How does optical fiber communication transmit information and what are the disadvantages of optical fiber communication

Optical fiber communication plays an important role in life, but everyone is not very familiar with the knowledge of optical fiber communication, such as how optical fiber communication transmits information, what are the advantages of optical fiber communication, and what are the disadvantages of optical fiber communication. In order to improve everyone’s understanding of optical fiber communication, this article will discuss these three issues.

How does optical fiber communication transmit information and what are the disadvantages of optical fiber communication

1. Optical fiber communication information transmission

Optical fiber communication uses lasers with the least attenuation in the optical fiber at 1330nm and 1550nm for signal transmission, and turns all the information to be transmitted into digital signals, which are all represented by 1 and 0, then the signal can be represented by light. 1. No light means 0, the transmitted laser keeps flickering, but the frequency is quite high, the human eye cannot detect it, but it is always on.

(1) The carrier of optical fiber communication

Optical fiber communication uses light waves as the carrier and optical cable as a communication method for transmitting coal. It must be based on light waves as carriers. Light waves carry digital signals and propagate in the optical fiber.

(2) Application fields of optical fiber communication

The application field of optical fiber communication is very wide, mainly used for local telephone trunks. The advantages of optical fiber communication can be fully exerted here, gradually replacing cables and being widely used. It is also used for long-distance trunk communication. In the past, it mainly relied on cable, microwave and satellite communication. Now it is gradually using optical fiber communication and has formed a global dominant bit transmission method; it is used in global communication networks and public telecommunication networks in various countries (such as China’s national It is also used for high-quality color TV transmission, industrial production site monitoring and dispatching, traffic monitoring and control command, urban cable television networks, and shared antenna (CATV) systems. Used in fiber optic local area networks and other applications such as in aircraft, spaceships, ships, underground mines, power sector, military, and corrosion and radiation.

How does optical fiber communication transmit information and what are the disadvantages of optical fiber communication

The optical fiber transmission system is mainly composed of: optical transmitter, optical receiver, optical cable transmission line, optical repeater and various passive optical devices. To realize communication, the baseband signal must also be processed by the electrical terminal and then sent to the optical fiber transmission system to complete the communication process.

It is suitable for optical fiber analog communication systems, but also for optical fiber digital communication systems and data communication systems. In the optical fiber analog communication system, electrical signal processing refers to amplifying and pre-modulating the baseband signal, while electrical signal inverse processing is the inverse process of the originating processing, that is, demodulation, amplification and other processing. In the optical fiber digital communication system, electrical signal processing refers to amplifying, sampling and quantizing the baseband signal, that is, pulse code modulation (PCM) and line code coding processing. For data optical fiber communication, electrical signal processing mainly includes signal amplification. Unlike digital communication systems, it does not require code conversion.

Second, the advantages and disadvantages of optical fiber communication

(1) Advantages of optical fiber communication

1. Large communication capacity

In theory, an optical fiber as thin as a human hair can transmit 100 billion voice channels at the same time. Although it is far from reaching such a high transmission capacity, the experiment of transmitting 240,000 voice channels at the same time with one optical fiber has been successful, which is tens or even thousands higher than the traditional open wire, coaxial cable, microwave, etc. times more. The transmission capacity of an optical fiber is so huge, and an optical cable can include dozens or even thousands of optical fibers. If the wavelength division multiplexing technology is used to use an optical fiber as several or dozens of optical fibers, its The communication capacity is even more astonishing.

2. Long relay distance

Because the optical fiber has a very low attenuation coefficient (the current commercial silica fiber has reached below 0.19dB/km), if it is matched with appropriate optical transmitting and optical receiving equipment, the relay distance can reach more than hundreds of kilometers. This is incomparable with traditional cables (1.5km), microwaves (50km), etc. Therefore, optical fiber communication is especially suitable for long-distance primary and secondary trunk communication. According to reports, the experiment of transmitting 240,000 voice channels at the same time with one optical fiber and 100 kilometers without repeaters has been successful. In addition, the ongoing optical soliton communication test has reached the level of transmitting 1.2 million voice channels and 6,000 kilometers without repeaters. Therefore, it is entirely possible to realize global optical fiber communication without relays in the near future.

3. Good confidentiality

When the light wave is transmitted in the fiber, it is only carried out in its core area, and basically no light “leaks” out, so its security performance is excellent.

4. Strong adaptability

Strong adaptability means that it is not afraid of the interference of strong external electromagnetic fields, is corrosion-resistant, and has strong flexibility (its performance is not affected when the bending radius is greater than 25 cm).

5. Small size, light weight, easy construction and maintenance

The laying method of optical cable is convenient and flexible, which can be directly buried, pipeline laying, underwater and overhead.

6. Abundant sources of raw materials and low potential prices

The most basic raw material for making silica optical fibers is silica or sand, and sand is almost inexhaustible in nature.Therefore, its potential price is very low

(2) Disadvantages of optical fiber communication

1. The fiber is brittle and needs to be properly coated to protect it. In addition, in order to ensure that it can withstand a certain laying tension, more consideration should be given to the structure of the optical fiber.

2. When cutting and connecting optical fibers, high-precision cutting and splicing technology is required, which is not available when connecting cables.

3. The shunt coupling is inconvenient.

4. The optical fiber cannot transmit the power required by the repeater.

5. The bending radius should not be too small.

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