Because of its very good electromagnetic compatibility (EMC) characteristics. In Europe, most end users choose shielded cabling systems, especially in Germany, where approximately 95% of installations are shielded and 5% are fiber optic.
At present, the shielded wiring system has been recognized by more and more users, and its good performance in electromagnetic compatibility is also being recognized by more and more people. Therefore, the shielded wiring products on the market are not limited to European products, and more and more manufacturers provide shielded wiring products. In the newly released North American wiring TIA/EIA-568-B standard, shielded and unshielded cables are simultaneously used as the recommended medium for horizontal cabling, ending the history of no shielding systems in North America.
In China, more and more users, especially those involved in confidentiality requirements and strong radiation, have begun to pay attention to and use shielding systems, even six types of shielding systems.
Of course, there are some disputes about the shielded cabling system in the industry. For users, the shielding system may not be fully understood. So we chose some of the more common questions and answered them.
Q: What is EMC?
A: EMC is electromagnetic compatibility. It means that an electronic device or network system has a certain ability to resist electromagnetic interference, and at the same time cannot generate excessive electromagnetic radiation. That is to say, the device or the network system is required to work normally in a relatively harsh electromagnetic environment, and at the same time, it cannot radiate excessive electromagnetic waves to interfere with the normal operation of other devices and networks around.
Q: UTP cable is the ideal balanced transmission system. Why use an FTP cable?
A: UTP cable is achieved by twisting the core wire to achieve EMC performance, which means that EMI is first received by the UTP cable and then cancelled. However, as the frequency increases, the EMC performance of UTP will decrease. After measurement, it is found that the twisted pair cable can only meet the EMC performance of 30MHz, and the twisted pair of higher electromagnetic interference will be powerless. So far, most of the actual network applications work at less than 30MHz.
However, an ideal balanced transmission system does not exist. The balance characteristics of UTP cables do not depend solely on the quality of the components themselves (such as twisted pairs), but are affected by the surrounding environment. Because the metal around the UTP, the hidden "ground", the pulling, bending, etc. during construction will destroy its balance characteristics, thereby reducing EMC performance.
In fact, we install cables that are usually threaded into metal conduits, plastic conduits, or other protections with different ground impedances. Therefore, to achieve lasting performance on the ground, there is only one solution: add a layer of aluminum foil to all the core wires for grounding. Aluminum foil adds protection to the fragile twisted-pair core and creates a balanced environment for UTP cables. This means that the shielding solution based on the FTP cable is environment-independent, ie independent of the environment. FTP combines the balance characteristics of UTP with construction flexibility and STP shielding, which is the perfect combination of balance and shielding principles.
Q: What is the shielding principle of the FTP cable?
A: Different from the principle of balanced cancellation of twisted pair, the FTP cable is one or two layers of aluminum foil on the outside of the four pairs of twisted pairs. It uses the principle of reflection, absorption and skin effect of electromagnetic waves on metal (the so-called skin effect is It means that the distribution of current in the cross section of the conductor tends to be distributed on the surface of the conductor with increasing frequency. The higher the frequency, the smaller the skin depth, that is, the higher the frequency, the weaker the penetration of electromagnetic waves, and effectively prevent external electromagnetic interference from entering. The cable also prevents internal signals from radiating out, interfering with the operation of other devices.
Experiments have shown that electromagnetic waves with a frequency exceeding 5 MHz can only pass through 38 μm thick aluminum foil. If the thickness of the shielding layer exceeds 38 μm, for example, the PROUVON FTP cable is shielded by two layers of 25 μm thick aluminum foil, so that the frequency of electromagnetic interference that can enter the cable through the shielding layer is mainly below 5 MHz. For low frequency interference below 5MHz, the principle of twisted pair can be applied to effectively offset.
Q: Is FTP attenuation greater than UTP?
A: The attenuation index of the FTP cable is in full compliance with relevant standards such as ISO/IEC11801 and EIA/TIA 568B.
If a UTP cable is threaded into a metal conduit, its characteristic impedance will drop, resulting in increased attenuation. And because the FTP cable takes into account the effects of the surrounding aluminum foil during the manufacturing process, it has been compensated in the manufacturing process.
Q: Is the FTP transmission distance less than UTP?
Answer: The transmission distance of the cable is determined by the attenuation and propagation delay of the cable, and it has nothing to do with whether or not to shield.
The most critical factor affecting the transmission distance is the propagation delay, which is determined by the NVP value of the cable: the NVP of the ordinary UTP cable is about 0.66, the UVP of PROUVON, the NVP of the FTP, STP cable is around 0.68.
Q: Is the shielding performance of the system determined by the performance of the worst part?
A: Yes. The weakest part of the shielding system is the information socket and the modular jumper in the cabinet. The EMC performance can be improved by the following methods.
* Keep away from interference sources such as elevators, air conditioners, power equipment, fluorescent lamps, mobile communication base stations.....
* Use information socket and jumper with EMC shield
* Use shielded jumpers
More notable is the cable part. Compared with the information socket and the jumper disk, the cable is widely distributed throughout the building. The surrounding electromagnetic environment is more complicated and cannot be predicted and controlled. Therefore, the cable part is the most needed in the entire wiring system. The part of protection.
Q: If the grounding is not good, the shielding effect of the FTP cable will not exist?
A: Through the shielding principle of the FTP cable, we can understand that the shielding layer is shielded even if it is not grounded. The shielding effect of the aluminum foil shield is independent of grounding.
Q: If the grounding is not good, the shielding layer of FTP will become the source of interference?
A: Yes. As a passive product, the integrated wiring system does not generate electromagnetic radiation itself. If the grounding is poor, the shield of the cable will absorb external electromagnetic interference and radiate outward after conduction. However, the outward radiation also requires certain conditions, that is, the energy required for the radiation must be present and the size of its antenna is of the same order of magnitude as the wavelength of the electric wave. Only when the above conditions are met can the shield of the cable become a "potential antenna".
The PROUVON integrated wiring system has fully considered the problem of high-frequency grounding during the development and development of the entire system, achieving a large area of the cable shielding layer and 360o surrounding grounding, avoiding the so-called "antenna effect".
Q: How do I measure the performance difference between a shielded and unshielded system?
A: The advantage of the shielded system of the FTP cable is to provide better EMC performance than the UTP cable, which is based on isolating the system from the external electromagnetic environment. Because the external electromagnetic environment affects the data transmission of the entire wiring system. So far, there are no performance indicators or test methods to express or compare EMC performance. At present, the European Committee for Standardization CENELEC has begun this work (the PROUVON integrated wiring system is involved), and coupling attenuation is defined as an indicator for measuring EMC performance. This indicator has also been written into the second edition of the international wiring standard ISO/IEC11801.
1 What is an integrated wiring system?
The Integrated Cabling System is a standard structured cabling system for voice, data, imaging and other information technologies. A transmission network within a building or group of buildings that enables voice and data communication equipment, switch equipment, and other information management systems to be connected to each other. Compared with traditional wiring, it has many advantages. Its main features are its compatibility, openness, flexibility, reliability, first-hand and economical.
2 What are the main parts of the integrated wiring system?
The integrated wiring system can be divided into six subsystems: work area subsystem, horizontal subsystem, vertical trunk subsystem, equipment subsystem, management subsystem and building group subsystem.
3 What are the standards for integrated wiring?
There are two main standards popular in the world.：
One is the North American standard TIA/EIA568A/B [Commercial Building Telecommunications Cabling Standard, which defines the specifications for integrated wiring design, equipment, and components, as well as the installation and testing of five types of transmission performance. In 2000, a new addition to the entire standard, TIA/EIA568B, was released, which merged all the changes and TSBs that affected the A version, and recommended the use of the Super Five]
One is the international standard ISO/IEC 11801 [This standard proposes integrated wiring structure, scale, component transmission performance definition, installation specification and test regulations]
-- TIA/ EIA-568ACommercial Building Telecommunications Cabling Standard (CSA Works T529 in Canada)
-- EIA/ TIA-569Commercial building standards for telecommunications access and space（CSA T530）
-- EIA/ TIA-570Residential and N-type commercial telecommunications cabling standardsCSA T525
-- TIA/ EIA-606Management standards for commercial building telecommunications infrastructure（CSA T528）
-- TIA／EIA-607Commercial building grounding / connection requirements（CSA T527）
-- IEEE802.3-1990Carrier detect multiple access/collision detection（CSMA/CD）Access methods and physical layer specifications ie ANSI/IEEE Standard 802.3-1990 and ISO 8802-3:1990E
-- IEEE 802.5-1989Token Ring Network Access Method and Physical Layer Specification (ie ANSI/IEEE Standard 802.5-1989)
Domestic relevant standards:
--"Code for Design of Integrated Wiring System for Buildings and Buildings" (GB/T 50311-2000)
--"Construction and Building Group Integrated Cabling System Engineering Acceptance Specification" (GB/T 50312-2000)
--"Engineering and Building Group Integrated Cabling System Engineering Design and Acceptance Specifications" CECS72：97
Other relevant standards:
--AWG(American Wire Gauge)：American wire gauge for measuring wire diameter
--TSB568A/B：Modular socket and plug wiring scheme
The selection of the six types of products should pay attention to the following eight elements:
1. The true Category 6 system should meet the performance requirements of Category 6 from connectors, cables to links and channels, including modules, patch panels, jumpers and cables.
2. The system test report submitted must be the worst case model defined in the TIA/ISO standard, ie 3 connection point 90 m link or 4 connection point 100 m channel;
3. The manufacturer shall provide comprehensive test data in the range of 250 MHz bandwidth of the 6 types of products and systems, and stand up to the comparison with the parameters and indicators required by the six types of ISO/TIA standards;
4. The test results of some characteristic frequencies cannot represent the performance within the full test bandwidth. The manufacturer shall also provide test results of some domestic and foreign third parties and official institutions;
5, the product is mature, has been commercialized, and there are six types of systems for engineering applications;
6, the manufacturer can provide six types of products across the line, for users to choose from a variety of options, to adapt to any user installation methods and configuration requirements;
7. The user may also request on-site testing of the link or channel submitted by the manufacturer in accordance with international standards using a field tester to see if the six types of indicators can be met;
8. The manufacturer shall provide the integrators with specific training for the six categories, and the integrators may only participate in the installation and construction of the six types of projects after the training (the user may request the integrator to present such training certificates).
1) Since the outer diameter of the six types of cables is thicker than the general five types of wires, in order to avoid the winding of the cables (especially at the elbows), the filling degree of the pipe diameter must be paid attention to when designing the pipeline, generally the inner diameter is 20 mm. The line tube is suitable for placing two six types of lines.
2) The design of the bridge is reasonable to ensure a proper cable bending radius. When the other trunks are bypassed up and down, the turning slope should be gentle. It is important to pay attention to whether the cables can be covered without damage to the cables after the cables are drooped.
3) During the laying process, the main control is to control the pulling force. For cables with reel packaging, it is recommended to arrange at least one worker on each of the two ends. The reel is placed on the self-made pull rod, and the worker at the end of the line is first from the reel box. Pre-pulling a part of the cable for the collaborator to extract at the other end of the pipeline, the pre-pull line should not be too much, avoiding the entanglement of multiple wires on the site.
4) After the wire drawing process is finished, the redundant cables left at both ends should be arranged and protected. When the wire is wound, follow the original rotation direction. The diameter of the coil should not be too small. If possible, use the waste wire head to fix it on the bridge and ceiling. In the upper or carton, make a note to remind other people not to step on.
5) When arranging, tying, and arranging cables, the redundant cables should not be too long. Do not allow the cables to be superimposed and stressed. The coils should be consolidating and the fixed ties should not be too tight.
6) During the whole construction period, the process flow shall be notified in time, and the various project leaders of the building shall communicate in time, and immediately notify Party A of the problem, and complete the task of this type of work in time before the start of other follow-up types.
