Basic knowledge of optical communication

2020-06-16

Since the 1980s, fiber-optic communication systems have had a revolutionary impact on the telecommunications industry... Today, optical fiber communication network is increasingly developed, and the announcement of 5G network commercial use has made the development and construction of optical communication network enter the fast lane. At present, network transmission has become an indispensable part of our daily life, life, work, study...  Do you know who is the important "backer" of such a large communication network system? Yes, fiber optics; So we need to understand it in more detail, so as to better stimulate its potential.
Introduction to optical fiber communication
Introduction to optical fiber communication
1、optical fiber communication
Optical fiber communication is a kind of communication mode with light as the carrier of information and optical fiber as transmission medium,to communicate by transmitting light waves carrying information through optical fibers.
2、The composition of a communication system
The communication system can be divided into three parts: optical transmitter and optical receiver. Optical transmitter is composed of a conversion device that converts electrical signals with information into optical signals and a transmission device that sends optical signals into optical fibers. Optical fiber exists in the form of optical cable in the system.Optical receiver is composed of optical detector, amplifier circuit and signal recovery circuit.
 The composition of a communication system
3、Advantages and disadvantages of optical fiber communication
Optical fiber and cable
Optical fiber and cable
1、Optical fiber structure
Optical fiber is a kind of highly transparent glass wire, which is made with the complicated process of silica glass mirror, which is basically composed of three parts, as follows:
①Fiber core:High refractive index, used to transmit light;
②Cladding:Low refractive index, together with fiber core to form a total reflection conditions;
③Coating layer:High strength, can withstand greater impact, protect optical fiber
Optical fiber structureOptical fiber structure
2、Optical fiber working wavelength
Short wavelength(850nm),long wavelength(1310nm、1550nm),they are OTDR QX45 detecting wavelengths.
3、Fiber transmission mode
Single mode and multi-mode fiber
Single mode fiber:fiber core diameter is 8-10μm,cladding diameter is 125μm,coating is 250μm
Multi-mode fiber:fiber core diameter is 50μm or 62μm,cladding diameter is 125μm,coating is 250μm
Fiber transmission mode
In optical fiber communication, single-mode fiber can reach the rate of 100M/s or 1G/s in the allowed range and the transmission distance is at least 5km, so single-mode fiber is mostly used for remote signal transmission.
Multi-mode fiber is mainly used for short distance optical fiber communication, such as in buildings or campus.
4、Cable
Optical cable is a kind of communication line in which a certain number of optical fibers make up the cable core in a certain way, and some of them are covered with outer sheath, so as to realize optical signal transmission.
That is, the cable formed by the optical fiber through a certain process.
The basic structure of optical cable is generally composed of cable core, reinforced steel wire, filler and sheath, etc., and according to the needs of waterproof layer, buffer layer, insulating metal wire and other components.
Cable
(1)Classification of optical cables:
①According to the core number is divided into single core, double core, multi core;
②According to the structure is divided into layer stranded type, skeleton type, belt and so on;
③It can be divided into overhead, direct buried, pipeline, submarine and so on;
Jump cable
Jump cable
1、Jump cable
Fiber optic jumper is mainly used for the jump connection from equipment to fiber optic wiring link, with a thick protective layer. It is generally used for the connection between optical end machine and terminal box, and is mostly used in fiber optic communication system, fiber optic access network, fiber optic data transmission, LAN and other fields.
2、Common types of fiber optic connectors
①SC:the connector connecting GBIC light module, its shell is rectangular, the fastening mode is to use plug and bolt type, do not need to rotate;
SC
②FC:the external reinforcement is metal sleeve and the fastening method is screw buckle;
FC
③ST:It is commonly used in optical fiber distribution frame, the outer shell is round metal and the fastening mode is screw;
ST
④LC:The connector for SFP module is made of modular jack (RJ) latch mechanism with easy operation.
LC
3、Application
Common FTTH and the data center of the computer room and other working scene.
Application
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