Table of Contents

附录C Introduction to connecting cables· C-1

C.1 Introduction to configuring cables· C-1

C.2 Ethernet twisted pair C-1

C.2.1 introduce· C-1

C.2.2 Preparation method: C-5

C.3 optical fiber C-6

附录C  Introduction to connecting cables

C.1  Introduction to configuring cables

The configuration port cable is an 8-core shielded cable, with an RJ45 connector at one end, which is plugged into the console port of the device; The other end has a DB-9 (female) connector that plugs into the serial port of the configuration terminal.

Configure port cables such as:图C-1shown.

图C-1 Schematic diagram of the configuration port cable

C-1 Configure the cable connections

C.2  Ethernet twisted pair

C.2.1  introduce

Twisted-Pair Ethernet Cable consists of 8 copper wires of different colors about 1 mm thick with insulation protection layer, and each two wires are twisted together according to a certain rule to form a total of 4 pairs of twisted wires. Twisting two insulated copper wires together at a certain density can reduce the degree of signal interference, and the radio waves emitted by each wire during transmission will be canceled out by the radio waves emitted by the other wire. Ethernet twisted pair is mainly used to transmit analog signals, but it is also suitable for the transmission of digital signals, especially for short-distance information transmission, and is currently a commonly used transmission medium on local area networks. The maximum transmission distance of the twisted pair Ethernet cable is 100m. If you want to increase the transmission distance, you can install a repeater between two twisted pairs of Ethernet cables, up to 4 repeaters. If 4 repeaters are installed to connect 5 network segments, the maximum transmission distance can reach 500m.

According to the different electrical performance, Ethernet twisted pair cables can be divided into Category 3 wires, Category 4 wires, Category 5 cables, super Category 5 cables, Category 6 cables and Category 7 cables. At present, the common ones in LAN are Category 5 lines, super Category 5 lines and Category 6 lines.

C-2 Introduction to common Ethernet twisted pairs

Ethernet twisted pair cables can be divided into shielded twisted-pair (STP) and unshielded twisted-pair (UTP) according to whether they are shielded with a metal mesh sleeve. Shielded twisted pair has a metal shield between the twisted pair and the outer insulating envelope. The shield reduces radiation, prevents information from being eavesdropped, and also prevents the entry of external electromagnetic interference. Although shielded twisted pair is better than unshielded twisted pair in terms of electromagnetic shielding performance, the conditions for shielded twisted pair application are more demanding and the price is higher. At present, most LAN networks use unshielded twisted pair cables.

Each twisted pair Ethernet cable connects various network devices through RJ45 connectors (commonly known as crystal heads) mounted on both ends. Insert the RJ45 connector into the RJ45 with the pin side up and the plastic snap down into the RJ45One end of the Ethernet port is outward, and the pins are marked 1-8 from left to right, such as:图C-2shown.

图C-2 Schematic diagram of RJ45 connector pin serial number

The serial number of the pins of the RJ45 connector has a certain correspondence with the color of the copper wire, and the EIA/TIA cabling standard specifies the wire sequence 568A and 568B of the two twisted pairs.

·     Standard 568A: white-green-1, green-2, white-orange-3, blue-4, white-blue-5, orange-6, white-brown-7, brown-8.

·     Standard 568B: White Orange - 1, Orange - 2, White - Green - 3, Blue - 4, White Blue - - 5, Green - 6, White Brown - 7, Brown - - 8.

Depending on the wire sequence, Ethernet twisted pair cables can be divided into straight-throughwisted-pair cables and crossover twisted-pair cables.

·     Through wire: The line sequence at both ends of the twisted pair wire is standard 568B, such as:图C-3shown.

·     Cross line: The line sequence at one end of the twisted pair is standard 568B, and the line sequence at the other end is standard 568A, such as图C-3shown.

图C-3 Schematic diagram of the line sequence at both ends of the through line

C-4 Schematic diagram of the line sequence at both ends of the intersection line

When using Ethernet twisted pair to connect devices, you should choose the type of Ethernet twisted pair according to the type of RJ45 Ethernet port connected. RJ45 Ethernet ports are divided into two types: MDI port and MDIX port, and the function distribution of each pin of MDI and MDIX port is as follows表C-1and表C-2shown.

表C-1 MDI port pin function assignment

表C-2 MDIX port pin function assignment

In order to ensure normal communication between devices, for two connected devices, the pin of the device port at one end of the device must be the pin of the device port to receive the data. Therefore, when both ends of the device are MDI ports or MDIX ports, cross wire connections are required, and when one end is MDI ports and MDIX ports at the other end, pass-through wire connections are required. The use of a straight line or crossover can be summarized as follows:

·     Pass-through cables are used to connect different types of devices.

·     Cross wires are used to connect devices of the same type.

If the RJ45 Ethernet port supports MDI/MDIX adaptive, the port can automatically adapt to different line sequences (automatic adaptation to pass-through or crossover lines) when MDI/MDIX adaptive is enabled.

C.2.2  Preparation method:

(1)     Use the wire cutting edge of the crimping pliers to cut out the twisted pair length you plan to use.

(2)     Use the wire cutting edge of the crimping pliers to cut the thread head evenly, then put the thread head into the special knife edge for wire stripping, hold the crimping pliers slightly firmer and rotate slowly, let the knife edge cut the protective rubber of the twisted pair wire, and remove this part of the protective rubber. (The length of the crimping cutter is usually exactly the length of the RJ45 connector, which can effectively avoid stripping too long or too short.) ）

(3)     Untie the 8 thin wires of the 4 pairs one by one, straighten them, and then arrange them neatly according to the specified line order.

(4)     Use the wire scissor edge of the crimping pliers to cut the top of the thin wire neatly, and slowly insert the 8 thin wires along the 8 wire ducts in the RJ45 connector at the same time, all the way to the top of the wire duct, and make sure that each thin wire has been tightly pushed to the end of the RJ45 connector.

(5)     Insert the RJ45 connector into the crimping plier's slot and squeeze the crimp firmly until you hear a slight "pop".

(6)     Test with a tester.

C.3  optical fiber

The optical fiber transmission mode has low loss and long transmission distance, which has advantages in long-distance transmission.

According to the transmission mode of light in the optical fiber, optical fiber can be divided into single mode fiber (SMF) and multimode fiber (MMF, Multi mode fiber). The core of single-mode fiber can only transmit one mode of light, the skin is generally yellow, and the multimode fiber allows multiple modes of light to be transmitted in the same core at the same time, and the skin is generally orange.

C-5 Characteristics of single-mode and multimode fibers

C-6 The maximum tensile and flattening force of the fiber

Optical fiber connector is an indispensable passive device in optical fiber communication system, and its use realizes the detachable connection between optical channels, making the debugging and maintenance of optical system more convenient. There are many types of fiber optic connectors, and LC type fiber optic connectors look like this图C-4shown.

图C-4 LC type fiber optic connector appearance