Network cabling overview

Catalog

One . Signal Overview

Two . Twisted pair

3、 ... and 、 Fiber optic Overview

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One . Signal Overview

Information ： People's understanding of the existence mode or movement state of things in the real world
data ： A specific quantity used to describe an attribute of a thing
The signal ： The medium of information transmission

Signals can be divided into analog signals and digital signals .
（1） analog signal
Analog signals are signal parameters （ Range 、 Frequency, etc. ） Electromagnetic waves of varying magnitude , It can be transmitted on the media at different frequencies , It's a continuously changing physical quantity .

（2） digital signal
Digital signals are discontinuous physical quantities , The signal parameters do not change continuously . Digital signals use several discrete physical states to represent numbers . Now the most common digital signal is the amplitude value , Generally, there are only two kinds （0 and 1） A waveform signal , It's called binary signal . The appearance of the pulse indicates 1, The absence of indicates 0. Digital signal has strong anti-interference ability , The advantages of long transmission distance and quality assurance .

The difference between analog signal and digital signal ：
（1） analog signal ： Continuous signal , The amplitude is not fixed .
（2） digital signal ： The signal is discrete , The amplitude is fixed .

The signal will be distorted due to noise or attenuation in the transmission process

Two . Twisted pair

1、 Twisted pair

1. in total 8 Two twisted pairs , Two twisted together
2. Commonly used 5 class 、 super 5 Classes and 6 class

2、 Twisted pair classification

（1） Shielded twisted pair

1. The copper wire is covered with a metal mesh
2. It is used in the industrial environment with very complex electromagnetic environment

（2） Unshielded twisted pair

1. Used in relatively weak electromagnetic interference environment

3、 Twisted pair standards and classification
1. EIA/TIA-568 ---------“ Telecommunications cabling standards for commercial buildings ”
2. Cat 5： It is mainly used for 100Base-T and Base-T The Internet
3. Cat 5e： Less attenuation , Less crosstalk , Better performance than the 5 Quasilinear
4. Cat 6： Transmission rate up to 1Gbps
5. Cat 7: Transmission rate up to 10Gbps

Connection specification for twisted pair

T568A: White and green , green , White orange , blue , White and blue , orange , White brown , Brown
T568B: White orange , orange , White and green , blue , White and blue , green , White brown , Brown
Linear sequence 1、2 Used to send data
Linear sequence 3、6 For receiving data

Standard network cable （ Also known as the through line 、 Parallel lines ,straight-through） Namely RJ-45 Both ends are used at the same time T568A or T568B Standard solution .
Cross network cable (Crossover) Then... Is used at one end T568A Standard production , The other end uses T568B Standard production .
All negative （Rolled) The line sequence is generally one end is T568B, The color of the other end is reversed （ Linear sequence 12345678-876654321）, It mainly connects computers and switches 、 The router Console mouth .

Straight lines are used between different equipment ： route - In exchange for 、PC- In exchange for
Cross lines are used between the same equipment ：PC-PC、 route - route 、 In exchange for - In exchange for 、PC- route （PC The network port is the same as the router network port ）
 

Twisted pair connectivity test

（1） Common problems of cable connectivity

The cable is open , Wrong wiring , Poor cable contact

（2） Check connectivity

Tools ： Simple tools , Advanced tools

Cable open circuit detection , Wrong cable connection detection

3、 ... and 、 Fiber optic Overview

1、 Characteristics of optical fiber
High transmission bandwidth
Long transmission distance
Strong anti-interference ability
2、 Optical fiber classification
（1） Single mode fiber
The core of a single-mode fiber is very thin , Its diameter is only a few microns （ Some have reached nanoscale ）. At the same time, the light source of single-mode fiber should use more expensive semiconductor laser , You can't use cheaper LEDs , Therefore, the light source quality of single-mode fiber can transmit tens of kilometers or even hundreds of meters at a high speed without using repeaters .

（2） Multimode fiber
The core of multimode fiber is thick , Its diameter is generally 50~100 micron , Low manufacturing cost . Poor light quality , And the transmission process loss is relatively large , Therefore, the transmission distance is much closer than that of single-mode fiber , It's usually hundreds to thousands of meters .