The rapid development of network applications continues to increase the demand for bandwidth. In June 2002, the ANSI/TIA/EIA568-B copper twisted pair Category 6 wire standard met most commercial applications with its 250MHz bandwidth. However, with the continuous progress of technology, the 250MHz bandwidth cannot fully meet people's needs.
The selection of cable type should be comprehensively considered from various aspects such as cable usage, required transmission capacity, transmission bandwidth, and price. There are three types of cables: unshielded twisted pair, shielded twisted pair, and optical cable.
1) Unshielded twisted pair UTP is the most widely used cabling system in China, suitable for network applications with transmission bandwidth below 250MHz and no special performance requirements. Its advantages are good overall performance, low price, and convenient construction and maintenance. The Category 6 cabling system has reached the performance limit of unshielded twisted pair.
2) Aluminum foil shielded twisted pair FTP has a large bandwidth, strong anti-interference performance, and low smoke and zero halogen characteristics. Relatively speaking, the price and installation cost of shielded wire are higher than that of unshielded wire, and the bending performance of the cable is slightly poor. Six types of wires and previous shielding systems often use this form.
3) Independent shielded twisted pair STP, each pair of wires has an aluminum foil shielding layer, and four pairs of wires together have a common metal braided shielding layer, which is the standard structure for Class 7 wires. It is suitable for high-speed network applications, providing highly confidential transmission, supporting future new applications, and helping to unify the cabling platform of current network applications, so that various information from email to multimedia video can be transmitted in the same high-speed system. The additional shielding layer gives Class 7 cables a larger diameter, which requires special care when designing installation routes and termination spaces, leaving a large space and a large bending radius. Corning has already launched Class 7 cabling systems in China.
As early as 1997, wiring standardization agencies and manufacturers had proposed the concept of seven types of copper cable wiring systems. It can provide a comprehensive attenuation to crosstalk ratio of at least 500MHz and an overall bandwidth of 600MHz. Its connector requires all line pairs to provide at least 60dB of comprehensive near-end serial winding at 600MHz. The Super Class 5 system only requires 43dB at 100MHz, while the value for Class 6 at 250MHz is 46dB. Moreover, due to its excellent shielding design and high bandwidth, a typical Class 7 channel can even provide a pair of 862MHz bandwidth for transmitting cable TV signals, transmit analog audio signals in another pair, and then transmit high-speed local area network information in the third and fourth pairs.
Compared to fiber optic local area networks, the seven types of system solutions provide the desired performance and bandwidth, but their overall cost is only a fraction of that of fiber optic. Some people may believe that fiber optic systems can bring enough bandwidth to people, and that fiber optic cables are priced close to Category 7 cables. However, if the cost factors of fiber optic routers, optical switches, and optical network cards are considered, the price advantage of fiber optic will quickly be lost.