Shield system on how to choose the problem with non-shielded system, has been plagued by many users. Here we will be shielded twisted pair and unshielded twisted pair technology to illustrate the difference between their applications.
To be able to adapt to network technology, International Organization for Standardization ISO / IEC to develop a series of cabling standards, ISO11801 standard defines the bandwidth of Category 5 cable is 100MHz, the amendment under discussion in the Category 6 standard also defines the cable bandwidth is 200MHz, 7 type cable bandwidth is 600MHz.
It should be noted that cable bandwidth (MHz) and the data transmitted in the cable rate (Mbps) are two distinct concepts.Mbps is a measure of transmission lines per unit time the number of bits; and MHz is the unit of time measurement circuit oscillation frequency of electronic signals, for Category 5 twisted pair, and its bandwidth is 100MHz, so that any application of Category 5 line network should be less than the 100MHz signal to transmit data to more stable and reliable.
The encoding network bandwidth and speed to establish a link between good coding scheme to the limited bandwidth in high speed data transfer. A few years ago, IEEE used a coding method called Cap64 in the Category 5 twisted-pair on a 622Mbps data transfer experiment. Making process is a precursor to Gigabit Ethernet 1000Base-T, also in Category 5 cable based on the data to be transferred 1000Mbps.
However, when a high frequency signal transmission lines, if certain measures are not taken, will continue because of external electromagnetic interference and crosstalk within the cable itself generate a lot of transmission errors, thereby reducing system performance, as many Network administrators do not want to run in the Class 3 cable 10M network systems, they are found in Category 5 unshielded twisted-pair network system running on the performance of 100M is not as fast as they thought, so reliable. So, the use of shielded twisted-pair situation what will happen? Category 6 unshielded twisted pair with what should be done?
IBM, La Gaude laboratory address this issue rigorously experiment is to compare the unshielded twisted pair and shielded twisted-pair network in the actual system by the strong electrical power lines and the strong impact of transmission errors resulting rate. Network system with ATM 155, and allowed to continue to work in the rate of 120Mbps. Follow the EN 801-4 standard experiment, the object is IBM's SFTP and UTP 5 class system and the other manufacturers UTP6 class system.
When the interference generated by alternating signal strength gradually increased from 200V to 3500V when, SFTP 5 class system, no transmission of data signals any errors. In Category 5 UTP systems, the situation is not so good: When the voltage increases to 200V when, UTP system began generating data errors and loss. In practice, often with strong electric cable laying cable very close, strong in the 220V AC power line of cabling system performance has become an important source of interference.
Network device discovery error during transmission, will spend a lot of time to resend the data and restore these errors, so the actual impact can be greatly flow, which just confirms the concerns that network administrators.
Plug the RJ 4 5 (Block) performance improvements and improve the cable signal to noise ratio, 6 unshielded transmission system bit error rate lower than the half 5 class system, however, still make the network transfer rate has been greatlyimpact. Facts have proved that when the transmission network cabling system requirements closer to the bandwidth limits, elimination of electromagnetic interference outside the system to become more important.
In summary, when the network routing environment in the vicinity of strong electromagnetic fields (such as power plants, substations, etc.) can be shielded cabling system system to ensure the normal transmission of network information. The strength of electromagnetic interference according to the environment, usually taken in three different levels of shielding. In the general case of electromagnetic interference, can be shielded metal bridge and pipeline approach, that is, to all cables are enclosed in a metal tray and pre-paved the pipeline, and to the metal bridge and the pipeline to maintain good groundThis can also interfere with currents in the earth, to achieve better shielding effect, but also can save a lot of money. There is a strong source of electromagnetic interference in the case, can be shielded and shielded twisted-pair shielded connector system, and then assisted to the metal bridge and the pipeline and typically can achieve good shielding effect. In the case of a strong electromagnetic interference, you can use fiber optic cabling. High cost of using fiber optic cabling, but shielded the best, and can be extremely high bandwidth and transmission rates, the use of fiber optic cabling network in 20 years to ensure that it has advanced, network cabling system will not lag behind and eliminated.