"Entering the Information Highway" into the information age PPT courseware

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"Entering the Information Highway" into the information age PPT courseware

1. Information superhighway

Refers to the communication network of ________ and ________ that can exchange various information. Signals and data files such as telephone, television, radio, etc. can be transmitted on the "information highway" formed by ________ without interfering with each other.

2. Optical fiber

(1) Definition: Optical fiber, referred to as optical fiber, is a medium for transmitting ________.

(2) Principle: Optical fiber communication is acoustic signal → electrical signal → ________ → electrical signal → acoustic signal.

(3) Features: The transmission loss of light in optical fiber is _______, it can be transmitted over long distances, the communication capacity of optical fiber communication is _______, it is not afraid of lightning strikes, it is not affected by electromagnetic interference, the communication quality is high, and the confidentiality is good.

3. Modern telecommunications networks

(1) Modern telecommunications networks are composed of ________, ________, and ________.

(2) The base stations of mobile phones are laid out in a ________ structure, which greatly increases the effective area of ​​radio coverage and reduces the number of base stations that transfer information.

4.Internet

The English name is Internet, also known as ________. It uses ________ and ________ to connect computer networks distributed around the world to transmit computer signals.

1. Optical fiber communication

Optical fiber is the abbreviation of optical fiber, which is a medium for transmitting optical signals.

(1) Structural characteristics of optical fiber: The optical fiber is very thin and has two layers: inner and outer layers. Since the refractive power of the inner layer and the outer layer is different, when light passes through the optical fiber, total reflection occurs, and the light will not travel to the outer layer. as the picture shows.

(2) Advantages of optical fiber communication: Optical fiber has strong anti-interference ability, small signal attenuation, large amount of information transmitted, and good confidentiality.

(3) Principle of optical fiber communication: Optical fiber communication is a communication method that uses electro-optical conversion technology to convert electrical signals into optical signals, allowing light waves to pass through the optical fiber, and then converts the optical signals into electrical signals at the receiving end, thereby realizing information transmission. ,as the picture shows. The light source of optical fiber communication is the laser emitted by the laser. The laser has the characteristics of high brightness, good directionality and pure color, that is, good monochromaticity.

2. Modern telecommunications networks

Modern telecommunications networks consist of satellite communications, microwave communications, and mobile communications. ① The satellite communication system consists of communication satellites, ground relay stations and transmission systems. Communication satellites receive signals from ground relay stations, process them, and then send them to another or several ground relay stations. Global communications can be achieved by arranging three synchronous communication satellites evenly around the earth. Satellites have the characteristics of large communication capacity, strong anti-interference, flexible use, long transmission distance, and high reliability. ②Microwave communication refers to electromagnetic waves with wavelengths between 1 mm and 1 m. The properties of microwaves are closer to light waves. They propagate roughly in straight lines and cannot be diffracted along the earth's surface. Microwave communication is communication using microwaves through ground relay stations. Microwave communications are restricted by ground relay stations. ③Mobile communication refers to the communication method consisting of mobile phones using microwave signals to communicate with the telephone network. The base stations of mobile phones are laid out in a cellular structure, which greatly increases the effective area of ​​radio coverage and reduces the number of base stations for transferring information.

Knowledge point 1 Optical fiber

1. According to reports, my country has completed the construction of 80 million optical fiber broadband ports in 2011. Many new residential areas have installed optical fiber networks. The main purpose of optical fiber is ()

A.Power transmission B.Communication C.Thermal conduction D.Lighting

2. (Double choice) The correct propagation of laser in optical fiber is ()

A. The laser only reflects at the inner core and outer layer, without refraction.

B. Laser propagates only in the inner core

C. Laser propagates back and forth between the core and cladding of the fiber

D. At the bend of the optical fiber, the laser light will leak out.

Knowledge Point 2 Modern Communication Network

3. As shown in the figure, which of the following statements about microwave communication is incorrect ()

A. Microwaves have shorter wavelengths and higher frequencies.

B. Microwave communication requires relay stations

C. Microwave propagation is diffracted along the earth’s surface

D. The properties of microwaves are closer to those of light waves

4. Among the three commonly used electrical appliances, radios, mobile phones, and televisions, the one that can both receive and emit electromagnetic waves is ()

A. Radio B. Mobile phone

C. Television D. Either way

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Update Time: 2024-06-29

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