Introduction to several common network transmission media

As the network process of computer applications continues to accelerate, computer technicians have higher and higher requirements on some basic network knowledge. I will only give some introductions on network transmission media based on my years of work experience.
The transmission medium is the intermediate medium between devices connected to the network, and also the media for signal transmission. Common media include:
Twisted Pair (Twisted-Pair)
Twisted Pair wires are the most common transmission medium. They are composed of two copper wires that are insulated from each other and have a typical diameter of 1mm. The two wires are twisted together to prevent the electromagnetic induction from generating interference signals in the adjacent wires. The current twisted pair cable generally contains four twisted pair cables, specifically orange 1/orange 2, Blue 4/Blue 5, green 6/Green 3, Brown 3/brown white 7. The computer network uses two sets of line pairs: 1-2 and 3-6 to send and receive data respectively. Twisted Pair connector is a RJ-45 plug and outlet with international standards. Twisted Pair wires are divided into shielded twisted pair STP and Unshielded twisted pair UTP. Unshielded twisted pair wires have outer cables as shielded layers, which are suitable for scenarios with low network traffic. Shielded twisted pair wires have a sheath, which has strong resistance to Electromagnetic Interference EMI (Electromagnetic Interference) and are suitable for high-speed network protocol applications with large network traffic. Twisted Pair wires can be divided into 5 categories, 6 categories, and 7 categories based on performance. Currently, five types of unshielded twisted pair wires are commonly used, and their frequency bandwidth is 100 MHz, it can reliably run 4 MB, ICME, and 16 MB network systems. When MB Ethernet is running, shielded twisted pair wires can be used to improve the anti-interference performance of the network during high-speed transmission. Cat6 and cat7 twisted pair wires can work on a bandwidth of MHz and MHz respectively, and use specially designed RJ45 plug (seat ). It is worth noting that,
The frequency bandwidth (MHz) differs from the data transmission rate (Mbps) of the cable. The Mbps is measured by the number of binary bits transmitted by the line per unit of time,
MHz is the number of electrical signals on the line per unit time.
Twisted Pair wires can be used in CMSA/CD-based (Carrier Sense Multiple Access/Collission Detection,
Carrier-induced Multi-Channel Access/conflict detection) technology, that is, 10 BASE-T (10 Mbps) and 100 BASE-T (Mbps) Ethernet (Ethernet), specific provisions include:
● The maximum length of a twisted pair is 100, and only one computer can be connected.
● Each end of the twisted pair requires an RJ45 plug-in (Head or seat ).
● Each segment of twisted pair wires are connected through the Hub (10BASE-T reseller of the Hub). The twisted pair wires can be used to connect up to 64 sites to Repeater ).
● The 10BASE-T reseller can use the transceiver cable to connect to the Ethernet coaxial cable.
Coaxial)
There are two widely used coaxial cables: A 50Ω coaxial cable (the ratio of the electromagnetic voltage to the current at each point along the Cable Conductor) used for digital signal transmission, it is the baseband coaxial cable, and the other is the 75Ω coaxial cable, which is used for transmission of analog broadband signals, that is, the broadband coaxial cable. The coaxial cable uses a single copper wire as the inner core, wrapped in an insulating material, and covered with dense mesh conductor. The outermost layer is a protective plastic layer. The metal shielding layer can reflect the magnetic field back to the center conductor and protect the center conductor from external interference. Therefore, coaxial cables have higher bandwidth and better noise suppression characteristics than twisted pair cables.
There are two kinds of Ethernet coaxial cable connection methods: RG-11 coarse cable with a diameter of 0.4 cm adopts the drilling joint connection method, and RG-58 fine cable with a diameter of 0.2 cm adopts the T-head connection method. The crude cable must comply with the 10BASE5 media standard. An external transceiver and transceiver cable is required for use. The maximum length of a single device is 500 meters, which is highly reliable and can connect up to 100 computers, the minimum distance between the two computers is 2.5 m. The cable is directly connected to the T-head connector (BNC connector) of the NIC according to the 10BASE2 media standard. The maximum length of a single segment is 185 meters and up to 30 workstations can be connected, the minimum site distance is 0.5 meters. Optical Fiber (Fiber Optic)
The optical fiber is soft and fine, and uses the internal total reflection principle to transmit the transmission medium of the beam. It can be either single-mode or multi-mode. Single-Mode (Mode, incident angle) optical fiber is mostly used in the communication industry. Multi-mode optical fiber is mostly used in network cabling systems.
The optical fiber is cylindrical and consists of three concentric parts: the core, the package layer and the sheath. Each optical fiber consists of two, one Receiving and one sending. The LAN technology that uses optical Fiber as the network medium is mainly the Fiber-optic Data Distributed Interface (FDDI ). Compared with coaxial cable, optical fiber can provide extremely wide band with low power loss, long transmission distance (more than 2 kilometers), and high transmission rate (up to thousands of Mbps) strong anti-interference (no electronic listening), is an ideal choice for building a secure network.
Microwave Transmission and satellite transmission
The two transmission modes use air as the transmission medium and electromagnetic waves as the transmission carrier, and the network mode is more flexible.