1.Preface
With the rapid development of computer technology, the amount of information on the network has increased by leaps and bounds, and users' requirements for the speed of information transmission have been increasing. If there is an eternal theme in network construction, it is the increasing demand for bandwidth, and the bandwidth of the integrated cabling system, which is the communication platform of the network, has also increased accordingly. Digital cables for integrated cabling systems have evolved from Category 5 to Super Category 5, and now Category 6 and 7 cables are also receiving increasing attention from industry professionals at home and abroad. High bandwidth applications require the latest network cabling technology, and Category 6 cabling technology meets today's commercial applications with its 250MHz bandwidth, which represents the highest bandwidth capability that unshielded twisted pair and shielded twisted pair (for total shielded twisted pair) can support. However, technology is still advancing and it is only a matter of time before 250MHz is not enough to meet the needs of the population, so Category 7 cable (total shield plus pair shield) with bandwidths up to 600MHz has been developed to greatly expand the capabilities of the LAN.
2. Design and manufacture of Category 6 cables
Category 6 systems open up a whole new concept of bandwidth, providing a bandwidth 2.5 times higher than the existing Category 5 standard, with high noise immunity, ensuring high bandwidth, large data volume, long transmission distance and high interference immunity, which provides a smoother path for future network applications. With the promulgation of the Category 6 cabling standard, many manufacturers have stepped up the promotion of Category 6 cabling systems, but there are not many manufacturers of products that are truly compliant with the Category 6 standard. compatibility. The key factors for the production of a qualified Category 6 cable are: the ability to guarantee the equipment, a scientifically sound product design and precise process control. Category 6 technology uses a completely different cable structure to that used before Category 5 and can support network bandwidths of up to 250MHz.
2. Key points in the development of Category 6 cables
The key to developing a Category 6 data cable is to improve and guarantee the manufacturing accuracy, stability and uniformity of the cable. Twist back, which is actually pre-twisting, means that the individual wires are given a certain amount of twist in the opposite direction before the twist is applied to the pair, resulting in a smoother characteristic impedance versus frequency curve. An increase in the detwist rate improves the electrical performance, but also has the side effect of partially destroying the structure of the mono-wire. The more difficult to pass performance specifications for Category 6 cables are: attenuation, near-end crosstalk attenuation and its power and, far-end crosstalk attenuation and its power and, return loss, which can be improved by increasing the diameter of the conductors and choosing better materials. By designing a reasonable pitch for the four pairs, the near-end crosstalk and far-end crosstalk are optimised, while the plastic crossbones in the centre of the cable stabilise the relative positions of the four pairs and isolate the pairs from each other, reducing crosstalk interference and improving transmission quality to ensure a stable and reliable electrical performance. Category 6 cables are also available in a non-skeletal configuration. However, the relative position of the 4 pairs of wires can change due to external forces, affecting the crosstalk attenuation performance of the finished cable, resulting in a less stable electrical performance than the skeleton type. This type of cable is less commonly used today. This type of cable is less commonly used today.
3. Design and manufacture of Category 7 cables
1. Trends in Category 7 cables
When shielded cables were forced by unshielded cables in China a few years ago into a narrow field with high confidentiality requirements, when it was predicted that Category 6 represented the ultimate limit of copper cables and that optical fibre would replace copper as a higher speed transmission medium, no one could have imagined that people's desire for speed would be so rapid that a 10 Gigabit network would come into reality in the blink of an eye, and that shielded cables, represented by Category 7, would have new opportunities in a high-speed environment. The shielded cables represented by Category 7 have a new opportunity to develop in a high-speed environment. At a time when shielded cables are being criticised as expensive and difficult to maintain, the unique advantages of Category 7 cables in carrying high frequency signals have given shielded cables a new lease of life. Category 6 cables can be used for 10 Gigabit Ethernet transmission, but are limited to distances of no more than 100 metres. This is because high-frequency signals are prone to crosstalk, and the shielding layer between pairs of Category 7 shielded cables has made copper transmission of 10 Gigabit Ethernet the dominant method. It is extremely secure, with separate shielding of pairs to reduce RFI and eliminate the need for expensive electronics to reduce crosstalk. It is because Category 7 cables have a "killer application" in 10 Gigabit applications that the use of shielded cables is no longer limited to a single area of high confidentiality requirements such as e-government, opening up a wider application environment for shielded cables, and Category 7 cables are therefore closely linked to the development of the 10 Gigabit Ethernet to ~ up.
Category 7 cables are therefore closely linked to the development of 10 Gigabit Ethernet.
The shielded cabling system, which originated in Europe, has excellent EMC characteristics and confidentiality by means of the twisted balance of the twisted pair and the shielding effect of the metal shielding layer, which effectively prevents external electromagnetic interference signals and electromagnetic radiation from the cable hooks from escaping. The shielded cable can be individually metal shielded for each pair or for four pairs of wires, due to the skin effect and the reflection and absorption effect of the metal shield. This allows for better separation of the surrounding electromagnetic fields and reduces crosstalk between individually shielded pairs or between four pairs of wires. The IEC 61156-5 standard was published by the International Electrotechnical Commission (IEC) in March 2002. The IEC 61156-5 standard provides a basis for the production of Category 7 cables, which are typically of the SSTP construction (wire pair shielding plus total shielding). After theoretical calculations and research and development, we have designed the main structural parameters of the Category 7 cable and the deficiency requirements are shown in the table below.
3. Key points in the development of a Category 7 cable
Attenuation and crosstalk are two of the most important transmission parameters, and increasing the diameter of the copper conductors reduces attenuation. The use of a physical blister jacket and a blister jacket insulation reduces the outer diameter of the cable and reduces the capacitance, which in turn reduces attenuation. Separate aluminium foil shields are provided for each pair. Crosstalk between pairs can be eliminated and electrical interference from the environment can be eliminated and reduced, improving electromagnetic compatibility. Avoid wrinkles in the longitudinal aluminium foil to ensure shielding and transmission performance. The use of large pitch twisted pairs with small pitch differences reduces cable deformation and reduces time delays and delay differences. Twisted pairs should be grouped together. Twisting should minimise extrusion deformation at the contact points of the stranded cores and should be done at the same tension to reduce resistance and capacitance imbalance values. Twisted pairs can improve impedance fluctuations caused by eccentricity of the individual wires or uneven wire diameters. This makes transmission performance more stable. Twist-out prevents deterioration of the transmission performance of the twisted pair due to torsional deformation. The use of copper braid or aluminium foil shielding on the outside of the cable core reduces transfer impedance, eliminates or reduces ambient electromagnetic interference and stabilises the cable structure and transmission parameters.
4. Category 6.7 cable process control and equipment requirements
For the production of high-performance Category 6 and Category 7 cables, precise structural design alone is far from sufficient. Strict process control and excellent equipment performance in all processes are important to meet the requirements of the cables.
1. Single wire
The copper conductors must have a coefficient of resistance that is not significantly different; annealed to a balanced elongation of ±1%; conductor diameter limited to ±0.002ram; insulation outside diameter limited to ±0.01mm; coaxial capacitance limited to ±1.5pF/m; concentricity greater than 96%; conductor preheating temperature fluctuations small, so that the copper wire and insulation between the good bond; the equivalent dielectric constant of the insulation on the entire single line must be uniform. The equivalent dielectric constant of the insulation must be uniform. The extrusion of the foaming material must be uniform, the variation in injection pressure, the variation in screw speed, the variation in take-up and take-down tension must be as small as possible, and the foam layer must be uniform and dense.
2. Twisting and Screening
The change in tension of the single wire must be less than ±10 % throughout the twisting process. The bending radius of the wire must be greater than 50 mm to avoid reducing the adhesion of the copper wire to the insulation. The problem of concentricity and non-uniformity of the insulation can be solved by the provision of appropriate de-twisting devices, with a tolerance of ±0.5 mm between the twisted pairs. The symmetry and axial separation between the two conductors must be maintained during production to prevent asymmetry in the twist. The tension of the shielding tape should vary by less than ±10 % throughout the shielding process. All stranded pairs must be shielded with equal compression.
3. Cable formation and shielding
The geometrical stability of the stranded pair must be ensured when forming the cable. Retwisting is a practical option. The extension tension of the stranded pair should be kept within ±10% throughout the cable formation process and the bending radius of the stranded pair should be greater than 75 mm. The reverse tension of the four pairs of stranded wires should be the same to ensure good cable geometry. The tension of the masking tape should be kept constant during the aluminium foil screening process and cyclical fluctuations in tension should be prevented and should be less than ±10%. For copper braiding shields, the tension and braiding density of the braided copper wire should be effectively controlled. Cables containing 4 stranded pairs should have a bending radius of 150 mm or more.
5. Selection of digital cable equipment
It is well known that there are two methods of manufacturing digital cables: one-step and two-step, so the following aspects should be taken into account when selecting equipment.
One-step pair screening can only be carried out with a single tape. The intermediate storage of the stranded wires is eliminated, thus saving labour. The one-step method is less expensive than the two-step method for the same production capacity, and it is suitable for the production of established digital cables, which are more professional and efficient. However, it also means that a variety of process routes are abandoned. The two-step method can be equipped with an optional pay-off device with adjustable retracting function in the range of 0 to 50%. The simple single-wire pay-off route allows for better control of the pay-off tension, and for shielded cables the shielding tape can be designed to be softer and more than one shielding tape can be wrapped around the wire pair. The cable can also be formed with an optional pay-off device with an adjustable twist-off function in the range 0-100% to prevent changes in the twisted pair structure so that neither the twisted pair pitch nor the screen changes during cable formation. By adjusting the pay-off tension, the stranded wire tension is consistent over the entire cable length. If you are planning to produce more advanced digital cables in the future and intend to expand the frequency of cable use to IGHz and beyond, then you should choose a two-step production line that is flexible and versatile enough to meet all new requirements.
6. Market forecast
The next few years will see the market for Category 6 and Category 7 cabling systems at its peak, and the choice of Category 6 cable is important to meet the future needs of the network, as it will certainly offer higher performance and bandwidth than Super Category 5. If you are at the forefront of networking technology then it is important to have Category 6 cabling.
Category 6 cabling systems are currently gaining momentum in the integrated cabling market, with various cabling manufacturers launching Category 6 cabling products.
Although Category 6 cabling is only gaining momentum, the leading cabling manufacturers are not letting this opportunity pass them by. The education industry, large data centres and other areas with high network speed requirements will be the first areas of application for Category 7 cable, which has already been successfully used in Germany and is expected to be used mainly in the European market in the coming years. As shielded cabling systems become more widely accepted by users and the importance of electromagnetic compatibility is more widely recognised, the use of shielded systems is no longer limited to the European market. Category 7 cables will have a small share of the North American market, but are not expected to dominate this market in the near future.
7. CONCLUSION
The development of digital cables over the past few years has shown that the integrated cabling market is changing, and where the market outlook is uncertain now, it may not be in the future. This is because the development of new products sometimes requires a rather long and arduous process. For all new products, the necessary technical reserves should be made so that they can be followed up as soon as the market starts, in order to take the initiative in the market, otherwise the opportunity will be lost.