| 1. Overview With the development of | | | | indicators: |
| information society, Network Technologies | | | | (1) attenuation Attenuation (Attenuation) is a |
| become more complex, and as the cornerstone | | | | measure of signal loss along the link. Cable |
| of the network, the keel?? Network cable is even | | | | attenuation and length of relationship, with the |
| more important. Currently used network, there | | | | increase in the length of the signal attenuation is |
| are three main Cable Media: Cable , Coaxial cable | | | | also increased. Attenuation with the "db" for units |
| And the number of twisted pair cables. This paper | | | | that source the signal transmitter to the receiver |
| analyzes the largest number of applications of the | | | | signal strength ratio. Since attenuation varies with |
| twisted cable. | | | | frequency, so the application should be measured |
| Data cable is a pair Integrated wiring The most | | | | within the entire frequency attenuation. |
| commonly used engineering transmission medium. | | | | (2) crosstalk Crosstalk, near-end crosstalk and |
| It consists of two layers with insulation Copper | | | | far-end crosstalk points (FEXT). NEXT loss is a |
| Wire form. The two insulated copper wires | | | | measure of a UTP link from a pair of lines to |
| twisted together with each other by a certain | | | | another signal on the line coupling. The UTP link, |
| density, which reduces signal interference level, | | | | NEXT is a key performance indicator, is also the |
| every wire in the transmission of radiation of | | | | most difficult to accurately measure a target. As |
| radio waves will be another online radio waves off | | | | signal frequency increases, the measure will |
| the root. If one or more pairs of twisted pair on | | | | increase the difficulty. |
| an insulating sleeve has become twisted pair | | | | NEXT not imply that the crosstalk produced by |
| cables. The current twisted pair cable into two | | | | the proximal point value, it simply means that the |
| categories: non-shielded twisted pair (UTP: | | | | measuring point in the proximal to the crosstalk |
| UnshieldedTwisted Pair) and shielded twisted pair | | | | value. This value will change with different cable |
| (STP: Shielded Twisted Pair). | | | | lengths, the longer the cable, and its value |
| LAN using twisted pair cables used bandwidth | | | | becomes smaller. While the transmitter signal will |
| depends on the quality of wire, length and | | | | decay, on the other line on the crosstalk is |
| transmission technology. As long as carefully | | | | relatively smaller. |
| selected and installed, it can be achieved within a | | | | (3) DC resistance DC loop resistance will consume |
| limited distance of a few million bits per second | | | | part of the signal, and transform it into heat, |
| transfer rate and reliable. When the distance is | | | | which is a pair of wire resistance and the. |
| short, and the use of appropriate transmission | | | | ISO11801 specifications for twisted pair shall not |
| equipment and transmission protocol, transmission | | | | be greater than the 19.2 ohm DC resistance. |
| rate up to 100Mbit / s ~ 155Mbit / s, or even | | | | Differences between each pair can not be too |
| gigabit. Shielded twisted-pair cable of outer-foil | | | | large (less than 0.1 ohm), or that poor contact, |
| package, to reduce the twisted pair transmission | | | | you must check the connection point. |
| information generated by the surrounding radiation. | | | | (4) characteristic impedance The characteristic |
| Unshielded twisted pair cables become the | | | | impedance, including resistance and frequency 1 ~ |
| mainstream, mainly because it is cost-effective, | | | | 100MHz inductive impedance and capacitive |
| easy to install, and has the independence and | | | | impedance, with the distance between a pair of |
| flexibility for structured cabling. | | | | wires, and electrical properties of the insulator. All |
| 2. Digital cable pair Main performance In ANSI and | | | | kinds of cables have different characteristic |
| EIA/TIA568 standard and application-level physical | | | | impedance, while the twisted-pair cable is 100 |
| characteristics according to the cable is divided | | | | ohms, 120 ohms and 150 ohms are several. |
| into several categories. LAN applications, the | | | | (5) ACR (ACR) In some frequency range, the |
| current practice mainly five categories, over five | | | | ratio of crosstalk and attenuation performance |
| and six as a data transmission on twisted pair | | | | relationship is reflected in another important |
| cable. At present three types of cable is mainly | | | | parameter cable. ACR sometimes signal to noise |
| used as a voice line. | | | | ratio (SNR: Signal-NoiceRatio) said it from the |
| Three types of cable transmission frequency is | | | | worst value of attenuation and NEXT margin |
| 16MHz, for voice transmission and a maximum | | | | calculation. ACR value is greater, indicating a |
| transmission rate of 10Mbit / s data transmission, | | | | stronger anti-interference ability. General system |
| mainly for 10base-T; five cable routing density | | | | requires at least greater than 10 dB. |
| increases, a quality jacket insulating materials, | | | | (6) Cable properties Communication channel cable |
| transmission frequency of 100MHz, for voice | | | | quality is by its characterization. SNR is the signal |
| transmission and data transmission, mainly for | | | | interference, taking into account the |
| 100base-T Ethernet cable; super five and six | | | | circumstances, a measure of signal strength data. |
| cables to meet the emerging Gigabit Ethernet | | | | If the SNR is too low, will lead to the data signal is |
| applications, the performance There are no | | | | received, the receiver can not distinguish between |
| perfect indicators of the final. | | | | data signal and noise signal, eventually causing data |
| From the perspective of the actual network | | | | errors. Therefore, in order to limit data errors |
| application, as the underlying network link, its | | | | within a certain range, you must define a |
| electrical performance is very important. | | | | minimum to receive the SNR. |
| Performance analysis on the cable in two ways: | | | | On these indicators tested in several different |
| one is Laboratory Test The method, which | | | | ways, the index slightly different requirements. |
| according to international standards and China's | | | | Performance index above are required according |
| relevant performance test on the cable applied | | | | to the physical characteristics of cables, in real |
| normalized and environmental performance | | | | network applications, more people want to know |
| testing; the other is field-based performance | | | | what their transfer bandwidth should meet the |
| testing, completion of construction in the premises | | | | requirements of what. In the cable analysis, the |
| cabling system to measure Assessment After | | | | physical bandwidth of (0 ~ 100MHz) and data |
| laying cable routing performance overall. | | | | transfer bandwidth (0 ~ 100Mbit / s) are two |
| Practice we are most concerned about is the | | | | totally different concepts. |
| characterization of the performance of several | | | | |