In the network hardware, there is also a kind of network transmission media that can not be ignored. We usually call it network cable. At present, the common network cable is divided into thin twisted pair, optical fiber cable, coaxial cable and thick coaxial cable.

1. Optical fiber cable

Fiber optic cable is a new generation of transmission medium. Compared with copper medium, fiber optic cable has greatly improved in security, reliability and network performance. In addition, the bandwidth of optical fiber transmission is much larger than that of copper cable, and its maximum connection distance is more than two kilometers, which is the inevitable choice to build a large-scale network. Because optical fiber cable has the advantages of good anti electromagnetic interference, strong confidentiality, high speed and large transmission capacity, its price is also relatively expensive, and it is rarely used in domestic occasions. At present, there are two common types of fiber, single-mode fiber and multimode fiber (the so-called "mode" refers to a beam of light entering the fiber at a certain angle). Multimode fiber is generally used for network connection in the same office building or relatively close area. The single-mode fiber is usually used to connect office buildings or geographically dispersed networks because of its higher data quality and longer transmission distance. If the fiber optic cable is used as the network transmission medium, the optical transceiver and other equipment need to be added, so the cost investment is larger and less used in general applications.

2. Twisted pair

Twisted pair is a kind of flexible communication cable, which contains pairs of insulated copper wires. It is characterized by low price, so it is widely used, such as our common telephone lines. According to the different maximum transmission rate, twisted pair can be divided into three categories, five categories and over five categories. The rate of three types of twisted pair is 10MB / s, five types can reach 100MB / s, while super five types can reach 155Mb / s or more, which can meet the needs of future multimedia data transmission, so it is recommended to use five types or even super five types of twisted pair. Twisted pair can also be divided into shielded twisted pair (STP) and unshielded twisted pair (UTP). STP twisted pair has a lower speed (only 4MB / s), but its anti-interference is stronger than UTP twisted pair, so the price is much more expensive. Now, the price of STP twisted pair is a few yuan per meter, and the price of STP twisted pair is more than ten yuan. In contrast, UTP twisted pair price is generally about one meter one yuan, relatively low. In addition, the popular names of 10 m and 100 m unshielded twisted pair are 10 Base-T and 100 Base-T, which are often seen on the market. RJ45 crystal head is also used with twisted pair to make the joint between twisted pair and RJ45 interface of network card. Its quality is directly related to the stability of the whole network and cannot be ignored.

3. Coaxial cable

Coaxial cable is a kind of transmission medium that many friends are familiar with. It is a cable that is wrapped by layers of insulated wires with central copper conductor. Its biggest feature is good anti-interference ability, stable transmission data, and low price, so it was once widely used, such as closed-circuit television line. However, in the past, coaxial cable was widely used, mainly due to the low cost of the bus structure network composed of coaxial cable, but the damage of a single cable may cause the whole network to be paralyzed and difficult to maintain, which is its biggest disadvantage. The coaxial cable in Ethernet application is mainly divided into two types: coarse coaxial cable (10BASE5) and thin coaxial cable (10base2). Now the coarser coax cable is not used much, and the thinner coax cable has some market. The market price of thin coaxial cable is a few yuan a meter, not too expensive. In addition, the coaxial cable is used to connect with the BNC head. The coaxial cable sold on the market is generally the finished product that has been connected with the BNC head, and you can choose it directly.