Application of integrated wiring system in data center

In terms of application, after decades of development, the integrated cabling system has reached maturity in terms of technology and products, and has multi-media high-speed transmission capabilities including unshielded cabling systems, shielded cabling systems and fiber optic cabling systems, providing physical transmission support for computer, communication and control fields and all walks of life.

As various systems in intelligent buildings gradually move towards networking, the application areas of integrated wiring systems will be further extended and expanded. This article will make a simple comparison between the application of unshielded systems and shielded systems for readers' reference only.

1. Common types of twisted pair cables

The Chinese wiring standard (GB50311-2007) stipulates the representation method of shielded cable types as follows:

The metal foil is generally aluminum foil, and the metal woven mesh is generally copper woven mesh.

In the naming rules, unshielded twisted pair cables and shielded twisted pair cables are treated the same, and "balanced cable" is used to collectively refer to all twisted pair cables, while different letters (U, F, S) are used to distinguish various shielding types.

For example: U stands for unshielded, F stands for aluminum foil shielded, and S stands for silk screen shielded. “/” is used to distinguish whether shielding is performed outside the four pairs of core wires or on each pair of core wires.

In ISO/IEC11801-2002, there are naming rules for 5 common types of twisted pair cables:

According to the naming rules, some other types of shielded twisted pair cables can also be derived. For example:

F/FTP: Aluminum foil overall shield/aluminum foil pair shield twisted pair

SF/FTP: Silk screen + aluminum foil overall shield/aluminum foil wire pair shield twisted pair

F2TP: It can be classified as F/UTP twisted pair cable, but the overall shielding layer of the cable has two layers of aluminum foil, and a metal drain conductor is provided between the two layers of aluminum foil.

2. Statistical table of 4-pair 8-core twisted pair cable diameters

As the transmission bandwidth of the product increases (category 6A and above), the increase rate of the cable diameter of the shielded twisted pair cable slows down significantly, and ultimately it only has a corresponding relationship with its shielding structure, but has a relatively small relationship with the transmission bandwidth.

3. Choice of unshielded and shielded systems

In the wiring system, the noise sources in the channel mainly include PowersumNEXT (the sum of the power of near-end crosstalk), PowersumFEXT (the sum of the power of far-end crosstalk), return loss, interference from adjacent cables and external interference.

The first three types of interference come from inside the cable. In high-speed network systems, digital signal processing (DSP) technology can be used to compensate and offset them. The last two types of interference come from outside the cable, are random and unpredictable, and cannot be offset using DSP technology.

Therefore, only by shielding the twisted pair cables can the noise entering the cable be greatly reduced, thereby improving the signal-to-noise ratio.

Regarding the selection of unshielded systems, the following paragraph may explain everything: For applications with transmission bandwidth higher than 16MHz, that is, the network data transmission rate gradually increases, the signal-to-noise ratio requirements are higher. The twisted pair structure of twisted pair wires helps to improve the anti-interference ability of the transmission line, but mechanically limiting the twist density will weaken the twisting effect.

In addition, during the installation process, if the cable is subjected to excessive tension or the bending radius is too small, the balance of the twisting will be destroyed, resulting in a decrease in anti-interference ability. Therefore, the twisting principle of cable pairs can effectively adapt to 30 to 40MHz data transmission.

In the European integrated wiring standard EN50173.1-2007, electromagnetic compatibility is one of the four types of harsh environments, and for this reason, it divides the electromagnetic compatibility level into three levels: E1 (commercial environment), E2 (semi-industrial environment) and E3 (industrial environment). This level also has similar divisions in other standards.

The environment in which people usually live and work is called the "business environment". Shielded cabling systems are often used in places where transmission quality and efficiency need to be considered, in areas with large electromagnetic interference, in rooms with precision instruments, shielded machine rooms, and places where leakage is not desired.

Therefore, shielded wiring systems are often installed in factories, shielded computer rooms, airports, hospitals, government agencies, military agencies, banks, financial institutions, self-use office buildings, precision laboratories and other places with high requirements for transmission performance. They are also used in certain occasions involving trade secrets.

4. Comparison of construction technology between non-shielded and shielded systems

As for the unshielded system, from an engineering perspective, with the development of integrated wiring for decades, engineering teams across the country have mastered its construction technology very maturely. I will not introduce it in detail here.

The following mainly introduces the construction of the shielding system in order to reach a consensus.

The use of shielded wiring must meet two conditions: "full shielding" and "correct and reliable grounding of the shielding layer." Full shielding means that the patch panels, cables, connectors, jumpers, network devices, and network cards used in the wiring system are all shielded products, and the shielding layers maintain good contact and connection.

For the integrated wiring system, the most ideal grounding method is grounding at both ends, that is, grounding at both ends of the shielded twisted pair (the wiring frame in the work area and the telecommunications room).

5. Grounding of shielding system

The shielding layer of the information socket in the work area of ​​the integrated wiring system is not specially grounded. The shielded information socket in the work area is connected to the shielding layer of the shielded network equipment through a shielded jumper.

The grounding is naturally achieved through the PE terminal of the terminal equipment power line. Make equipotential bonding on one side of the wiring cabinet.

It should be noted that shielded patch panels also have "cabinet column grounding" and "series grounding" methods, but this article recommends the star grounding method shown in the figure above. The reason is that each shielded patch panel is equipped with 1 to 2 grounding terminals, which are directly connected to the cabinet grounding busbar using grounding wires. A failure at any grounding point will only affect one shielded patch panel, which helps to improve system reliability.

6. Technical parameters and explanations of unshielded and shielded systems

Most of the link and channel technical parameters of the shielded cabling system are the same as those of the unshielded cabling system, with only a few shielding parameters added.

According to the standards of the integrated wiring system, the wiring system should test the electrical performance of its own twisted pair, which includes:

1. Wiring diagram (WIREMAP), including the connectivity test of the shielding layer; 2. Length (LENGTH); 3. Insertion loss (INSERTLOSS); 4. Near-end crosstalk (NEXT); 5. Near-end crosstalk power sum (PSNEXT); 6. Near-end attenuation crosstalk ratio (ACR-N); 7. Near-end attenuation crosstalk ratio power sum (PSACR-N); 8. Far-end attenuation crosstalk ratio (ACR-F); 9. Far-end attenuation crosstalk ratio power sum (PSACR-F); 10. Return loss (RETURNLOSS); 11. Propagation delay (DELAY); 12. Propagation delay deviation (DELAYSKEW); 13. DC loop resistance (DCLOOPRESISTANCE).

Among the above performance parameters, except for the addition of a shield continuity test in the wiring diagram, the others are the same as the same type of unshielded wiring.

After selecting the shielded wire test standard and connection model in the instrument and testing, you can get the corresponding results. The wiring diagram report will automatically include the shield layer continuity results.

7. Conclusion

In recent years, the application of integrated cabling systems in data centers has become more and more widespread, and major manufacturers have also rushed to launch data center cabling products with their own characteristics.

Recommendations: 1. The copper cable part of the data center wiring should adopt a shielded wiring system 2. The copper cable part of the data center wiring should adopt a pre-connection system 3. The copper cable part of the data center wiring should adopt a 6A or above wiring system.