Cable	Port type	Application
Console cable	Console port at one end and 9-pin serial port at the other end	Enables users to perform debugging, configuration, maintenance, management, and software loading on the device.
USB console cable	USB console port at one end and USB port at the other end
Ethernet twisted pair cable	RJ-45 Ethernet ports	Transmits data.
Optical fiber	SFP+/SFP/CFP/QSFP+ ports	Transmits data.
SFP+ DAC/SFP28 DAC cable	· SFP+ DAC cable: Connects SFP+ ports · SFP28 DAC cable: Connects SFP28 ports	Transmits data.
SFP28 AOC cable	SFP28 ports	Transmits data.
QSFP+ DAC/QSFP28 DAC cable	· QSFP+ DAC cable: Connects QSFP+ ports · QSFP28 DAC cable: Connects QSFP28 ports	Transmits data.
QSFP+ AOC/QSFP28 AOC cable	· QSFP+ AOC cable: Connects QSFP+ ports · QSFP28 AOC cable: Connects QSFP28 ports	Transmits data.
QSFP+ to SFP+ DAC cable	A QSFP+ port at one end and four SFP+ ports at the other end	Transmits data.

NOTE:

For information about the console cable and USB console cable, see "Setting up the configuration environment."

Ethernet twisted pair cable

An Ethernet twisted pair cable consists of four pairs of insulated wires twisted together. It mainly transmits analog signals and is advantageous in transmitting data over shorter distances. The maximum transmission distance is 100 m (328.08 ft).

RJ-45 connector

An Ethernet twisted pair cable connects network devices through the RJ-45 connectors at the two ends. Figure 9-1 shows the pinouts of an RJ-45 connector.

Figure 9-1 RJ-45 connector pinout diagram

Cable pinouts

EIA/TIA cabling specifications define two standards: 568A and 568B for cable pinouts.

· Standard 568A—pin 1: white/green stripe, pin 2: green solid, pin 3: white/orange stripe, pin 4: blue solid, pin 5: white/blue stripe, pin 6: orange solid, pin 7: white/brown stripe, pin 8: brown solid.

· Standard 568B—pin 1: white/orange stripe, pin 2: orange solid, pin 3: white/green stripe, pin 4: blue solid, pin 5: white/blue stripe, pin 6: green solid, pin 7: white/brown stripe, pin 8: brown solid.

Cable type

Based on performance

Ethernet cables can be classified into category 3, category 4, category 5, category 5e, category 6, category 6A, and category 7 cable based on performance.

Table 9-2 Ethernet cable description

Type	Description
Category 5	Transmits data at a maximum speed of 100 Mbps, with a bandwidth of 100 MHz.
Category 5e	Transmits data at a maximum speed of 1000 Mbps, with a bandwidth of 100 MHz.
Category 6	Transmits data at a speed higher than 1 Gbps, with a bandwidth of 250 MHz.
Category 6A	Transmits data at a speed higher than 10 Gbps, with a bandwidth of 500 MHz.
Category 7	Transmits data at a speed higher than 10 Gbps, with a bandwidth of 600 MHz.

Based on pinouts

Ethernet twisted pair cables can be classified into straight through and crossover cables based on their pinouts.

· Straight-through—The pinouts at both ends comply with standard 568B, as shown in Figure 9-2.

· Crossover—The pinouts at one end comply with standard 568B, and those at the other end comply with standard 568A, as shown in Figure 9-3.

Figure 9-2 Straight-through cable

Figure 9-3 Crossover cable

A cross-over cable connects devices of the same type. A straight-through cable connects devices of different types.

An RJ-45 Ethernet interface with MDI/MDIX autosensing enabled can automatically negotiate pin roles. The RJ-45 Ethernet interfaces on the switch support MDI/MDIX. By default, MDI/MDIX autosensing is enabled on a port.

Optical fiber

CAUTION:

Use the same types of transceiver modules, pigtail cords, patch cords, and fiber cables. If you use single-mode optical fibers, the transceiver modules, pigtail cords, patch cords, and fiber cables must be single-mode.

Optical fiber

Optical fibers are widely used in fiber-optic communications, which are advantageous for long-distance communications.

Optical fibers can be classified into the following types:

· Single mode fiber—It has a core size of 10 µm or smaller, and has a lower modal dispersion. It carries only a single ray of light. It is mostly used for communication over longer distances.

· Multi-mode fiber—It has a core size of 50 µm or 62.5 µm or higher, and has a higher modal dispersion than single-mode optical fiber. It is mostly used for communication over shorter distances.

Table 9-3 Allowed maximum tensile force and crush load

Period of force	Tensile load (N)	Crush load (N/mm)
Short period	150	500
Long term	80	100

Optical fiber cable

An optical fiber cable is a cable containing one or more optical fibers. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube. Optical fiber cables fall into single-mode and multi-mode.

Patch cord

A fiber that has connectors at both ends is called a patch cord. A patch cord connects one optical device to another for signal routing. Patch cords fall into single-mode and multi-mode patch cords.

· Single-mode patch cord—The jacket is yellow. It permits transmission over longer distances.

· Multi-mode patch cord—The jacket is orange. It permits transmission over shorter distances.

Patch cords are classified into SC, LC, FC, and so on based on interface type. The length of a patch cord can be 0.5 m (1.64 ft), 1 m (3.28 ft), 2 m (6.56 ft), 3 m (9.84 ft), 5 m (16.40 ft), 10 m (32.81 ft), and so on.

Pigtail cord

A pigtail cord is an optical fiber that has an optical connector on one end and a length of exposed fiber on the other. The end of the pigtail is fusion spliced to a fiber, connecting the fiber cable and transceiver.

Pigtail cords fall into single-mode (yellow) and multi-mode (orange), and can also be classified into SC, LC, FC, and so on based on interface type.

Fiber connector

Fiber connectors are indispensable passive components in an optical fiber communication system. They allow the removable connection between optical channels, which makes the optical system debugging and maintenance more convenient and the transit dispatching of the system more flexible.

Figure 9-4 SC connector

Figure 9-5 LC connector

Precautions

· Make sure the fiber connector and fiber type match the transceiver module type.

· The fiber ports on some cards have shielded covers. Remove the shielded covers before using the fiber ports. Fiber interfaces must be installed with shielded covers when they are not in use. Keep them safely.

· Fiber connectors must be protected under safe and reliable outer packing, and be fitted with dust caps. Fiber connectors must be installed with dust caps when they are not in use. Take care not to scratch their end face. Replace the dust cap if it is loose or polluted.

· Before connecting a fiber, use dust free paper and absolute alcohol to clean the end face of the fiber connector. You can brush the end face only in one direction. You also need to brush the end face of the fiber port.

· Never bend or curve a fiber when connecting it. After a fiber is installed well, the bend radius must be not less than 40 mm (the minimum dynamic bend radius is 20 D, and the minimum static bend radius is 10 D. D indicates the outer diameter of dust caps).

· If the fiber has to pass through a metallic board hole, the hole must have a sleek and fully filleted surface (the filleting radius must be not less than 2 mm). When passing through a metallic board hole or bending along the acute side of mechanical parts, the fiber must wear jackets or cushions.

· Insert and remove a plug with care. Never exert a fierce force to the fiber or plug; otherwise the plug might be damaged or the fiber might be broken. Never pull, press or extrude the fiber fiercely. For the allowed maximum tensile load and crush load, see Table 9-3.