Contents

Appendix C Cable and connection line introduction·································· C-1

C.1 Console cable introduction····································································································· C-1

C.2 Ethernet twisted-pair cable······································································································ C-1

C.2.1 Introduction·················································································································· C-1

C.2.2 Production method······································································································· C-5

C.3 Optical fiber··························································································································· C-5

 

Appendix C Cables

Console cables

A console cable is an 8-conductor shielded cable; one end has an RJ45 connector to plug into the device's Console port, and the other end has a DB-9 (female) connector to plug into the serial port of the console terminal.

The console cable is Figure 1.

FigureC-1 Console cable diagram

 

TableC-1 Console cable signal pinout

RJ45	Signal	Direction	DB-9
1	RTS	←	7
2	DTR	←	4
3	TXD	←	3
4	CD	→	1
5	GND	-	5
6	RXD	→	2
7	DSR	→	6
8	CTS	→	8

 

Ethernet twisted pair cable

Introduction

Ethernet twisted-pair cable (Twisted-Pair Cable) consists of eight copper conductors of different colors, each about 1 mm thick and covered with insulation. The conductors are twisted together in pairs according to specific rules to form four twisted pairs. Twisting two insulated copper conductors together at a certain twist density reduces signal interference: the electromagnetic waves radiated by one conductor are canceled by those from its mate. Ethernet twisted-pair cable mainly transmits analog signals but also supports digital signal transmission. It is especially suitable for short-reach (SR) transmissions and is the common transmission medium on current local area networks (LANs). The maximum transmission distance for Ethernet twisted-pair cable is 100 m. To extend the distance, install repeaters between segments; you can install up to four repeaters. With four repeaters connecting five segments, the maximum transmission distance can reach 500 m.

By electrical performance, Ethernet twisted-pair cables are classified as Category 3, Category 4, Category 5, enhanced Category 5 (5e), Category 6, and Category 7, etc. The higher the number, the higher the grade and the wider the bandwidth. Commonly used in LANs today are Category 5, enhanced Category 5 (5e), and Category 6.

TableC-2 Description for commonly used Ethernet twisted pair cables

Cable type	Introduction
Category 5	Suitable for data transmission at a maximum speed of 100 Mbps
Category 5e	Suitable for data transmission at a maximum speed of 1000 Mbps
6 categories	Suitable for data transmission at a speed higher than 1 Gbps

 

Ethernet twisted-pair cable can be divided by whether it has an added metallic wire mesh shielding layer into Shielded Twisted-Pair (STP) and unshielded twisted pair (UTP). In STP, a metallic shielding layer sits between the twisted pairs and the outer jacket. The shielding layer reduces radiation, prevents eavesdropping, and blocks external electromagnetic interference (EMI). Although STP outperforms UTP in electromagnetic shield (EMS) performance, STP requires more stringent application conditions and costs more. Currently most local area networks use unshielded twisted pair (UTP).

Each Ethernet twisted-pair cable connects various network devices using RJ45 connectors (commonly called plugs) installed at both ends. With the RJ45 connector's pin side up and the plastic latch down, insert it into the RJ45 Ethernet port with the plug end facing out; the pins are numbered 1–8 from left to right.

FigureC-2 RJ45 connector pin numbering diagram

 

Connect devices' RJ45 Ethernet ports with Category 5 or higher twisted-pair cable.

 

RJ45 pin numbers correspond to copper conductor colors. The EIA/TIA wiring standards specify two wiring schemes, 568A and 568B.

·     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.

"White-green" means light green or white with green dots or stripes; "white-orange," "white-blue," and "white-brown" follow the same pattern.

 

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

·     Straight-through cable: both ends use the 568B standard wiring.

·     Crossover cable: one end uses 568B and the other end uses 568A

FigureC-3 Straight-through cable

 

FigureC-4 Crossover cable

 

When connecting devices with Ethernet twisted-pair cable, select the cable type based on the RJ45 Ethernet port types. RJ45 Ethernet ports are classified as MDI and MDIX.

TableC-3 RJ-45 MDI port pinouts

Pin	10Base-T/100Base-TX		1000Base-T
	Signal	Feature	Signal	Feature
1	Tx+	Sends data	BIDA+	Bi-directional data cable A+
2	Tx-	Sends data	BIDA-	Bi-directional data cable A-
3	Rx+	Receives data	BIDB+	Bi-directional data cable B+
4	Reserved	-	BIDC+	Bi-directional data cable C+
5	Reserved	-	BIDC-	Bi-directional data cable C-
6	Rx-	Receives data	BIDB-	Bi-directional data cable B-
7	Reserved	-	BIDD+	Bi-directional data cable D+
8	Reserved	-	BIDD-	Bi-directional data cable D-

 

TableC-4 MDIX port pin function assignments

Pin	10Base-T/100Base-TX		1000Base-T
	Signal	Feature	Signal	Feature
1	Rx+	Receives data	BIDB+	Bi-directional data cable B+
2	Rx-	Receives data	BIDB-	Bi-directional data cable B-
3	Tx+	Sends data	BIDA+	Bi-directional data cable A+
4	Reserved	-	BIDD+	Bi-directional data cable D+
5	Reserved	-	BIDD-	Bi-directional data cable D-
6	Tx-	Sends data	BIDA-	Bi-directional data cable A-
7	Reserved	-	BIDC+	Bi-directional data cable C+
8	Reserved	-	BIDC-	Bi-directional data cable C-

 

·     Tx = transmit data

·     Rx = receive (Rx)

·     BI = bi-directional data

 

To ensure normal communication, the transmit pins on one device's port must correspond to the receive pins on the other device's port. Therefore, when both connected ports are MDI or both are MDIX, use a crossover cable; when one end is MDI and the other is MDIX, use a straight-through cable. The use of straight-through or crossover cables can be summarized as follows:

·     Straight-through cables connect devices of different types—For example, router to PC and router to switch.

·     Crossover cables connect devices of the same type—For example, switch to switch, router to router, and PC to PC.

If an RJ45 Ethernet port supports MDI/MDIX autosensing and autosensing is enabled, the port will automatically adapt to different wiring (automatically adapt to straight-through or crossover).

The device's RJ45 Ethernet ports support MDI/MDIX autosensing.

 

Making an Ethernet twisted pair cable

Table 1 Cut the cable to a required length with the crimping tool.

Table 2 Use the Crimping tool's cutter to trim the wire ends even, then place the end into the stripper slot. Squeeze the Crimping tool slightly and rotate slowly to score and remove the jacket from the twisted pair. (The Crimping tool's stop is usually the same length as the RJ45 connector, which helps avoid stripping too much or too little.)

Table 3 Untwist and straighten the eight conductors one pair at a time, then align them in the specified wiring order.

Table 4 Use the Crimping tool's cutter to trim the conductor ends squarely, then gently push all eight conductors into the eight slots of the RJ45 connector until they reach the end of the slots, ensuring each conductor seats at the connector's end.

Table 5 Place the RJ45 connector into the Crimping tool's slot and squeeze firmly until you hear a slight "click."

Table 6 Use a cable tester to verify the connectivity of the cable.

Optical fiber

Optical fibers feature low loss and long transmission distance.

Based on light transmission modes, optical fiber divides into single-mode fiber (SMF) and multimode fiber (MMF). Single-mode fiber's fiber core supports only one propagation mode; its jacket is generally yellow. Multimode fiber allows multiple propagation modes in the same fiber core; its jacket is generally orange.

TableC-5 Characteristics of single-mode and multimode optical fibers

Feature	Single-mode fiber	Multimode fiber
Core	Small core (10 micrometers or less)	Larger core than the single-mode fiber (50 micrometers, 62.5 micrometers, or greater)
Dispersion	Less dispersion	Allows greater dispersion and therefore, signal loss exists.
Light source and transmission distance	Uses lasers as the light source often within campus backbones for distance of several thousand meters	Uses LEDs as the light source often within LANs or distances of a couple hundred meters within a campus network

 

TableC-6 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

 

Fiber connectors are passive components essential to fiber-optic communication systems; they provide removable connections between optical channels, making system setup and maintenance more convenient. There are many types of fiber connectors; the LC fiber connector looks like Figure 1 shows.

Figure 1 LC connector

 

·     Follow these guidelines when you connect an optical fiber:

Before you connect an optical fiber, make sure the connector and cable type match the interface module.

·     The Ethernet fiber ports on the device support only LC connectors.

·     Before you connect an optical fiber, use dust free paper and absolute alcohol to clean the end face of the fiber connector. You can brush the end faces only in one direction.

·     Never bend or curve a fiber.

·     If the fiber has to pass through a metallic board hole or bend along the acute side of mechanical parts, the fiber must wear jackets or cushions.