in the vacuum. In order to achieve the accurate test of the actual length, this value needs to take the actual measurement length of the batch of cables before the test to correct the test instrument, the sample length is generally 25 meters. After a pre-corrected field test, the link length is close to the actual cable exterior size.
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3. Attenuation)

When the signal is transmitted over the cable, the signal strength gradually decreases as the distance increases. The attenuation is related to the line length, core line diameter, temperature, impedance, and signal frequency. The attenuation value to be emphasized here is relatively fixed under the same test conditions. The factors that affect the project performance are mainly related to the cable manufacturing process. However, in order to achieve better transmission performance, the IDC room should be located as close as possible to the plane center of the construction environment during the design of the cabling project, so as to minimize the routing.

The attenuation requirements are inconsistent in different wiring level standards. However, when the core line diameter cannot be increased in a large scale, the attenuation values between different performance levels are not as different as crosstalk.

4. Impedance)

Characteristic Impedance refers to the impedance of the cable when the cable is infinitely long. The Characteristic Impedance of a cable is a complex property. It is determined by various physical parameters of the cable, such as the inductance, capacitance, and resistance values. These values depend on the conductor shape, concentricity, distance between conductors, and cable insulation material. The good running of the network depends on the consistent impedance in the whole system. Sudden changes in the impedance will cause signal reflection, which will cause distortion in signal transmission and network errors.

The standard value of characteristic impedance is 100 ±20Ω. It is ideal if it can be maintained within 100 ±10Ω.

5. DC resistance (Resistence)

TSB67 does not have this parameter. DC loop resistance consumes part of the signal and converts it into heat. It refers to the sum of a pair of wire resistors. in ISO/IEC 11801, the DC resistance of a twisted pair cannot exceed 19.2 ohm. The difference between each pair cannot be too large (less than 0.1 ohm). Otherwise, it indicates poor contact and the connection point must be checked.

6. transmission Delay Propagation Delay) and Delay deviation Delay Skew)

The appendix to the TIA/EIA568A-1 added in 1997 contains the specification for transmission latency and latency deviation. According to various IEEE network transmission standards, the maximum latency for network transmission cannot exceed 570ns, this requires that the test of the Integrated Wiring link be added to the project. For Category 5 or 6, the Standard Rules for transmission latency are basically the same, that is, the latency is 550ns, And the latency deviation is 50ns. It can be said that delay is the main factor restricting the transmission distance of copper networks. Therefore, even if we increase the transmission distance by increasing the wire diameter or signal strength, we cannot change the transmission delay parameter, this is because it is influenced by the material of the conductor, which is why we emphasize the 100 m limit when answering the customer's questions.

7. Near-end crosstalk NEXT)

NEXT) signal coupling between a transmission line on the cable side and other adjacent receiving lines on the same side. Defines the dB of the near-end crosstalk value) and the difference dB that causes the sent signal reference value of the crosstalk to be set to 0 dB) is the near-end crosstalk loss. The larger the NEXT value, the larger the losses of the near-end crosstalk. Because there is a sensitivity difference between the acquisition of signals in the measurement of the near-end crosstalk, the near-end crosstalk signals outside 40 meters are inaccurate, therefore, both ends of the link authentication test must be tested on this value.

Near-end crosstalk is related to cable category, connection mode, frequency value, and construction technology. If the contact chart is normal, if the value is negative, the general cause should be related to the cable quality and construction technology. Factors that have a great impact on the quality of cables are generated during the production process. The core wires of the insulation layer are replaced with the same core degree on the series machine; the density, uniformity, and adhesion of the twisting process; the comprehensive twisting distance during cabling, the balance of the four core wires, and the damage to the structure of the four core Cables during the off-package insulation layer. The performance of a qualified twisted pair cable must fully meet the required parameter requirements. The production unit must strictly control specifications, raw material procurement, production equipment, and personnel quality.

For quality problems caused before leaving the factory, it is generally excluded from acceptance before construction. The construction process is the most relevant part for the majority of practitioners. In order to get a better balance of the project, we recommend that you use the standard as much as possible during project implementation to minimize possible causes of problems in structural design, route configuration, and IDC location; at the same time, the worker's wire pulling strength, bending radius, and opening length are controlled during construction guidance. If there is a negative crosstalk value at the end of the information point during acceptance, you should consider the Link model in the acceptance test. For T568B and later standards, the Basic Link has been eliminated, the replacement of its Permanent Link is also controlled at a maximum length of 90 meters. Various parameters of the Link beyond this length are prone to negative values during testing, if Channel is used for testing, the result may still be in the normal range. On the other hand, check the end connection of the distribution frame and information module, and control the distance of the pair to three categories of 7 CM, five categories and above 1.3 within the range permitted by the standard ), A long open pair distance will cause a great damage to the balanced structure of the twisted pair, resulting in near-end crosstalk.

8. Comprehensive Power near-end crosstalk PSNEXT)

From the cat5e cabling system, in order to support the Gigabit Ethernet protocol based on 1000Base-T, the test parameter has an additional comprehensive power Near-end crosstalk value, this value is the sum of the end-to-end Crosstalk of multiple pairs during full-duplex transmission. This value is critical for gigabit transmission, the problem is basically the same as that of the near-end crosstalk, and the effect is more obvious.

9. Equivalent remote crosstalk ELFEXT) and remote crosstalk FEXT)

The negative signal coupling between the transmitter and the adjacent line to the near end is the remote crosstalk FEXT) loss. The remote crosstalk loss is represented by the dB corresponding to the received signal level. According to the standard of measuring method for Electrical Parameter performance of insulation and sheath of ASTMD4566-94 telecom cable, the same level remote crosstalk loss of the cables and cables connected to the cables should be measured ). In addition, since each pair of duplex channels will be affected by more than one pair of duplex channels, it should be specified that the overall power of the cabling and cables is equivalent to the remote crosstalk PSELFEXT ).

10. Near-end crosstalk attenuation ratio ACR)

It is the difference between ne x t and attenuation of the near-end crosstalk at the same frequency. It can be expressed as: a c r = attenuation signal-noise of the near-end crosstalk, it does not belong to the TIA/EIA-568B standard, but it has important value for expressing the relationship between signal and noise crosstalk. In order to achieve a satisfactory bit error rate, both near-segment crosstalk and signal attenuation should be as small as possible. ACR is a quantitative indicator indicating the ratio of the attenuation value at the receiver end to the crosstalk value. In order to achieve better performance, the ACR index needs to be around several db. If ACR is not large enough, errors will occur frequently. In many cases, even a small increase in the ACR value can effectively reduce the error rate in the entire line.

11. Return Loss of Return Loss)

Ripple loss is the reflection energy produced by unmatched impedance in the cabling system. Ripple loss is especially important for applications that transmit data at the same time. The ripple loss is represented by the dB corresponding to the reflected signal level. The standard requires a 100 Ω link system. If the characteristic impedance of the components fluctuates too much, the return loss will occur. On the other hand, irregular operations during construction will also result in.

12. External crosstalk ANEXT)

The latest IEEE 802.3an has listed 10GBASE-T as the standard, which specifies the details of using copper to transmit 10 Gbps bandwidth, because the transmission frequency of 10 Gigabit unshielded copper cables is very high and requires more than MHz), the problem of near-end Crosstalk of external cables is even more serious, it is considered as the maximum limiting factor for increasing channel capacity. ANEXT is defined as the interference of one line in the cable to the other line. The ANEXT interference between two lines of the same color is the most obvious, because in this pair of lines, their twisting distance is actually the same. The deeper consideration must be based on the comprehensive out-of-Line crosstalk, that is, PSANEXT, because there is also noise interference between all adjacent line pairs, not just between those lines of the same color. In addition to cables, the two ports adjacent to the distribution frame also have strong ANEXT interference. There is no mature and feasible on-site testing solution for this parameter.

The test parameters for the copper link of Integrated Wiring have been basically completed. Most of the parameters are not described in this article. If you need to have a deep understanding of each parameter, we hope that you will conduct research on TIA/EIA568B and relevant standards.